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Handling Machining Assembly Control Pneumatics Electronics Mechanics Sensorics Software Chinese English French German Russian Spanish Blue Digest on Automation 053 789 Hesse Rationalization of Small workpiece feeding Orienting, sorting, checking and feeding

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Page 1: Pneumatic Feeding

Handling

Machining

Assembly

Control

Pneumatics

Electronics

Mechanics

Sensorics

Software

Chinese

English

French

German

Russian

Spanish

Blue Digest

on Automation

053 789

Hesse

Rationalization of Small workpiecefeeding

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Orienting, sorting, checking and feeding

Page 2: Pneumatic Feeding

Hesse

Rationalisation of Small workpiece feedingOrientating, sorting, checking and feeding

Page 3: Pneumatic Feeding
Page 4: Pneumatic Feeding

Rationalisation of Small workpiece feedingOrientating, sorting, checking and feeding

Blue Digeston Automation

HandlingPneumatics

Stefan Hesse

Page 5: Pneumatic Feeding

Blue Digest on Automation

© 2000 by Festo AG & Co.Ruiter Straße 82D-73734 EsslingenFederal Republic of GermanyTel. 0711 347-0Fax 0711 347-2155

All texts, representations, illustrations and drawings included in this book arethe intellectual property of Festo AG & Co., and are protected by copyright law.All rights reserved, including translation rights. No part of this publication maybe reproduced or transmitted in any form or by any means, electronic,mechanical, photocopying or otherwise, without the prior written permission of Festo AG & Co.

Page 6: Pneumatic Feeding

Without order, modern production is impossible. The question always is “Howcan workpieces be brought from a disorderly state into the required orientationfor a particular process?” This is also important from the economic point of view,since the orientation process can be complicated and expensive. Attempts are,of course, always made to retain the orientation achieved during componentproduction. In many cases, however, this is not particularly advantageous –magazining costs may be high, the original orientation may in any case be lost inthe course of a process, or the parameters for post- production operations maysimply be different. Re-orientation is very often a better solution. But how canwe achieve this? How are workpieces orientated?

This book is concerned with equipment and methods that promote the orientation of workpieces. These include, for example, vibratory feeders, whichare suitable for the feeding of over 80% of small bulk workpieces. Other hopperfeeding devices, however, also have their uses. Astonishing performances arebeing achieved today using imaging systems. These are flexible in their application, can “learn” from sample workpieces and can even be used for theoptical evaluation of quality features.

Everyone who is involved with factory rationalisation and planning and is sear-ching for suitable technology requires an overview of the available possibilities.The aim of this book is to help provide this. It is addressed at practical engineerswho do not wish to keep “re-inventing the wheel” but are glad to make use ofwhat is already available. And what is available is a wealth of both equipmentand experience.

Stefan Hesse

Foreword

Page 7: Pneumatic Feeding
Page 8: Pneumatic Feeding

Contents

Foreword

1 Workpiece handling in component production and assembly ............................ 9

1.1 Development of feeding technologyk ............................................................... 91.2 Requirements and areas of application .......................................................... 121.3 Flexible orientating and feeding systems ........................................................ 14

2 Workpiece hopper feeding devices ............................................................................ 18

2.1 Vibratory feeders ................................................................................................... 182.1.1 Mode of operation ................................................................................................. 182.1.2 Types ......................................................................................................................... 232.1.3 Spiral drum .............................................................................................................. 252.2 Centrifugal feeders ................................................................................................ 302.2.1 Design and mode of operation .......................................................................... 302.2.2 Typical conveyed material and system performance .................................. 312.3 Multi-stage feeders ............................................................................................... 312.3.1 Design and mode of operation .......................................................................... 312.3.2 Range of applications ........................................................................................... 322.4 Segment feeders .................................................................................................... 322.4.1 Design and mode of operation .......................................................................... 322.4.2 Typical conveyed material and system performance .................................. 332.5 Inclined and steep conveyors ............................................................................. 332.5.1 ADesign and mode of operation ........................................................................ 332.5.2 Typical conveyed material and system performance .................................. 34

3 Orientation technology .................................................................................................. 35

3.1 Basic principles of orientation ........................................................................... 353.2 Orientation using mechanical devices ............................................................. 393.3 Orientation using pneumatic components ..................................................... 533.4 Orientation using electromagnetic effects ..................................................... 573.5 Orientation using optical detection technology ........................................... 593.5.1 Advantages and methods .................................................................................... 593.5.2 Detection device .................................................................................................... 623.5.3 Analysis of features ............................................................................................... 643.5.4 Programming of optical detection, orientation and sorting devices........ 663.6 Orientating and sorting mixed workpieces .................................................... 68

4 Checking and counting workpieces ........................................................................... 71

4.1 Important process-related workpiece parameters ....................................... 714.2 Counting .................................................................................................................... 72

5 Magazining orientated workpieces ........................................................................... 74

5.1 Outlet design of vibratory feeders .................................................................... 745.2 Magazine designs .................................................................................................. 77

6 Ancillary equipment ........................................................................................................ 81

6.1 Noise protection devices ...................................................................................... 816.2 Hopper top-up systems ........................................................................................ 816.3 Level monitoring ..................................................................................................... 84

Page 9: Pneumatic Feeding

7 Handling technology systems ..................................................................................... 86

7.1 Basic technological components........................................................................ 867.2 Examples of applications ..................................................................................... 877.2.1 Vibratory feeders ................................................................................................... 877.2.2 System with contactless feature detection .................................................... 917.2.3 Orientation using the EMAGO method ............................................................ 927.2.4 Stepwise orientation using imaging systems ................................................ 947.2.5 Orientation using aerodynamic devices .......................................................... 94

8 Selection of workpiece feeding devices ................................................................... 96

8.1 Workpiece shape and degree of handling difficulty .................................... 968.2 Performance profile ............................................................................................... 978.3 Selection algorithm ............................................................................................. 1008.4 Economic factors ................................................................................................. 102

9 Glossary ........................................................................................................................... 103

Further literature ............................................................................................ 107

Glossary of technical items ............................................................................................ 111

Page 10: Pneumatic Feeding

1 Workpiece handling in component production and assembly

Modern production demands a high degree of automation in the feeding andhandling of individual components, modules and complete products. The auto-mation of production equipment has allowed machining times to be reduced inmany processes. Feeding operations on the other hand, are frequently still carried out manually, which means that handling now accounts for a greater proportion of the overall working cycle time. Our task must be to exploit thispotential for rationalisation.

Another current trend is to link material or workpiece flow together with the flowof information. Handling technology plays an important role within this widefield, and one of the most costly and difficult handling operations is the auto-matic orientation of small workpieces. These workpieces are the most commontype and in terms of size and weight have a length of around 200 mm, a dia-meter of around 50 mm and a weight of around 0.5 kg.

The need to re-organise and rationalise the feeding of materials and componentsemerged only with the development of the mass production of items such aslight bulbs, needles, ammunition, buttons and screws. For example, a man calledSpencer constructed an automatic lathe with automatic feeding of bar materialin the USA in 1873, whilst a scoop-arm feeding device was used as early as 1865in an automatic machine for the production of wood screws. By the mid-1920s, ithad become standard practice to use scoop-segment hoppers to feed glass rodsand envelopes in the light-bulb manufacturing industry.

Vibratory conveyors, too, became popular. Vibrating devices were in use by theend of the 19th century, particularly imbalanced vibratory conveyors for thescreening of bulk materials. When it was recognised that it was also possible toconvey individual workpieces by this method, linear vibratory conveyors werealso developed. Problems were, however, experienced, since smooth workpiecescan often “stick” together. The reason for this was the surface adhesion createdby the film of oil on the workpieces and the aerodynamic effect which at highspeeds produced a kind of suction effect with the workpieces instead of separat-ing these.

The first patents for vibratory devices were granted as early as 1850. A patentapplication was filed in the mid-1940’s by the Syntron Company of America forthe orientating, conveying and magazining of workpieces in a vibratory bowlfeeder. Other hopper feeding devices were, of course, also developed, forexample with scoop segments, pins and tubes. These are still in use today.Magazine feeding devices have always been and remain the preferred choice foruse with machine tools. The magazines in question have generally been filledmanually. This operation included a visual inspection, often a vital part of theprocess. Progressive companies soon recognised that vibration technologyprovides relatively simple and inexpensive feeding systems or even assemblysystems. There is, for example, a description in an old book [1] of how watchcomponents were assembled using a “shaker box” or in other words a vibratorydevice. How did this operate with these small workpieces (shafts)?

9

1

Workpiece handling in

component production

and assembly

1.1 Development of feeding technology

Page 11: Pneumatic Feeding

“Here in the factory, the workpieces are placed into a round iron drum. Theshanks into which the shafts are to be fitted are positioned upright on a diskwhich forms the base of the drum. Within the heap of workpieces, so small thatthey can hardly be distinguished individually, are larger steel rollers. The electricdrive is switched on and vibrates the drum. The rollers, like pike in a carp pond,churn up the tiny shafts, which gradually vibrate their way into the shank open-ings, whose diameter appears about equal to the width of a fly’s foot!”

What this author was witnessing 60 years ago in Germany’s Black Forest was theassembly of microscopic watch components in a vibrator.

Workpieces of many different shapes can be easily orientated in a vibrator. Asthe workpieces move upwards within a spiral drum, they come into contact withorientating devices (chicanes) which create uniform orientation, generally inseveral stages (Fig. 1-1).

The following are examples of the throughput that can be achieved with thisconventional technology:• Cylinder pressure springs 0.5 x 5 x 16.5 20 per minute• Washers for spark plugs, diameter 16.9 mm 38 per minute• Caps for spark plugs, diameter 14 mm 38 per minute• Ceramic wafers 50 per minute• Cable nuts 38 per minute

The orientation technology in the vibrator naturally becomes more complicatedas the number of workpiece features to be distinguished and thus the number ofdifferent orientations (asymmetry) increase. Ways were therefore soon proposedof replacing mechanical orientating devices with contactless checking devices.Fig. 1-2 shows a solution in which a workpiece contour is detected in 2 planesand evaluated. The image information from these two views is combined and fedvia fibre optic cables to a CCD line scanning camera. After evaluation, the work-pieces are guided into appropriate sorting channels. This principle has now beendeveloped into a robust industrial solution and represents the present state ofthe art in the feeding of small workpieces. We shall return to this subject anddiscuss it in detail later.

1 Workpiece handling in component production and assembly10

Fig. 1-1:

Principle of orientation in

a vibratory bowl feeder

1 Workpiece

2 Vibrating spiral drum

3 Desired lifting/rotary

vibration

4 Orientating device

4

1 2 3

Ordnen durch Gleichrichten

Ordnen durch Auslesen

Orientation through correction of position

Orientation through selection

Page 12: Pneumatic Feeding

1 Workpiece handling in component production and assembly

We must never consider feed technology in isolation. It is part of the overallproduction process and must accordingly be considered holistically. From thepoint of view of the production process, workpiece feeding is an auxiliary pro-cess that occurs on various levels, as shown in Fig. 1-3 in schematic form. If, forexample, small workpieces are manufactured directly on the assembly conveyorbelt, this simplifies their handling considerably. The degree of flexibility whichcan be achieved in this case is, however, low. It is also simple to feed compo-nents in a belt, such as electronic components, since flowing or semi-flowingmaterials are easier to handle in technical terms. Flexibility is certainly provided,notwithstanding that the workpieces must first be placed into the belt at someother point.

11

Fig. 1-2:

Imaging system with scan-

ning in 2 planes (according to

Cronshaw, 1980)

1 Parallel light source

2 Fibre optic cable

3 Combination of fibre

optic cables

4 CCD camera

5 Lens

6 Feed device

7 Rail

Fig. 1-3:

A number of technological

variants for the feeding

of small workpieces for

component production,

assembly and checking

Workpiece feeding

FeedingDistributing

Single magazineTop-up cassette

OrientatingMagazining

Bulk material Stack magazine

FeedingDestacking

FeedingDistributing

Endlessmagazine (belt)

V M

M

M

M

ProductionFeeding

Integratedpre-production

7

2

3

4

5

1

1 6

Page 13: Pneumatic Feeding

This method also uses additional ancillary material, which subsequently be-comes waste. In many cases, it is very practical to present workpieces inmagazines, particularly if they can be placed into magazines in preceding pro-cesses without any great effort. If the magazining process takes place at anotherlocation, the magazine costs may be a significant factor. In the case of short-cycle working processes, however, the resulting frequent changing of magazinesmay lead to a loss of productive time. In the case of magazine stacks, the localfeeding system must be able to resolve the three-dimensional arrangement ofworkpieces on the workpiece-carrier magazines. It is, however, often the casethat workpieces are supplied randomly orientated in crates, sacks or othercontainers. In this case, it is the recipient’s task to bring the workpieces from adisorderly heap into an orientated state. This is generally the state of work-pieces in a magazine [2 to 5].

Before a workpiece can be processed in any way, it must be brought to the placeat which processing is to be carried out, generally the working area of amachine. It must then be removed from this area again after processing (exceptin the case of an assembly operation). There is generally a requirement that theworkpiece must be in a certain state (= orientation and position), usually withno specification of how the workpiece is to reach the processing point. Theoperation required to achieve this is referred to as “feeding”. This is shown ingeneral symbolic form in Fig. 1-4.

In order to choose suitable orientating components, we need to know thebehaviour of the workpiece, for example on vibrating chutes. As Fig. 1-5 shows,cylindrical workpieces with a longitudinal attitude rotate about their own axis atthe outlet of the vibrator. If the workpiece has lateral features, the rotating effectcan be used to achieve orientation. Under these special conditions, the motionbehaviour of the workpiece becomes the decisive operative principle. But whatdo we mean by “workpiece behaviour”?

1 Workpiece handling in component production and assembly12

1.2 Requirements andareas of application

Fig. 1-4:

Feeding operation as a

black-box representation

1 Workpieces in undefined

(random) order (heap)

2 Feeding of workpieces

defined in terms of time

and physical arrangement

U Disorder

Input Feeding system Output

U = Umax

Feedingoperation

Umax – Umin

U = Umin = 0

1 2

S

w

v

u 0 x

y

z

Page 14: Pneumatic Feeding

Workpiece behaviour is the totality of all the typical states of one or more

workpieces that are the result of the action of external forces, including

gravity.

We distinguish between 12 basic behavioural types according to their shape:Tangle, flat, cylindrical, block-shaped, mushroom-shaped, conical, pyramidal,hollow, spherical and long, together with complex workpieces made up of differently shaped components and irregular solid workpieces.

In order to automate feeding operations, we must possess adequate knowledgeof the workpiece to be handled. The important factors are:• A description of the workpiece• Its behaviour at rest • Its motion behaviour.

A handling workpiece can be described by the following variables:• Mass (reference mass, mass tolerances, mass after processing)• Materials properties:

- Mechanical (elasticity, hardness, porosity, etc.)- Electromagnetic (conductivity, permeability. etc.)- Thermal (heat conductivity, absorption capacity, etc.)- Chemical (corrosion resistance, hygroscopic tendency, etc.)

• Geometry- Shape (internal shape, external shape, etc.)- Dimensions (length, width. height, etc.)- Dimensional ratios

• Surface properties- State (temperature, humidity, presence of oil film, etc.)

• Special features relating to handling (position of centre of gravity, available gripping points, etc.).

1 Workpiece handling in component production and assembly 13

Fig. 1-5:

Rotary motion during

conveying can be exploited

for orientation purposes

Page 15: Pneumatic Feeding

It will probably also be necessary to distinguish between prototype workpiecesand those from series production. Experiments and the selection of feedingequipment should always be based on a large quantity of series-produced work-pieces, preferably from different batches and produced using different tooling.Plastic workpieces, for example, may occasionally be distorted or exhibit largedimensional variations or differences in surface quality (peak-to-valley height,gloss, fluid skin). These factors may have a major influence on the free move-ment of workpieces in chutes.

Applications cover all areas of industry whereby which small-sized material isused. The main areas are as follows:• Metalworking industry (shafts, hardware fittings, drill bits, pins, etc.)• Electrical engineering/electronics (terminal strips, ceramic wafers, switch

contacts, etc.)• Woodworking industry (dowels, play bricks, fittings, screws, etc.)• Electroplating (sensor housings, nuts, sockets, fittings, etc.)• Manufacture of plastic workpieces (inserts, plastic housings, brush compo-

nents, etc.)• Pharmaceutical and cosmetics industries (tablets, toothbrush components,

lipstick cases, etc.)• Assembly and packaging (threaded pins, shafts, washers, nuts, etc)• Jewellery industry (stampings, glass beads, watch housings, carton

components, etc.)• Textile and clothing industries (buttons, zip-fastener components, needles, etc.)• Precision engineering/optics (lenses, mounts, rings, stampings, etc.)• Food industry (bottle caps, pressurised containers, spray-can valves, etc.)• Medical technology (syringe components, glass ampoules, slip-on caps, seals,

etc.).

In view of the frequent need to deal with large numbers of workpiece types andvariants, together with the trend towards short-run production, workpiece fee-ding systems are required to offer high flexibility for changeovers from one work-piece to another. Ideally, this facility should be programmable. It would other-wise be necessary to have special feed systems for each workpiece type, whichwould in most cases demand too much investment and destroy the overall viability of an automation solution. Accordingly, the English company Bowl-Feeders Automation produced vibratory conveyors in the 1960s that had inter-changeable spiral sections including workpiece-specific orientating devices. The output spiral section with an arc angle of 100° in each case reflected thespecial feature of the workpiece concerned. Solutions of this kind, however, did not gain widespread acceptance.

1 Workpiece handling in component production and assembly14

1.3 Flexible orientating and feeding systems

Page 16: Pneumatic Feeding

1 Workpiece handling in component production and assembly

A special aspect of flexibility is the detection and separating-out of defectiveworkpieces that may be mixed in with the other workpieces. Automatic assemb-ly, however, demands workpiece feeding that conforms 100% to specification.In the case of bolts, for example, these may be defective due to the fact thatthey have no threads or a false thread with no pitch. These workpieces must beeliminated. Fig. 1-6 shows the defective workpieces that have been encounteredamongst stampings. These are produced at the extreme start and end of stripmaterial and if the side cutting edge of the tool does not work correctly. Similarremnants will be encountered when working with bar material.

It is possible to list the following vital features for flexible feeding systems [6 to 9]:• Creation and maintenance of a defined workpiece state (position, orientation)

with a high degree of repetition accuracy• Prevention of any mechanical damage or deformation of sensitive workpieces• Reliable detection and elimination of workpieces which are unusable due to

the fact that they are the wrong type or damaged or do not conform to dimensional or shape tolerances

• Short changeover times, perhaps even changeover at the press of a button,and tolerance of minor interference (dirt, burrs, etc.)

• Large capacity achieved through compact storage of workpieces and easyinterchangeability of workpiece magazines

• Easy access of transfer position for automatic gripper devices (gripper space)• Adequate feed delivery and high technical availability.

Of all the various flexible orientation systems, the one which has been widelyadopted is the vibratory bowl feeder (and in certain cases other hopper typedevices) in combination with automatic imaging detection and distributordevices. A major advantage of this type of device is that it allows orientation andsorting from a mixture of workpieces. Since these systems operate withoutmechanical chicanes in most cases, we can speak of a programmable feedsystem.

15

Gutteil

Falschteile

Fig. 1-6:

Defective workpieces and

remnants in the workpiece

flow can seriously disrupt

production

Good workpiece

Defective workpieces

Page 17: Pneumatic Feeding

Another method involves the automatic filling of flat magazines. These areequipped with workpiece-specific shaped nests. If workpieces are caused tomove across the magazines by linear vibration, they drop into the shaped nestsas they adopt correct orientation at random. Excess and incorrectly orientatedworkpieces are fed back from the end of the magazines and are fed past theseagain. Fig. 1-7 shows a system of this kind. Only the magazines need to be madeworkpiece-specific [10].

In electronics production, flat belt conveyors have been used for a considerabletime to fit components to printed circuit boards. The components are located onflat bands or blister strips and are fed cyclically as flowing material. It is alsopossible to produce sequence tapes, which contain all the various componentsrequired for a particular assembly sequence. A typical feature of these systemsis that the overall feeding system does not need to be adapted for differentworkpieces but need only be matched to the magazine belts or bands, which arealways the same. This provides a certain measure of flexibility.

A further method is to devise a system that imitates the way human beings “dip”into a crate to pick up workpieces. Human beings find this easy – they see withtheir eyes how the workpieces are lying in random order, pick up a workpiecewhich is favourably positioned and feed this into a machine. The principles ofthis operation can be transferred to a robot. Prototype solutions already existand will in time be developed for practical industrial use. For this purpose,robots are equipped with 3D laser cameras that generate three-dimensional images. Gripping points are then calculated on the basis of the detected work-piece contours. The workpieces in question can lie in any random order but musthave gripping points which can be accessed by the jaws of the relevant gripperwithout collisions. Systems of this kind are already working well on a laboratoryscale.

1 Workpiece handling in component production and assembly16

Fig. 1-7:

Flexible magazining system

for small assembly work-

pieces

1 Assembly module

2 Magazine loading device

3 Vibratory bowl feede

4 Plate magazine

5 Linear vibrator

6 Assembly line

7 Workpiece carrier

8 Assembly robot

9 Feed position for

assembly workpieces

4 1

23

7

5 6

98

Page 18: Pneumatic Feeding

1 Workpiece handling in component production and assembly

Things become somewhat simpler if workpieces are picked up from a table orconveyor belt. The “table” can be a linear vibratory system like the one shown in Fig. 1-8.

The principle is easy to explain. If enough workpieces are brought into the fieldof vision of a camera, for example by means of a linear vibrator, there will almostalways be a workpiece in the right position for gripping. The workpieces passover tipping steps and are thus brought into a stable position; workpiecesstanding on end fall over, while workpieces lying on top of others fall away. Oncethe detection system has found a suitable workpiece, the relevant gripping coor-dinates are output to the industrial robot. This picks up the workpiece by meansof a mandrel gripper. Excess workpieces run back into the hopper. It is of coursepossible to use an intermittently running conveyor belt instead of the linearvibrator.

The workpiece shape is programmable, which means that the solution is flexiblewithin certain limits. For many applications, camera-aided robotics representsthe current state of the art.

17

Fig. 1-8:

Orientating by picking up

from a table

1 Camera

2 Field of vision

3 Robot with gripper

4 Workpiece in correct

position

5 Screen of detection device

6 Table with tipping steps

7 Workpiece in incorrect

position

8 Vibrator

5

6

7

1

2

3

4

8

Page 19: Pneumatic Feeding

Hopper feeding devices accept bulk workpieces and are equipped with com-ponents that are able to correctly orientate these workpieces. The workpiecesthen leave the hopper feeders in an orderly fashion, generally in a string. Thefollowing operating principles are used to pick workpieces out of a randomlyordered heap:

• Scooping with swivel segments, rams, wing rails or tubes• Sliding along alignment edges which provide orientation• Falling into profile apertures and travelling through shaped passages• Application of vibration in combination with alignment components• Exploitation of centrifugal force effects• Removal of workpieces with the aid of magnetic forces.

Fig. 2-1 shows the principle of the design of devices of this kind. All the com-ponents used to achieve the desired orientation operate in contact with theworkpieces. This may result in disadvantages, in particularly the following typesof workpiece damage:

• Roughness or loss of gloss due to friction• Impact dents caused by falling workpieces• Accumulations of dirt due to electrostatic effects, particularly with plastic

workpieces.

We will consider the most important types of hopper feeding devices in greaterdetail below [11 to 13].

Electromagnetic vibratory feeders are especially important in conveyingtechnology for 4 reasons:

• The drive of these feeders operates without the friction of components slidingover each other and thus provides a trouble and maintenance-free conveyingdevice with a very low rate of wear.

• Open- and closed-loop control of these conveyors can be achieved by usingsimple electrical-engineering components.

• The conveyors have low power consumption, since they operate in the areaclose to natural resonance.

• They are robust and of simple design and are distinguished by their lowpurchase costs.

Electromechanical vibratory feeders are spring/mass systems and obey the lawsof vibration mechanics. They can be produced in numerous variants.

2

Workpiece hopper

feeding devices

2.1Vibratory feeders

2.1.1Mode of operation

2 Workpiece hopper feeding devices18

Page 20: Pneumatic Feeding

Fig. 2-1:

Examples of hopper feeding

and orientating devices

1 Drum-type feeding device

2 Orientation with parallel

rollers

3 Vibratory bowl feeder

4 Vibrating dish hopper

5 Magnetic rotory hopper

6 Scoop segment hopper

7 Scoop tube hopper

8 Vibratory mat system

9 Centrifugal conveyor

10 Drum type with shaped

passage

11 Scoop wheel hopper

12 Step-type lifting feeder

13 Rotary hook hopper

14 Horizontal belt conveyor

15 Inclined conveyor

16 Disc hopper

17 Hook-wheel hopper

18 Conical-disc hopper

2 Workpiece hopper feeding devices 19

1 2 3

4 5 6

7 8 9

10 11 12

13 14 15

16 17 18

v

Page 21: Pneumatic Feeding

Depending on the type of workpiece motion on the conveyor spiral, we distin-guish between micro-projection conveyance and friction conveyance [14 to 17].In the case of micro-projection conveyance, the workpieces lift away from thechute during the conveyance operation for brief periods, travel in free flight andthen impact onto the conveyor again. This impact phase creates a number ofproblems. For one thing, the position of the workpieces is not precisely defined,and for another, workpieces made of very brittle material may suffer damage.There is also a not inconsiderable noise nuisance. It is, however, possible toachieve very high conveyance speeds with this method of working. Fig. 2-2shows the principle involved, The forward motion of the working material is in asense made up of a series of small ballet-like leaps. Due to the small size ofthese “leaps”, however, a viewer has the impression of a continuous flow ofmaterial.

Fig. 2-2:

Principle of micro-projection

conveyance

a) Vibratory system

b) Motion conditions

1 Workpiece

2 Guide

3 Spring mounting

4 Spring

5 Magnet

6 Motion of working material

7 Chute motion

F Flight time

K K Contact

t Time

2 Workpiece hopper feeding devices20

2 1

a)5

3

4

b)

7

0

6

FK

t

Hub

läng

eSt

roke

leng

th

Page 22: Pneumatic Feeding

Under friction-conveyance conditions, the workpieces do not lift off the chutebut slide along this. This virtually eliminates the problem of uncontrolled work-piece motion and significantly reduces the noise level but at the same timeinvolves a loss of speed. This type of conveyance is facilitated via single or dual-mass oscillators coupled by leaf or rubber springs and excited by special elec-tromagnets at a frequency close to their natural resonance. The acceleration forces which act on workpieces during friction conveyance are less than 1 G (1 G = 9.81 m/s2). In the case of micro-projection conveyance, on the otherhand, periodic acceleration forces occur of 9 to 16 G. Wear of the chute surfaceis nonetheless low with micro-projection conveyance, since the workpieces“jump”. Tests have shown that the wear on replaceable guide plates that havebeen used to convey 300,000 tonnes of granite stone was less than 12 millime-tres.

Conveyance behaviour depends on the relevant vibration characteristics, whichare governed principally by the following parameters:

• Relationship of working mass to counter-mass• Relationship of workpiece mass to working mass• Relationship of operating frequency to natural resonance• Amplitude of exciter force• Time curve of exciter force• Mass moments of inertia• Angle of introduction of force relative to working mass motion path• Parallelism of working mass planes• Centring of working mass and counter-mass relative to leaf-spring suspension• Equal angles of incidence of leaf springs• Spring stiffness.

By varying the voltage, it is possible to control the amplitude and thus the driveforce and the speed of travel of the fed workpieces.

For friction conveyance, sensor-guided spring/mass drives can be used. Anelectronic closed-loop control system controls the two parameters of frequencyand amplitude. The reference variable is the distance/time signal, which isconverted within the computer into acceleration values. The controller keeps theacceleration values constant to the preset desired values at all times,irrespective of the instantaneous load state of the vibratory bowl feeder.Frequencies of 5 to 20 Hz are used.

2 Workpiece hopper feeding devices 21

Page 23: Pneumatic Feeding

Vibrators should be installed on vibration insulators. They should nonethelessnot be installed in the immediate vicinity of precision machine tools. They mustalso be aligned carefully on the horizontal plane. If vibratory bowl feeders areinstalled at an angle, this will lead to variations in the angle of the spiral. As thevalues of the chute rise angle and chute lateral inclination angle are small, aninclination of the overall device may lead to malfunctions, such as the formationof accumulations at certain points.

Of all the types of vibratory conveyors used in mechanical engineering, elec-tromagnetic vibrators have proved to be the most popular. For the conveyance ofconstruction materials, for example, the preferred choice is vibratory chutes withimbalanced drive. These vibratory systems are also significantly larger and veryrobust.

We can distinguish between electromechanical vibratory systems on the basis oftheir design features as follows:

• The number and orientation of the electromagnets fitted to conveyors withvertical, horizontal or multiple tangentially arranged springs

• The nature of the elastic suspension of the conveyor drum with single ormultiple flat springs or round bar springs

• The way in which motion behaviour is controlled within the conveyor:- By varying the voltage by means of a control transformer- By varying the current and voltage drop across the electromagnet by means

of a resistor- By varying the force by controlling the air gap of the electromagnet and- By varying the number of electromagnetic coil windings that are fed with

current.• The way in which the resonance setting is controlled:

- By varying the springs or spring assemblies in the case of multiple springs- By varying the effective spring length and- By varying the system mass by using mass trimmer pieces

• The shape and type of the workpiece-carrying component (chutes, cylindricaland conical vessels, tubes and plates.

Vibratory feeders can be used for almost all kinds of workpieces (of small size),provided that these do not have surfaces which are sticky, crumbling or generatesurface adhesion and that they do not lock together. Vibrators have even beenused for materials as hot as 900°C and as cold as –50°C. They can also be usedfor conveyance in air-exclusion or vacuum environments. Conveyance speeds aregenerally up to 7.5 m/min., but high-speed vibrators have already achievedspeeds of 100 m/min. [18 to 21]. On forging presses, vibrators are used to feedworkpieces with masses of, for example, 5 kg.

2 Workpiece hopper feeding devices22

Page 24: Pneumatic Feeding

Vibratory feeders are produced in various forms. Fig. 2-3 shows a selection ofthese. The spiral feeders with cylindrical or stepped drums will be familiar.Feeders with an external spiral are used for vertical conveyance. These consist ofa support tube around which the conveyor path winds. The conveyance height istheoretically unlimited. The path cross-section can be square or round. In thecase of tube feeders, the vibratory system is located on the tube. These feederscan be used for both bulk materials and individual parts. Alternate driven andnon-driven tube sections can be connected up to form long pipelines.

Vibratory towers, which use one vibrator system to drive several drum typeconveyors, are required in assembly operations to provide a parallel feed ofsmall workpieces. They are not needed if feed systems are installed which areable to separate and feed mixed workpieces from a random heap. Linear vibra-ting chutes and spiral feeders with multiple outlet paths represent a modifica-tion of the basic design principle. Fig. 2-4 shows the design of a circular spiralconveyor. There are also versions with a single central magnet, with round barsprings and with decoupled vessel bases (Fig. 2-4b).

Feed vibrators and storage vibrators are sometimes combined to form a singleunit. If the level of workpieces in a spiral conveyor falls, the storage vibrator topsthis up. A storage vibrator of this kind can be of very simple design, as shown inFig. 2-5. The angle at which the magnet is connected to the bin is chosen toensure that the vibration not only provides a conveyance function but also helpsto separate interlocked working material. This allows controlled dosing and fee-ding to be achieved. The fed material can be nails, pins, screws or bolts, outputin batches for top-up purposes.

2 Workpiece hopper feeding devices 23

1 2 3

4 5 6

2.1.2 Types

Fig. 2-3:

Typical designs

1 Spiral feeder with

stepped drum

2 Vertical feeder with

external spiral

3 Vibrating tube

4 Vibrating tower

5 Linear vibrating chute

6 Spiral feeders with

multi-path outlet

Page 25: Pneumatic Feeding

2 Workpiece hopper feeding devices24

1

11

12

13

4

4

16

15

14

b)

1

3

7

8

9

7

1

10

2

5

6

4

a)

1

2

3

4

Fig. 2-4:

Design of a spiral vibratory

feeder

a) Micro-projection principle

b) Principle of friction

conveyance (Feldpausch)

1 Spiral drum

2 Hopper base

3 Leaf spring link

4 Electromagnet

5 Stand

6 Leaf spring

7 Base mounting

8 Base plate

9 Foot

10 Spiral outlet

11 Decoupled base

12 Intermediate mass

13 Counter-mass

14 Springs for vertical

motion

15 Springs for horizontal

motion

16 Rubber vibration dampers

Fig. 2-5:

Storage vibrator

1 Hopper container

2 Spring

3 Table

4 Vibrator magnet

Page 26: Pneumatic Feeding

The actual workpiece hopper is referred to as a spiral drum, feeder drum or sim-ply “drum”. The internal drum surface, and more rarely the external drum sur-face, is equipped with a spiral feeder with an outlet at its upper end. Typicaldrum types are shown in Fig. 2-6. Each type has its advantages and disadvan-tages.

The cylindrical type is easier to manufacture but has the disadvantage that sepa-rated-out workpieces fall down the full height of the drum. In the case of conicaland stepped drums, on the other hand, the workpieces fall only as far as thenext lowest spiral. There is also no possibility that they will jam against theunderside of the next highest spiral. In the case of a conical drum, the increment“0a” of the spiral diameter is smaller than one spiral width. In the case of a step-ped drum, the increment “a” is equal to the spiral width. Fig. 2-7 shows con-veyor drums made of polyamide or aluminium into which a spiral has not yetbeen cut. Standard spiral pitches “h” are 10, 15, 20, 25, 30 and 40 mm. The dia-meter “D” ranges from 100 to 630 mm or even larger. Spiral drums are alsoconstructed from sheet brass, sheet steel, V2A and V4A materials and glass-fibre-reinforced plastics (GRP).

With small workpieces, the diameter of the spiral drum should be approximately8 to 12x the length of the workpieces to be conveyed. A slightly smaller diameterwill be obtained by using the graph in Fig. 2-8. This is also based on empiricalvalues.

2 Workpiece hopper feeding devices 25

1 2 3 4

a a

a) b)

·

25 – 40°

a

h

D

2.1.3 Spiral drum

Fig. 2-6:

The most commonly used

drum types

1 Cylindrical drum

2 Conical or funnel-shaped

drum

3 Stepped drum

4 External spiral drum

Fig. 2-7:

Spiral designs

a) Standard spiral

b) Drum feeders

a Spiral width

h Spiral pitch

Page 27: Pneumatic Feeding

Tumbling motions of the workpieces and contact between these may cause theworkpieces to move inwards during their upward motion and fall back into theworkpiece sump. To combat this, the spiral should be fitted with a low edge orthe channel should be given a lateral inclination a of up to 10°.

The spiral pitch H must be selected so as to ensure that workpieces on 2 spirallevels cannot obstruct each other. Allowance should be made for all possibleworkpiece orientations (Fig. 2-9). The clearance should be 10 to 20% of thepitch H.

2 Workpiece hopper feeding devices26

0 200 400 600 800 1000

Aufsatzdurchmesser in mm

40

80

120

160

Wer

kstü

cklä

nge

in m

mH

Spie

l

·

Fig. 2-8:

Empirical values for drum

diameters as a function of

workpiece length (according

to Robertson)

Fig. 2-9:

Spiral pitch “H”

Wor

kpie

ce le

ngth

in m

m

Clea

ranc

e

Drum diameter in mm

Page 28: Pneumatic Feeding

The base of the drum is shaped as a shallow cone; the angle of inclination of thismust be greater than the angle of friction between the base and workpiece. Thevalue chosen is usually around 10°. The coefficient of friction between the work-piece and drum base should be as low as possible, while that between the work-piece and spiral channel should be as high as possible. This allows higherconveyance speeds. In certain cases, the conveyor spiral within the vibratordrum is given a coating in order to improve conveyor or noise characteristics orboth. Various materials are used for this:• Rubber: This improves operation and reduces operating noise. Ribbed sur-

faces improve the conveyance of small oily products.• Polyurethane: This consists of PUR, which is approved for the pharmaceutical

and food industries. This material can be applied with a spray gun to give anydesired surface from the roughness of emery paper to mirror smoothness. Thethickness of the coating can be varied, and Shore A hardness values of 50, 80,90 and 98 can be achieved. The coatings can have any desired colour. Coatingallows the noise level of conveyors to be reduced by as much as 20 dB(A).

• Brush lining: Vibrating channels can be covered with a brush lining. Thisrepresents an elegant way of conveying workpieces while protecting theirsurfaces.

Brush linings operate on a very interesting principle that is based on the de-formation of inclined polyamide bristles which are under load and are thensubjected to vibration. Conveyance is virtually silent. Typical materials conveyedin this way are bent-wire workpieces, sheet-metal workpieces, solid metal work-pieces (including those with a relatively small contact surface), gearwheels, alloyhousings, light bulbs, lenses, etc. (Fig. 2-10). The bristle hardness must bematched to the workpieces in each case.

2 Workpiece hopper feeding devices 27

S

S

Fig. 2-10:

Brush lining for workpiece

conveyance.

S Direction of vibration

Page 29: Pneumatic Feeding

Normally a horizontal vibratory system is used which generates micro-projection.It is, however, also possible to generate a conveying motion with verticalvibration. The motion is slower in this latter case and is generated by the in-clination of the polypropylene bristles. Brush linings can also be used to createorientating devices with a two-dimensional/linear mode of operation as shownin Fig. 2-11. In the case of vertical vibration, it is the bristle alignment alone thatdetermines the direction in which the workpieces are conveyed. It is accordinglypossible to bring workpieces to a desired feed position by means of only asuitable lining, without any further active guide components. This method at thesame time orientates or pre-orientates the workpieces. Depending on the work-pieces concerned, gradients of up to 10° are possible.

But let us return to spiral feeders: In the interests of better understanding, weshould note the following regarding directions of workpiece travel and outletconnections. We generally refer to a feeder with clockwise motion as “right-handed” (Fig. 2-12).

2 Workpiece hopper feeding devices28

1

2

3

a) b)

3

4

a) b) c)

Fig. 2-11:

Planar/linear ordered feeding

device (Ficon)

a) Brush-lining modules

for the creation of conveyor

systems

b) Plan view of a feed system

1 Workpiece

2 Brush lining

3 Lateral guide

4 Workpiece in feed position

Fig. 2-12:

Directions of workpiece travel

and outlet connections

(plan views)

a) Left-handed outlet

b) Right-handed outlet

c) Lateral outlet

Page 30: Pneumatic Feeding

Fig. 2-13:

Method of connecting up

gravity chutes, based on the

left-handed vibrator

Further conveyor devices and magazine chutes can be connected up in a numberof ways. Fig. 2-13 shows 6 examples of these. The chute for further conveyancemust not, however, be connected up rigidly (examples are shown in Fig. 5-2). Incertain cases, rubber tubing can be used.

2 Workpiece hopper feeding devices 29

Page 31: Pneumatic Feeding

A centrifugal feed device is a hopper feeder system with a central flat or conicalturntable which drives the working materials on this via a rotary action. Theresulting centrifugal force causes workpieces to separate out of the heap andmove towards the edge of the drum. Here they meet the delivery ring and slideonto the ramp. The speeds of the turntable and delivery ring can be adjustedseparately. Separated-out workpieces can be aligned by orientating devices andthus proceed to the pick-up point correctly orientated. Incorrectly orientatedworkpieces pass back into the hopper. Complex workpieces can be fed by meansof a conveyor belt, for example, in order to obtain the desired orientation for agiven process or to separate out all incorrectly orientated workpieces. Anyexcess conveyed workpieces fall back into the heap in the hopper. In terms ofphysics, the friction force FR and the internally-orientated force component “g”resulting from the workpiece mass “m” must be somewhat smaller than thecentrifugal force FZ resulting from the rotation (Fig. 2-14). Incidentally,centrifugal conveyors operate very quietly.

2 Workpiece hopper feeding devices30

2.2 Centrifugal feeders

2.2.1 Design and mode ofoperation

Fig. 2-14:

Centrifugal feeders [22]

a) Design

b) Forces

1 Adjustable hopper

suspension mounting

2 Workpiece already on

output channel

3 Rotating delivery ring

with drum lining

4 Continuously-rotating

turntable, e.g. with

10° angle of inclination

b)

FR

m · g

FZ

4

3

2

1

a)

Page 32: Pneumatic Feeding

The diameter of the drum of a centrifugal feeder can be 400 to 1200 mm, whilstthe conveyance speed can be 25 to 60 m/min. This allows workpiece through-puts to be achieved of 60 to 3000 units/min. This is very high, but despite this,the workpieces are handled very gently. Typical conveyed materials are smallitems such as bolts, screws, rings, screw caps, cans, can lids, jar and bottle caps,lamp sockets and socket sleeves (1200 units/min). It is also possible to feedcontainers and bottles with capacities of up to 0.5 litres at high speed.Workpieces should be of low weight. Centrifugal conveyors have accordinglyproved extremely valuable in the pharmaceutical and cosmetics industries and inpackaging applications. In comparison with vibratory bowl feeders, centrifugalfeeders are significantly larger and thus require more installation space.

In the case of stepped or lifting-plate feeders, small workpieces are conveyedupwards in several steps by intermittently-moving plates. The plates are ar-ranged in an ascending sequence, thus creating steps on which the workpieceslie. The step thickness (which is equal to the plate thickness, e.g. 10 or 20 mm)is matched to the workpiece dimensions. The plate mechanism is slightly in-clined. Workpieces picked up by the lowest step assume a preferred orientationand thus are at least pre-orientated by the time they exit from the feed device.Further orientating devices will generally be installed at the outlet of the feeddevice. The continuously rising and falling masses of the lifting plates demand agood guide system and a high-quality crank drive mechanism, particularly as thelifting steps can be up to 1400 mm wide.

Fig. 2-15 shows a special stepped feeder in which an additional pendulumsegment pushes the workpieces into the vicinity of the lifting plates.

2 Workpiece hopper feeding devices 31

2.2.2 Typical conveyed material and systemperformance

2.3 Multi-stage conveyors

2.3.1 Design and mode ofoperation

Fig. 2-15:

Stepped feeders

a) Stepped feeders with

pendulum segment

(Köberlein)

b) Lifting-plate mechanism

1 Lifting step

2 Outlet or orientation zone

3 Hopper chute

4 Pendulum segment

5 Fixed step

6 Lifting drive

2

5

1

6

b)

2

1

3

4

a)

Page 33: Pneumatic Feeding

Stepped feeders have a noise level below 78 dB(A). Another advantage is thelow top-up height of the hopper. Additional lifting devices for filling the hopperwith workpieces will generally not be required.

The hopper volume will often be 40 to 80 litres. Systems of this kind with inte-grated top-up belt conveyors can offer a total of over 400 litres of storage space.This allows long periods of operation without human intervention. The averagethroughput is up to 200 workpieces/min. Higher performance is possible butdepends on the workpiece shape. The workpieces to be conveyed may be madeof metal, glass, ceramics, wood or non-ferrous metal. Electronics componentsare also possible. Typically, workpieces will be of low weight, such as bolts andscrews, washers, nuts, sleeves, pins, plastic mouldings and sheet-metal stam-pings. Slightly oily or dirty workpieces will not cause malfunctions.

From as early as the 1920s, scoop segment hoppers have been used to feedsmall workpieces, such as glass rods or tubes in electric lamp manufacture.These hoppers operate quietly and without damaging workpieces and are wellable to feed machines with workpieces in a 2-second cycle. The principle ofthese devices is shown in Fig. 2-16; there are numerous design variants.

2 Workpiece hopper feeding devices32

1

2

3

4

6

5

2.3.2 Range of applications

2.4 Segment feeders

2.4.1 Design and mode of operation

Fig. 2-16:

Some design variants of

scoop segment hoppers

1 Arc-shaped slide

2 Hopper

3 Workpiece

4 Scoop segment

5 Outlet

6 Examples of

scoop-segment design

Page 34: Pneumatic Feeding

The scoop segment dips into the heap of workpieces and generally picks upseveral workpieces at the same time, which then align themselves against theedges of the segment. Twin-rail segments are used for workpieces that arecapable of being suspended. The segment is able to move in an arc or a straightline. In the case of some solutions, the segment remains stationary and thehopper rises and falls. Since the filling level of the hoppers has an influence onthe feed rate and, moreover, the orientation operation has a random quality, anintermediate magazine is always installed between the scoop segment hopperand the machine tool being fed. Segment feeders cannot tolerate chips or work-piece fragments mixed in with the workpieces, since this debris becomesjammed between the scoop segment and the segment guide [23].

Segment feeders are used for small and not excessively complicated workpieces.In the case of cylindrical workpieces, the ratio of workpiece length to workpiecediameter should be 2:1 to 5:1 or greater. The workpieces should be unaffectedby jolts, although glass workpieces can be conveyed at a rate of approximately25 double strokes/min., with a probable upper limit of 40 double strokes/min.One design-related limiting factor is the time which the workpieces require toslide or roll from the topmost point of the scoop segment into the magazine. The scoop-segment length should be chosen as 5 to 8 x the workpiece length.Typical conveyed material includes bolts and screws, washers, rollers, pins,nails, hardware fittings, small tubes, welding studs, U-pieces and rivets.Segment feeders will generally not be suitable for sensitive plastic workpieces orworkpieces with high-quality finishes. Feed rates are 80 to 300 workpieces/min.

Steep conveyors are of a very simple and robust design. As can be seen in Fig. 2-17, a conveyor belt inclined at about 10° from the vertical is fitted withcarrier vanes. These pick up workpieces which are by chance correctly orientatedand lift them out of the workpiece hopper. Shortly before they reach the topguide roller, the workpieces slide or roll into the outlet channel at the side. Thelateral inclination of the carrier vanes must be matched to the rolling or frictioncharacteristics (coefficient of friction) of the workpieces. An additional com-pressed air nozzle can be used to assist output. Instead of carrier vanes, slotswith a lateral inclination can also be used as active components. This designprinciple facilitates quiet operation with a high level of reliability. The hopper isclose to the floor and can be filled easily. The output level is approximately 1.5mhigher. The hopper must be designed to ensure that there is always enoughworking material in the scoop zone, since otherwise an unnecessary number ofworkpiece carrier positions will remain empty. This is achieved by providing thehopper floor with a suitable inclination (sometime adjustable). It can also beadvantageous for the hopper floor to take the form of a conveyor belt with anintermittent action. The speed of the steep conveyor belt should also beadjustable, since this allows it to be matched to the behaviour of the work-pieces. For the conveyance of hollow workpieces, the carrier vanes can be re-placed by hooks that engage in the openings in the workpieces. In this case, a side outlet will no longer be possible. Instead, the workpiece must tip into achannel or chute when they reach the uppermost point of the conveyor.

2 Workpiece hopper feeding devices 33

2.4.2 Typical conveyed material and systemperformance

2.5 Inclined and steep conveyors

2.5.1 Design and mode of operation

Page 35: Pneumatic Feeding

Steep conveyors can be used for medium-sized and also relatively heavy work-pieces, and have a hopper capacity of 10 to 1000 litres, and a feed throughputof 10 to 1500 workpieces/min. These workpieces will be capable of being slid,rolled, suspended or poured and may be made of metal, plastic, rubber, wood,etc., provided that they are not susceptible to jolts and do not have sensitivesurfaces. With certain workpieces, however, only partial orientation is possible.In these cases, further orientation stages must follow.

2 Workpiece hopper feeding devices34

1

2 3 21

6

5

4

Fig. 2-17:

Steep conveyor as hopper

feed device

1 Workpiece

2 Hopper

3 Filling level

4 Output chute

5 Conveyor belt

6 Side wall

2.5.2 Typical conveyed material and systemperformance

Page 36: Pneumatic Feeding

The term “orientation technology” covers all the technical equipment andmethods used to bring workpieces into a desired state.

Orientation means bringing a workpiece into a desired state in terms of positi-

on and attitude relative to a defined coordinate system (see also Fig. 1-4).

In the case of hopper feed devices, the task is reduced to the achievement of adesired workpiece attitude. This involves turning workpieces about one or moreaxes.

Orientation is a dynamic process. It involves the generation or application ofmotion. During this process, the working material in a heap or group must neverbe so constricted that it is totally unable to move. It is immaterial what forces(gravitation, vibration, air nozzles, positive actuation, magnetic fields) are usedto initiate the motion [13, 24 to 26].

The orientation process can be illustrated well by the example of a gaming dice(Fig. 3-1). This is able to assume 24 different attitudes (orientations). In connec-tion with workpieces, however, only one of these attitudes is useful.

3 Orientation technology 35

3

Orientation technology

3.1 Basic principles of orientation

Fig. 3-1:

Possible orientations illus-

trated by the example of a

cube with numerous features

(gaming dice)

a) Possible attitudes at 90°

intervals

b) Assignment of possible

attitudes to a 90°

rotational angle network

a) b)

Page 37: Pneumatic Feeding

If, for example, the initial orientation is 1 and the desired orientation is 13, thereare various ways of achieving this through rotation:

1 - 24 -13 = –180° about y axis,1 - 2 - 3 - 8 - 13 = +180° z, + 180° x or1 - 6 - 23 - 20 - 13 = –90° x, -180° y, -90° x etc.

The objective is now to achieve the desired orientation in as few steps as possible and the shortest possible time.

If we take the opposite approach and separate out the incorrectly orientatedworkpieces, we may have a problem dealing with the volumes concerned, sinceof 24 orientations, it will always be necessary to separate out 23 orientations.This brings us to the question of methods.

There are 3 methods that can be used to bring workpieces into a uniform ori-entation (Fig. 3-2). These are as follows:

• Orientation by selection (selection principle), also described as passive ori-entation. Incorrectly orientated workpieces are fed back to the hopper andthen pass through the orientation zone again.

• Orientation by correction (positive-actuation principle), also described asactive orientation. Each incorrectly orientated workpiece is acted on in such away that it assumes correct orientation.

• Orientation by division, also described as passive/active orientation.Incorrectly orientated workpieces are collected separately and are also ori-entated during this process. They are then fed to the processing station alongwith the others.

3 Orientation technology36

Page 38: Pneumatic Feeding

3 Orientation technology 37

a)1 2 3

b)

c)

Fig. 3-2:

Orientation methods (symbols

in accordance with VDI 2860)

a) Orientation by selection

b) Orientation by correction,

c) Orientation by division,

1 Spiral, linear feeder

2 Workpiece

3 Chicane

Page 39: Pneumatic Feeding

The use of auxiliary energy is not a criterion for classifying a method as “activeorientation”. Fig. 3-3 shows a number of typical workpieces and how these canbe orientated by “selection”. Chicanes (another word for “orientating devices”)are relatively easy to produce.

The behaviour of workpieces as these move against alignment edges (spiraledges, chicanes, tipping edges, baffle plates) will vary from one type of work-piece to another. It is, however, possible to identify the probability with which adefined orientation will be achieved, for example if a workpiece free-falls onto atable surface. This is known as the orientation probability factor [33 to 35].

The orientation probability factor is the ratio of the number of favourable ori-

entations for a given purpose to the overall number of possible orientations

(attitudes) of a workpiece.

This factor will vary in accordance with dimensional conditions. As an exampleand demonstration, Fig. 3-4 shows the conditions and effects relating to a drum-shaped workpiece. This graph is based on experiments in which the workpiecewas repeatedly allowed to fall onto a flat surface.

3 Orientation technology38

a)

1

2

3

b)

4

1

3

·

c) d )

3

5

1

36

1

Fig. 3-3:

Examples of orientation by

selection

a) Orientation of U-pieces

b) Orientation of conical

control knobs

c) Orientation of round

workpieces with a spigot

d) Orientation of sealing caps

1 Vibratory bowl feeder

2 Milled spiral zone

3 Workpiece

4 Inclined chute

5 Curved guide slot to

eliminate incorrectly-ori-

entated workpieces

6 Drop opening

Page 40: Pneumatic Feeding

The curves within the graph will of course shift if, for example, the workpiecebase is thicker than its walls, since this will result in a shift of the centre of gravi-ty. In designing feed devices, we will attempt to take as a desired orientation the workpiece orientation that has the highest orientation probability. If neces-sary, we will accept that it will be necessary to re-orientate each workpiece as itpasses from the hopper to the point of processing on a machine. This can oftenbe achieved by simple means. A critical factor is, of course, the level of perform-ance that the feed device in question is required to provide.

Orientating devices arranged along a conveyor zone, such as spiral vibrators, arealso referred to as chicanes. These operate in contact with the workpieces. Theirtask is to orientate workpieces by rotating or straightening these or turningthem over, making skilful use of geometrical details on the workpiece and alsocentre-of-gravity distances. Incorrectly orientated workpieces are either broughtinto the correct orientation or separated out. This is always achieved through theuse of several chicanes that create a kind of handling-technology sequence.

As a general principle, workpieces are always slowed down by orientating de-vices, which reduces throughput. For example, the conveyance efficiency in thefeeding of cylindrical pins is approximately 0.5. The conveyance efficiency is cal-culated as follows:

ËF = VP/Vth

whereVP Conveyance speed achieved in practiceVth Conveyance speed theoretically possible.

The sequence shown in Fig. 3-5 gives a throughput of 32 workpieces/min. This isa good guide value for many small workpieces when these are orientated in avibrator.

3 Orientation technology 39

00.1

0.2

0.4

0.6

0.8

1.0

Ori

enta

tion

pro

babi

lity

0.2 0.3 0.5 0.8 1.0 1.5 2.0 3.0

L/D ratio

B

A

CL

D

S

y

Fig. 3-4:

Graph for determination of

orientation probability for

centre-of-gravity distance S

and y = 0.282 L

A Open end downwards

B Closed end downwards

C Lying on side

S Centre of gravity

3.2 Orientation usingmechanical devices

Page 41: Pneumatic Feeding

The most importance types of chicanes will be described in brief below. Now justas in the past, much depends on experience. Making chicanes work properlydemands the attention of mechanical-engineering specialists and also costs agreat deal of time. In recent times, simulation programs have been developedwhich allow orientating chicanes to be tested out on the computer screen. Theanimated 3D displays provided by these programs reflect the relevant physicaleffects such as gravity forces, impact forces resulting from collision with otherobjects, and frictional forces [27 to 30]. As we shall see, there are other ways of achieving correct orientation. These involve the replacement of mechanicalcomponents by software-supported device (imaging systems). We shall studythis in Chapter 3.5.

Let us briefly consider each of the most important types of chicanes. These are:

Top deflectors

This type of deflector (wiper) is installed at a defined height (Fig. 3-6). It is usedto separate out and push away workpieces which are lying on top of others(“piggyback” position) or which are standing on end. The working height “h” isthe relevant workpiece height plus an allowance for the micro-projection effect(“jump” height).

3 Orientation technology40

100 Stück

30%

10%

1

70 Stück

32 Stück

63 Stück50%

2

10

Fig. 3-5:

Typical sequence for

orientation in a vibrator

(according to Lotter)

1 Break-up of accumulation

2 Workpiece

32 units

100 units

70 units

63 units

Page 42: Pneumatic Feeding

Top deflectors are, however, not suitable for use with flat workpieces, sincethese workpieces are often not perfectly level and can then easily jam (Fig. 3-7).It is better to allow “piggyback” workpieces to tip away to one side, either to theinside or the outside. These workpieces will not be supported by the wiper edgeand will follow another path. If the workpieces are led away to the outside, theycan be guided to the spiral below (Fig. 3-8).

3 Orientation technology 41

h h

Spie

l

1D

4

5

2

3

Fig. 3-6:

Top deflectors are simple

metal wipers

Fig. 3-7:

Flat workpieces jamming

against a deflector due

to a wedge effect

Fig. 3-8:

Workpiece feedback

1 Spiral drum

2 Workpiece

3 Feedback

4 Inclined spiral

5 Spiral

“h” Height of wiper edge

D Drum diameter

Clea

ranc

e

h

Page 43: Pneumatic Feeding

Shaped deflectors

Incorrectly orientated workpieces can be separated out by appropriate mirror-image components. Only correctly orientated workpieces are able to passthrough the shaped deflector (Fig. 3-9), while incorrectly orientated workpiecesare pushed further to the outside and tip back into the hopper. Shaped deflec-tors can also be made adjustable.

Notches

Notches are local constrictions (narrowings) of the conveyor spiral. They havethe task of separating out workpieces that are lying on top of each other or areincorrectly orientated. This produces a uniform single row of workpieces. Fig. 3-10 shows some typical forms of notch devices. A multiple notch (4) can,for example, be used to separate out caps which arrive with their open sidefacing downwards. They become unstable at this point and fall back into thehopper.

Notches can also be combined with local guide rails. Only correctly orientatedworkpieces can pass through this chicane. Fig. 3-11 shows 2 examples of this. In the case of the configuration shown in Fig. 3-11b, workpieces are able to passif they lie on the upper rails. The condition is a > b. Incorrectly orientated work-pieces fall through.

3 Orientation technology42

4

1

2 3

Fig. 3-9:

Shaped deflectors have

a profile that is a mirror

image of the workpiece

contour

Fig. 3-10:

Orientation based on tipping

at a notch

1 Spiral

2 Correctly orientated

workpiece

3 Incorrectly orientated

workpiece

4 Multiple notch

Page 44: Pneumatic Feeding

Drop opening

Drop or profile openings can in principle provide very simple chicanes. They may,however, also be an unwelcome source of trouble. Workpieces can pass over thedrop opening only if they are by chance orientated in a certain way, which maybe correct or incorrect. The openings always provide one orientating operation.Fig. 3-12 shows a number of typical configurations. The best configurationshould be determined by practical tests to decide, for example, whether theedges of the opening should be sharp or, as shown in Fig. 3-13, rounded-off.

3 Orientation technology 43

1

2

3

·

a) b)

3

4

ab

3

m · g

a)

b) c)

Fig. 3-11:

Combination of notch and

upper rails

a) Orientation of a bracket

b) Orientation of a shoul-

dered cylindrical

component

1 Retaining rail

2 Inclined spiral track

with notch

3 Workpiece

4 Support rail, upper rail

Fig. 3-12:

Design examples of drop

openings

a) Openings for vee-shaped

or triangular workpieces

b) Opening linked to

magazine for round

workpieces with internal

contour feature

c) Drop opening for round

workpieces with external

feature

Page 45: Pneumatic Feeding

It can also be advantageous to provide a cover over the drop opening with asmall clearance relative to the workpiece as shown in Fig. 3-14. This prevents the workpieces from tipping prematurely and becoming jammed in an inclinedposition.

Profile openings can also be covered by a spring flap, as shown Fig. 3-15. Theflap opens only in the case of incorrectly orientated workpieces, due to the factthat their centre of gravity is offset. Workpieces that are separated out in thisway pass to the next-lowest spiral and begin to circulate again. Chicanes of this type with moving parts considerably reduce workpiece throughput speedand are also susceptible to malfunctions. Today, better devices are used whichoperate with optical detection, as we shall see.

3 Orientation technology44

42

1

3

1

1

2

3 4 5

Fig. 3-13:

Drop opening

with chamfered inlet

1 Workpiece

2 Spiral drum

3 Magazine

4 Drop opening

Fig. 3-14:

Profile opening with cover

1 Cover

2 Workpiece

3 Tube magazine

4 Inclined chute

5 Spiral

Page 46: Pneumatic Feeding

Profile openings can also be placed at the side, in the drum wall. The workpiecesmust, however, be upright for this purpose, as demonstrated by the example inFig. 3-16. In this case, the incorrectly orientated workpieces are separated outand pass via a friction chute into the hopper or onto a downstream spiral zone.The angle a of the wall inclination is approximately 70°. Multiple “drop aper-tures” are arranged in series, each with contours matched to a certain workpieceorientation.

3 Orientation technology 45

1 2

3 4

1

2 3

4

4

·

A B1

56

7

A B

8

Schnitt A-A Schnitt B-B

Fig. 3-15:

Orientation using

a spring flap

1 Workpiece

2 Vibrator spiral

3 Flap

4 Torsion spring

Fig. 3-16:

Orientation with side profile

apertures

1 Top deflector

2 Ejected workpiece

3 Profile opening

4 Catch chute

5 Workpiece

6 Oscillatory motion

7 Correctly orientated

workpiece

8 Return track Section B-BSection A-A

Page 47: Pneumatic Feeding

Profile rail

Rails profiled in accordance with the outer contours of workpieces are highly suitable for separation functions. Devices of this kind frequently exploit theeffect of the centre of gravity of the workpieces, as shown Fig. 3-17.

As the examples show, only workpieces with simple geometry can be orientatedin this way. On the other hand, these types of chicanes are relatively easy to pro-duce and are also reliable. A completely different method is used to orientatethe workpiece shown in Fig. 3-18, which has a trapezoidal cross-section. Theworkpieces are orientated gradually by the effect of gravity, and the profile spiralthen terminates in a rectangular channel. It is, however, costly to produce rails ofthis kind.

By the way, it is also possible to use twisted profile rails or spirals to re-orien-tate workpieces. The spiral zone in this case produces a “spin”, as shown in Fig. 3-19. The workpieces in this case are turned through 90°. The actual orien-tating operation is carried out before this.

3 Orientation technology46

I IIS

a) b)

I II

c)

I II

IVIIIIII 1 2

3

Fig. 3-17:

Separating-out of incorrectly

orientated workpieces using

rails with various profiles

a) Round workpiece

with spigot

b) A sleeve is brought into

a longitudinal orientation

c) Rectangular-shaped work-

piece with longitudinal rib

I Correct orientatio

II Incorrect orientation

S Centre of gravity

Fig. 3-18:

Orientating via a shaped

channel

1 Vibrator spiral

2 Workpiece

3 Alignment channel

Fig. 3-19:

Re-orientating using a spiral

twist groove

Page 48: Pneumatic Feeding

Profiled rails can also provide a useful way of orientating workpieces in linearvibratory chutes. The device shown in Fig. 3-20 is used to orientate wire springs.The springs are first allowed to fall onto a rail, from which they hang. They arethen transferred to the magazine rail during linear conveyance. This, however,occurs only in the case of workpieces whose longer shank is on the right (as seen in the illustration). Workpieces that do not succeed in transferring tothe magazine rail fall back into the hopper.

Fig. 3-21 shows the orientating of shaped dynamo plates. Once again, thismethod exploits the difference in the length of the two shanks. Workpieces withright and left-handed orientation are separated by purely mechanical means andmagazined separately. There is no return of workpieces to the hopper.

3 Orientation technology 47

1

2

B A

B A

2

1

I II

I II3

Schnitt A-A

Schnitt B-B

1

2

3 4

S

Fig. 3-20:

Orientating wire springs on

the basis of shank length

1 Magazine rai

2 Rail for separating-out

of incorrectly orientated

workpieces

3 Workpiece

I Correctly orientated

workpiece

II Workpiece is separated

out

Fig. 3-21:

Orientation of dynamo plates

of non-symmetrical U-shape

using linear vibrator

1 Workpiece

2 Linear vibrator system

3 Magazine rail

4 Feed rail

S Vibration

Section A-A

Section B-B

Page 49: Pneumatic Feeding

Inclined spiral with raised edge

Inclined spiral zones can be used to cause workpieces to fall back into a hopperif their centre of gravity is located beyond the tipping edge. The shape and inclination of the spiral must be matched to the position of the centre of gravityof the workpieces concerned, just as in the case of the solutions using profilerails. Fig. 3-22 shows some typical configurations. Orientation on the basis oflateral position is made much easier if the workpiece has a chamfer. This is amajor factor in the design of workpieces that are compatible with automationand handling-friendly design is one part of this [5].

Although many details of these chicanes are worked out empirically by testing, itis also possible to work with calculations. It is, for example, possible to calculatethe required angle of inclination a of the spiral. We can demonstrate this with anexample.

Example: We wish to determine the maximum angle of inclination a for the workpiece shown in Fig. 3-23 in order to ensure that workpieces with their centre of gravity uppermost tip of their own accord.

arc tan (20/(2(21 – 5 – 0.3))) = arc tan (20/31.4) = 32.5°arc tan (20/(2(35 – 21 – 5 – 0.3))) = arc tan (20/17.4) = 49°

The length of the spiral zone with a raised edge is selected as approximately 100 mm, while the track width is selected as 22 mm.

3 Orientation technology48

S

S

m · g

Fig. 3-22:

Examples of applications

of chicanes of the “inclined

spiral with raised edge” type

m Mass

g Gravitational acceleration

S Centre of gravity

Page 50: Pneumatic Feeding

Inclined spirals can also be combined with upper rails to create either a work-piece guide or an ejector, as shown in Fig. 3-24. Workpieces that will not run inthe spiral slot fall away. The inclined discharge plane in the spiral is present onlyin the vicinity of the chicane over a length of some 100 to 200 mm.

3 Orientation technology 49

20

S

b

·

21

35

C

C

B

B

A

A

Schnitt A-A Schnitt B-B Schnitt C-C

·

Fig. 3-23:

Sample workpiece

b Track width

S Centre of gravity

· Angle of inclination

Fig. 3-24:

Inclined spiral combined

with an upper rail

Section B-BSection A-A Section C-C

Page 51: Pneumatic Feeding

Spiral with longitudinal slot

This chicane is used to suspend workpieces with heads, such as bolts. If theseare required with a head-first orientation, this can be achieved by using a ramprail which inclines the workpiece shank as the workpieces pass through. This isshown in Fig. 3-25a. There must of course be enough room below the spiral forthe workpieces to hang. Otherwise, the suspended workpieces are forwarded insuspension, for example to a feed unit for a power wrench.

The following guide values can be used for sizing:b1 = 1.1 · Db2 = 1.2 · D b3 = 0.6 (D – d)h = (l – s) 1.1m1 = 1.5 · lm2 = 2.5 · l

3 Orientation technology50

D

d

h

s

m1

·

b 2

a)

b 1

b3

b)

b 2 b 3

m2

Fig. 3-25:

Design of longitudinal slot for

suspendable workpieces with

heads

a) Re-orientating into

head-first attitude

b) Suspension of workpieces

for axis-parallel

magazining

Page 52: Pneumatic Feeding

Overflow

For most orientation operations, workpieces are required to flow as a single-rowchain. This can be achieved by using an overflow device. Excess workpieces lyingadjacent to others are pushed off and fall back into the feeder drum. The over-flow device (Fig. 3-26) is also able to clear workpiece jams to a certain extent byensuring that any excess conveyed workpieces are removed from the spiral. Atypical combination of several chicanes is shown in Fig. 3-27. First, upright work-pieces are ejected. The overflow device then forces the workpieces into a singlerow. Finally, to conclude the orientating operation, the screws are suspended tocreate an axis-parallel order.

3 Orientation technology 51

Fig. 3-26:

Example of design

of overflow device

Fig. 3-27:

Handling technology for

orientation of cheese-head

screws

1 Vibrator spiral

2 Overflow chicane

3 Top deflector

4 Spiral section with

longitudinal slot

5 Separating-out of work-

pieces moving in parallel

6 Separating-out of screws

standing on their heads

3

54

6

21

Page 53: Pneumatic Feeding

Tipping stage

Tipping stages are use to orientate or re-orientate workpieces. This allows, forexample, rotationally-symmetrical workpieces to be re-orientated from lying ontheir sides to standing on end. One design of tipping stage is shown in Fig. 3-28.An advantage of this design is that the workpiece is still guided at the sideduring the tipping operation. Vee-shaped workpieces, too, can be stood on endby using tipping stages. Tipping can also be carried out against support sur-faces, thus creating a true orientation operation. The asymmetrical position ofthe centre of gravity and the workpiece shape are used to achieve a certain orientation.

In the solution shown in Fig. 3-29, the only workpieces that come into contactwith the support surface are those travelling with their smaller diameter leading.These catch against the support and are turned as they fall. Correctly orientatedworkpieces tip away immediately, as soon as their smaller trailing diameter canno longer be supported by the tube. A similar principle is used in the solutionshown in Fig. 3-30 to orientate L-shaped workpieces.

3 Orientation technology52

1

2

3

Fig. 3-28:

Tipping stage for cylindrical

workpieces

1 Workpiece

2 Tipping edge for tipping

against external wall

3 Vibrator spiral

Fig. 3-29:

Tipping stage

with support surface

1 Tube with profile opening

in outlet

2 Support edge

3 Correctly orientated

workpiece

3

2

1

Page 54: Pneumatic Feeding

A somewhat difficult tipping operation is shown in Fig. 3-31. Workpieces arrivepre-sorted into 4 different orientations. Only workpieces in orientation I canengage with the tipping edge. Workpieces with orientations II to IV fall back intothe drum hopper. It undoubtedly requires some skill to make a chicane solutionof this kind operate reliably. Modern imaging systems offer a faster answer. Weshall discuss systems of this kind later.

A fine air jet can provide a useful separation function during the orientation ofworkpieces. Hollow workpieces such as light-bulb sockets for example, that arelying with their open ends downwards of a spiral or a linear zone, can be ejectedhighly effectively by means of an air jet (Fig. 3-32).

3 Orientation technology 53

I II

III IV

II III IV

1

2

3

4

pp 3

2

1

Fig. 3-30:

Orientation using a tipping

stage

1 Workpiece shapes

2 Tipping zone in vibrator

spiral

3 Support edge

4 Correctly orientated

workpiece

Fig. 3-31:

Orientation of small levers

by tipping

1 Workpiece

2 Tipping edge

3 Friction surface

4 Magazine

I to IV

Possible workpiece

orientations

3.3 Orientation using pneumatic components

Fig. 3-32:

Orientation of a light bulb

socket

1 Workpiece

2 Vibrator spiral

3 Compressed-air nozzle

p Compressed-air jet

4321

Page 55: Pneumatic Feeding

Air jets also provide a simple means of orientating the discs shown in Fig. 3-33by their chamfered side.

Another method is to use an air jet to eject profiled workpieces via a profile opening through which only incorrectly orientated workpieces can pass. This isillustrated in Fig. 3-34a. In order to be on the safe side, 2 profile openings andair jets are provided in series. Workpieces lying with their slot uppermost areejected. Other incorrectly orientated workpieces are separated out before thisoperation.

Fig. 3-34b shows a workpiece ejector consisting of a circular panel with threeriveted legs. Correctly orientated workpieces present too small an area to the airjet to be ejected. This solution can be implemented very easily.

A combination of a sensor and air jet nozzle can be seen in Fig. 3-35. It is, howe-ver, necessary to have gaps between the workpieces. The air jet is activated onlywhen an optical or inductive sensor below the spiral detects the leading edge ofa workpiece. Workpieces that arrive slot first can continue on their way, since the brief air jet is not able to generate any ejector force in this case. A system

3 Orientation technology54

1

2

3

2

1

p

p

p

3 4

5

a) b)

2

1

4

5

Fig. 3-33:

Orientation in accordance

with an edge feature

1 Air jet

2 Workpiece (e.g. disc)

3 Vibrator spiral or channel

Fig. 3-34:

Orientation using com-

pressed-air nozzles

a) Orientation of U-shaped

workpieces

b) Orientation of circuit

boards

1 Spiral

2 Air nozzle

3 Profile opening

4 Incorrectly orientated

workpiece

5 Correctly orientated

workpiece

p Compressed air

Page 56: Pneumatic Feeding

of this kind is costly, and a optical detection system would therefore probably bea better choice.

Compressed-air jets can, by the way, also be used to good effect to accelerateworkpieces in feed channels (Fig. 3-36). If the workpieces in question are lyingon a linear vibrator, the speeds of the vibrator and air jet are combined and it isnot necessary to incline the vibrator. With an appropriate arrangement of the airjet it is also possible to eject excess workpieces from accumulation zones.

3 Orientation technology 55

1 2

3

4

a)

2 3

1

14 3 2

b)

c)

5

4

Fig. 3-35:

Separating out incorrectly

orientated workpieces using

an air jet and presence

sensor

1 Air nozzle

2 Correctly orientated

workpiece

3 Incorrectly orientated

workpiece

4 Sensor (e.g. inductive

proximity sensor)

Fig. 3-36:

Accelerating workpieces

with an auxiliary air jet

a) Normal operation

b) Behaviour in accumulation

operation

c) Combination with vibration

conveyor

1 Compressed air

2 Workpiece

3 Guide channel

4 Acceleration nozzle

5 Vibrator drive

Page 57: Pneumatic Feeding

A sophisticated form of fluidic orientation is hydrodynamic or aerodynamic feed [36]. Fig. 3-37, for example, shows an oil-jet hopper in which pressurised oil is used to force workpieces upwards in an eddy pattern. During this process,the workpieces orient themselves according to the laws of fluid mechanics andland in an orientated form in an output magazine. With an oil pressure of 69 x 103 N/m2, the achievable orientation throughput is less than 60 workpiecesper minute.

This orientating operation becomes neater from the technical point of view if airjets are used. The workpieces remain dry and do not need after-treatment.Orientation based on fluid mechanics exploits the following physical effects:• Boundary-layer flows along the surfaces of bodies,• The aerodynamic flow paradox (flow at a gap)• The Coanda effect (lateral flow onto bodies)• Separation of flow• Turbulent free jets.

If these effects are exploited in the right way, they can produce jet impact forcesand force effects which are related to the drag form of the body in the air flow inquestion. Drag form is expressed by the familiar coefficient of drag cw, which isparticularly important in the design of vehicles. This drag coefficient cw is pro-portional to the turbulence behind the flow body. In view of the fact that bodieswhich are to be orientated as part of a feed process also need to be guidedmechanically, there are a large number of reciprocal effects between the guidegeometry, the workpiece and the air flow. These effects can be controlled by thechosen nozzle type and flow generation method and any air film gliding surfacesdeployed. Fig. 3-38 shows typical orientation effects in schematic form.

1

2

3

8

5

9

7

6

4

10

3 Orientation technology56

Fig. 3-37:

Oil-jet hopper [37]

1 Cover

2 Oil jet

3 Hopper

4 Workpiece filling level

5 Workpieces (e.g. made of

metal, glass, ceramics

6 Magazine tube

7 Pressurised-oil line

with nozzle

8 Oil overflow

9 Pump

10 Oil level

Page 58: Pneumatic Feeding

The requirements for the design of aerodynamic feeding systems are listed in[36] as follows:• Separation of transport (conveyance) and orientation functions• Transport preferably by means of mechanical processes• Orientation preferably by means of aerodynamic effects• Exploitation of friction for stabilisation and damping• Ensurance of “open” feeding devices.

“Open” here relates to the operating area for an orientation process withinwhich there is no possibility of workpieces jamming against any component ofthe feeding device in question.

Workpieces can be detected via electronic means by measurements using a high-frequency magnetic field. Workpieces are passed through this field (Fig. 3-39) and continuous measurements are taken. The workpieces must be fed singly. The guides used can take the form of tubes, channels, gravity chutesand also conveyor belts. There are, however, limits to the precision of detectionthat can be achieved.

This is how it works: The workpiece to be detected can, for example, be dividedinto 4 measurement zones. The system is pre-programmed as to which zone is to be checked for asymmetry against which other zone. The detection operationgenerates switching signals that can be used, for example, to control down-stream sorting channels. In the case of the example below, the values for thezones b and c are checked against each other for asymmetry.

3 Orientation technology 57

t t t t

54

dcba

1S S

3 5

2

Fig. 3-38:

Orientation effects in a flow

field (according to Lorenz)

a) Exploitation of global

cw factor

b) Exploitation of an

asymmetrical centre

of gravity S

c) Tipping operation

d) Swivelling

1 Flow field

2 Double-inclination track

3 Gap nozzle

4 Point nozzle

5 Workpiece

t Time

3.4 Orientation using electromagnetic effects

Page 59: Pneumatic Feeding

The workpieces must all exhibit clear symmetrical differences. In the case ofcomposite workpieces, symmetry can also be the criterion for a complete assem-bly operation. To a certain degree, internal features can also be detected, forexample in the case of workpieces that are externally symmetrical with press-fitted components of a different material (Fig. 3-40). Other detection methodscannot do this. Preliminary testing should be carried out in all cases before adecision is taken in favour of one method or another.

3 Orientation technology58

1

2 3

4

a)

b)

a b c d

Fig. 3-39:

Orientation detection with

the aid of high-frequency

magnetic fields

a) Sensor configuration

b) Sample workpiece for

checking

1 Measurement zone

2 Feed tube

3 Workpiece

4 Electronics

Fig. 3-40:

Examples of workpieces

for which electromagnetic

orientation or detection can

be used

Page 60: Pneumatic Feeding

3 Orientation technology 59

3.5 Orientation using optical detection technology

3.5.1 Advantages andmethods

It is, by the way, also possible to identify workpieces by “enveloping” them withsound. This is a particularly interesting method for small workpieces and detectsworkpieces by measuring reflected ultrasound. In contrast to camera and lasersystems, which detect only the periphery or shadow of workpieces, ultrasoundmeasurements permit a three-dimensional checking operation. The sound wavessurround the entire workpiece and can even penetrate into internal contourssuch as drilled holes, internal hexagons, etc. This is what gives the process itscomprehensive detection capability. It can be used for all workpieces made ofsound-reflecting material, such as ferrous or non-ferrous metals, plastics, cera-mics or glass, and also for pre-assembled modules of virtually any configuration.As the workpieces travel through the system, they pass several sound meas-uring heads whose signals are used to create an acoustic “map”. The system“learns” from good workpieces and uses these to derive the desired soundreflection pattern with which every workpiece is compared.

The simplest method of visual contour detection is to compare a workpiece contour with a number of contour templates, each of which represents a partic-ular orientation or workpiece shape. If the contours coincide, this provides anindication of the identity of the contours or of the current orientation of theworkpiece in question. This was “Mark I” imaging, as actually practised 25 yearsago with rotating template discs. Today, workpieces maps are acquired and stored electronically and are also compared with reference patterns by electronicmeans.

Orientation by means of imaging systems has the following major advantages:• The only workpiece pre-orientation required is a few simple chicanes in a

hopper feed device. These chicanes can generally be set up very quickly.• Imaging systems can detect not only incorrectly orientated workpieces but

also defective workpieces which should not be in the system at all.• Imaging systems can generally be reset for a different workpiece without

any physical conversion work, particularly if the old and new workpieces aremembers of the same workpiece family.

• Different workpieces from a single hopper feed device can be detected simultaneously, divided into types and fed separately. This saves space in thevicinity of an assembly station.

• In addition to orientation, various software characteristics can also bechecked and documented via software.

• The data material which is generated can also be used for counter functions.These can count not only good and bad workpieces but also predeterminedquantities. The resulting data can be processed for statistical processes.

• Certain mechanical chicanes react acutely to small physical changes (voltage,mains frequency) in the drive system. Optical detection does not place stringent and expensive demands on feed technology.

• In view of the fact that workpiece features are stored as data, more sortingsteps can be utilised than in the case of mechanical selection devices.

Page 61: Pneumatic Feeding

3 Orientation technology60

• The latest imaging systems today (for example, Festo’s Checkbox) are designed to be set up using the teach-in method, which does not require anyspecial knowledge.

One approach that is being pursued with great success at the present time is to combine classic feeding systems with optoelectronic detection systems. Asystem of this kind could, for example, consist of a vibratory feeding system, a top-up hopper, a CCD camera with lighting, a controller, display devices andsoftware for programming (generally using the teach-in method) and for algo-rithms for orientation detection or quality-assurance and checking tasks. Testalgorithms can, for example, be developed for the following kinds of tasks:• Detection of workpiece features in order to derive an indication of workpiece

type and orientation. The software used must be able to compare workpiecemaps with reference data records.

• Measurement of workpieces or selected areas of these as part of the quality-assurance process. For this purpose, edges are located in the workpiece mapby software means and the distances between these are measured. In order toenhance accuracy, subpixeling methods are used in certain cases. These arean electronic means of increasing resolution.

The tasks described above are almost always carried out with workpieces whichare in motion on a non-stop continuous-throughput basis at remarkably highspeeds. It is possible with today’s line cameras to achieve resolutions rangingfrom 0.1 mm per pixel, down to 0.01 (0.001) mm at conveyance speeds of over 1 metre per second. Special cameras can achieve a multiple of this speed.

If mechanical orientating components are used, these will generally operatereliably if workpieces are fed singly. This also applies as a general principle tothe optical detection of workpieces. Workpieces in multiple rows must be se-parated out. This can be achieved in a vibrator by, for example, providing a kinkin the pitch of the spiral (Fig. 3-41a). This produces a change in the speed of theworkpieces from v1 to v2, where v2 > v1. A mechanical trick of this kind is notnecessary when working with a detection unit such as the Festo Checkbox,which has an integrated conveyor belt and whose speed can be adjusted easily.

Page 62: Pneumatic Feeding

How can we produce a map of our workpieces?

There are two ways of recording workpiece images as silhouettes:• A two-dimensional image can be recorded with a large-area CCD camera as a

kind of “snapshot”• An image can be recorded with a CCD line camera and continuously moving

workpieces on a “slice by slice” basis. An image is produced only when thereis relative motion between the line camera and the workpiece.

The latter variant is suitable for conveying operations and is also simpler in tech-nical terms. The principle of this method is shown in Fig. 3-42. A prerequisite isthat workpieces must not overlap or touch other workpieces, since this will leadto misinterpretation of the image data.

3 Orientation technology 61

V2 V1

a)

b)1 2

V2

V2V2 > V1

Werkstück 1 2 3

v,t

Fig. 3-41:

Differential separation

of working material

a) With a kink in the pitch

of the conveyor spiral

b) With an external

variable-speed conveyor

belt

1 Detection device

2 Vibratory bowl feeder

Fig. 3-42:

Generation of a mono-

chrome contour image on a

continuous-throughput basis

using a line camera

1 Recording of a greyscale

image in slices

2 Conversion of strip images

into monochrome contours

3 Generation of a complete

digital image and checking

of this for features

t Time

v Conveyance speed

Workpiece

Page 63: Pneumatic Feeding

The workpiece is fed past the line camera and scanned step by step. The imagedata is then digitised into a binary contour image, which is then used as thebasis for all feature-analysis operations. The resolution in the direction of conveyance is equal to the “slice” width as follows:

v · tc = b 1 BE

v Speed of conveyancetc Camera exposure timeb “Slice” widthBE Pixel.

Example: Let us assume a speed of conveyance of v = 300 mm/s and an expo-sure time tc = 256 microseconds. 1 pixel thus represents 300 x 256 x 10–6

0.0768 millimetres on the workpiece in the horizontal direction. The verticalresolution of the selected line camera is fixed at, for example, 512 pixels.

The principle of a workpiece detection system is shown in Fig. 3-43 by the ex-ample of a Festo Checkbox. This is available in several sizes for different classesof workpiece size and has a maximum throughput window size of 80 x 80 milli-metres. Scanning is by transmitted light, which has the following advantages:• The system is robust and unaffected by external light and variations in light

levels• There is high contrast between the workpiece and the background• Colours and surface patterns are not recorded and do not affect the

evaluation.

In order to obtain high-precision workpiece maps, the camera is equipped withtelecentric lenses. These are lenses with which all light rays travel through thesubject field parallel to the optical axis. These are used in cases where thedistance between the test subject and the lens is not precisely defined or wherethe length of the optical path varies during the evaluation of different featuresand a precise mapping scale is required (Fig. 3-44). Normal lenses cannot achie-ve this. The choice of lenses is thus a question of the accuracy required.

3 Orientation technology62

1

2

a) b)

345

2

8

9

10

76

5

D

AB

C

3.5.2 Detection device

Fig. 3-43:

Principle of a workpiece

detection system

(Festo Checkbox family)

a) Scanning principle

b) Overall view of “Sortbox”

device

1 Viewing angles and

throughput windows

of the various sizes

2 Line camera

3 High-intensity

LED lighting

4 Workpiece

5 Conveyor belt

6 Lateral guide

7 Ejector nozzle

8 Input zone

9 Sorting channel

10 Control unit

A to D

Workpiece sorting channels

Page 64: Pneumatic Feeding

Once a workpiece or workpiece orientation has been detected, the actuator signal which is generated by this is fed down parallel to the direction of travel tothe appropriate ejection position for the scanned workpiece. An ejector nozzle isactivated at this point and the workpiece is propelled into the relevant sortingchannel. If the conveyance speed is changed, the signal transit times for theejection operation also change automatically without the need for interventionby the operator. The ejection of “normal” workpieces such as those shown in Fig. 3-45a presents no problems. Some workpieces, however, are very streamli-ned and also have very smooth surfaces. In these cases, the air ejector pulsemay not prove to be strong enough, and it will be necessary to change the nozz-le geometry and possibly also the timing of the ejector pulse. Tests are alsoadvisable with very light workpieces.

It is, however, possible with optical devices to detect the workpieces shown inFig. 3-45b, which frequently have only fine features of the order of magnitude oftenths of a millimetre. Generally speaking, mechanical orientation devices areunable to achieve this.

3 Orientation technology 63

1

2 3 4

a b

36

R 0,5

0,1 tief

Ø 1

0,8

Fig. 3-44:

Light beam path with

telecentric imaging

1 Subject

2 Lens or lens group

3 Aperture

4 CCD chip

Fig. 3-45:

Workpieces suitable

for optical detection

a) Typical very easily

recognisable turned

workpieces

b) More difficult workpieces

which have nonetheless

been detected success-

fully

0,1 deep

Page 65: Pneumatic Feeding

In comparison with mechanical orientation components, it is only necessary withimaging systems to press a button in order to change the system over to anotherworkpiece (for which data has been stored previously) or to another test algo-rithm. The replacement of workpiece-specific hardware components by softwareis the most important advance that has been made to date in the automatic fee-ding of workpieces for orientation.

In order to make it possible to analyse a digital image (and in principle othertypes of images as well) for various features even at high conveyance speeds,we need high-speed imaging computers, equipped for example with digital sig-nal processors. Typical features that are capable of analysis are illustrated in Fig. 3-46 by an imaginary workpiece. This shows how the height and length of an image can be measured. The line sensor measures a distance by counting the number of pixels. The values H and L can be used to determine the area andthe aspect ratio H/L. The precise contents of an area can be determined by simply counting the pixels. The contour image can be used to determine the cir-cumference, the surface centre of gravity and the contour centre of gravity. The distances S and K can be used for detection purposes, as can the polardistances that result if circles are plotted based on the centre of gravity and allowed to intersect with the contour line.

It is also possible to determine the moments of inertia of a surface about theaxes x-x and y-y and use these to determine the surface’s orientation. With certain workpieces, it is sufficient to analyse only a selected (programmable)window (a contour zone or digital image strip). This is of particular interest inconnection with quality assurance. The relevant window (region of interest orROI) may be a threaded part of the workpiece or a recess.

3 Orientation technology64

y y

a)L x

H

1

b)xx/2

y

c)x

y/2

y

d)

xe) f )

y

g) h)x

y

x

y 1

x1

S

2

34

y

x

R1R2

y

x

3.5.3 Analysis of features

Fig. 3-46:

Selected features for the

investigation of digital

contour images

a) Dimensions, counting

of area pixels

b) Area X/2

c) Area Y/2

d) Area centre of gravity S

e) Radius of inscribed

maximum circle (R2)

and minimum circle (R1)

f ) Window investigation

g) Investigation of vertical

strips

h) Investigation of selected

edge zone

1 Contour image

2 Window

3 Strip (vee strip)

4 Upper external contour

Page 66: Pneumatic Feeding

If we are concerned only with detecting the orientation of a workpiece, relativecomparisons are sufficient, which means that absolute measurements are notrequired. In quality assurance work, absolute measurements can be taken andcompared with absolute reference dimensions. It is often, however, enough inthese applications also to carry out relative comparisons with good workpieces.In most cases, the system will require only a correctly dimensioned workpiece inorder to “learn” data for comparative measurements.

With certain workpiece shapes or topologies, a particular method may fail,which will mean switching to other workpiece features or evaluation algorithms.

It is of course not possible to read an infinite amount of data from an opticalcontour image in the form of a silhouette. There are process-specific limitations.Features that are not optically visible are lost for detection purposes. These features fall into the following groups:• Workpieces with features which remain externally invisible in contour images,

such as:- Internal contours,- Symmetrical workpieces made of more than one material- Symmetrical workpieces with varying surfaces or colours.

• Workpieces which cannot be separated reliably, such as:- Sticky workpieces or those sticking together- Workpieces which tend to lock together

• Workpieces which are larger than the evaluatable image window and thosewhich do not assume a stable position on the conveyor belt and, for example,roll backwards and forwards during scanning.

• Workpieces which are very dirty, have burrs which do not show in the scan orremaining cutting residues will either be incorrectly rejected or passed asgood, despite the fact that rework is required. Highly reflective workpieces willalso often be rejected. Practical testing is vital.

• Very thin flat workpieces that offer hardly any cross-section. Workpieces ofthis kind can sometimes be scanned better at an oblique angle. Flat work-pieces can also be detected by using translucent conveyor belts. The principleof a detection device of this kind is shown in Fig. 3-47. It will also not be possible to detect features which are very fine (small) in relation to the overallworkpiece. In the case of dimensional checks, it will not be possible to detectfine details of the order of magnitude of the system resolution.

3 Orientation technology 65

7

1 Sichtfeld 5

6234

Fig. 3-47:

Silhouette detection with a

transmitted-light system

1 Feed hopper

2 Speed sensor

3 Translucent conveyor belt

4 CCD camera

5 Multiple gripper

6 Mirror

7 Lighting

Area of view

Page 67: Pneumatic Feeding

The Festo Checkbox is prepared for use by means of the teach-in method. Thisinvolves allowing a number of sample workpieces to pass through the devicecorrectly orientated. A contour map is recorded in each case. It is also necessaryto “teach” the system all the other incorrect orientations that may occur. Fig. 3-48 shows an example of this. All orientations other than those shown areeliminated beforehand in the hopper feeding device. The number of teach-inworkpieces required will vary from one workpiece to another. In the case, forexample, of semi-transparent workpieces, more will be required for statisticalreasons.

The sample teach-in workpieces must have all the features of good workpieces.The sample workpieces will, of course, also exhibit shape and dimensional var-iations. These variations will also be incorporated into the reference data list andrepresent a distribution. The following rule applies:

The greater the deviations between the sample workpieces, the greater the

permissible deviations among subsequent workpieces evaluated as “good”.

This is of course not a disadvantage. Even with manually inspected workpieces,items are accepted as “good” provided that they fall within defined tolerances.

As shown in Fig. 3-49, the teach-in mode stores the workpiece data that willlater be used in the automatic mode as reference data to correlate the workpie-ces to certain types or orientations.

3 Orientation technology66

1

2

3

S

F F

F

4

5

3.5.4 Programming of opticaldetection, orientationand sorting devices

Fig. 3-48:

One orientation must be

declared as the desired

orientation

1 Support surface

2 Conveyor belt

3 Direction of view

4 Workpiece

5 Direction of conveyance

F Incorrectly orientated

workpieces

S Desired orientation

Page 68: Pneumatic Feeding

Digital images form the basis for all necessary operations. For this purpose, theimage captured by the camera in 256 shades of grey is analysed into black-and-white values using a threshold value (binary level). The function of this thresholdvalue is shown in Fig. 3-50. A change results in a different relative ratio of pixelswith white and black declarations. If the binary level is raised in our example,the number of pixels detected as black will rise. The definition of the binary levelwill depend on the optical properties of the scanned material and the backgro-und and thus on the lighting. The advantage of digitisation are the high signalprocessing speed which this allows, due to the fact that the volume of data isconsiderably reduced in comparison with a greyscale image.

If the system is used with a workpiece mix, the complete teach-in process mustbe repeated several times. In the automatic mode, all contour images will thenbe compared with all correct and incorrect orientations of each workpiece type.

In rare cases, incorrect sorting may occur during air ejection due to projectingburr edges on workpieces and, for example, suction effects. At high throughputspeeds, these errors can be detected by monitoring with a video camera. Thisapplies to an even greater degree to orientation in a vibrator, where sorting and

3 Orientation technology 67

Work-piece

Threshold valuefor digitisation

Workpiece motionExposure timeAnalogue/digitalconverter

Algorithmsfor contourdetection

Digitalcontourimage

Digitalgreyscaleimage

Work-piecefeatu-res

Decision,update,counting,classifier

Teach-in data

Generationof teach-indata

Storageand loadingof teach-indata

Comparison withreference data

Automaticmode

Teach-inmode

Signals tocontrol work-piece flow

Deflector,ejectornozzle,otheractuators

a)

b)

w

s

1

2

w

s

Fig. 3-49:

Sequence diagram showing

the generation of switching

signals for actuators

Fig. 3-50:

Digitisation of analogue

signals

a) Binary level

b) Number of pixels

1 Analogue signal

2 Binary level

s Black,

w White

Page 69: Pneumatic Feeding

orientation errors of this kind occur far more frequently. We must always bearthe consequences in mind - any incorrectly sorted workpiece or overlookedreject may bring the operation of a downstream assembly station to a halt.

Every assembly operation involves the feeding of several workpieces. This re-quires an appropriate number of feeding devices. In order to save space in thevicinity of assembly stations, occasional use has been made of tower vibrators.These are a series of vibrators, each matched to a particular workpiece andinstalled in tiers on a single vibratory system. A tower vibrator is thus a dedi-cated solution that cannot be used for other workpieces (Fig. 3-51a).

Modern checking and sorting devices allows workpiece mixes to be storedunsorted, with orientation and sorting then taking place in the course of the feeding process. The principle of this is shown in Fig. 3-51b. Since the systemintelligence is primarily located in the imaging unit, while the hopper feedingsystem (centrifugal conveyor, vibrator, inclined conveyor, etc.) can be largelynon-workpiece-specific, systems of this kind offer enhanced flexibility, at leastwithin the limits of their size. The space saving due to the reduction in the num-ber of feed systems required is a decisive advantage, particularly in the assem-bly of small workpieces. The required investment is also lower. The “sorting”process can be defined as follows:

Sorting is the automatic separation of mixed workpieces. A volume of different

articles is arranged into groups on the basis of certain classes of features

(type, properties).

The golden rule in production operations is not to discard correct orientationonce this has been achieved. For certain processes, such as heat treatment andelectroplating, a different approach must often be taken. In the interests ofachieving the maximum degree of utilisation of electroplating lines, differentworkpieces are often temporarily mixed. The resulting complex mixture of work-

3 Orientation technology68

1

C DA B

3

2

a) b)

A B C D

6

7

5 4 2

3.6 Orientating and sortingmixed workpieces

Fig. 3-51:

Orientated feeding of several

types of small workpieces

a) Workpiece types stored

separately in the hopper

b) Workpiece mix in vibratory

feeder

1 Tower vibrator

2 Vibratory feeder

3 Outlet

4 Conveyor belt

5 Sorting and checking

device (Festo Sortbox)

6 Ejector nozzle

7 Separated workpiece

magazine

A to D

Workpiece types

Page 70: Pneumatic Feeding

pieces must then be separated again. The difference between the workpieces isfrequently a matter of a few millimetres. Manual sorting after production can virtually never be justified in economic terms.

An example of a solution for tasks of this kind is shown in Fig. 3-52. Variousworkpieces are fed from a spiral conveyor. The workpieces have different shapesand arrive at the output belts or rails in a chaotic order. Each workpiece is re-corded by a CCD camera. If the orientation of the workpiece is acceptable, it is able to pass the ejector nozzle and continue to the deflector, which has nowbeen set to the appropriate magazine channel, allowing the workpieces to proceed to the pick-up point. Incorrectly orientated workpieces are returned tothe bowl feeder by the ejector nozzle.

The deflector adjustment is static, i.e. it is adjusted before each workpiece ar-rives. For this purpose, it is necessary for the workpieces to be fed singly andnot in a continuous stream. The example also indicates that it is possible toadjust the channel widths for the various workpieces to ensure that these main-tain their orientation. Servo motors allow programmable width adjustment at thetime of a workpiece changeover.

Fig. 3-53 shows a 25-year-old idea for the sorting of workpieces. This is a contin-uous-throughput method in which the electrophysical properties of the 2 work-piece types are investigated by proximity means in a magnetic field. Based onthe results of this, the workpieces are then transferred by an ejector nozzle to aparallel conveyor track or left on the same track. The sorted workpieces exit fromthe system via separate feed channels. Pre-orientated workpieces can be fed tothis device, for example, from a vibratory bowl feeder.

3 Orientation technology 69

12

3 8

9

4 5 7

610 11 12

Fig. 3-52:

Vibratory bowl feeders

with parallel output rails

for different workpieces

(according to Schmid)

1 CCD camera

2 Conveyor belt

3 Return ejector nozzle

4 Gravity chute

5 Belt drive

6 Vibratory bowl feeder

7 3-position pneumatic drive

8 Magazine belt drive

9 Deflector

10 Magazine channel

11 Motor for automatic track

width adjustment

12 Side edge guide

Page 71: Pneumatic Feeding

A special kind of workpiece mix is involved when we are sorting natural prod-ucts, such as nuts. The workpieces are all of the same type, but differ in size and details. Fig. 3-54 shows a sorting method using a Festo Checkbox. The nutsare scanned in free fall from 2 angles of view at a 90° interval and their volumeis calculated from the resulting measured values. Images from the two view-points are fed via a mirror and prism to a line camera in a way similar to thesolution shown in Fig. 1-2. This is a difficult task, since the nuts rotate abouttheir own axis during their free fall, resulting in motion blur. After the measure-ment operation, air nozzles are activated and blow the workpieces as they fallinto the appropriate sorting channel K1, K2 or K3. It is a tribute to the high levelof performance of the Festo Checkbox that it is also able to provide a solution foran application of this kind.

3 Orientation technology70

1

2

p 3

4

5

1

5

2

3

K1

K2

a

K3

c

1

4

8

9

b

86 7 5

Fig. 3-53:

Sorting 2 workpiece types

(according to Kanaew)

1 Electromagnet

2 Ejector nozzle

3 Workpiece in feed channel

4 Output chute with separate

channels for each

workpiece type

5 Conveyor rotor

p Compressed air

Fig. 3-54:

Sorting nuts in free fall

(Festo)

a) Drop system

b) Beam path of measuring

system

c) Angles of view

of workpieces

1 Feed channel

2 Nozzle ring

3 Pulsed air jet

4 Sorting channel

5 Line camera

6 Lighting

7 Mirror

8 Sorting workpiece

9 Angles of view

Page 72: Pneumatic Feeding

Automatic production with fast cycle rates demands workpieces which are 100%checked, since otherwise malfunctions will occur and production or assemblymachines will be effectively operating additionally as checking machines, leading to a drastic fall in throughput. The use of imaging systems means that itis possible to record data that provides an indication of major workpiece qualityparameters.

Screws provide a standard example of quality parameters. Before these leavethe manufacturer’s, they are checked and sorted according to the following criteria:• Bent shanks• Squashed heads• Damaged, short or absent threads• Length, head height• Excess material on tips• Sorting to exclude incorrect workpieces• Check for presence of single slot or cross-slot.

The aim is to achieve workpieces of zero-defect which are 100% correct. In thecase of screws, there is generally a facility for counting off a preselected quantityfor a given pack size.

Further checks may include the following:• Measurement of contour segments• Relative comparison of distances• Absolute comparison with reference values• Measurements of length and height• Detection of features e.g. 0.1 mm and larger• Detection of fluidic skins, burrs and chips• Number of contour features.

It would seem appropriate to make statistical use of the large volume of datagenerated during checking operations. In this way, quality features can be docu-mented, trends can be spotlighted and long-term developments affecting com-ponent quality or individual features can be traced. The Festo statistical software“CheckStat”, for example, allows quality data to be recorded over any desiredperiod and evaluated in any application in which a Festo Checkbox is installed.The results are shown in a screen graphic. Fig. 4-1 shows an example of thisvisualisation.

4 Checking and counting workpieces 71

4

Checking and counting

workpieces

4.1 Important process-related workpiece parameters

Page 73: Pneumatic Feeding

Counting is an essential operation, particularly during packing and order picking,but also in order to obtain data on workpiece throughput for use in modern production control systems. Data of this kind allows conclusions to be drawnregarding the condition of the tools of preceding machines. Counting operationscan thus help monitor tool service life and initiate maintenance work. Countingitself is relatively simple to accomplish if optical, acoustic or inductive sensorsare installed in the workpiece flow.

Counters are digital circuits that add and store the pulses with which they are

fed (incremental counters) or subtract and store these (decremental counters)

and display the number of pulses which they have counted.

A typical application of incremental counters is for the continuous recording ofthe number of good workpieces produced for production control purposes.Decremental counters are used in the main as predetermining counters. A de-sired quantity is preset, and when the counter reaches zero a signal is output to the next machine on the production line. After this has been acknowledged, a new counting cycle is started.

To allow counting, however, there must be gaps between the moving workpie-ces. Gaps can be introduced into a chain of workpieces by transferring them to a faster-running conveyor or by reducing the spiral pitch at the outlet of avibratory bowl feeder. Counting is more difficult if the workpieces travel in achain without gaps. Fig. 4-2 shows a solution in which the workpieces tip away,aided by an air jet. This tipping operation can be reliably detected by a sensorwhich supplies a counting pulse.

4 Checking and counting workpieces72

Fig. 4-1:

Statistical software helps

visualise test results with the

Festo Checkbox system

4.2 Counting

Height

Pol. min.

Length

Base

Page 74: Pneumatic Feeding

A special form of counting is represented by order picking of workpieces andcomponents, for which sorting systems supported by imaging devices can alsobe used, provided that the workpieces are not too large.

Order picking is the process of collecting together particular quantities of dif-

ferent workpieces from larger stored quantities in response to the demands of

a consuming system.

A typical example of order picking is the compilation of particular quantities offixing materials (bolts, washers and nuts) for manual assembly systems. Orderpicking tasks are also frequently encountered in packing systems. In the past,only one type of workpiece was usually fed to each packing station. If severaltypes of workpiece are fed from a single hopper feed system, the packing linecan be made considerably shorter, thus saving space in the production work-shop and the investment cost of hopper feeding devices.

4 Checking and counting workpieces 73

Fig. 4-2:

Counting a continuous stream

of workpieces without gaps

1 Compressed air tube

with ejector nozzle

2 Diffuse sensor

3 Workpiece chain

4 Vibratory feeder

1

2

3

4

Page 75: Pneumatic Feeding

The orientation of workpieces is meaningful only if this orientation can be main-tained in a magazine. There are various ways of achieving this, with shaft maga-zines being the most common type used. They may be stationary or also mobile.We will study a few possibilities below.

Orientated workpieces (often they are only pre-orientated) must be fed into amagazine when they exit from a hopper feeding device. The transfer from onesub-system to another may result in technical problems. This applies particularlyto spiral vibratory conveyors. The connection of a magazine rail forms a transiti-on from a vibratory system to a static system and is a critical point. The points of transition from a vibratory system to another moving system (conveyor belt,linear vibrator chute) also requires careful thought. The reason can be seen inFig. 5-1. The further the channel is extended, the more unfavourable the effectof the force component which moves the workpieces forward. The outlet channelshould therefore never project by more than the drum radius D/2. This alsomeans that it is not permissible to have fixed links to further magazine channels.

The channels must therefore be separated. A number of examples are shown in Fig. 5-2. A right-angle transitional gap is generally used when the workpiecelength L is > 4b (b = channel width). If the workpieces are shorter than this, anangle transition is better.

If a fixed connection of the magazine rails is made, it must be made in such away that the lateral motion components are kept away from the coupled maga-zine rail. This can be achieved, for example, by using a ball and vee or leaf springconnection.

5 Magazining orientated workpieces74

D/2

D

5

Magazining orientated

workpieces

5.1 Outlet design of vi-bratory conveyors

Fig. 5-1:

Extended vibratory channels

oscillate simultaneously in

curvilinear form

Page 76: Pneumatic Feeding

In addition to magazine channels, small conveyor belts or linear vibrator chutescan also be used to forward orientated workpieces. The different theoreticallypossible variants are shown in Fig. 5-3.

A small conveyor belt can also be placed at 90° to the position shown in Fig. 5-3a. Especially for feeding bulk materials in random order, outlet channelsare cut at an angle at their end points at which the material in question is trans-ferred to a conveyor belt. This results in optimum distribution across the fullwidth of the channel. Fig. 5-4 shows a configuration of this kind.

5 Magazining orientated workpieces 75

a) b) c)

b

a) b)

c) d)

1 2 3

45

Fig. 5-2:

Connection of magazine

channels

a) Right-angle transitional

gap

b) Comb-like transition

c) Angle transition

Fig. 5-3:

Forwarding orientated

workpieces

a) Small conveyor belt

b) Linear vibrator chute

c) Shaft magazine

d) Drop transfer device

Page 77: Pneumatic Feeding

Workpieces that travel into a magazine by gravity (Fig. 5-3c) must not jam whilstdoing so. Conversely, it must be possible for a single workpiece to travel downthe magazine channel without turning over. Workpieces that have a tendency todo this should be brought to their pick-up point by a conveyor belt or linearvibrator chute. Magazine rails and channels should have openings which allow avisual inspection and, if necessary, manual interventions to correct malfunctions.They must also not be affected by dirt.

In modern hopper feeding and orientating devices, the outlet conveyor belt isequipped with imaging devices. In cases of this kind, we must consider howseparated-out workpieces can be returned to the hopper. Return channels canbe used for this purpose, as shown in Fig. 5-4. Other solutions included parallelreturn conveyor belts or collecting the workpieces in bins and emptying theseback into the hopper (probably the simplest variant).

5 Magazining orientated workpieces76

1

2

3

Fig. 5-4:

Transfer point

to a conveyor belt

1 Side edges

2 Outlet channel of vibrator

3 Small conveyor belt

Fig. 5-5:

Incorrectly orientated

workpieces are returned

to the hopper drum (Festo)

Page 78: Pneumatic Feeding

Magazines are always placed between hopper feeding devices and workstations,due to the fact that feeding directly from a disorderly body of workpieces is ran-dom to a certain degree, while workstations operate in a fixed cycle. The stan-dard solution is magazines that match the contours of the workpieces. The mainproblem is that it must also be possible for individual workpieces to passthrough the magazine without turning over or otherwise losing their orientation.A typical magazine solution is shown in Fig. 5-6.

All kinds of profiles are used to create magazines, including tubing and spiralwire sleeves. A number of examples are shown in Fig. 5-7. It should be ensuredthat magazines remain accessible, for example to allow jammed workpieces tobe freed quickly. Dirt grooves are also important, in order to ensure that theworkpiece contact surfaces do not collect dirt and gradually develop encrustati-ons.

5 Magazining orientated workpieces 77

3

1

2

5

a) b)

32

5

312

4

1 2

6 7

3 4

8

5

12

13

11109

5.2 Magazine designs

Fig. 5-6:

Shaft magazine

with gravity operation

a) Horizontal pick-up

b) Vertical feed

1 Magazine guide wire

2 Workpiece

3 Wire securing ring

4 Distributor

5 Infeed from hopper feeding

device

Fig. 5-7:

Examples of outlet

or magazine rails

1 Open channel

2 Fully covered channel

3 Partial cover

4 Suspension rail

5 Workpiece

6 Channel with cover rails

7 Wire rail cover

8 Spiral wire sleeve

9 Wire rail magazines

10 Open tube

11 Tube magazine with

internal profile

12 Drop funnel

13 Magazine tube

Page 79: Pneumatic Feeding

If channel magazines are required with only a slight inclination, we can considerair cushion channels. With these devices, workpieces glide on a virtually fric-tionless film of air (Fig. 5-8). The devices can thus operate with angle of inclina-tion a of only 1° to 3°.

There is occasionally a requirement to output orientated workpieces to mobilemagazines, for example panel magazines, which are then transferred to an automatic assembly machine or workstation. The principle of this is shown inFig. 5-9. In order to fill all the magazine positions, the magazine must be indexedone longitudinal row at a time, while the end of the tube is indexed in each caseby one lateral row. This requires positioning axes or other mechanical deviceswith either a fixed step width or a mechanically adjustable width. It may benecessary to stop the workpiece feed for a short time to allow magazine changing.

5 Magazining orientated workpieces78

1

2

3

m · g

·

5 2

1

3

4

3

1

1

2

3

4

5

6

7

Fig. 5-8:

Design of air cushion

magazines

1 Compressed air channel

2 Workpiece

3 Nozzle bore

4 Lateral guide

5 Air film

· Angle of inclination

Fig. 5-9:

Magazine filling device

1 Feeding conveyor

2 Infeed funnel

3 Flexible tubing

4 Workpiece

5 Positioning axis

6 Magazine guide

7 Panel magazine

Page 80: Pneumatic Feeding

If different types of workpieces are fed and orientated at the same time, eachtype must be magazined or accumulated separately. Random-order accumu-lation is used, for example, to count out packaging quantities. In this case, the packaging material or bulk material container is fed automatically.

Orientated storage in channel magazines requires controlled magazine inlets.The relevant control signal must accompany the workpiece up to the magazineinlet.

For multiple magazines, various organisational variants have been devised toensure that each type of workpiece is fed to the right magazine. These areshown in Fig. 5-10. The positioning motions are provided by pneumatic multi-position cylinders. The critical factor is whether there is one or more pick-uppositions for the handling device. If there is only one, this means that pick-and-place devices can be used for handling, while multiple pick-up positions willgenerally demand programmable handling systems. In the solution shown in Fig. 5-10b, a distributor in each case releases the next workpiece to arrive at thepick-up point by gravity. The filling and emptying of the magazine channels areindependent of each other.

5 Magazining orientated workpieces 79

Page 81: Pneumatic Feeding

5 Magazining orientated workpieces80

1

2

3

4

5

G1 G2

G3

a)

b)

3

1

2

6

G

8

c)

1

11

3

7

9

3

10

G

Fig. 5-10:

Multiple magazining

a) Variable pick-up position

and variable infeed

position

b) Fixed pick-up position and

variable infeed position

c) Fixed pick-up position and

fixed infeed position

1 Feed belt

2 Multi-row magazine

3 Multi-position cylinder

4 Linear guide

5 Assorted workpieces

6 Distributor

7 Lateral guide

8 Trunnion pin mounting

9 Conveyor belt

10 Outfeed position

11 Deflector

G Pick-up position

Page 82: Pneumatic Feeding

There has long been a demand for quiet technologies and devices. Certain hopper feeding devices and particular vibratory units, are notorious for theirnoisy operation, due to their design principle. Sheet-metal spirals in combina-tion with sheet-metal workpieces generate a noise level of 90 to 100 dB(A) ifthey operate on the micro-projection principle. Friction conveyor systems ope-rate with frequencies of 5 to 20 Hz and a noise level of less than 78 dB(A). The following noise-reduction methods are available:• Lining the feeder drum with, for example, polyurethane 1 mm thick, or ap-

plying other coatings by spraying. It is also possible to apply a lining of brushmaterial.

• Encapsulating the vibrators in a sound-absorbing hood. Depending on theworkpieces in question, a reduction of noise level of 20...25 dB(A) can beachieved. This measure in combination with sound-absorbing drum coatingsmakes it possible to achieve an operating noise level of 60 dB(A).

• Complete enclosure of feed system. This may, however, restrict accessibility.Enclosures should always be designed in such a way that a view of the con-veyor is retained. It must be possible to rectify malfunctions quickly.

In order to ensure continuity of workpiece feed, the supply of workpieces in thehopper feed device must not be completely used up. Top-up devices installedupstream of the hoppers are therefore activated when sensors signal that theworkpiece level has fallen below a defined minimum. Topping-up is particularlyimportant with vibratory bowl feeders, which must not under any circumstancebe completely filled, since this will excessively restrict the movement of theworkpieces and prevent the feeder from operating correctly. Typical top-up devices are vibratory conveyors, linear vibratory hoppers and hopper conveyors.Fig. 6-1 shows a solution with a hopper conveyor.

6 Ancillary equipment 81

6

Ancillary equipment

6.1 Noise protection devices

6.2 Hopper top-up systems

Fig. 6-1:

Hopper conveyor

for workpiece top-up (Intec)

1 Hopper conveyor

2 Controller

3 Stand

4 Gravity chute

5 Level sensor

6 Vibratory bowl feeder

2

4

3

6

5

1

Page 83: Pneumatic Feeding

This allows periods of operator-free working to be created of greater or lesserlength, depending on the hopper volume, workpiece size and the required feedthroughput. The hopper conveyor itself of course also needs periodic refilling.As its filling height is approximately 1.80 m, hopper conveyors are also producedwith a built-in lifting axis, as shown in Fig. 6-2, which allows them to be broughtclose to the floor for refilling.

If the fed workpieces are ferromagnetic, they can also be topped up using ahandling device equipped with a magnetic gripper. This is shown in Fig. 6-3. It may be possible to take workpieces directly from a box pallet. The magnetgripper is a simple bell-shaped electromagnet with suspension mounting.

6 Ancillary equipment82

1

2

3

1600

mm

1

2

3

4

Fig. 6-2:

Topping-up using a hopper

conveyor with lowering

facility

1 Vibratory bowl feeder

2 Telescopic cylinder

3 Hopper conveyor

Fig. 6-3:

Topping-up using a handling

device

1 Magnetic gripper

2 Vibratory bowl feeder

3 Handling device

4 Box pallet

Page 84: Pneumatic Feeding

Topping-up can also be carried out relatively easily using an inclined conveyor.This type of conveyor is commercially available in numerous forms and activatesitself automatically only when required.

Solutions using auxiliary vibratory hoppers are also possible, as shown in Fig. 6-4. The auxiliary hopper supplies 2 vibratory bowl feeders. A deflector switches the top-up flow to the vibrator requiring this at any given time.

A further interesting way of providing a topping-up function with bulk materialsis a pneumatic workpiece conveyor system. Fig. 6-5 shows a system of this kindin schematic form, which allows workpieces to be conveyed over distance of upto 50 m entirely without damage. A separator halts the conveyed material andguides it to the relevant hopper feed unit. Workpieces for use with systems ofthis kind should be light in weight, such as plastic articles of all shapes up to a size of around 80 mm or small light metal workpieces. Workpieces that have atendency to lock together are not suitable.

6 Ancillary equipment 83

1

3 4 5

2

123

4 5

a) b)

Fig. 6-4:

Topping-up using an auxiliary

vibratory hopper

1 Hopper drum

2 Vibrator for workpiece feed

3 Deflector

4 Outlet channel,

5 Vibratory bowl feeder

Fig. 6-5:

Pneumatic top-up system

a) Conveyor system

b) Examples of workpieces

which can be conveyed

by pneumatic means

1 Distributor with up

to 7 branche

2 Tubing

3 Pneumatic elevator

with hopper e.g.

400 litre capacity

4 Vibratory bowl feeder

5 Separator with output tube

Page 85: Pneumatic Feeding

With hopper feeding devices, it is necessary to monitor the instantaneous fillinglevel to ensure that topping-up – automatic or manual – can be initiated in goodtime. Depending on the type of hopper design, it is possible to use optical, acoustic (ultrasound), inductive or tactile sensor; binary-type sensors, which isto say those which supply only yes/no information, are fully adequate. Opticaland inductive sensors are fitted to the outside of the hopper at the desired minimum filling level. In the case of vibratory bowl feeders, we can use a “finger” directly over the centre of the drum to scan the workpiece surface. Fig. 6-6 shows an example of this. We can see that it is also possible to fit thelevel sensor directly to the top-up hopper. It is particularly important to re-fillvibratory bowl feeders frequently, since in order to ensure correct operation thebowl must not be more than one third full.

It is of course also necessary to monitor the filling level of the magazines thatfollow the orientating device. It is thus useful if an orientation module is able toprocess the signals from buffer-zone sensors. Fig. 6-7 shows an example of atypical configuration with monitoring of the minimum and maximum fillinglevels. When the upper limit is reached, any further working material must bereturned to the hopper and the hopper feeder switched off. In the exampleshown, the sensors cover 3 magazine zones (A, B and C).

6 Ancillary equipment84

1

2

3

AB

4

7

8

9

C6

5

6.3 Level monitoring

Fig. 6-6:

Level sensor (Intec)

and top-up hopper

a) Top-up hopper with level

sensor for vibrator

underneath

b) Example of a level sensor

1 Hopper

2 Controller

3 Stand

4 Level sensor

5 Conveyor belt

6 Mounting

7 Adjustable arm

8 Sensor lever

9 Sensor

Fig. 6-7:

Example of buffer-zone

sensors

1 Top-up hopper

2 Orientation device

3 Conveyor belt

4 Handling device

with gripper

5 Vibratory bowl feeder

6 Controller

7 Workpiece bin

8 Sensor

9 Pick-up position

A to C

Magazine zones

3

2

1

10

8

9

76

4

5

Page 86: Pneumatic Feeding

• Magazine zone A: This zone must have sufficient capacity to hold all thealready-checked workpieces which are still on the conveyor belt at themoment the feed unit is switched off.

• Magazine zone B: This zone is the actual magazine whose contents may fluctuate between maximum and minimum limits. The bigger the capacity of this zone, the less frequently it will be necessary to switch off upstream feeding devices.

• Magazine zone C: This zone has the task of holding enough workpieces tobridge the time until the first newly-conveyed workpiece is received when theconveyor is switched back on. This is intended to prevent unnecessary down-time at the workstation due to a shortage of workpieces.

The reasons for the fluctuations of quantity in the magazine are as follows:

• The stochastic process of orientation• Interruptions in the delivery of workpieces by the hopper feeding device• Interruptions in workpiece pick-up due to brief standstill periods at the

workstation• The proportion of correct workpieces. A large proportion of incorrect work-

pieces will reduce the feed throughput.

6 Ancillary equipment 85

Page 87: Pneumatic Feeding

We can define a “handling technology system” as a sequence of sub-functionsthat are used to bring a workpiece from a random orientation into a desired orientation. It is not easy to develop a practical handling system, and there willgenerally be a choice of devices as potential function providers. We will alsoneed reliable knowledge of the static and dynamic behaviour of the workpieces,their centre of gravity, their frictional and rolling properties and factors relatingto their contours. The successful operation of an orientating device is often amatter of small adjustments of feed channels, chicanes and workpiece contactsurfaces.

A “handling technology system” describes the type, sequence and configurationof the equipment items (chicanes, motion units, grippers) which can be used toachieve a desired orientation and target position. In a more general sense, wecan use the term to cover the overall feed process. Fig. 7-1 shows sketches ofexamples of handling technology systems. Vibratory bowl feeders are featuredhere only as representatives of feeding devices in general. We will always carryout technological planning on the basis of overall processes, by considering howa workpiece can be brought quickly and inexpensively from a random heap tomeet up with a basic assembly component or to another target position. Basictechnological components provide the functions such as storage, motion, gripping, orientation, positioning, buffering, checking and controlling.

7 Handling technology system86

1 2

34

5

6 2

4

7 8

9

Workpieces are output withdesired orientation, butsystem is not flexible

Various different workpiecescan be orientated.Flexibility is available

A top-up hopper allowslonger periods of operationwithout human intervention

Complete feeding andhandling system, suitablefor flexible applications

7

Handling technology

system

7.1 Basic technologicalcomponents

Fig. 7-1:

Examples of various

equipment levels

1 Hopper feed unit

2 Control unit

3 Orientating device

4 Controller

5 Level sensor

6 Top-up hopper with stand

7 Pick-and-place unit

8 Workstation

9 Assembly transfer line

Page 88: Pneumatic Feeding

Vibratory bowl feeders equipped with mechanical (i.e. contact-type) chicanes for orientation continue to be used in mass production systems. The followingexamples illustrate which components need to be combined in order to obtainthe desired orientation effect.

The first example (Fig. 7-2) involves the orientation of an open wire circlip.Correctly orientated workpieces are taken up onto a mandrel and then alignthemselves through vibration-induced auto-rotation relative to the web plate.The workpieces are thus magazined. The crucial moment is the transfer of theworkpieces to the magazining mandrel.

Handling technology system: Notch – deflector for hanging workpieces (sectionC-C) – top deflector – trough channel – threading mandrel – magazine rail.

7 Handling technology system 87

AB

C

C

5

4 1 3

Ansicht ASchnitt C-C

21

Ansicht B

7.2 Examples of applications

7.2.1 Vibratory feeders

Fig. 7-2:

Orientating open circlips

1 Magazining mandrel

2 Trough outlet

3 Web plate

4 Vibrator

5 Workpiece

View B

View ASection C-C

Page 89: Pneumatic Feeding

The next example concerns the feed of corner brackets with a fitted stud. At the tipping point, the workpieces fall in such a way that some land with theirstuds in the slot rail. These then align themselves in accordance with their centreof gravity and are output. Although the workpiece is rather complex, relativelyuncomplicated chicanes are sufficient to achieve the desired orientation (Fig. 7-3).

Handling technology system: Notch – tipping stage – spiral slot with raisededge – Spiral slot – spiral slot with raised edge.

7 Handling technology system88

1

C

C

B

B

A

A

2

3

3

4

30°

Schnitt A-A Schnitt B-B Schnitt C-C

Ansicht X

b + s

X

Fig. 7-3:

Orientation of corner bracket

with fitted studs

1 Tipping stage

2 Notch in track

3 Workpiece

4 Outlet

b Workpiece width

s Clearance (0.2 to 1.0 mm)

Section C-CSection B-BSection A-A

View X

Page 90: Pneumatic Feeding

In the third example (Fig. 7-4), we have a workpiece whose orientation cannotimmediately be recognised from a contour image obtained by optical means. The visibility of the slot depends on the rotary attitude of the workpiece. As theworkpiece moves up the drum, an attempt is made to make it “ride” on a rail.Incorrectly orientated workpieces are not able to do this and fall back into thehopper.

Handling technology system: Wiper – deflector – profile rail – covered magazinerail.

7 Handling technology system 89

1

B

B

A A

4

2

3

5

6

7

8Schnitt A-A

Schnitt B-B

Fig. 7-4:

Orientation of a profiled disc

1 Rail

2 Raised edge

3 Wiper

4 Deflector

5 Workpiece

6 Correctly orientated

workpiece

7 Incorrectly-orientated

workpiece

8 Direction of conveyance

Section A-A

Section B-B

Page 91: Pneumatic Feeding

A final example (Fig. 7-5) shows that if high throughput performance is required,a vibratory drum can be fitted with numerous outlet tracks. The workpieces aregradually orientated within each channel, finally achieving the same orientation.

Handling technology system: Top deflector – spiral extension – profile channel –longitudinal slot – magazine outlet.

7 Handling technology system90

B

B

1

2

3

6

D

D

C

C

A

A

5

4

3

7

Schnitt A-A Schnitt B-B

Schnitt C-C Schnitt D-D

Fig. 7-5:

Orientating syringes

1 Vibratory bowl feeder

2 Top deflector

3 Workpiece

4 Step

5 Parallel channel zone

6 Suspension slot

7 Channel magazine

Section A-A Section B-B

Section C-C Section D-D

Page 92: Pneumatic Feeding

We have already described in some detail the advantages of contactless work-piece detection. Fig. 7-6 shows a typical equipment configuration of this kind,together with some examples of workpieces which have been fed successfullyusing this equipment. It is noteworthy that even features with only small dimen-sional differences (conical springs, flats on chain links) can be detected reliablyeven at high throughput speeds.

Handling technology system: Top deflector – notch – belt transfer – conveyance– shape sensing/imaging evaluation – ejection – feeding into bulk containers.

7 Handling technology system 91

7.2.2 System with contact-less feature detection

Fig. 7-6:

Contactless optical contour

detection of conveyed

workpieces (Festo)

a) Overall view of device

b) Examples of fed

workpieces

1 Conveyor belt

2 Sorting box

3 Detection unit

4 Control and programming

unit

5 Vibratory bowl feeder

6 Ejector nozzle

Messing-buchse

Werkstück Kamerabild

Lüster-klemmen-einsatz

Ketten-lasche

Ventil-feder

0 128 256

128

256

0 128

128

256

128

4

5

3 6 1

2

Valve spring

Workpiece Camera image

Brass bush

Terminal insert

Chain link

Page 93: Pneumatic Feeding

There are 10 good reasons to use imaging-based orientation systems:

1 Reliable stand-alone industrial-quality solutions are available

2 Systems can be programmed quickly and easily using the teach-in method

and sample workpieces

3 High-volume throughput can be achieved even with “orientation

by selection”

4 Can be combined with various hopper feeding systems

5 Can be used to separate out different workpiece types from workpiece mix

6 Various different quality features can be evaluated

7 Hardware is largely not specific to a given workpiece shape, resulting

in increased flexibility

8 High residual value of equipment when a particular automation solution

is dismantled

9 Systems can supply data to allow counting of “good” or correctly-

orientated workpieces

10 Systems can be linked into higher-level information structures.

EMAGO is an acronym for ElectroMAGnetic Orientation of workpieces. This is amethod for the automatic orientation of small metallic components, particularlythose with internal contours (hidden features). With this method, the workpiecespass through an electromagnetic field. The principle of this is shown in Fig. 7-7.As we can see, the electromagnetic field penetrates the workpieces and genera-tes forces within the metal which are more than adequate for the orientation ofsmall workpieces.

The motion effect is due to the fact that the magnetic forces have an unbalancedaction with asymmetrical workpieces and cause the workpiece to turn until itreaches a new orientation in which there is an equilibrium of forces.

7 Handling technology system92

1

6b)

c)

M

B

FM

a)

5

4

3

2

7.2.3 Orientation using the EMAGO method

Fig. 7-7:

Electromagnetic orientation

a) Schematic view

b) Direction of magnetic field

c) Action of forces in

magnetic field

1 Vibratory bowl feeder

2 Workpiece

3 Feed channel

4 Pole shoe for magnetic

field generation

5 Coil

6 Magnet

B Magnetic induction

FM Electrodynamic force

action

M Torque

Page 94: Pneumatic Feeding

The workpieces must be metallic but need not be ferromagnetic – this methodalso works with materials such as brass, silver, copper and aluminium. Examplesof especially suitable workpieces are shown in Fig. 7-8. Technical parameters areas follows:

• Induction 0.1 ... 1.0 T• Frequency 50 ... 50,000 Hz• Effective power 0.1 ... 1.5 kW• Time required for orientation 0.1...1.2 s

With workpiece dimensions of 10 x 10 x 2.5 mm, the orientation throughput canbe 350 to 400 workpieces per minute, using an effective power of no more than100 W. Systems of this kind are simple and exhibit hardly any wear [31, 32].Typical workpiece masses are around 20 grams, with a maximum of 50 grams.Throughput may be up to 400 workpieces a minute.

7 Handling technology system 93

1 3

2

Fig. 7- 8:

Examples of workpieces sui-

table for the EMAGO method

1 Workpiece

2 Material different from

workpiece material, e.g.

bimetallic component

3 This method is highly

suitable for workpieces

with internal contours

Page 95: Pneumatic Feeding

A device that operates on the principle of orientation by correction is shown inFig. 7-9. This uses a number of active components in order to change the instan-taneous workpiece orientation. As we have seen, orientation is a process thatrequires constant alternation between stable and unstable workpiece positionsuntil the desired position is reached. In order to do this, however, the workpie-ces must be set in motion. In the solution shown above, this is achieved in a virtually perfect textbook manner. Vibration-induced motion is used to break up the workpiece heap and ensure that workpieces arrive singly (although stillrandomly orientated) on the second continuously running conveyor belt.

For this purpose, the hopper conveyor belt is able to execute forward and back-ward steps. In a second phase, the incorrectly orientated workpieces are ma-nipulated via a camera-guided pulse head. A selected workpiece is given a targeted blow, thus generating torque and turning the workpiece round. Theblow is against the conveyor belt. The pulsed driver is positioned at a suitablepoint on the X/Y plane in accordance with the result of an image evaluation.Following this, a further camera localises the gripper position and supplies therobot controller with the pick-up coordinates. Any remaining incorrectly orien-tated or excess workpieces are returned to the hopper. This system, too, ope-rates in a way that is very largely independent of a specific workpiece shape.

Lightweight workpieces can be orientated by using an appropriate combinationof mechanical and aerodynamic means, which allows a high throughput. Oneexample of this is the plastic workpiece shown in Fig. 7-10 [36]. This has a complex shape with many details. Orientation using only mechanical chicaneswould be difficult and also highly susceptible to malfunction.

7 Handling technology system94

1

2

3 4

5

6 7 8 9

15

1413

101112

7.2.4 Stepwise orientationusing imaging systems

Fig. 7-9:

Workpiece feed and

orientation system (Adept)

1 Camera to monitor pick-up

position

2 Industrial robot

3 Pulsed drive, controlled

in X/Y direction

4 Workpiece

5 Camera to control position

of pulse ram

6 Field of vision

7 Sensors to monitor

break-up of workpiece

heap

8 Workpiece heap

9 Infeed hopper

10 X/Y slide

11 Continuously running

conveyor belt

12 Lighting

13 Impact vibrator

14 Return flow of incorrectly

orientated and excess

workpieces

15 Parametrisable conveyors

with vibratory effect

7.2.5 Orientation using aerodynamic devices

Page 96: Pneumatic Feeding

The workpieces are fed at high speed from a conveyor (centrifugal conveyor orhigh-capacity vibration conveyor). In the first orientation stage, incorrectlyorientated workpieces are turned through 180° about an axis at right angles tothe conveyance direction by exploiting the position of the centre of gravity. In thecase correctly orientated workpieces, the spin generated by the air nozzle is not sufficient to turn these workpieces around in “mid-air”. Thesecond phase is concerned with orientation about the longitudinal axis. For thispurpose, the workpieces pass by a nozzle array, in which the air exits via honey-comb-like channels. The orientated workpieces must then be picked up in such a way that they retain their orientation, which is not so easy. The throughput ofsystems of this kind can be around 250 workpieces per minute, considerablybetter than with other orientation methods, particularly mechanical ones.

7 Handling technology system 95

1

S2

3

6

5

4

5

7L = 42 mmL/D = 7

Fig. 7-10:

Sequence of orientation

components for aerodynamic

orientation (according to

Lorenz and Grimm)

1 Workpiece

2 Feed hopper

3 Gravity track

4 Point nozzle

5 Direction of travel,

6 Honeycomb-shaped

nozzle array

7 Guide rail

S Centre of gravity

Page 97: Pneumatic Feeding

The selection of workpiece feeding devices is a multi-stage process, and theequipment technology chosen for the functional sequence; hopper filling – feeding – orientating/sorting – magazining/bulk storage may vary. The equip-ment must be appropriate to the workpieces, the required performance level anddegree of flexibility and feed conditions. The equipment should also be availableat short notice at the right price.

The difficulty of handling different components varies. Characteristic features ofdifficult components are as follows:

• Asymmetrical dimensions• Asymmetrical position of centre of gravity• Asymmetrical internal contours and features• Asymmetrical physical properties, such as difference in materials • Asymmetrical surface features, such as engraved logos.

The greater the degree to which features are asymmetrical, the more handlingoperations are required to bring a workpiece into the desired orientation, or thegreater the number of workpieces which need to be separated out of a randomheap. The greatest influence on handling behaviour is the workpiece shape. Toillustrate this, Fig. 8-1 shows typical workpieces classified according to features.The principle of this table is that the difficulty of handling increases from top leftto bottom right. This is easy to understand – a sphere is ideally symmetrical.Irregular built-up workpieces, on the other hand, have many points that maylock together with other workpieces in a random heap and can in fact be fedautomatically, if at all, only by using special untangling technology. Designersare of course called on to keep their workpiece designs as simple as possible inthe interests of easy handling [5]. Experience has shown however, that whenautomating handling processes, it is generally no longer possible to changeworkpiece properties.

8 Selection of workpiece feeding devices96

Examples of basic workpiece shapes

Form elements Sphere Bar Flat Mushroom Irregular

Workpieces withsmooth exterior

Internal and externalcontour features

Workpieces witheccentric features

Irregular built-inworkpieces

8

Selection of workpiece

feeding devices

8.1 Workpiece shape anddegree of handling difficulty

Fig. 8-1:

Classification of workpieces

according to basic shapes and

form elements

Page 98: Pneumatic Feeding

In order to evaluate the suitability of feed technology for a given task, we mustfirst decide which properties and characteristic data are relevant. We can use thefollowing as the basis for comparisons:

• Maximum permissible workpiece mass• Feed throughput per unit time• Maximum storage capacity or achievable operating time without human

intervention• Workpiece stress during feeding operation (risk of damage)• Compatibility of technology with relevant workpieces• Conversion capability or properties giving enhanced flexibility• Verified technical availability and service life• Accuracy (precision) of detection of workpiece features and dimensions• Accessibility to allow correction of malfunctions• Facility for incorporation of additional functions• Facility for linkage of control unit to higher-level control systems.

The required feed speed is heavily dependent on the orientation method used. If this involves correcting the orientation of workpieces where necessary, whichis often the case with vibratory feed devices, initially incorrectly orientated workpieces will also be counted as successes in the end. If, on the other hand,the orientation method involves separating-out incorrectly orientated work-pieces, which is often the case with orientation based on imaging systems, onlya fraction of the initial volume of workpieces will pass through as correctly orien-tated. It will thus be necessary in this case to feed larger quantities of work-pieces through the orientation (detection) system, which in turn demands a higher speed of conveyance. These two orientation methods are also describedas “active” and “passive” orientation respectively.

The process of defining the feed speed will now be explained by taking theexample of the frequently used spiral vibratory conveyor. The feed speed mustbe chosen in such a way as to ensure that the machine being fed is never forcedto wait for workpieces. The feed throughput PZ must therefore be slightly higherthan the throughput PS of the processing machine (PZ = (1.1...1.3) PS ).Allowance must also be made for fluctuations in the flow of workpieces on thevibratory conveyor. Our first calculation is as follows:PZ = PS/(1-k1) in r.p.m. or workpieces/min. where

k1 Coefficient of fluctuation of workpiece delivery (k1 is approx. 0.2...0.3 with a vibratory conveyor)

Our next step is to determine the required feed speed v. This is calculated as follows:v = PZ · L/(60 k2) in mm/s where

L Workpiece length in direction of travel in mmk2 Coefficient of filling level of spiral with already correctly orientated

workpieces

8 Selection of workpiece feeding devices 97

8.2 Performance profile

Page 99: Pneumatic Feeding

The factor k2 is determined as follows:k2 = F · L/(L + s) where

F Coefficient of probability of correctly orientated workpieces on the spirals Average value for gap between workpieces travelling on spiral.

The factor k2 represents the density of the flow of workpieces and the probabil-ity of correctly-orientated workpieces on the spiral. It will generally be deter-mined by experiment. It will thus also incorporate allowance for the preferredorientation which workpieces assume when input into the system. Fig. 8-2shows the average preferred orientation assumed by simple rotationally sym-metrical workpieces. As we can see, dimensional conditions play an importantpart, as described already in chapter 3.1 (Fig. 3-4). The coefficient F depends onthe following factors:• Workpiece shape• Materials properties• Orientation system (chicane sequence)• Design features of spiral• The method used for separation from a random heap• The projection factor of the vibratory conveyor.

The following equation provides a guide value for F with passive orientation:

F = 1/√1 + (d/L)2

In the above, L must be > d; the equation applies to symmetrical shafts andshouldered workpieces with a cylindrical shape. For these workpieces, the equa-tion also applies for active orientation.

2 1 0,5

90 10 70 30 44 56

D

LWerkstück

L/D

Vorzugs-lage inProzent

8 Selection of workpiece feeding devices98

Fig. 8-2:

Preferred orientations

of a simple workpiece

Workpiece

L/D

Preferred assumed orien-tations in percent

Page 100: Pneumatic Feeding

In the case of the passive orientation of shafts with asymmetrical ends, the following applies:

F = 0.5/√¯1 + (d/L)2

For the feeding of thin symmetrical panels with b < L >> a and of long sym-metrical cylindrical workpieces (L > 10 d), we can take F = 1 (b = Width, a = Thickness). The feeding of asymmetrical workpieces requires a more com-plicated orientation system. The coefficient F can be determined on by experi-mental means in these cases.

Example: We wish to calculate the required average feed speed for the work-piece shown in Fig. 8-3. The automatic machine to be fed requires PS = 80 cor-rectly orientated workpieces per minute. If we take the factor k1 as = 0.25, weobtain the following:

F = 1/√¯1 + (d/L)2 = 1/√¯1 + (8/40)2 = 0.98

In the case of active orientation at the top of the spiral, we can assume a gap-free chain of workpieces, i.e. s = 0. We now determine the factor k2:

k2 = F · L/(L + s) = 0.98 · 40/(40 – 0) = 0.98

The feed speed v thus becomes:

v = L · PZ · 1.2/(60 k2) = 40 · 80 · 1.2/(60 · 0.98) = 65 mm/s

40

R

8

8 Selection of workpiece feeding devices 99

Fig. 8-3:

Workpiece for sample

calculation

Page 101: Pneumatic Feeding

The steps in the selection process can be specified only in general terms, asshown in Fig. 8-4. The reason for this is that the decisive factor may often bespecific parameters. In the case of an assembly line, for example, the questionof space requirements may be very important. This means that selection criteriamust be weighted, and this weighting will vary from one application to another.

One of the parameters at the start of the process will always be an estimation of the workpiece behaviour and properties (tendency to assume stable positionsduring orientation or pre-orientation, edge strength, brittleness, reaction to frequent handling, tendency to electrostatic charges, etc.).

The choice of a hopper feeding device will also depend on the equipment al-ready in service at the location in question. A uniform pool of equipment cansimplify maintenance work and the management of stock of spare parts. Theneed for top-up hoppers will depend on the size of the workpieces concernedand the required performance. In many cases, hopper feeding devices are availa-ble already combined with top-up systems, which means of course that there isno need to select a top-up system separately.

The question of the best orientation method will depend primarily on the state inwhich workpieces are intended to be after this procedure, for example sortedbut not orientated or else orientated and magazined. Features need to be availa-ble which the orientation method concerned can use. It is, for example, entirelypossible to check internal features by means of mechanical chicanes, which isnot possible with optical scanning by a camera.

The type of magazining chosen will be governed by the way workpieces or mag-azines are transferred to the relevant production system. Distribution can be carried out by means of slides, a gravity feed or a pick-up by a gripper.

We must consider the following cost factors and parameters:• Hardware costs

- Design and development costs- Planning, construction, testing, functional testing- Installation costs- Minimisation of hardware costs by boosting performance- Costs resulting from equipment depreciation

• Operating costs- Servicing and maintenance costs- Conversion and reprogramming costs- Costs of debugging operating sequence- Cost of installation space

• Purchasing cost- Purchasing of pre-tested off-the-shelf modules

• Residual value- Reuse value after end production of initial workpiece

• Personnel costs- Training costs- Proportional personnel costs for supervision of feeding device.

8 Selection of workpiece feeding devices100

8.3 Selection algorithm

Page 102: Pneumatic Feeding

8 Selection of workpiece feeding devices 101

Start

Record initial data and parameters:Investigate workpiece behaviour

Select a hopper feeding device onthe basis of weighted criteria

Device found?

Select a hopper top-updeviceg

Device found?

A Centrifugal conveyor

B Vibratory bowl feeder

C Inclined or steep conveyor

D Multi-stage conveyor

E Segment conveyor

F Other conveyor

Equipment Ve Mo

Equipment

G

H

I

J

K

Hopper conveyor

Vibratory hopper

Inclined conveyor

Magnetic gripper

Other equipment

Vo Ge Ve

Methods

L

M

N

O

P

Q

Active orientation, mechanical

Passive orientation, mechanical

Orientation using imaging system

Orientation from workpiece mix

Orientation and counting

Other method (EMAGO, etc.)

Le Fl

Magazines

Shaft, channel, tube

Bulk container

Indexing magazine

Assortment magazine, multi-row

Custom solution

Sp Au

R

S

T

V

U

Price/performance ratio

Amortisation

Self-built

Price service life

Finance

Other criteria

Good

Unsuitable

Select an orientation, sortingand counting method

Method defined?

Possible verification ofchecking parameters

Define magazining technology

Magazine found?

Define overall solution, e.g. B-G-N-T

Clarification of all commercialand economic questions

Solution accepted

End

No

No

No

No

No

Fig. 8-4:

General steps in the selection

of a hopper feeding device

Au Cost

Fl Flexibility

Ge Noise level

Le Performance

Ma Mass of individual

workpiece

Sp Storage capacity

Ve Tendency to tangle

Vo Maximum storage

capacity

Page 103: Pneumatic Feeding

In conclusion, we should emphasise that the selection algorithm presentedabove is a working guide which can be expanded or reduced at any time asappropriate to a given requirement profile.

It is typical of modern industry that the work which is still carried out manually,often referred to as “residual” work, is gradually being automated. This workincludes handling operations such as the orientation and feeding of small work-pieces. From the economic point of view, it is generally a question of comparingvariants, for example the variants “manual feed” (extremely flexible), “hopperfeeding device with mechanical chicanes for orientation” (extremely workpiece-specific, virtually inflexible) and “feed technology with optoelectronic workpiecedetection” (teach-in programming, flexible).

The vital factor after all comparisons have been made is the cost per workpieceor per workpiece batch. For individual automation measures, the criterion of success is the break-even point [33]. Up to this point, the costs are higher thanthe benefits, and the measure concerned is thus making a loss. Only after thebreak-even point has been passed does the automation measure concernedgenerate an economic advantage (Fig. 8-5).

8 Selection of workpiece feeding devices102

8.4 Economic factors

Fig. 8-5:

The break-even point is the

gateway to economic savings

Total benefit

Cost

s, b

enef

its

Total costs

Throughput, volume

Break-even point

Page 104: Pneumatic Feeding

9 Glossary

Aerodynamic orientation

Orientation of workpieces in air-flow zones using air nozzles, the cw coefficient ofthe workpiece, the position of its centre of gravity and other useful aerodynamicfeatures of the workpiece.

Asymmetry

Geometrical irregularity in cases where there is no mirror image on either side ofthe axis of a body.

Resolution

In imaging systems, the number of scanning points per unit length in a digitisedimage in the horizontal or vertical direction.

Throughput

Number of workpieces that are output via a vibratory or other hopper feedingdevice in the desired orientation per unit time (workpieces per minute).

CCD

Charge-coupled device, a light-sensitive sensor which supplies an analogue signal which must then be digitised before processing in a computer.

Single-mass oscillator

Vibratory system for vibrators in which the working mass is formed by the con-veyor channel, the oscillator to which this is permanently linked and the workingmaterial in the channel.

Speed of conveyance

Speed at which workpieces (or to be exact, their centres of gravity) move on alinear or curved path.

Guide stability

Ability of a workpiece to maintain a defined orientation during motion on a support surface.

Friction conveyance

Forward motion of a workpiece on a vibrating track in which the workpieces donot lift off the track but flow like a viscous mass.

Good workpiece

Workpiece which is identical with the specified sample workpiece on the basis ofall criteria and thus does not does exceed any permissible deviations.

Workpiece heap

Term for working material lying in random arrangement in a hopper. Describes achaotic state with regard to position and orientation.

103

9

Glossary

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High-performance vibrator

Vibrator designed for a very high speed of conveyance well in excess of theusual speed of 10 m/min.

Edge finding

A mathematical process used in imaging systems to find edges (lines) in animage (scene, subject map). Operations such as smoothing and edge en-hancement are usually carried out before the edge image is produced by digitising a greyscale image.

Contour

Enclosed area that generally represents the outline of an object. Contour segments are non-enclosed lines.

Positional stability

Ability of a workpiece to remain standing on the same face during friction conveyance on an inclined and/or vibrating surface.

Feature

Special physical or calculable attribute of a workpiece that distinguishes thisfrom other workpieces of a different type.

Feature memory

In imaging systems, a memory that holds data on the features to be used toidentify (compare) objects.

Feature distribution

The degree of fluctuation of features which is recorded in the teach-in mode withone or more sample workpieces and a detection device due to shape-related,dimensional and positional errors.

Micro-projection

Forward motion of a workpiece on a vibrating track in which the workpieces arethrown forward by distance in the micron range.

Sample workpiece

Workpiece used in the teach-in mode of a detection device to supply data oncharacteristic features. This data is stored for reference purposes.

Top-up system

System that automatically supplies hopper feeding devices with fresh work-pieces and is generally activated periodically.

Orientation probability

Statistical relationship between the number of favourable orientations for agiven purpose to the overall number of possible orientations (positions and attitudes).

9 Glossary104

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9 Glossary

Orientation

The process of changing the axial direction of workpieces from undefined to defined, without consideration of the workpiece position.

Positioning

The process of changing the position of workpieces from undefined to defined,without consideration of the workpiece orientation.

Chicanes

Orientating devices in the motion path of a workpiece which use a selection or correction function to change the workpiece orientation from undefined todefined.

Vibration mechanics

The sub-area of mechanics (dynamics) that is concerned with the study of vibration.

Subpixeling

In imaging systems, a method for “photometry averaging”. This gives a highertheoretical resolution and thus more precise data concerning an object imagedby a sensor array. The scanning accuracy is thus higher than that indicated bythe pixel centre-to-centre distance.

Symmetry

Characteristic of bodies and figures in which there is a mirror image on eitherside of an (imaginary) centre axis.

Degree of disorientation

Indication of the maximum number of translatory and /or rotational motions thatare required for a workpiece to reach a desired defined state. In the case ofworkpieces in a random heap, U = 6.

Preferred orientation

Stable workpiece orientation that a workpiece tends to assume on an even surface or vibrating conveyor due to its geometry and the position of its centreof gravity. The preferred orientation can be determined approximately by experi-ment.

Projection index

Indication of the drive acceleration of a vibratory conveyor. This expresses theratio of the drive acceleration component aligned normally to the conveyor trackto the gravitational acceleration component acting in the same direction. With amicro-projection vibrator, the projection index is between 1 and 3.3.

105

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Dual-mass oscillator

Vibratory system for vibrators in which the effective mass mN is linked to a counter-mass mG consisting of a supported or suspended frame (Fig. 9-1).

9 Glossary106

Fig. 9-1:

Principle of dual-mass

oscillator

1 Spiral drumFN

mG

mN

FG

1

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Further literature

[1] Jacques, N.: Wirbel der Welt (“The way of the world”), published in German by L.E. Wittich Verlag, Darmstadt 1942

[2] Schütze, R.: Lagerichtiges Zuführen – Voraussetzung für automatisiertesHandhaben (“Orientated feeding - the prerequisite for automated hand-ling”), article in German in Fachberichte Metallbearbeitung Coburg 62(1985) 7-8, pp. 390 to 391

[3] Frank, H.-E.: Das Verhalten von Werkstücken in der Fertigung bei automati-scher Handhabung (“The behaviour of production workpieces during auto-matic handling”), article in German in VDI-Zeitschrift 118 (1976) 12, pp. 573 to 578

[4] Schmid, pp.: Lagerichtig eingeschleust ("Orientated feeding”), article inGerman in Schweizer Maschinenmarkt No. 16, 1993, pp. 16 to 21

[5] Hesse, S.: Montageatlas – Montage- und automatisierungsgerecht konstru-ieren (“The assembly atlas - Designing for easy assembly and automation”),published by Vieweg Verlag, Wiesbaden 1994

[6] Frank, E.: Das Ordnungsverhalten von Werkstücken bei automatisierterHandhabung (“The orientation behaviour of workpieces during automatichandling”), article in German in wt-Z. ind. Fertigung 62 (1972), pp. 154 to 160

[7] Weiss, K.: Entwicklung flexibler Ordnungssysteme für die Automatisierungder Werkstückhandhabung in der Klein- und Mittelserienfertigung(“Development of flexible orientation systems for the automation of work-piece handling in small- and medium-run production”), published in German by Springer Verlag, Berlin and Heidelberg 1985

[8] Hilgenböcker, H.: Methodische Entwicklung von Zuführsystemen(“Methodical development of feeding systems”), in German inBetriebstechnik No. 97, VDI-Fortschrittsberichte Reihe 2, published by VDI Verlag, Düsseldorf 1985

[9] Schmidt, I.: Ordnen von Werkstücken mit programmierbaren Handhabungs-geräten und Werkstückerkennungssensoren (“Orientation of workpiecesusing programmable handling devices and workpiece detection sensors”),published in German by Springer Verlag, Berlin and Heidelberg 1984

[10] Sabajkovic, V. A.: Programmiertes Ordnen von Teilen (“Programmed orien-tation of workpieces”), published in Russian by Verlag Hochschule, Lwow 1983

[11] Spur, G.; Stöferle, Th.: Handbuch der Fertigungstechnik, Band 5: Fügen,Handhaben, Montieren (“Manual of production technology. Volume 5:Joining, handling, assembly”), pp. 499 to 589, published in German by Hanser Verlag, Munich 1986

107

Further literature

Page 109: Pneumatic Feeding

[12] Hesse, S.; Mittag, G.: Handhabetechnik (“Handling technology”), published in German by Hüthig Verlag, Heidelberg 1989

[13] Hesse, S.: Systematisches Entwerfen von Einrichtungen zum automatischenOrdnen von Werkstücken (“Systematic development of devices for the auto-matic orientation of workpieces”), article in German in FeingerätetechnikBerlin, 32 (1983) 7, pp. 292 to 295

[14] Habenicht, D.: Die Gleitförderung von Werkstücken in Schwingzuführsys-temen (“Friction conveyance of workpieces in vibratory feeding systems”),article in German in fördern und heben 35 (1985) 2, pp. 90 to 93

[15] Ahrens, H.; Habenicht, D.: Werkstückbewegung beim Zuführen und Ordnenmit Vibrationswendelförderern “Workpiece motion during feeding and orientation with vibratory bowl feeders”), article in German in wt-Z. ind.Fertigung 74 (1984), pp. 23 to 26

[16] Ahrens, H.: Vorgehen zur Auslegung von Vibrationswendelförderern“Method of sizing vibratory bowl feeders”), article in German in Z. wirtsch.Fertigung, Munich 79 (1984) 8, pp. 401 to 404

[17] Habenicht, D.: Hilfen zur Optimierung von Vibrationswendelbunkern – För-derarten (“A guide to the optimisation of vibratory hoppers – Conveyancemethods”), article in German in VDI-Zeitschrift 123 (1981) 8, pp. 297 to 301

[18] Habenicht, D.: Hilfen zur Optimierung von Vibrationswendelbunkern – Be-rechnungsgrundlagen (“A guide to the optimisation of vibratory hoppers –Principles of calculation”), article in German in VDI-Zeitschrift 123 (1981) 3,pp. 82 to 86

[19] Ahrens, H.: Auslegungs- und Betriebskriterien für Vibrationswendelförderer(“Dimensioning and operating criteria for vibratory bowl feeders”), article in German in VDI-Zeitschrift 126 (1984) 22, pp. 881 to 884

[20] Habenicht, D.: Hilfen zur Optimierung von Vibrationswendelbunkern –Parametereinfluss (“Aids for the optimisation of vibratory bowl feeders –The influence of parameters”), article in German in VDI-Zeitschrift 123(1981) 6, pp. 215 to 218

[21] Stoevesandt, G.: Auslegung von Vibrationswendelförderern (“Sizing ofvibratory bowl feeders”), article in German in VDI-Berichte 323, pp. 49 to 54, published by VDI Verlag, Düsseldorf 1978

[22] Cokayne, A.: The Way of the World – A Review of Current Practice inAutomatic Parts Recognition, Feeding and Orientation, AssemblyAutomation 11 (1991) 4, pp. 29 to 32

[23] Hesse, S.: Atlas der modernen Handhabungstechnik “Atlas of modern hand-ling technology”), published in German by Vieweg Verlag, Wiesbaden 1995

Further literature108

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Further literature

[24] Groh, W.: Das Ordnen von Massenteilen und ihre selbständige Zuführung indie Werkzeugmaschine (“Orientation of bulk workpieces and automatic feedto machine tools”), article in German in Werkstattstechnik und Maschinen-bau 47 (1957) 8, pp. 402 to 410

[25] Hesse, S.: Betrachtungen zum automatischen Ordnen von Werkstücken(“Notes on the automatic orientation of workpieces”), article in German inMaschinenbautechnik Berlin, 24 (1975) 8, pp. 374 to 378

[26] Hesse, S.: Selbständiges Ordnen von Massenteilen (“Automatic orientationof bulk workpieces”), article in German in Fertigungstechnik und Betrieb 23(1973) 8, pp. 462 to 466

[27] Rockland, M.; Stetter, R.: Flexibles Ordnen und Zuführen (“Flexible orienta-ting and feeding”), article in German in Z. wirtsch. Fertigung 89 (1994) 1-2,pp. 55 to 57

[28] Caine, M.: The Design of Shape Interactions Using Motion Constraints,Proceedings IEEE Robotics and Automation Society, May 1994, California,pp. 366-371

[29] Kettner, H.; Ahrens, H.; Stoevesandt, G.: Zum Fördervorgang im Vibrations-wendelförderer “The conveyance process in vibratory bowl feeders”), articlein German in VDI-Zeitschrift Düsseldorf, 122 (1981) 8, pp. 311 to 315

[30] Redford, A.: Small Parts Feeding, Assembly Automation 11 (1991) 4, pp. 8 to 11

[31] Blume, F.: Elektromagnetische Orientierung – eine neue Methode zurHandhabung von Bauteilen (“Electromagnetic orientation – A new methodfor the handling of workpieces”), article in German in Fertigungstechnik undBetrieb, Berlin, 27 (1977) 10, pp. 612 to 613

[32] Davidenko, E. P. et alia: Elektromagnetische Verfahren und Vorrichtungenzur Orientierung, Fixierung und Erkennung von Geräte- und Maschinenteilen(“Electromagnetic methods and equipment for the orientation, positioningand detection of device and machine components”), article in German inMaschinenbautechnik Berlin, 26 (1977) 10, pp. 470 to 473

[33] Boothroyd, G.; Dewhurst, P.: Part Presentation Costs in Robot Assembly,Assembly Automation 5 (1985) 8, pp. 138 to 145

[34] Werkstückhandhabung in der automatisierten Fertigung – Ein Leitfaden zurLehrschau (“Workpiece handling in automated production – A trainingguide”), published in German by Württembergischer Ingenieurverein,Stuttgart 1968

109

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110 Further literature

[35] Richtlinie VDI 2860, Handhabungsfunktionen, Handhabungseinrichtungen,Begriffe, Definitionen, Symbole (“VDI guideline 2860: Handling functionsand equipment – Terminology, definitions and symbols”), 1990

[36] Lorenz, B.-M.: Aerodynamische Zuführtechnik (Diss. Uni Hannover)(“Aerodynamic feed technology – A Hanover University thesis”), published in German by VDI-Verlag, Düsseldorf 1999

[37] Lund, M.B.; Boothroyd, G.: A compendium of small parts feeders,Massachusetts (USA) 1979

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111

Glossary

of technical items

A Air jet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54Air nozzle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95, 103Alignment edges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

B Basic behavioural types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Break-even point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102Brush lining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

C CCD camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60, 69Centrifugal conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19, 30, 31Centrifugal feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Chicanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39, 40, 48, 105Contour image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65Conveyance speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22, 60, 97Counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

D Decremental counters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72Desired orientation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66Detection device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62Digital image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64, 67Direction of workpiece travel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28Drop opening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

E EMAGO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92

F Feed vibrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12, 102Flat belt conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Flat magazines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Friction conveyance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21, 103Further conveyor devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

H Handling technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86Hopper feed device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18, 19, 84, 101

I Imaging systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59Inclined spiral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48, 49Incremental counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

L Lifting-plate feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

M Magazine zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85Magazine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77, 78Micro-projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

N Notch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

O Optical detection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60Order picking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73Orientation probability factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38, 39Orientation . . . . . . . . . . . . . . . . . . . . . . . . .35, 36, 38, 45, 46, 47, 53, 54, 94

P Packing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

Glossary of technical items

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112 Glossary of technical items

Pneumatic workpiece conveyor systems . . . . . . . . . . . . . . . . . . . . . . . . . . .83Profile openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45Profile rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

R Reference data list . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66Reference patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59Relative comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65Rotationally-symmetrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98

S Scoop-segment hopper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19, 32, 33Segment feeder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32, 33Separating-out of defective workpieces . . . . . . . . . . . . . . . . . . . . . . . . . . .15Sequence tapes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Shaped deflectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Shaped nests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59Spiral conveyor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23, 69Spiral drum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25, 44, 106Spiral feeder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28Standard spiral pitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Steep conveyors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33, 34Stepped feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31, 32Storage vibrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23, 24Subpixeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60, 105Surface qualities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

T Teach-in method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66Teach-in workpieces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66Test algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64Tipping stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52Tower vibrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23, 68Tube feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

U Ultrasound measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59

V Vertical feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23Vibrator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Vibratory bowl feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10, 69Vibratory conveyor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97Vibratory feeders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18Vibratory system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Visual contour detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59

W Wiper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40, 89Workpiece behaviour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Workpiece detection system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62Workpiece flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98Workpiece images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61Workpiece maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59Workpiece mix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70