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Handling Machining Assembly Organisation Pneumatics Electronics Mechanics Sensorics Software Chinese English French German Russian Spanish Blue Digest on Automation 053 753 Hesse Modular Pick-and-Place Devices

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Page 1: Pneumatic Pickplace

Handling

Machining

Assembly

Organisation

Pneumatics

Electronics

Mechanics

Sensorics

Software

Chinese

English

French

German

Russian

Spanish

Blue Digest

on Automation

053 753

HesseModularPick-and-PlaceDevices

327,5 mm

160 mm

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Page 2: Pneumatic Pickplace

Hesse

Modular Pick-and-Place Devices

Page 3: Pneumatic Pickplace
Page 4: Pneumatic Pickplace

ModularPick-and-Place Devices

Blue Digeston Automation

HandlingPneumatics

Stefan Hesse

Page 5: Pneumatic Pickplace

Blue Digest on Automation

© 2000 by Festo AG & Co.Ruiter Strasse 82D-73734 EsslingenTel. (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, mechani-cal, photocopying or otherwise, without the prior written permission of Festo AG.

Page 6: Pneumatic Pickplace

The phrase “handling technology” is derived from the word “hand” – and as weall know, the human hand is capable of a very great number of things. If weattempt within the context of industrial production to replace the human handwith technical devices, we expect first and foremost movements which are fast,repeatable and accurate. Flexibility is a quite separate matter. For tasks such assealing bottles or assembling ballpoint pens, for example, flexibility is not requi-red. Tasks of this kind are the territory of pick-and-place devices. The main appli-cation of these devices is workpiece handling in component manufacture andassembly, rather than the handling of tools. Despite the fact that programmablerobots are now commonplace in production operations, with numbers growingday by day, these have in no way taken the place of pick-and-place devices. Interms of units, there are still more pick-and-place devices sold than robots. Thesimple reason for this is that, today and in the future, there are and will still bemany handling operations for which programmable handling devices are clearlyover-qualified.

Pick-and-place technology is unfortunately rather poorly represented in tech-nical literature. This is the reason why this book has been produced. It is intend-ed to illustrated the modern devices and methods which can be used today toproduce solutions for simple handling tasks. Modular construction is naturallyan important factor, as are in particular pneumatic actuators, reflecting the factthat, notwithstanding the gain in functionality, the devices which allow themechanisation of handling operations should also be inexpensive. This book istherefore addressed at practical users who are looking for ideas and solutionswhich will allow production processes to be raised to a new level of efficiency.

Stefan Hesse

Foreword

5

Page 7: Pneumatic Pickplace
Page 8: Pneumatic Pickplace

Table of contents

1 Workpiece handling as an auxiliary process ................................................................. 9

1.1 Tasks of handling technology ......................................................................................... 91.2 Basic principle of pick-and-place devices ............................................................... 111.3 Area of application ........................................................................................................... 17

2 Modular design ......................................................................................................................... 20

2.1 Pneumatic automation components ......................................................................... 202.2 Pick-and-place devices in cyclic operation ............................................................. 222.3 Advantages of modern design ..................................................................................... 252.4 General design of basic units ....................................................................................... 29

2.4.1 Function of a linear unit .................................................................................... 292.4.2 Function of a rotary unit .................................................................................... 342.4.3 Machine frames from modular components ............................................. 392.4.4 Determination, overdetermination and synchronisation .................... 41

2.5 Motion patterns ................................................................................................................. 432.6 End-position cushioning ................................................................................................ 46

3 Positioning technology ......................................................................................................... 523.1 Freedom of programming .............................................................................................. 523.2 Servopneumatic positioning axes .............................................................................. 553.3 Electromechanical positioning axes .......................................................................... 563.4 Assessment and selection ............................................................................................. 57

4 Use of pick-and-place devices ........................................................................................... 60

4.1 Modular handling systems ............................................................................................ 604.1.1 Use of rotary units ............................................................................................... 604.1.2 From a single-axis to a multi-axis system .................................................. 64

4.2 Pick-and-place units for assembly work ................................................................. 674.2.1 Man or machine? .................................................................................................. 674.2.2 Assembly with pneumatics .............................................................................. 684.2.3 Peripheral helpers ................................................................................................ 72

4.3 Feeding machines with pick-and-place units ........................................................ 744.3.1 Automatic feed is replacing manual work ................................................. 744.3.2 Reaching into the machine ............................................................................... 79

5 Gripper technology .................................................................................................................. 81

5.1 Grippers and gripped objects as a system ............................................................. 815.2 Precision and special grippers ..................................................................................... 835.3 Miniature grippers ............................................................................................................ 865.4 Magnetic grippers ............................................................................................................. 87

6 Criteria, characteristic values and components ......................................................... 89

6.1 Don’t just dream – combine! ........................................................................................ 896.2 Assessment and selection ............................................................................................. 906.3 Guides and smoothness of operation ...................................................................... 946.4 And, finally, ... ..................................................................................................................... 95

Literature ........................................................................................................................................... 96Glossary ............................................................................................................................................ 98

Appendix: Typical configurations of pick-and-place devices produced with Festo’s modular system .............................................................................. 102

77

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1 Workpiece handling as an auxiliary process

Each age generates its own future and takes pleasure in the latest technical ad-vances. In fact, every advance builds on previous achievements, and the originsof any development generally lie much further back in the past than most peopleimagine. For example, the great physicist Heinrich Helmholtz (1821–1894) hadthis to say in a lecture given in 1854:

“We are now no longer trying to build machines which are able to imitate thethousand different types of work which a human being can carry out; on the con-trary, our objective is to build machines which can carry out one type of workand replace thousands of human beings.”

Helmholtz’s thinking was far ahead of his time. His words essentially contrastthe “universal” (universal robots) and the “special” (special machines). Pick-and-place devices clearly come under the heading of “special machines”, and weshall be discussing these in detail. Pick-and-place devices and simpler relateddevices are not mini robots but are a separate class of device of great impor-tance within production technology. With the development of industrial produc-tion, workpiece gradually also learned to move.

Products manufactured in millions have motivated the trend away from manualhandling assisted by mechanical devices and towards fully-automated handling.Early examples of products of this kind were sewing needles, followed later bylight bulbs and automobiles. Fig. 1-1 shows the device for stamping the eyes of needles produced by themechanical engineer Kaiser of Iserlohn in 1871. Kaiser’s idea was to produce twoneedles joined eye to eye as an automation-compatible semi-finished product.This was divided into two needles later, after stamping and perforation. Thismethod allowed the production sequence to be automated. The cam for thestamp ram was driven by a transmission, as you can see. Pictorial symbols forthe graphic representation of feed functions were defined for the first time 40years ago in the VDI Standard 3239. The effect of this was to help place moreemphasis on workpiece handling within the context of planning work.

9

1

Workpiece handling as

an auxiliary process

1.1 Tasks of handlingtechnology

Fig. 1-1:

A 19th century feed system

used to stamp the eyes of

needles. The symbols

indicate: Stack magazine –

feeding – holding – shaping –

outward transfer.

Page 11: Pneumatic Pickplace

“Workpiece handling” means all the operations used to produce a flow of mate-rials and workpieces in the vicinity of production equipment. Workpieces arepositioned in the right orientation and quantity at a particular time at the pointof processing, are clamped, processed, released again and transferred outwards.

Early examples of feed technology can also be found in devices used with coin-stamping presses, automatic lathes (turning from bar material), and the produc-tion of munitions. For simple handling operations, pick-and-place devices aremore than adequate, even in the age of the robot. Devices of this kind continueto be used ten to twenty times more frequently than industrial robots. For cer-tain applications, an industrial robot is over-qualified or only designed for a spe-cial application, such as paint-spraying. Technical development and the expansi-on of the range of possible applications have meant that pick-and-place deviceshave become more like programmable industrial robots. There are, for example,already NC-compatible two-axis pick-and-place devices. The critical factors arethe motion pattern required for technological reasons and various other parame-ters. Fig. 1-2 provides a general overview of these. In mechanical and electricalengineering in general, production work can be said to be made up of the follo-wing:–- One third machining,– One third assembly, and– One third, handling, conveying and storage.

1 Workpiece handling as an auxiliary process10

Fig. 1-2:

Approximate classification

system for technical/indus-

trial handling operations

Tool handling

From initial to endposition withoutpath conditions

With geometricalor technologicalpath conditions

Workpiecehandling

Handling

operations

Positioning of tool Welding Adhesive bonding

PalettingDepalleting

JoiningFeeding

Page 12: Pneumatic Pickplace

1 Workpiece handling as an auxiliary process

This class of device includes two-axis motion units with a fixed sequence, usedto handle objects, in particular workpieces of small and medium size and mass.

Pick-and-place devices have fixed motion sequences, paths or angles which

can be changed only by replacing components or re-adjusting these.

There are a number of other terms which mean the same thing as “pick-and-place device”, such as “loader”, “feeder”, “non-servo robot” or “fixed-sequencerobot” (Japan). Because of the hard impact which devices of this kind used toproduce at end positions, American engineers have also christened them “bang-bang robots”. “Pick-and-place device” is nonetheless a good term, reflecting thefact that an object is lifted and set down at a defined point. A typical motionsequence for a pick-and-place device is shown in Fig. 1-3. The following motionoperations take place:

– Workpiece gripping (pick-up)– Workpiece movement (transfer)– Opening of gripper, setdown of workpiece (placing).

We can distinguish between compact and modular devices. These latter aremade up from standard modules, allowing application-specific requirements tobe taken into account. Fig. 1-4 shows an interesting compact unit with electricalrotary drives. The parallelogram gear unit converts a rotary motion into a pus-hing action. The drive in the base unit turns the entire assembly. This actualexample does not feature a vertical motion, but this could be incorporated ifdesired.

A general problem, and one which often results in a more or less good compro-mise, is the feed of a power supply and any signal lines required for the finalactuating element. The solution is generally tubing arcs or coils or power supplychains.

11

1.2 Basic principle of pick-and-place devices

Fig. 1-3:

Types of motion for pick-and-

place operations

1 Transfer motion

2 Vertical motion

3 Clamping

4 Release

1

32

2

24

Page 13: Pneumatic Pickplace

A typical configuration for handling devices made up of modular components isshown in Fig. 1-5. Panels are picked from a stack and transferred to a conveyor.Two linear axes are sufficient for this. In this example, rodless pneumatic cylin-ders, linked by a cross-member, are used for the horizontal motion. In the caseof light small panels, one of the cylinders can be replaced by a linear guide, forexample, a roller strip. The suction-cup spider travels in an open rectangularmotion cycle.

1 Workpiece handling as an auxiliary process12

1

2

3

4

H

b)a)

Fig. 1-4:

Compact pick-and-place devi-

ce with parallelogram arm

(Bühler Automation)

a) General view

b) Handling sequence

1 Parallelogram arm

2 Parallel-jaw gripper

3 Rotary platform

4 Motor housing and base

unit

H Maximum stroke

Fig. 1-5:

Modular pick-and-place

device with pneumatic linear

axes

1 Standard cylinder

2 Cross-member

3 Rodless cylinder

4 Suction cup

5 Rack with free support

6 Conveyor system

7 Workpiece

Page 14: Pneumatic Pickplace

1 Workpiece handling as an auxiliary process

One way of distinguishing between pick-and-place devices is on the basis of thetype of power supply which they use. Nothing will work without a power supply.But what types of power are used?

Electrical energy

Electromechanical devices use spindles or control cams to generate motionswhich may be linear or circular. In the case of multi-axis devices, the resultingmotion is the product of several individual motions. A separate cam is used foreach motion, with the possibility of fitting two cams in one housing. Fig. 1-6shows the principle of a device of this kind. The cam supplies information (onthe desired path) and is also the energy carrier. Devices of this kind are very fast(less than 1 second per motion cycle!). They are used only in mass productionoperations (the types used are disc, slot or globoid cams). An example of a com-pact device for a lift/turn cycle is shown in Fig. 1-7.

The motor drives a cam which acts via a roller-tipped star wheel to produce a jolt-free backwards and forwards motion. The lifting motion is produced by adisc cam. The gripper is pneumatically driven. The modular design also allowsthe creation of application-specific devices such as a twin-arm configuration or alifting column with an additional stabilising support or supplementary guide forcases involving the handling of large masses.

13

Fig. 1-6:

Schematic view of trans-

mission for electrically-driven

pick-and-place device with

cam-controlled linear motions

Fig. 1-7:

Lift/turn loader (Ferguson)

1 Swivel arm

2 Gripper

3 Lift/turn unit

4 Cam control system

5 Geared motor

Page 15: Pneumatic Pickplace

We sometimes hear people say that cam-controlled devices are old-fashioned.This is not correct, as practical examples show. Device of this kind are very quietin operation, the motion sequence is free of drift and the speed very high. Giventhe right cam shape, it is possible to achieve a speed curve free of jolts andimpacts. This design is, however, subject to limits with regard to adjustment ofits stroke. It is often possible to adjust only the stroke position and not the pathwhich is stored in the cam. Suitability for use thus depends on the intendedapplication.

Some quite unusual kinematic characteristics have been produced for specialapplications. Fig. 1-8 shows how an elliptical pick-and-place cycle can beproduced with a single drive by deriving a second motion from the first. Themotion nonetheless concludes with a short straight-line approach to the endposition. The drive wheel powers a pinion which is fitted with a plain guide forthe handling arm. This arm, however, has no fixed pivot point relative to themachine frame. It is connected to a non-driven straight slide. This kinematic lin-kage causes the end point of the handling arm to describe the path shown.

Electrically driven linear modules all have a fixed base frame. Motion can betransmitted to the slide or handling arm via a spindle, chain or toothed belt. Inthe case of direct electrical drives, this can be achieved without a tractive device.Rotary and linear drives of this kind are, however, expensive and have up to nowbeen used only rarely. On the other hand, they offer high accuracy and speed inpositioning applications Slide-type devices are available as yoke and base-frameversions, which each account for around half of the linear drives on the marketin the case of pneumatic linear units.

Pneumatic energy

Pneumatic linear units are of direct-drive type, and thus produce a motion with-out intermediate gearing. This also applies to rotary vane motors. Often, how-ever, rack-and-pinion gearing is used to convert the linear pushing action ofopposed pistons into a rotary motion. This rotary drive is thus free of backlash inits end positions.

1 Workpiece handling as an auxiliary process14

Z

X

4

1

3 2

5

Z

X

6

Fig. 1-8:

An unusual pick-and-place

device, shown in kinematic

form

1 Pinion

2 Handling arm

3 Plain guide

4 Drive wheel

5 Linear guide

6 Motion path of end point

of arm

Page 16: Pneumatic Pickplace

1 Workpiece handling as an auxiliary process

As a general principle, the following pneumatic components can be used to crea-te pick-and-place devices:

– Pneumatic cylinders with or without guide units– Linear units with parallel cylinders (twins)– Rodless linear units– Rotary and swivel drives– Swivel/linear units– Mechanical and suction grippers– Pneumatic motors.

A fast-running pneumatic motor can, for example, provide a viable solution forspindle drives in environments with explosion hazard. They can be used, forexample, as lifting drives for balancers. Pneumatic motors are also used for fric-tion-wheel drives, for example to feed flat workpieces or panels. These motorsrequire little installation space and produce high feed speeds.

As we know, pneumatic devices are fast. Production engineers are, however,interested in something else, namely the cycle time which can be achieved, forexample in a feed application. Is the cycle time a question of black magic? No!There is always a choice of variants, as shown in the example in Fig. 1-9.

Let us assume we have a cross-gantry. The axes in the X and Y directions arepositioning axes or, if only a small number of positions are required, can also belinear units with intermediate stops. As a variant, it should also be possible tohave a lifting/rotary axis fitted with a double gripper in the Z direction. Blanksand finished workpieces can be palleted optionally either separately or together.As a further option, a buffer store of workpieces can be maintained in the vicini-ty of the clamping point. If we now document operational variants for these opti-

15

Fig. 1-9:

An example of machine feed

1 Cross-gantry axes

2 Machine tool

3 Intermediate storage

4 Blanks pallet

5 Finished-workpiece pallet

6 Manual rotary axis with

double gripper

Page 17: Pneumatic Pickplace

ons, we obtain the sequences of actions shown in Fig. 1-10. It is not immediatelyobvious which is the best solution. It is necessary to add together the individualprocessing times and the auxiliary process time.

Auxiliary process time is the time for which the machine stands still and no

processing of the workpiece can take place due to the fact that the workpiece

is being changed over.

The objective must be to make the machine ready to resume work as quickly aspossible. Production engineers speak of "machining-to-machining time”.Intelligent organisation of machine operation can help minimise the cycle time.Once the desired variant has been identified, it is possible to formulate therequirements to be placed on the automation components. There are of coursecertain parameters for which allowance must be made. Variants 3 and 5, forexample, assume that the finished workpieces can be placed back onto the stor-age positions on the blanks pallet, despite the geometric changes to the work-pieces which have resulted from machining.

1 Workpiece handling as an auxiliary process16

Page 18: Pneumatic Pickplace

1 Workpiece handling as an auxiliary process

The first thing that must be said is that the main applications of this technologyare limited to small workpieces. There are of course manufacturers who form theexception to this rule by producing heavy-duty modules able to carry loads ofseveral tonnes. In the fields of mechanical engineering, electrical engineering,precision engineering and automobile construction, however, it is estimated that80% of workpieces weigh less than 5 kg. This fact explains the vast number ofcommercially-available linear and rotary modules which are designed to workwith workpieces of this size.

17

Fig. 1-10:

Illustration of the influence

of the gripper, storage device

and motion sequence on the

machine processing time tB

and the handling cycle time

tH.

M Machine

W Waiting position of hand-

ling device or buffer

position close to clamping

point

R Blank workpiece handling

F Finished workpiece

handling

L Idle motion

1.3 Area of application

Lösungsvariante Ablaufgrafik Zeitbedarf

1 Single gripper picks blank,buffer at W, finished work-pieces set down on separate pallet1L– 2F – 3R – 4L– 5F – 6L– 7R

2 Single gripper picks blank,finished workpieces setdown immediately onseparate pallet1L – 2F – 3L – 4R – 5L

3 Single gripper, finishedworkpieces set back downon blanks pallet1L – 2F – 3L – 4R – 5L

4 Double gripper, separateblanks and finished work-pieces pallets1L – 2FR – 3F – 4L – 5R

5 Double gripper, finishedworkpieces set back downon blanks pallet1R – 2FR – 3F – 4L – 5R

Page 19: Pneumatic Pickplace

A very large number of pick-and-place devices are used in the assembly of smallworkpieces. Applications range from plug-in assembly to the oiling of mechani-cal clocks and watches. Further examples include feed devices for IC test ma-chines and devices to pick up finished products for packing, fit covers to palletsand handle chipboard panels in furniture production (Fig. 1-11), and new appli-cations are being found every day. Chipboard panels are heavy and their hand-ling requires numerous suction grippers, which should preferably be operatedwith a low vacuum. Due to the porous structure of the material, a high vacuumwill lead to air being drawn through the material, resulting in a loss of grip, evenwith thick panels.

Must we now regard fast handling systems as “genies in a bottle”? By this, wemean a situation with a potential for danger if it is opened up. Any form of auto-mation is in a sense a threat to the human workers currently employed in pro-duction and management. Some worried people are now asking whether auto-matic handing is also a threat to jobs. Handling systems are indeed much superi-or to human workers in terms of their capacity for work, which is of course thereason why they are used. Developments of this kind as the result of technicalprogress are of course not new – for example, cinema musicians became unem-ployed when silent films were replaced by the talkies. Brakemen riding thecaboose at the rear of freight trains were no longer required when railroad com-panies introduced full pneumatic braking systems.

How do human beings cope with this? Human beings are part of the overallsystem, and this must be controlled in such a way that people's existence is notthreatened. If fewer workers are required at the “base”, they must be trained forhigher-level work. If there is not enough work for everyone, we must reduce

1 Workpiece handling as an auxiliary process18

Fig. 1-11:

Destacking chipboard panels

1 Suction gripper

2 Lifting cylinder

3 Rodless cylinder

4 Panel stack

5 Support

6 Protection against torsion

7 Machining system

8 Panel carriage

9 Pneumatic or hydraulic

cylinder

10 Cable displacement

encoder

Page 20: Pneumatic Pickplace

1 Workpiece handling as an auxiliary process

working hours (hours worked per year, hours worked per week, hours worked ina lifetime). When agriculture was mechanised, many redundant farm workerstook up employment in factories. Workers who are now no longer required inthese factories are moving into the service sector. In short, there are no easyanswers. Progress and structural change are embedded in a social system,which has the responsibility of achieving an overall balance. It would be wrongto forbid electricity simply because this can be used for an electrical chair; itwould be just as wrong to pass legislation limiting the number of industrialrobots, as has once been suggested.

19

Page 21: Pneumatic Pickplace

Handling systems are in many cases necessary, indeed vital, accessories for theimplementation of fully-automated production processes. In general terms, anautomated production system can be said to consist of a processing or assemblysystem plus a handling system, disregarding for the moment the testing andpackaging functions which come after this. Often, handling and conveyorsystems account for half of total investment. If it is necessary to plan systems ofthis kind under severe time pressure, this will inevitably involve the use ofstandard peripheral components, industrial robots and motion modules. Theobjective with regard to material flow is to guide workpieces in such a way thatthey reach

– the right place– in the right condition– in the right orientation and position– in the right quality and– at the right time.

Modular equipment and control systems make it possible to achieve this.

Industrial pneumatics began to develop from around 1960 onwards, resulting inthe creation of components such as pneumatic cylinders as standard compo-nents and as parts of modular systems. Before this, power cylinders were produ-ced on an individual basis as appropriate to a given application. As Fig. 2-1shows, pneumatic drives play a leading role in the production process, evenoccupying first place in terms of importance in handling operations.

Pneumatic drives are distinguished by their simple and compact design. Weshould not, however, forget that the efficiency of these drives is significantlyworse (up to 20% worse) than in the case of electrical drives, which achievemuch better results, depending on their transmission type and ratio, despite themultiple energy conversion process involved. The “directness” of pneumaticdrives is often the decisive argument in their favour, particularly in cases wheresmall single-acting cylinders with low air consumption are used and a powerful

2 Modular design20

2

Modular design

2.1 Pneumatic automationcomponents

Fig. 2-1:

Small-product processes and

ranking in terms of energy

consumption

Machine tool

1 Electrics Pneumatics Elektrics Pneumatikcs Elektrics

2 Pneumatics Elektrics Hydraulics Elektrics Pneumatics

3 Hydraulics Hydraulics Pneumatics Hydraulics Hydraulics

Page 22: Pneumatic Pickplace

2 Modular design

system for the generation of pneumatic energy is already available. A furtherfactor today is that high-quality guide systems and pneumatic actuators havebeen combined to form handling modules.

Handling modules are series-produced devices which provide motions. They

can be combined in accordance with the needs of an application to form multi-

axis devices. Their travel is limited by adjustable components. Only position-

ing axes allow travel motions to be programmed freely.

If modules are to be combined, they must be compatible. This is not merely aquestion of matching hole patterns or finding suitable adapters – compatibilitymeans much more than this. Fig. 2-2 shows the various factors involved, such ascost-effectiveness or control-system interfaces. A further factor is that there arealso other differences between pneumatic and electrical modules. Some of theseare listed in Table 2-1.

Property Pneumatic Electrical

Max. duty cycle (linear unit) Approx. 60% Approx. 40%

Max. duty cycle (rotary unit) Approx. 95% Approx. 5%

Potential acceleration Higher Lower

Max. linear travel Approx. 800 mm 3000 mm

Max. travel speed High Less high

Repetition accuracy, linear ‹ ± 0.05 mm ‹ ± 0.05 mm

Repetition accuracy, rotary Approx. 0.02° Approx. 0.02°

Max. intermediate positions, linear Up to 4 Any number*

Max. intermediate positions, rotary Up to 2 Any number*

21

Fig. 2-2:

Modules must be compatible

and meet a variety of needs.

Table 2-1:

Some of the differences

between pneumatic and elec-

trical modules (* applies only

to electrical or servopneu-

matic positioning axes).

GeometricalTechnological

Technical

Economic

Control-related

Functional

Page 23: Pneumatic Pickplace

Compressed air is an interesting medium. It is able to transport energy and alsosignals over large distances. For various reasons, however, it cannot always beused as a “direct drive”; it is sometimes necessary to convert motions, for exam-ple from linear to rotary and vice-versa, as shown in Fig. 2-3. All the possiblevariants can be found in handling technology.

If motions are required in sections, suitable function providers must be selectedin accordance with requirements. Fig. 2-4 shows the theoretical choices, Eachvariant is also characterised by the number of positions which can be approa-ched. This number runs from 3 to infinity, the latter requiring the drive to becombined with a displacement or angle encoder. Servopneumatic axes, forexample, are used with great success as cross-gantries for the high-speed fittingof electronic components to printed circuit boards.

2 Modular design22

2.2 Pick-and-place devices

in cyclic operation

Fig. 2-3:

The principles of motion

conversion

1 Rotary into linear

2 Rotary into rotary

3 Linear into rotary

4 Linear into linear

Fig. 2-4:

Travel in defined motion steps

1 Multi-position cylinder

combination

2 Intermediate stops

3 Drum stop

4 Position controller

Page 24: Pneumatic Pickplace

2 Modular design

These technical options allow the creation of pick-and-place devices whichprovide a range of motion patterns. Some of these are shown in Fig. 2-5. Themotions consist of advance and return phases or closed loops. Additionalstopping points are possible. Roughly a quarter of the rotary units on the marketallow the use of intermediate stops. The proportion of linear units which allowthis is smaller. The exceptions are linear units with stop-drum attachmentsproviding, for example, 13 positions. The stop screws in the drum can be ad-justed precisely, and the rotation of the drum is indexed pneumatically (rotarydrive). The drum itself mounted on a shock absorber, allowing a cushionedapproach to each position. With this large number of intermediate positions,however, it is worth considering whether a positioning axis would be a bettersolution.

On the other hand, it sometimes happens that users are unaware of a simpleway of solving a problem and therefore do not use this. Fig. 2-6 shows an appli-cation where it is necessary to break up a 4x4 stack of pipes to feed a machinetool. Each pipe must be moved stepwise towards the output position. In order todo this, power cylinders can be combined to form a multi-position drive. A slightinclination of the stack magazine away from the horizontal prevents pipes fromslipping into the next gap.

23

Fig. 2-5:

Motion patterns of two-axis

pick-and-place devices

1 Travel path

2 Stopping (waiting) point

Fig. 2-6:

Breaking up a stack of pipes

1 Cylinder ejector ram

2 Proximity sensor

3 Workpiece

4 Driven roller conveyor

5 Multi-position lifting

cylinder

6 Loading frame

7 Linear guide

8 Mounting kit

9 Multi-position cylinder

Page 25: Pneumatic Pickplace

In order to produce the 4 positions, 2 cylinders with different stroke lengths canbe combined. The resulting cylinder positions are shown in Fig. 2-7. Each pistontravels only from one end position to the other. Since the complete cylindersmove, mobile line connections must be provided. Off-the-shelf mounting kits are available for the coupling of the cylinders, which eliminates the need forimprovisation.

We are also concerned with forces, and here, too, adaptation may be required.What are the possibilities? Fig. 2-8 shows the principles of 4 variants. In addi-tional to lever transmissions, inclined wedges are also used, particularly inclamping systems. These provide increased force at the expense of stroke(travel). So-called force cylinders are commercially available; these comprisepneumatic pistons with integrated wedge components.

2 Modular design24

Fig. 2-7:

Pneumatic cylinders

combined to form a 4-position

drive

Fig. 2-8:

Boosting pneumatically-

generated motion forces

1 Series connection

of cylinders

2 Parallel connection

of cylinders

3 Pneumohydraulic trans-

mission

4 Mechanical transmission

Page 26: Pneumatic Pickplace

2 Modular design

Even if we select only the simplest standard cycle, there are still variants, asshown in Fig. 2-9. Variables include the home position (advanced, retracted) andthe intermediate stops, in accordance with technical requirements. The result iseither a full cycle or a half cycle with an intermediate stop. In all cases, modularcomponents allow all the variants to be assembled and controlled easily.

The dynamic characteristics of a handling device are influenced by the movingmasses involved. Attempts are made to keep these as low as possible. The mainsource of mass is travelling drive motors. In the case of the handling unit inFig. 2-9, for example, the vertical drive must be constantly moved backwardsand forwards. The dead weight to be moved may even be larger than the pay-load. Clever inventors have accordingly come up with traversing drives. Theseare drives where the motors for all axes are fixed to the machine frame and donot move. Fig. 2-10 shows a handling device in which the required electricmotors (5-phase stepping motors) are fixed in position. The motion for thevertical stroke is transmitted to the slide via a slotted shaft.

25

2.3 Advantages of moderndesign

Fig. 2-9:

Standard cycles may be

variable.

H Home position

(initial position)

Z Intermediate stop

(waiting time)

Fig. 2-10:

Linear positioner

of boom-type design

(Berger Lahr/Positek)

Page 27: Pneumatic Pickplace

Is it possible to do this with pneumatic drives? It must first be said that the pro-blem is greater with electric motors, since these are heavier than pneumaticcylinders. But it is also possible with pneumatics, as Fig. 2-11 shows. Aswivel/linear drive is used in this case, with an additional slide and rack-and-pinion drive running on a round-section guide parallel to the piston rod.

The ability of a pick-and-place device to move is often specified as a degree offreedom. What is this? To be exact, it is a question of the degree of freedom ofthe transmission system. In view of the fact that this can be problematic, thepreferred way of quoting degrees of freedom even for robots is as the “Numberof moving axes”.

The degree of freedom F of a transmission system within a kinematic chain is

the number of driven axes which can move independently of one other. The

maximum degree of freedom for a workpiece is F = 6; in the case of a kinema-

tic chain, however, this number may be more.

Any technological task always requires a certain degree of freedom. This can beprovided in its entirety by a programmable handling device, or else certain moti-ons can be assigned to peripheral devices. Fig. 2-12 illustrates in schematic forma fact which is important in connection with use of pick-and-place devices:

The golden rule of handling technology is that degrees of freedom can be re-

distributed from one device to another. Any function which is omitted from a

handling device must be provided in the periphery.

2 Modular design26

Fig. 2-11:

Variant of a swivel/linear

drive (Festo) built up to form

a low-mass pick-and-place

device for small workpieces

1 Guide

2 Slide

3 Lifting tube with teeth

4 Suction cup

5 Drive pinion

6 Swivel/linear unit

7 Base clamping plate

Page 28: Pneumatic Pickplace

2 Modular design

If, for example, the periphery includes workpiece magazines on a sliding orcross-table, the requirements placed on the handling device become less, and it may be possible to use a cheaper pick-and-place device. The principle is torelocate motion axes in such a way that they can be implemented in thecheapest possible way. This decision naturally depends heavily on the degree of flexibility which will be required in the future.

We can explain this with the following practical example: Thin disks are to beremoved from a workpiece carrier magazine and set down on a workpiece carrierevery time at the same place (Fig. 2-13). The handling device has the degree offreedom F = 2, while the slide table has F = 1. A positioning axis is sufficient inthis case to cover the two-dimensional pattern of the pallet. The slide table isindexed line by line against external intermediate stops. In view of the fact that avery short stroke (10 to 30 mm) is sufficient to remove the disks from the maga-zine, a lifting axis was not used and instead a lifting-piston suction cup was cho-sen. When the vacuum is switched off, the lifting piston is advanced by springforce. Once the suction cup has established contact with the workpiece andvacuum has built up, the workpiece is held in position and the lifting piston tra-vels smartly back into its initial position without the need for a special controlsystem. The workpiece is held in place until the vacuum is switched off.

27

Fig. 2-12:

Degrees of freedom F can be

relocated from the handling

device to the periphery and

vice-versa.

Robot Periphery Robot Periphery

Page 29: Pneumatic Pickplace

The reason for the popularity which modular handling devices have achieved isthe high performance which they offer and the fact that they are available imme-diately as stock items. This ability to construct even complex installations in ashort time is something which the automation engineers of 20 years ago couldonly dream of. Today, on the other hand, a comprehensive arsenal of modularcomponents is available.

There is also a not inconsiderable demand for automation in the periphery ofrobot workstations, and not just for the sorting, feeding and magazining ofworkpieces. Pick-and-place devices are now also used to “fetch and carry” forindustrial robots.

Example: In the production of composite plastic/metal workpieces, the robotoperates the machine by removing finished workpieces but also by fitting theinserts into the injection-moulding machine. In the periphery, the metal work-pieces are sorted and separated. There is thus a clear division between thehandling operations resulting from a changeover of moulding tools and theconstant actions to feed the metal workpieces.

To sum up – what’s so interesting about modules? We can list the advantages inbrief as follows:– Fast short cycle times– No redundant function providers, since devices can be assembled as required

for a given task– Clear and tidy configuration– Unlimited range of applications, both inside and outside machine construction– Relatively unaffected by machining chips– Different series available, offering various performance levels– Well-proven reliable function units– Good availability of spare parts– Both electrical and servopneumatic axes are available for positioning

operations.

2 Modular design28

Fig. 2-13:

Covering two-dimensional

patterns with a pick-and-

place device

1 Transfer system

2 Workpiece carrier

3 Rotary unit 90°

4 Magazine

5 Linear unit with inter-

mediate stops (not visible)

6 Roller strip

7 Positioning axis

8 Lifting suction cup

9 Swivel arm

Page 30: Pneumatic Pickplace

2 Modular design

A body can be brought into any desired position in 3 dimensions by 3 shifts and3 rotations. Translation and rotation are thus basic motions, and we shall there-fore use a selected example to explain typical devices which provide thesefunctions. From the kinematic point of view, by the way, a screw motion can betaken as a generalised representation of these motions. If the “screw pitch” iszero, we have the special case of a rotary joint, while if the pitch is infinite, weobtain the special case of a sliding joint.

Modern linear units provide much more than just a to-and-fro motion of a rod.We shall take the Festo HMP linear module as an example. The sub-systems areshown in simplified form in Fig. 2-14. We see the following:

Drive system (Fig. 2-14a)

A differential piston runs in a double-walled cylinder. The compressed air supplycan thus be fed from one end.

Guide system (Fig. 2-14b)

The drive and guide are separate. A tube runs on backlash-free ball-bearingguides. This guide system ensures minimal deformation under load and has ahigh load-bearing capacity. The piston rod and guide are linked by a coupling(self-aligning rod coupler). This avoids lateral forces at the pneumatic cylinder;forces of this kind may result from even very small spacing and parallelismerrors.

Stop system (Fig. 2-14c)

This serves to define both the travel distance and stroke position. Easily-adjust-able stop discs are provided for this purpose. In the interests of long service lifeand smooth running, hydraulic shock absorbers are fitted, against which thethreaded spindle strikes when the position in question is reached. The shockabsorbers also have the task of keeping the settling times in the end positionsshort and preventing rebounding. It is not necessary to re-adjust the shockabsorbers after the stop discs are re-positioned.

Sensor system (Fig. 2-14d)

The controller requires acknowledgement signals when a certain position is rea-ched. In order to obtain these, electronic proximity sensors can be inserted intoslots provide for this purpose. The switches are tripped magnetically.

Intermediate stop system (Fig. 2-14e)

Linear units for pick-and-place operation are in many cases today able to acceptintermediate stops. In our example, up to 3 wing-shaped stop cams can be fittedto the threaded spindle. These stops are activated by a pneumatic rotary unitmounted on the inner wall of the housing. Depending on the rotary position ofthe intermediate stop (i.e. the position of the spindle), the stop is either over-travelled or stops the motion (Fig. 2-15).

29

2.4 General design of basicunits

2.4.1 Function of a linear unit

Page 31: Pneumatic Pickplace

Locking system (Fig. 2-14f)

In some applications, it is advantageous to be able to lock the motion unit. A rodclamping unit can be installed for this purpose. This consists of a clamping unitand a clamping rod which travels in and out. The principle is shown in Fig. 2-16.The unit is designed to provide clamping by means of a spring in the case of acompressed air supply failure. The effect of the spring is to force the clamp jawsapart, causing these to act as wedges and lock the clamping rod in place.

Since even with a maximum equipment level, all these sub-systems are inte-grated, the result is a very compact unit of attractive design.

2 Modular design30

Fig. 2-14:

Sub-systems of a modern

linear unit (Festo)

a) Drive system

b) Guide system

c) Stop system

d) Sensor system

e) Intermediate stop system

f) Locking system

1 Double-walled power

cylinder

2 Compensating coupling

3 Flange plate

4 Roller bearing

5 Guide profile, guide tube

6 Stop/shock absorber

7 Yoke stop

8 Stop disc

9 Threaded rod

10 Sensor

11 Rod rotary unit

12 Intermediate stop

13 Clamping unit

14 Clamp rod

15 Housing

Fig. 2-15:

Example of an intermediate

stop (HBM; Festo)

1 Zwischenanschlag

2 Gewindestange

3 Gabelanschlag

Stroke

Stroke

Page 32: Pneumatic Pickplace

2 Modular design

There are also other stop systems, as a further example will show. The stopsystem shown in Fig. 2-17 is a linear unit with a rodless power cylinder andexternal intermediate stops. This could be a gantry configuration or axis 1 of asmall multi-axis handling device close to the ground. Any desired number ofintermediate stops can be fitted, as long as sufficient space and travel are avail-able. In the example shown, the intermediate stop (Fig. 2-18) can be set up to beoperative from the left or right.

31

Fig. 2-16:

Principle of locking device

(Festo)

1 Button for manual release

of clamping

2 Pneumatic piston

3 Clamp piece

4 Clamp rod

Fig. 2-17:

Stop system for a linear unit

1 End stop

2 Intermediate stop

3 Rodless power cylinder

with integrated guide

4 Shock absorber

5 Slide

Fig. 2-18:

Example of an intermediate

stop system

1 Short stroke cylinder

2 Stop slide

3 Shock absorber

4 Shock absorber mounting

5 End stop block

6 Fine adjusting screw

7 Slide

Stroke

Stroke

Page 33: Pneumatic Pickplace

There are, however, limits to how close together intermediate stops can befitted, even with a flat cylinder as a drive. The smallest spacing is governed bythe width of a stop. If closer spacing is required, a second track for intermediatestops must be provided. This can be seen in Fig. 2-19. In this way, the number of different motionsequences can be considerably expanded. This requirement is, however, unusualin pick-and-place applications. It is nonetheless advantageous to have highaccuracy for all positions.

How are the motion units now controlled?For technical reasons, the linear unit shown in Fig. 2-14 allows only motioncycles between the end stop (E) and intermediate stop (Z). The unit must there-fore return to its end position in each case. Since the motions occur at highspeed, this is not necessarily a disadvantage if there are no technologicalreasons against this. Fig. 2-20 shows the sequence for a sample cycle. 4/2-wayor 5/2-way valves can be used to good effect for control purposes.

2 Modular design32

Fig. 2-19:

Example of a twin-track stop

system

1 Shock absorber

2 Intermediate stop

Fig. 2-20:

Sample cycle for motions bet-

ween end stop (E) and inter-

mediate stops (Z)

a) Motion sequence

b) 4/2-way or 5/2-way valve

A, B Lines to cylinder

Stroke

Page 34: Pneumatic Pickplace

2 Modular design

The stop system shown in Fig. 2-18 also permits a cycle in which the slide movesfrom one stop to the next. The slide remains under pressure when it halts at theintermediate stop. If it is now desired to have the slide travel to the next stop,the pressure of the slide against the stop must first be released, since otherwiseit will not be possible to withdraw the intermediate stop. There are two ways ofdoing this:

– No-pressure conditions can be established on both sides of the piston of therodless cylinder by using the open mid-position of a 5/3-way valve (Fig. 2-21). A disadvantage is that the air is then lost, i.e. the throttling isinoperative during further travel.

– System pressure is built up on both sides of the piston. Due to the fact thatthe piston areas on both sides are the same, the resulting pressure on theintermediate stop is zero. This can be controlled by a 5/3-way valve or acombination of two 3/2-way valves (Fig. 2-22).

33

Fig. 2-21:

Sample cycle for travel from

one intermediate stop to

another

Fig. 2-22:

Control of travel from one

intermediate stop to another

using one 5/3-way valve or

two 3/2-way valves

A, B Cylinder supply lines

Page 35: Pneumatic Pickplace

There are of course also other stop systems. Instead of extending slides, it ispossible, for example, to use a swivelling intermediate stop. In the solutionshown in Fig. 2-23, the slide travel can be shortened by activating the rotary unitand swivelling a “length piece” into position. The length in question can beprecisely adjusted. The rotary unit travels together with the slide. In view of thefact that the air supply line also travels, this solution is practical only for shorttravel distances.

Rotary units are no less important than linear units. Production automationsystems chiefly require angles of rotation of 360° or smaller, more rarely up to375°. Roughly half of commercially-available rotary units have ratings up to5 Nm. Very frequently motion is only between end positions, with cushioning atthese positions as standard. The most important designs with pneumatic driveare shown in Fig. 2-24. These are:

Rotary-vane type, double-acting, for angles from 0 to 270°. A mechanical free-wheel can be added to allow indexing in angle steps.

Toothed piston system: The piston motion is converted into a rotary motion by arack-and-pinion gear unit.

Rotary cylinder, double-acting. The piston motion is converted into a rotarymotion by a slot cam in the skirt of the piston. The cylinder is equipped with per-manently-installed rollers. The output drive shaft also has a cam/roller systembut with an opposite pitch. The two angles of rotation thus accumulate.

Twin-piston rotary drive for angles from 0 to 360°. The linear motion is onceagain converted into a rotary motion by a rack-and-pinion mechanism.

2 Modular design34

Fig. 2-23:

Swivel stop

1 Slide unit

2 Rotary unit

3 Swivel arm

4 Fine adjusting screw

5 Stop

6 Shock absorber

7 Bracket

2.4.2 Function of a rotaryunit

Stroke

Page 36: Pneumatic Pickplace

2 Modular design

It is important with the rack-and-pinion systems that these should be free ofbacklash in the various positions. Even a small amount of backlash in systemswith rotary arms can lead to large arc position errors. External locking compo-nents can of course be fitted (bushing + pin, wedge slot + slide), but this makesthe installation more expensive. There are 4 ways of achieving freedom frombacklash:

Conical toothing and axial shift between the pinion and rack, for example byspring force.

Radial pressure on meshed components. If spring force is used to press the rackonto the pinion, this requires appropriate freedom of movement for the rack.

Bracing of the gear rack.

In devices with double toothed pistons (Fig. 2-24d), the motion sequence isorganised in such as way that only one toothed piston is in its end position atany given time. The other toothed piston can move freely against the pinion andtension this.

Division of gear rack into two parallel parts braced against the pinion.

Fig. 2-25 shows an example of this last case. This provides freedom from back-lash only at a defined position, which is sufficient. The centre clamp piece is fit-ted loose. On impacting a shock absorber (stop), the system tensions andclamps the pinion. This also works with intermediate stops. The illustration doesnot show all the necessary design details.

35

Fig. 2-24:

Principles of a number

of rotary drives

a) Rotary vane

b) Toothed piston

c) Rotary cylinder

d) Twin toothed piston

Page 37: Pneumatic Pickplace

Some pneumatic rotary drives can also be equipped with intermediate stops.Pick-and-place applications seldom require more than 2 additional stop points.Fig. 2-26 shows a rotary unit which offers a centre position in addition to its twoend positions. The stops required for this are fitted to an auxiliary pistonsystem. The centre stop is activated by advancing this piston. A 3/2-way valve isused for control purposes, and a 5/3-way valve to drive the toothed piston. Thecentre position can be adjusted precisely. The centre stop takes the form of asupplementary module for a 2-position rotary unit.

2 Modular design36

a) b)

5

3

4

1

2

Fig. 2-25:

Divided gear rack to compen-

sate for backlash (Montech)

1 Rotary axis

2 Centre section of gear rack

3 Toothed piston

4 Shock absorber

5 Pinion

6 Stop lug

Fig. 2-26:

Pneumatic rotary drive with

additional centre position

(Festo)

a) Operating principle

b) Control

1 Actuator

2 Piston to activate stop

function

3 Toothed piston

4 Pinion

Page 38: Pneumatic Pickplace

2 Modular design

With the following solutions, too, stop pistons play a decisive part. The rotarydrive shown in Fig. 2-27 provides a total of 4 positions: each piston is single-acting, the toothed pistons are coupled via the pinion. The diameters aredimensioned in such a way that sufficient holding force remains in the inter-mediate positions.

If there is a requirement for the diameter of the stop piston to be no larger thanthat of the toothed piston, the necessary piston area must be divided betweentwo pistons. This case is shown in Fig. 2-28. The stop piston unit can be fitted onone side (giving 3 positions) or both sides. Retrofitting is also possible. If unitsare fitted on both sides, however, the result is quite bulky. Large interferenceedges may in particular impair usefulness as a rotary gripper axis.

37

Fig. 2-27:

Principle of a pneumatic

4-position rotary drive

1 Toothed piston

2 Stop piston

p Compressed air

Fig. 2-28:

Rotary unit with 2 inter-

mediate stops (Montech)

Page 39: Pneumatic Pickplace

Motion units can, however, take unconventional forms, as we shall see in con-clusion. Design rules, as we know, change with time. What was good yesterdaycan perhaps be done better (or at least differently) tomorrow when newcomponents emerge. This is true for pneumatics when we consider pneumaticmuscles.

Pneumatic muscles imitate the principle of contraction used by natural muscles.They are membrane contraction systems which behave in a similar way topressure hoses. Fig. 2-29 shows an historical example of a rubber-segmentmuscle developed by McKibben (USA) in the 1950s as an actuator for aprosthetic arm. The muscle consists of a rubber tube to the walls of which non-elastic threads are attached along the sheath line.

Since muscles of this kind can develop only tractive forces, two actuators arerequired in order to obtain a strong return action. Living beings have similarmuscles, for example to stretch and bend their arms. Given a suitable configu-ration, a handling arm can be created, as shown in principle in Fig. 2-30. Theangle of rotation can be controlled by means of the air pressure. For precisemotions, however, an external displacement encoder is required. Festo is nowoffering a “Fluidic Muscle” of this kind. This operates on familiar principles buthas been made suitable for industrial use with the most modern materials andproduction methods.

2 Modular design38

Fig. 2-29:

Prosthetic arm with rubber-

segment muscle as designed

by McKibben (USA)

Rubber muscle

CablesProsthetic hand

Page 40: Pneumatic Pickplace

2 Modular design

Modular motion units are like ants without an anthill. We need a number ofauxiliary components in order to be able to produce any kind of assembly. These are used to create frames.

Frames are the basic modules of machines and form the first link in a kine-

matic chain on which motion units are then mounted.

The most important sub-systems of frames are:

• Base components (profile columns, base plates and brackets)• Basic kits (base, foot, connector and adapter brackets for the mounting and

connection of columns, plates and motion modules, including bolts and capnuts).

• Component kits (direct, parallel and right-angle dovetail connectors formounting linear modules)

• Fine-adjustment kits (aids for the precise adjustment of linear modules onconnector brackets)

• Adapter kits (for mounting components on mini-slides and drives)• Installation components (cable/tubing conduits, distribution boxes, cable

ducts, connector components, etc.).

For the actual frame itself, the foundation of a handling unit which absorbsforces and discharges these into the floor, high-strength precision aluminiumprofiles have proved very suitable. These have a natural or black anodised finishand are scratch-resistant and corrosion-protected. The reason for the rapidgrowth in the popularity of these systems is that even complex structures can beproduced without machining. Profile slots can be used in a variety of ways, forexample to lay cables and tubing, or to secure structural components andcontrol devices. The manufacturers of profile systems generally offer all kinds ofaccessories such as hardware fittings, base feet and brackets.

39

Fig. 2-30:

Rotary drive for a handling

device with pneumatic

muscles

1 Arm with gripper

2 Tractive device for power

transmission

3 Pneumatic muscle

4 Controlled compressed air

2.4.3 Machine frames frommodular components

Page 41: Pneumatic Pickplace

To interconnect profiles, various systems are used, some of which requiremachining. Fig. 2-31 shows some of these. Dovetail clamp systems have theadvantage that they require no machining and that adjustments can be madeeven after frame assembly is complete, for example alignment to a workpiecemachining station.

Dovetail clamp connections are very strong, vibration-proof and suitable for bothstatic and dynamic use. Fig. 2-32 shows how the design of this connectionconverts tightening force into clamping force.

2 Modular design40

Fig. 2-31:

Examples of typical

connection systems

a) Profile connection

b Slot-nut connection

c) Fixing with centring bars

or bushings

d) Screw/pin connection

e) Dovetail clamp connection

Fig. 2-32:

Forces in a dovetail clamp

connection

1 Module, frame profile

2 Clamp piece

3 Clamp bolt

FS Clamping force

Page 42: Pneumatic Pickplace

2 Modular design

The purpose of an installation system is to feed energy (electrical or pneumatic)and signal to moving components. Telescopic tubes help avoid tangles of tubingbut have not been a roaring success (they are expensive and prone to trouble).Drag chains, on the other hand, have proved valuable with linear units, particu-larly with large unit or long-stroke linear modules. Fig. 2-33 shows a conduitsystem which has a side opening and can accept all the necessary cables andpneumatic tubing. This system can be used in conjunction with junction boxeswith a number of optional inlet openings, together with cable ducts and hard-ware fittings. The advantages of this solution are:

– Fast dismantling and refitting during servicing work– Quieter in operation than drag chains– Compact design– Good protective function.

What is over-determination? You will hear this term from time to time used inkinematics to describe joint pairings (guides) which have been dimensionedusing too many variables, resulting in the provision of guide properties whichare not actually needed. The guides of linear units, for example parallel rodguides, are often over-determined. Their operation is guaranteed only withinspecial dimensional tolerances, otherwise they may stick. We need not, however,worry about these, since they can in themselves be used without problems. Thedifficulty is when these are coupled to other guided components within amechanical structure. If the axes are not in perfect alignment, which is theo-retically always the case to a greater or lesser extent, the result will be increasedloading of bearings, plain guides and seals, leading to greatly reduced servicelife. Compensating devices must therefore be used for coupling, as shown inFig. 2-34. It will often be sufficient if working cylinders are suspension-mounted

41

Fig. 2-33:

Linear unit with installation

components (Festo)

2.4.4 Determination, over-determination andsynchronisation

Page 43: Pneumatic Pickplace

instead of being bolted into place. Clevis foot mountings with spherical bearingsare available for this purpose.

Another problem is the synchronisation of drives, for example with parallel linearunits, which is necessary to create cross-gantry configurations. Fig. 2-35 showsthe principle involved. In the configuration shown in Fig. 2-35a, it would bepossible to use two separate electrical drives, but it would then be necessary touse displacement encoders to continuously monitor and compensate for anypositional difference resulting from slippage or variations in coefficients offriction. In the interests of simplicity, it is better to use a torsionally-rigid shaft totransmit motion from one side to the other. In the case of pneumatic linear units,synchronised motion can be obtained by using a linking bridge.

The purpose of the configuration shown in Fig. 2-35c is not the synchronisationof motions. In this case, the drive axis (electrical or pneumatic) is combined witha non-driven guide axis. This variant is frequently selected when high torsionalrigidity is required and high moments of force need to be absorbed.

2 Modular design42

Fig. 2-34:

Avoid over-determination

of structures.

a) Rigid axis connection

is over-determined

b) Couplings to compensate

for radial and angular

alignment errors,

e.g. ±4° and ±1 mm

1 Pneumatic cylinder

or piston rod

2 Fixed sleeve coupling

3 Clevis foot mounting

4 Elastomer component

5 Compensating coupling

(self-aligning rod coupler)

6 Connected rod

Fig. 2-35:

Synchronisation of linear

motions

a) Electrical drive

b) Pneumatic drive

c) Drive with supporting

guide axis

1 Synchronising shaft

2 Guiding drive axis

3 Drive motor

4 Linking bridge

5 Slide

6 Non-driven guide unit

7 Drive axis

a) c)b)

1 2 3

5

4

2

46

7 5

Page 44: Pneumatic Pickplace

43

Technical progress and the short life of products have forced the development ofmodular working and handling units. In order to speed up the sequence, typicalin the special-machine sector, of design followed by construction and testing, itwas essential to sub-divide desired motion sequences into sub-functions whichcan be provided by inexpensive and proven function units. This has meant a shiftin emphasis away from conventional design and towards combination(planning). In the same way, control-system modules were also developed.Modular components were also the prerequisite for the development of CADsoftware, for simulation before physical manufacture and product documen-tation. Industrial robot technology and modular handling components have ledto major changes in special-machine production.

Motion units govern configuration and are selected in the main on the basis ofthe motion pattern desired for the handling task in question. There is sometimesconfusion as to how we can describe motion forms. Fig. 2-36 accordingly showstypical motions as symbols. All these motions will be encountered in handlingtechnology. A conveyor belt, for example, may execute a step motion, i.e. amotion with a rest (intermediate stop). A screw motion with rest is also used.

Example: A bolt is inserted and tightened to a defined torque. Once this isreached, the bolt is halted and then turned back by a defined angle. This auto-matically produces a defined play between the connected parts which is un-affected by any thickness tolerances.

Alternating-direction motions without rest are, on the other hand, typically usedin pick-and-place tasks.

2 Modular design

2.5 Motion patterns

Fig. 2-36:

Symbols for the major types

of motion Linear Rotary Screw

Wec

hsel

sinn

Gle

ichs

inn

Type of motion

without rest

step motion

without rest

with rest

without rest

with rest

Pilg

ersc

hrit

t

Page 45: Pneumatic Pickplace

44 2 Modular design

Handling tasks generally require several axes. If we assume 3 axes (k = 3), anyof which can be a linear or rotary axis (number of elements n) and can be alignedin any one of 3 dimensions, we find the following number V of configuration vari-ants:

V = nk = (2 x 3)3 = 216 variants.

We certainly do not need to consider all 216 of these, since some kinematicchains are not usable for handling purposes, for example because they do notcover any working area or have a separate identity in kinematic terms only intheir designation. However, the choice of practical possibilities is still large, andthe more commonly used configurations are shown in Fig. 2-37 in schematicform. These can all be assembled from modular components. We can state thefollowing as proportions of total applications: Variant 2 approx. 50%, variant 2/1approx. 10 to 15%, variant 4 approx. 3%, variant 6 approx. 15 to 20%, variant6/2 approx. 5%, variant 11/1 around 5% and variant 11/2 approx. 2%. Depending on the modular system concerned, the process of assembly can becarried out either directly or using adapters and more or less conveniently (interms of time and adaptation required and the range of sizes and grippersavailable).

Fig. 2-37:

Some combination variants

for linear(L) and rotary units

(D)

a Linear unit

b Cross-travel unit

c Rotary or swivel unit

A Axis

Page 46: Pneumatic Pickplace

45

We will of course first consider whether compact units which offer precisely thedesired motion pattern are available commercially. The difficulty is that we mustalways consider the whole task. The selection of variant will be strongly influen-ced by the gripper system required. To illustrate this, Fig. 2-38a shows a numberof configuration variants for grippers. Double grippers, for example, mayproduce time advantages in assembly and feed operations. This of course callsfor a rotary axis, which in turn increases the moving mass and thus influencesthe choice of the size of the associated unit (performance data). Modular assem-bly has the further advantage over compact units that the individual units can beselected and combined on the basis of the required performance.

Fig. 2-38b also shows an application of a parallel gripper configuration, whichthus becomes a transfer gripper device. This is used for an indexed assemblysequence involving several stations. The grippers execute a open rectangularcycle to transport the base workpieces step by step from one station to the next.The handling unit can be assembled almost entirely from a modular system. Ifwe assume that the assembly operations involve press-fitting and screwing,which are also possible by pneumatic means, we see that it is possible toproduce this whole small production device using only one type of energysupply.

The next example is a machine feed device. If, with variant 4 from Fig. 2-37, themain axis is placed horizontally, or variant 11/1 is used, this allows a simpledouble-arm loader to be created from modular units. As Fig. 2-39, shows, themotion modules are located at the top of the machine tool. The rotary unit mustprovide 3 positions. The mid-position is used to park the double arm during themotion. The feed sequence is simple:

2 Modular design

Fig. 2-38:

Configuration variants

for grippers

a) Disc, turret and crown

turret configurations

b) Grippers combined to form

transfer gripper device

1 Mounting disc

2 Swivel unit

3 Disc segment

4 Parallel-jaw gripper

5 Twin linear unit

6 Short-stroke unit

7 Mounting plate

8 Workpiece

9 Distributor

M Assembly operation

Page 47: Pneumatic Pickplace

46

Fig. 2-39:

Feeding an automatic lathe

with a double-arm loader

1 Swivel/linear unit

2 Workpiece

3 Output channel

4 Feed channel

5 Three-jaw gripper

6 Double arm

7 Machine tool

2.6 End-position cushio-ning

2 Modular design

– Gripper G1 in magazine position, G2 in rotary chuck position,– Linear motion: Gripping of blank with G1, gripping of finished workpiece

with G2,– Linear stroke: Lifting-out of workpieces– Swivel: G1 to chuck, G2 to output channel– Linear motion: Pushing in workpieces– Open grippers, return stroke motion– Swivel to park position– Finally, start of workpiece machining.

Despite the complexity of this sequence, all that is required is two linear endpositions and three swivel-arm positions.

Every motion must be stopped in a controlled way, even under varying loadconditions. Hard impacts against fixed stops are prevented by shock absorbers.These should act in a way similar to a human hand which catches a ball andadapts to the speed and mass of the moving object concerned, bringing this to asmooth and even halt. Deceleration should not begin abruptly, and the end ofthe stopping process should be reached without rebounds or a long settlingperiod. The technical devices which can be used for cushioning have varyingcharacteristics. Typical curves are shown in the overview in Fig. 2-40.

Page 48: Pneumatic Pickplace

Fig. 2-40:

Deceleration force curve

for various braking devices

1 Pneumatic end-position

cushioning (air buffering)

2 Coil or rubber spring

3 Shock absorber with pro-

gressive action

4 Industrial shock absorber

5 Hydraulic cushioning cylin-

der

47

Springs and buffers provide a braking effect with a steeply rising characteristicand tend to store energy more than they absorb it. This leads to rebound effectsand to considerable component load.

Hydraulic cushioning cylinders of the simplest design have an effect whichbegins very abruptly. This peak resistance at the start of the stroke then reducesrapidly, which means that most of the energy is absorbed in the initial phase.This leads to braking forces which are higher than necessary.

Pneumatic end-position cushioning cylinders achieve their maximum brakingforce at the end of their stroke, which means that most of the kinetic energy isabsorbed at this point. This may lead to considerable component load, depen-ding on the mass and speed involved.

Industrial shock absorbers are based on the concept of absorbing the entireenergy with a constant rate of retardation and no jolts or rebound. The loadplaced on machine components is low, due among other things to the “soft”interception of the mass at the start of the stroke.

Fig. 2-41 shows a comparison of two typical shock absorbers. The area belowthe force/displacement curve represents the work required by the brakingoperation (Fig. 2-41a). If we assume that the areas are of the same size, then wecan see in Fig. 2-41b that the industrial shock absorber achieves a braking timeapprox. 60% shorter than that of a simple hydraulic shock absorber. Industrialshock absorbers are therefore also frequently used in handling technology.

2 Modular design

Kraf

t

Bremsweg

1

2

3

4

5

Deceleration distance

Forc

e

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48 2 Modular design

Shock absorbers with a progressive characteristic have been developed in anew series (YSRW) by Festo for its HMP and HMPL motion units. These shockabsorbers have a soft initial action. Fig. 2-42 shows a comparison between thecharacteristics of the YSRW and the previous type of standard shock absorber(self-adjusting, hydraulic, with return spring). It can be seen that, due to the pro-gressive from of the force/displacement characteristic, the increase in brakingforce per displacement element dF/ds is significantly smaller. The new shockabsorber thus operates with lower cushioning forces compared with theprevious type of shock absorber (while providing the same performance with thehigher cushioning forces permissible under full load) and also has a greaterreserve against “bottoming-out”. At the same time, the progressive shockabsorber reduces initiated oscillations.

Kraf

tBremsweg Bremszeit

Ges

chw

indi

gkei

t

a) b)

1

2

1

2

t1 t2

Fig. 2-41:

Comparison of simple

hydraulic shock absorber 1

and industrial shock

absorber 2

a) Force/displacement

characteristic

b) Speed/time characteristic

Fig. 2-42:

Force characteristics for

different shock absorbers

(Festo)Shock absorber

Distance

Forc

e

Shock absorber

YSR-…-C YSRW

Page 50: Pneumatic Pickplace

49

Shock absorbers can generally also be used as stops, as in the case of thepower cylinder in Fig. 2-43. The shock absorbers are fitted externally in this case.In selecting shock absorbers, ensure that the following values are not exceeded:

– Maximum permissible energy absorption– Maximum permissible residual energy – Maximum impact force at end position.

In order to do this, it is necessary to know the conditions present at the time ofimpact, namely the force, equivalent mass and impact velocity. With thesevalues, we can use graphs to select a suitable shock absorber. A further checkmust be made to see that the selected shock absorber can handle the desiredvolume of cushioning work per hour, since the absorbed energy has to bedischarged to the atmosphere as heat.

Example: Let us assume a working cylinder which is use to move a mass m witha force F horizontal to the end stop (shock absorber activated; Fig. 2-44). In aseries of working steps, we find the characteristic data which we need to select a shock absorber. There are also computer programs which do this. We can thensee from the technical documentation which shock absorber is suitable. Wemust then of course also check whether this can be accommodated within themechanical configuration so as to be easily accessible.

2 Modular design

Fig. 2-43:

Linear unit with shock

absorbers

1 Piston rod

2 Yoke plate

3 Stop and fine adjusting

screw

4 Shock absorber

5 Pneumatic cylinder

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50 2 Modular design

If the operating conditions are different from those assumed in Fig. 2-44(inclined position, swivel lever or rotating disc), the formulae must be modifiedaccordingly. Suitable software is available for this. Fig. 2-45 shows the screenmask for the program in question.

Fig. 2-44:

Example showing the

principles of the method used

to select shock absorbers

Fig. 2-45:

Screen mask for “Shock

absorber selection” program

Performance tables and graphs

Kinetic energy

W = v2m/2Work resulting from drive force WA

WA = F s

Total cushioning work WGes

WGes = W + WA

Equivalent mass mE

mE = 2 WGes/v2

Cushioning work per hour Wh

Wh = WGes m

Cushioning

type + size

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51

There are, however, other ways to achieve a fast but controlled approach to endpositions. Let us assume that a linear module is being used as a gantry slide andthat assembly workpieces need to be brought from peripheral buffer locationsinto the working zone. The time taken for the feed motions, which are not alwaysshort, affects the cycle time which must be allowed for the assembly station as awhole. A major factor is to approach the end position quickly but gently. Adynamically sophisticated solution is shown in Fig. 2-46 and includes an end-position controller. This not only provides smoother operation but also savestime. The end-position shock-absorbers, which would otherwise be heavilyloaded, can be eliminated. With a moving mass of, for example, 30 kg, the timerequired to travel a distance of 1200 mm is no more than 1 second. The peakspeed for 3 m/s is attained only briefly. The controller requires inputs for anumber of system parameters such as moving mass and the geometrical data for the pneumatic cylinder. The controller then learns the travel distance, guaran-teeing a precise end position even if the mass and load cycle change. Therepetition accuracy is 0.01 mm.

2 Modular design

Fig. 2-46:

Smart Soft Stop system

(Festo)

1 Linear potentiometer

2 End-position controller

3 Adjustable end stop

4 Proportional 5/3-way valve

Page 53: Pneumatic Pickplace

52 3 Positioning technology

Yesterday’s technology is the foundation of today’s. Nowhere is this more truethan in mechanical engineering and pneumatics. Since the time of Heron ofAlexandria (around 75 AD), pneumatics has been part of an engineer’s training.Today, a supply of compressed air is available in every factory, and pneumaticdrives are simple and inexpensive, giving faster motions and very precise posi-tioning in the case of motions against fixed stops. But how can we obtain precisepositioning at “halfway” points, despite the compressibility of air? When shouldwe choose electromechanical positioning axes instead?

For many handling tasks, industrial robots are unnecessary, since a simple pick-and-place unit can offer sufficient functionality. This fact has encouraged thedevelopers of motion units to provide not just an unchanging back and forthmotion between two stops but also a facility to approach any desired positionsunder program control. Axes of this kind are often referred to as positioningaxes. If we combine axes of this kind to form handling units, these will oftenprovide solutions which are technically fully adequate and cost-effective.Desired positions can be reached by two methods:

– Open-loop control– Closed-loop control.

An open-loop-controlled axis (Fig. 3-1a) executes a specified path or angle with-out checking whether the target position has actually been reached accurately.For example, a stepping motor receives a command to turn its rotor through anangle of 2592 degrees. In the case of a spindle connected to the motor withoutintermediate gearing and with a pitch of 3 mm, this will means that the axis slidetravels a distance of 2592 x 3/360 = 21.6 mm. Positioning errors are not detec-ted and thus also not corrected. If, on the other hand, the axis is operated with aclosed-loop control (Fig. 3-1b), the programmed setpoint and the instantaneousactual value are constantly compared with each other. The axis stops when thesetwo values agree. In order to do this, we need a displacement encoder and acomparator. This configuration is also known as a closed-loop position controlcircuit. In order to make the axis control process more dynamic, it is also possi-ble to measure the electrical current consumption and speed and include thesevalues in the closed-loop control process. We then have inner, middle and outerclosed-loop control circuits and therefore speak of a cascade control. In princi-ple, any number of positions may be approached within the range of motion ofan axis, and these positions may lie very close together.

3

Positioning technology

3.1 Freedom of pro-gramming

Page 54: Pneumatic Pickplace

53

Accuracy depends on the step size of the encoder, i.e. its resolution. The size ofthe smallest position change which can be detected governs how accurately aposition can be reached. A critical factor for users is repetition accuracy, which isthe difference between positions reached at different times in response to thesame control commands.

How can we measure distances or angles? There are many ways of doing thisand of creating measuring systems. The most important difference is betweenabsolute and relative (incremental) systems. Absolute systems always provide adistance value relative to a measuring-system zero point. Relative systems, onthe other hand, add or subtract distance quanta (increments) to or from apreviously-reached position. The distance to a zero or reference point thusresults from a computing operation. The principles of the most important dis-placement encoders are shown in Fig. 3-2. Many systems are available in bothlinear and round designs.

3 Positioning technology

Fig. 3-1:

Control of positioning axes

a) Open path of action

b) Closed-loop control

1 Stepping motor

2 Slide

3 Positioning axis

4 Programmer and controller

5 Displacement encoder

6 Servo motor

Fig. 3-2:

The major designs of dis-

placement encoders

1 Code rule

2 Graduated scale,

incremental encoder

3 Potentiometer, e.g. conduc-

tive-plastic potentiometer

4 Resolver

1. Absolut digital 2. Incremental

3. Absolute analogue 4. Phase-cyclical

Page 55: Pneumatic Pickplace

54 3 Positioning technology

If we are dealing with a rotary drive, which always incorporates intermediategearing, we can sense a gear wheel and use the teeth of this as increments.Fig. 3-3 shows an example of this. The teeth are scanned by a proximity sensor.The spindle pitch and gearing ratio can be used to calculate the distance resolu-tion which can be achieved. It is, however, not possible to detect the direction ofrotation. Further refinement is required in order to do this.

In the case of brushless DC motors, it is also possible to use the signals from therotor position encoder, which supplies data for coil switching, as the basis forposition detection. The speed, too, can be derived from this.

Conductive-plastic potentiometers for displacement encoding no longer haveanything in common with the scratchy volume controls of old radios. Thesecomponents today achieve a service life of up to 100 million strokes and haveturned into high-quality measuring systems.

Magnetostrictive displacement encoders operate by non-contact means and arealso interesting in terms of physics. We use the transit time of an ultrasonicpulse to determine the position of a slide. The principle is shown in Fig. 3-4. Theultrasonic pulse emerges from an end surface into a “guide wire”, over which apermanent-magnet system is moved by the piston (or slide). The acoustic pro-perties of the magnetised point change, causing reflection of the pulse. Themeasurement of distance is thus reduced to a measurement of time (distancebetween two pulses), which as we known can be achieved easily by digitalmeans.

Fig. 3-3:

Sensing of a gear wheel to

generate distance increments

1 Inductive sensor

2 Mounting bracket

3 Gear wheel

Page 56: Pneumatic Pickplace

55

A further factor is the way the measuring system is fitted. Some motions unitshave integrated measuring systems not visible from the outside, while otherhave external systems. Measuring systems can, however, also be fitted to anysuitable mechanical component of a machine.

Linear servopneumatic axes have been on the market since around 1985. Incontrast to hydraulics, which operates with virtually incompressible fluids, aircan easily be compressed and thus has no precisely definable volume. It wastherefore believed for a long time that freely-programmable pneumatic axeswere not feasible. However, this has changed. Development was triggered by thedemands, among other things, of assembly systems, which require very fast andaccurate positioning with small to medium load capacities.

A servopneumatic positioning axis consists of the following components:

– Pneumatic cylinder, e.g. rodless– Displacement encoder– Proportional valve– Parking brake if necessary– Axis controller.

Usable results can then be achieved only by carefully matching the individualcomponents one to another and exploiting microcomputer technology andappropriate closed-loop-control strategies. The principle of a closed-loop servo-pneumatic position controller is shown in Fig. 3-5.

3 Positioning technology

Fig. 3-4:

Magnetostrictive distance

measurement

1 Tube

2 Acoustic waveguide

3 Position encoder

4 Permanent magnet

5 Displacement during

positioning

3.2 Servopneumaticpositioning axes

Page 57: Pneumatic Pickplace

56 3 Positioning technology

These axes typically require at least a two-stage chain of action in order toproduce a linear motion with defined properties using a spindle or endlesstoothed belt. Pneumatic drives, on the other hand, are single-stage and are thusreferred to as direct drives. An electromechanical positioning axis consists of:

– A motion axis with motor, motor flange and coupling– An integrated or external displacement encoder– A power electronics unit or servo amplifier, depending on the type of motor,

designed for a single axis or multiple axes– Pre-assembled sets of cables.

Common types are spindle and toothed-belt drives, the principles of which areshown in Fig. 3-6.

Positioning axes can be equipped with various types of motors. Stepping motorsare ideal drive units for handling systems requiring motor ratings < 1 kW. Themotor is the link between digital data and an incremental motion. Very precisepositioning is possible with a resolution of, for example, 500 or 1000 steps perrevolution. Motors are accelerated in accordance with specified ramp functions.

As an alternative, servo motors can also be fitted. These are electric motorsincorporated into a closed-loop control circuit. In order to do this, the desiredtarget variables (rotary speed, position or angle) must be monitored. This ensu-res close conformity to setpoints and a highly-dynamic response to setpointchanges.

Fig. 3-5:

Principle of closed-loop

servopneumatic position

control

1 Brake

2 Proportional valve

3 Controller and programmer

4 Displacement encoder

system

3.3 Electromechanicalpositioning axes

Actual

value

SetpointNC input

Page 58: Pneumatic Pickplace

57

Positioning axes with spindle drive are the preferred choice in cases requiringmaximum accuracy and high axial thrust forces. Toothed-belt drives are a goodchoice when especially fast approaches are required to positions over longdistances.

Every user reaches a point in his/her deliberations when a final choice must bemade of a certain positioning axis. First and foremost, this must fulfil the giventechnical requirements. If there are several variants which do this, then costbecomes a criterion. As a general principle, for a given level of dynamic charac-teristics, servopneumatic positioning axes are considerably cheaper than elec-trical positioning axes. Servopneumatic axes are triggered by 5/3-way propor-tional valves with an actuating time of 5 milliseconds, ensuring a highly dynamicsystem. Pneumatic axes can achieve acceleration values of up to 10 g.

What variants are available from the Festo modular positioning system? Fig. 3-7 provides an answer in overview.

The decisive factors in the selection of a positioning axis are mass, speed oftravel, repetition accuracy and effective stroke length. An initial selection can, forexample, be made on the basis of dimensioning graphs which provide an initialresult in a small number of easily understandable steps. As a first approxima-tion, it is also possible to compare the requirement profile of the application andthe performance profile of a given item. Fig. 3-8 shows the general correlation

3 Positioning technology

Fig. 3-6:

Design of electromechanical

positioning axes

a) Axis with spindle drive,

maximum speed 1.7 m/s;

strokes up to 2 m;

positioning accuracy

± 0.02 mm

b) Axis with toothed-belt

drive, maximum speed

5 m/s; strokes up to 5 m;

positioning accuracy

± 0.1 mm

3.4 Assessment and selection

Page 59: Pneumatic Pickplace

58 3 Positioning technology

between these. Fields a to k represent the performance profile of a typical func-tion provider. The marked fields correspond to the technical data in the 3x3 tablebelow.

Fig. 3-7:

Modular positioning system

(Festo)

Fig. 3-8:

Typical performance profiles

of selected positioning axes

and guides

a) Toothed-belt drive with

Vee guide

b) Toothed-belt drive with

recirculating-ball guide

c) Ball screw drive with Vee

guide

d) Servopneumatic drive

with plain-bearing guide

e) Vertical chain drive

with Vee guide

f) Electromechanical tooth-

ed-belt drive with heavy-

duty guide

g) Electromechanical axis

with spindle drive

h) Electromechanical axis

with toothed-belt drive

i) Servopneumatic axis

with heavy-duty guide

k) Roller-ring threaded drive

with Vee guide

Level Linear speed Load capacity Repetition accuracy

High 0,5…5 m/s 100…500 N ±0,05…±0,0005 mm

Medium 0,02…0,5 m/s 20…100 N ±0,1…±0,05 mm

Low Less than 0,02 m/s Less than 20 N ±0,5…±0,1 mm

Electromechanical

Internal guidance External guidance

Internal guidance External guidance

Spindle or toothed-belt drive

Stepping or servo motor

Absolute digital Incremental

Integrated or fitted externally

Absolute – analog

Axis controller

Steu

erun

gW

egm

essu

ngA

ntri

eb u

nd F

ühru

ng

Single-axis controller Muliti-axis controller

Phase cyclic

Pneumatic

Page 60: Pneumatic Pickplace

Fig. 3-9:

Torque and force loads acting

on linear units

1 Coordinate origin

2 Guide slide or carriage

3 Profile rail

F Force

M Torque

Fig. 3-10:

Combination of pneumatic

axes to form a twin unit

(Univer)

59

In individual cases, however, we must check whether the application falls withinthe performance profile. This applies first and foremost to forces and torque andthe points at which these act. The individual loads as shown in Fig. 3-9 are usedto determine the combined load, which is then compared with the specificationsof permissible forces and torque. The data of the graphs in the applicationguidelines relates to the coordinate origin on the slide. If the actual valuesexceed the permissible operating conditions, we must consider whether we canreduces the forces and torque, for example by moving points of action closer tothe centre of gravity, or whether higher-performance guides must be used.Additional guides which provide support, such as a castor guide consisting of asupport rail and castors, can also provide a remedy.

Dynamic loads can become high with multi-axis configurations, since in thesecases the load represents a continuously changing motion system. For thisreason, linear modules are sometimes combined to form a parallel unit. Fig. 3-10shows what is meant by this. This has a gantry unit as a base axis which not onlydevelop higher motion forces but has significantly less sag in the case of largespans. The combination slide is connected free of backlash to the piston of therodless cylinder. The roller guide is an integral component of the assembly and isable to absorb high maximum torque values.

Finally, we note that the uniform design of the mechanical interfaces in thissystem (profile housings) means that electrical and pneumatic motion axes canbe combined, as can positioning and end-position axes. If, however, two types of power are used within a system, each supply must be routed and controlledseparately, which is a disadvantage.

3 Positioning technology

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60 4 Use of pick-and-place devices

In handling technology, too, the rule is – first simplify the processes, and thenautomate. Equipment which is selected too hastily rarely provides an optimumsolution. But how are we to automate? Must we use an industrial robot? Or will a pick-and-place unit do?

Sometimes not even a two-axis handling device is required. There are manyhandling operations which can be carried out with simple equipment, naturallyusing standard industrial pneumatic components. These simple devices shouldnot be underestimated – the simpler, the better. What is not present cannot gowrong. In this article, we shall look at some examples of this kind of solution.

Rotary units turn objects through a certain angle and can be used in many dif-ferent ways. For some purposes, a rotary unit can be assembled from linearcylinders. Fig. 4-1 shows an example of this. The workpieces are fed in at rightangles to the plane of the illustration and are then ejected to the left or right. In order to achieve this, three positions are required for the ejector plate. Thecentre position is produced by spring force when the two cylinders are switchedto no-pressure conditions. The achievable positioning accuracy is sufficient forthis application. Distribution functions of this kind are common in logistics ope-rations. The requirements in this case can, however, also be met by a rotary driveif this can approach three positions.

The solution sketched in Fig. 4-2 shows how a workpiece flow can be distributedas desired. The plates are transported on conveyor belts which terminate in atilting plate.Depending on the situation in the workstations, the plates are distributedequally or, if one workstation is malfunctioning, in one direction only. The rotarydrive simplifies the mechanical configuration and is inexpensive. Turning devicescan also be created in this way to accept flat workpieces in-line on a conveyorbelt and turn these through 180°. The workpiece carrier would need to be ofslip-in design in this case.

4

Use of pick-and-place

devices

4.1 Modular handlingsystems

4.1.1 Use of rotary units

Fig. 4-1:

Linear cylinders combined

to form a rotary unit

1 Workpiece, package

2 Ejector plate

3 Grooved ball bearing

as roller

4 Single-acting cylinder

5 Conveyor belt

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61

In order to use a rotary drive, we must know what its load rating is. This can befound from load graphs available for every module version. These graphs showthe mass moment of inertia, angle of rotation and rotation time. The massmoment of inertia of the components fitted to the rotary unit must be calculatedseparately. Fig. 4-3 show a sample case. It should be noted that only the adapterdisc is directly on the rotary axis, assuming that it is not an integral part of therotary drive. For all masses not on this axis, we assume point masses at adistance equal to the centre of gravity and reduce the moment of inertia to therotary drive axis. Only then is it permissible to add moments of inertia together. This procedure is known as the Steiner method.

The total moment of inertia is thus as follows:

Jtotal = JZ1 (disc) + JZ2 (arm) + JZ3 (gripper) + JZ4 (workpiece)

Jtotal = JZ1 + JS2 + m2 . r22 + JS3 + m3 . r1

2 + JS4 + m4 . r12

Using the value for Jtotal, we can now use a performance graph, for examplewith a curve for an angle of 180°, to see what rotation time is possible andpermissible. In our example, we would also have to check whether the gravita-tional forces resulting from the masses are permissible, i.e. whether in the casein question they remain below the axis load shown on the Z axis.

For the calculation of mass moments of inertia, by the way, Festo offers a con-venient program which coves various basic bodies and standard Festo com-ponents. Once the dimensions and details of materials and eccentricity havebeen input, the moment of inertia and total mass are calculated.

4 Use of pick-and-place devices

Fig. 4-2:

Distribution of a workpiece

flow

1 Rotary unit

2 Workstation

3 Conveyor belt

4 Workpiece

5 Feed line

6 Diversion line or second

workstation

Page 63: Pneumatic Pickplace

62 4 Use of pick-and-place devices

The values can be stored and printed out. Fig. 4-4 shows the screen mask usedin this program.

Fig. 4-3:

Rotary unit with swivel arm

and gripper as example of

calculation of mass moment

of inertia J

1 Rotary drive

2 Adapter disc

3 Swivel arm

4 Gripper

5 Workpiece

Fig. 4-4:

Screen mask for program

“Calculation of mass

moments of inertia”

m1

ÚSteel = 7850 kg/m3

ÚAluminium = 2700 kg/m3

Full cylinder

JZ1 = · D4 · L · Ú/32 kgm2

Block

JS = h · b3 · a · Ú/12 kgm2

Point mass, reduced

JZ = JS + mr2 kgm2

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63

The rotary arm unit shown in Fig. 4-5 roughly corresponds to the conditionsshown in Fig. 4-3. An interesting feature is the hollow shaft through whichvacuum can be fed (or compressed air if a venturi nozzle is used to generate thevacuum).

And now another example from the field of process technology. Rotary units canalso be used to good effect to control free-flowing bulk materials. An example isshown in Fig. 4-6. The trick is to place the channels in the driver drum correctly.In terms of a handling function, we are concerned here with the branching of aflow of material, with dividing a flow into sub-flows. In the case of flammablematerials, by the way, a pneumatic drive is an advantage in terms of explosionprotection. This solution could also be used to distribute small metallic and non-tangling plastic workpieces to various points by means of suction air. Manyvariants of vacuum feed units (dosing units) are commercially available.

4 Use of pick-and-place devices

Fig. 4-5:

Rotary arm unit – a Festo

classic

Fig. 4-6:

Diversion of flows of materials

1 Feed channel

2 Rotary unit for 180° angle

of rotation

3 Distributor channels

4 Driver drum

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64 4 Use of pick-and-place devices

Before we conclude our study of rotary units, let us look at a distributor of thetype used, for example, on automatic assembly lines. This separates individualworkpieces from the mass flow. We can also call this marshalling into singles.Fig. 4-7 shows a double distributor for a twin-track workpiece flow. The twodistributor slides are coupled via toothed segments to ensure synchronousoperation. We could of course also use two rotary-vane units, which would makethe mechanical design simpler but would take up more room.

There are numerous handling operations which can be carried out equally wellby complicated and simple means. This will be demonstrated by some examples.It is often necessary within packing plants to divide a flow of workpieces. Specialconveyor belts are available for this, equipped with top deflector plates whichare actuated by cams under the belt in such a way that the transported work-pieces are moved sideways. The system in Fig. 4-8 uses a guide moved by acylinder combination in the form of a 3-position actuator. This can move in afixed sequence or, under external control signals, also in a chaotic sequence. The higher speed of the outward belt section provides the necessary separationof the stream of workpieces before the distribution movement.

In stamping mills and with certain special machines, it is necessary to achievestep transport of strip material. Fig. 4-9 shows a feed device consisting of a rod-less pneumatic cylinder and two parallel-jaw grippers. There are of coursespecial feed devices commercially available, but in individual cases and withspecial machines a custom-built solution can save space. The feed motion islimited by precisely-adjustable external shock absorber stops. The gripper jawsare open on the return stroke. No provision has been made for tongs to hold thestrip material during this phase. It is assumed that during the return stroke thematerial is still held by the stamping or cutting tool. The device is controlled by

Fig. 4-7:

Double distributor for the

marshalling of assembly

components

1 Rotary-vane unit

2 Toothed segment

3 Feed magazine

4 Axis

5 Channel to assembly

machine

6 Workpiece

7 Rotary slide

4.1.2 From a single axis to a handling unit

Page 66: Pneumatic Pickplace

65

a cam on the central shaft (vertical shaft). The best time for the advance motioncan be selected by adjusting the control cam.

Rotary units can also be used to create high-performance single-axis units. Theexample in Fig. 4-10 shows a transfer device which picks up plates by means ofsuction cups and transfer this from one conveyor section to another. The cou-pling rods are able to swing through between the roller-conveyor sections.Suction cups pick up the flat workpiece. There is plenty of time for the transferoperation. The rotary drive is required to turn slowly and evenly. The angle ofrotation is less than 180°. It is not easy to produce slow speeds with compres-sed air. It is therefore not sufficient in this case to use a one-way flow controlvalve for the cylinder exhaust air. A better solution is to use two double one-wayflow control valves (Fig. 4-11). The control behaviour is better in this case, sincethe supply and exhaust air flows can both be adjusted. The slower pressurebuild-up delays the start and reduces the impact at the end positions.

4 Use of pick-and-place devices

Fig. 4-8:

Belt distributor for low

conveyor speeds

1 Feed belt

2 Workpiece (product)

3 Guide edge

4 Rotary arm

5 Mounting kit

6 Pneumatic cylinder

7 Optical sensor

Fig. 4-9:

Strip material feed using

parallel-jaw grippers

1 Tool, press

2 Strip material

3 Parallel-jaw gripper

4 Upper plate

5 Pneumatic linear unit

6 External stop

7 Control cam in press drive

Return stroke

open

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66 4 Use of pick-and-place devices

If a single rotary unit cannot deliver sufficient torque, one rotary unit can be fit-ted on either side of the coupling gear. This creates a positive mechanical linkbetween the units.

Finally, Fig. 4-12 shows a handling unit with 4 motion axes. Only axis A1, how-ever, needs to be a positioning axis. All the other axes travel only betweencushioned end stops. The handling object is a compact disc (CD). This is pickedup by suction cups, raised, swung through an angle of more than 90° andbrought to the magazine. After setting the CD down in the magazine slot, theaxis A1 withdraws the suction cups slightly. The arm then returns to its pick-upposition.

As can be seen, a large part of the handling device can be made up of familiarcomponents. An industrial robot is not necessary.

Fig. 4-10:

Transfer device for flat

workpieces

1 Coupling gear

2 Transported workpiece

3 Roller conveyor section

4 Suction cups

5 Rotary unit

Fig. 4-11:

Double one-way flow control

valve

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67

Technical progress is bringing “intelligent pneumatics” ever closer to the realmof electronics. This is opening up new applications and is making pneumaticsmore and more interesting as an means of automating assembly operations.Pneumatic units are the preferred choice, particularly in applications needingfast linear motions and where accuracy requirements are not too stringent.Economic factors of course also play a major role. Moreover, the wide range ofaccessories available for pneumatics makes planning easier and supports rapidinstallation.

There are many reasons to automate assembly work. The emphasis is of coursegenerally on rationalisation, but there are also cases, for example, of moduleswhich are so small that they cannot be assembled efficiently (or at all) by hand.In the cases of complex assembly operations, very short production runs andmodules of a non-automation-friendly design, on the other hand, manualassembly is still the only answer. Fig. 4-13 shows in general terms the situationswhich may be encountered in practice. Automation of difficult operations alwaysinvolves a higher technical risk and higher implementation costs.

4 Use of pick-and-place devices

Fig. 4-12:

Magazining of CDs

1 Linear unit

2 Short-stroke cylinder

3 Positioning axis

4 Rotary arm

5 Rotary unit

6 CD

7 Suction cup

8 Feed line

9 Magazine

10 Stopper cylinder

4.2. Pick-and-place units for assembly work

4.2.1 Man or machine?

Fig. 4-13:

Degrees of difficulty

of assembly operations Difficult for machineEasy for humans

Difficult for both

Easy for both

Easy Difficult

Easy

Ma

chin

e

Humans

Diff

icul

t

Easy for machineDifficult for humans

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68 4 Use of pick-and-place devices

We therefore need to take account of a large number of factors. In the case ofmass products, the process speed which can be achieved is very important. Inthis respect, the leader is still the cam-controlled assembly machine. The controlcams of these machines not only drive the motion units but also store distanceand angle data (program memory). Motion characteristics can be stored veryprecisely in the shape of the cam, in a durable and drift-free form. This is a bigadvantage. Transmission systems generally run in an oil bath and are thus veryquiet. Motions can be transmitted directly via linkages or angle levers to motionunits. Designers have greater freedom if freely-routable tension/compressioncomponents are used to transmit motion. This is shown in simplified form inFig. 4-14. From the point of view of working speed, pneumatic drives are insecond place. A fast SCARA robot can, however, even today manage a motionsequence (pick-and-place cycle) of 25 mm up, 150 mm across and 25 mm downin an impressive 0.32 s.

Industrial pneumatic components are often used in assembly systems, mainlyfor the following purposes:

– Drives for joining units (presses, feed devices, etc.)– Drives for metering and indexing devices and mechanisms– Drives for grippers and clamping devices– Suction air components for grippers for holding and clamping functions– Stopper cylinders– Motion units for rotary, swivel and lift/turn functions– Linear motions against a fixed or intermediate stop, and free positioning with

servopneumatic motion units.

Fig. 4-14:

Motion transmission from

control cam to motion module

using tension/compression

components

1 Slide

2 Frame

3 Gripper

4 Tension/compression com-

ponent

5 Roller/stem block

6 Control cam

4.2.2 Assembly withpneumatics

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69

The use of pneumatics will be illustrated by a number of examples.

A work module consists of a drive and guide. This module can be used for manytasks for which a robot would be overqualified. Fig, 4-15 shows a rotaryindexing machine in which pins are pressed into a receiver workpiece. In theprevious station the numerous holes for the pins are drilled. The drilling unit isaccordingly mounted on a slide, which travels from one end position to another,powered by a pneumatic cylinder.

Normally machining and assembly operations should not be carried out on thesame machine due to the chips which the former generates. Given efficient chipextraction and less demanding requirements, however, this is possible. Theadvantage is that the centre of the unit for the insertion and pressing operationexactly coincides with the centre of the drilled holes.

The assembly unit shown in Fig. 4-16 has been created from rotary modules.Receiver workpieces for an assembly operation are brought from a magazine tothe workpiece carrier of an assembly transfer system. With a crank drive, thespeed of a derived linear motion follows a sinusoidal function, which is advan-tageous during the approach to the end positions, where the speed of the slidefalls away to zero.

4 Use of pick-and-place devices

Fig. 4-15:

Drilling and assembly

on a rotary indexing table

1 Pin feed

2 Complete module

3 Rotary indexing table

4 Receiver workpiece

5 Double press-fitting device

6 Drill feed unit

7 Slide

8 Pneumatic cylinder

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70 4 Use of pick-and-place devices

In view of the fact that travel time is a major criterion in assembly operations, itmay be advantageous to use a rodless pneumatic linear drive equipped with ahigh-speed “Smart Soft Stop” system. We have already seen the principleinvolved in Fig. 2-44. The cushioning action is controlled by software, with elec-tronic control of the approach to the end position. This system is available as anequipment package consisting of a matched cylinder/valve/potentiometer com-bination and allows the travel time from position A to position B to be reducedby up to 30%. It should be noted that optimum system behaviour is obtainedonly within the cylinder stroke. The travel distance must be limited within thecylinder stroke by fixed stops (Fig. 4-17). The handling device shown in the illus-tration accepts a printed circuit board, turns this and brings in to the other endposition with a fast stroke.

Fig. 4-18 shows a further example, of an assembly station for a plastic cap. Twopneumatic components are sufficient. A parallel-jaw gripper is used as a barriermetering device. Each separated-out cap falls into a carrier and is gripped byvacuum. The swivel motion through 90° is a derived motion produced purely

1

2

3

4

5 6 7

Travel

Cylinder stroke

Fig. 4-16:

Setting down a receiver

workpiece (Festo)

a) View of station

b) Motion conditions with

crank drive

c) Handling function diagram

1 Rotary drive

2 Pusher

3 Slide

4 Column frame

5 Workpiece carrier

6 Double-belt conveyor

7 Gripper

8 Connecting rod

9 Receiver workpiece

10 Feed chute

s Distance

v Speed

Fig. 4-17:

Transfer units for PCBs

1 Workpiece (PCB)

2 Gripper jaw

3 Parallel-jaw gripper

4 Adapter plate

5 Rotary unit

6 Pneumatic linear drive

7 Fixed stop

Receiver workpiece

Workpiece carrier Set-down

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71

mechanically by a guide radius for the press head. After the press-fitting operati-on, the vacuum line is switched to blast air to assist the detachment of the capfrom the press head.

It is often necessary at the end of an assembly line to re-orientate modules orproducts, e.g. to achieve the density required for packaging or palleting. Fig. 4-19 shows a way of achieving this. A swivel drive is used as the activecomponent. No further packaging workpieces must run on during the swivellingoperation. This is achieved by means of a spring-loaded roller arm. There is noneed for special control measures for this holdback device. The outfeedconveyor consists of twin belts between which the swivel arm can sink slightlyduring the transfer operation.

4 Use of pick-and-place devices

Fig. 4-18:

Assembly of caps

a) Transfer of assembly

component from magazine

b) Push-in assembly

1 Magazine

2 Assembly workpiece

3 Press head

4 Gripper as metering device

5 Metering pusher

6 Piston rod

7 Vacuum line

8 Transfer chain with work-

piece carriers

9 Receiver workpiece

10 Press head guide

11 Pneumatic cylinder

Fig. 4-19:

Setting up packaging

workpieces as a preparation

for packaging

1 Infeed and outfeed zones

2 Packaging workpiece

3 Holdback device

4 Rotary module

5 Conveyor belt

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72 4 Use of pick-and-place devices

Assembly with a pick-and-place unit or robot can generally be carried outefficiently only if the components for assembly are presented in the right way.This will be illustrated by an example. This involves the fitting of shaft retainingcirclips. The clips are first fed from a magazine by a pusher (Fig. 4-20). A three-finger gripper is then activated to open the circlip out to the external diameter ofthe shaft in a servopneumatic spreader station. The handling device transfersthe ring in this spread state. A wedge is inserted in the ring gap to maintain thespread. The assembly robot can now bring the circlip into the assembly positionand release the holding mechanism. The circlip now snaps into its slot. Thedegree of spread can be taken almost to the limit of plastic deformation by apressure regulator but must under no circumstances reach this limit. Thissophisticated spreading operation will be used only for the assembly of safety-critical modules.

Another kind of assembly workpiece feed device is shown in Fig. 4-21. The work-pieces are contained in box magazines which are fed head-down into the feedmagazine. They are emptied in stages. After passing through the machine, theempty magazine pallets are pushed into a collector magazine, in which they areformed into a stack. As the magazine pallet is divided into rows and columns, acorresponding number of feed tracks are arranged one behind the other.

4.2.3 Peripheral helpers

Fig. 4-20:

Feeding shaft retaining

circlips

1 Industrial robot

2 Fitting head

3 Magazine for circlips

4 Feed pusher

5 Three-finger gripper

6 Gripper finger

7 Lifting plate

8 Spreading-force regulator

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73

These examples of applications show that the necessary auxiliary motions canbe produced to good advantage using pneumatic components.

Finally, let us consider an example of the feed and assembly of small flat work-pieces. As Fig. 4-22 shows, the workpieces are stored in an inclined gravitymagazine. A pneumatically-driven metering device separates the workpieces,which are then swivelled into the feed position. This is achieved by a rotary-vanemodule. Once they reach a horizontal position, the workpieces are pushed intothe working zone (at right angles to the plane of the illustration) by a pneumaticlinear unit. In certain cases, this motion may form the assembly operation itself.

4 Use of pick-and-place devices

Fig. 4-21:

Magazine feed

1 Pressure weight

2 Magazine shaft

3 Magazine pallet

4 Assembly workpiece

5 Guide wheel

6 Magazine plate

7 Empty pallet

8 Holdback device

9 Ratchet pusher

Fig. 4-22:

Feeding flat workpieces

a) Separation operation

b) Pushing away

1 Gravity magazine

2 Rotary-vane drive

3 Swivel device

4 Insertion device

5 Flat or miniature cylinder

6 Workpiece

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74 4 Use of pick-and-place devices

Workpiece handling is a core problem in automated production systems. Whatmakes it difficult is the great variety of shapes, sizes, masses and degrees ofrobustness of workpieces coupled with the frequent need to set these downaccurately in confined spaces. In general terms, it is necessary to carry out twotasks:

– Automatic manipulation of workpieces and– the integration of this procedure into the control system for the fed machine,

including sensor monitoring of all actions.

A typical example of this is the “iron hands” which were installed at the start ofthe 1950s in the metalworking industry on sequences of presses. Today, a largenumber of automatic and manually-controlled loading and feed devices areavailable, covering a certain spectrum of applications.

Even today, there are some machines and systems which are fed by hand. Thismay sound surprising in view of the present state of technical development.There are, however, many reasons for this in individual cases:

– Workers can carry out visual inspections, which means that they cannot beeliminated even with automatic feed.

– The material in question is difficult to handle and would cause an unaccept-able level of malfunctions if handled automatically.

– There is a frequent need to change workpiece types; this change would alsoaffect handling equipment.

– No skilled technical personnel is available to set up and maintain feeddevices. Fed machines are unsuitable for conversion to automatic feed.

– There has simply been no attempt made to use automation components forthe feed operation.

The difficulties involved naturally also form the starting point for discussions ofautomation applications. It is without doubt true that attempts to achieve 100%automation are being more and more successful, including cases involving theretrofitting of existing machines. There are many examples of ways in which conventional machines have beensuccessfully upgraded by fitting a handling device. This is of course meaningfulonly if an automatic machining cycle can be achieved for the fed machine. It maybe necessary first to create a mechanical interface as the basis for installation ofa handling device. Fig. 4-23 shows the example of a lathe which has been fittedin “piggyback” fashion with a handling device. This approaches only 2 positions– the chuck and the magazine.

4.3 Feeding machines withpick-and-place units

4.3.1 Automatic feed isreplacing manual work

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75

The workpiece is inserted into the clamping device by a short-stroke unit. Thepickup and setdown positions are identical. In order to ensure that the setdowncomponent actually passes into the finished-workpiece magazine, this is brieflyraised. The pick-and-place device can then access the next workpiece blank. Theoverall motion capacity required has thus been divided between the peripheryand the pick-and-place device.

Fig. 4-24 shows the feed of a machine tool by means of an overhead swivelmotion. This operation is advisable only for relatively light workpieces. Duringtransfer, the swivel arm plunges between the indexed conveyor belts, passing oneither the inside or outside. The conveyor belt system must be configured toallow this. The feed device in this example is a direct local replacement for thehuman operator previously used.

4 Use of pick-and-place devices

Fig. 4-23:

Lathe retrofitted

with feed device

1 Rotary unit

2 Workpiece

3 Lathe

4 Pick-and-place device

drive

5 Roller conveyor

6 Finished-workpiece

magazine

7 Lifting cylinder

8 Lifting unit

9 Short-stroke handling axis

10 Gripper

Fig. 4-24:

Setting down panels with an

overhead swivel motion

1 Optical sensor

2 Lifting table

3 Swivel unit

4 Machine tool

5 Indexed conveyor belt

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76 4 Use of pick-and-place devices

The rotary loader shown in Fig. 4-25 is also made up of pneumatic components.The rotary unit must be capable of approaching 3 positions. The task in thisexample is to insert a blank workpiece into a clamping device such as a chuck.The finished workpiece is then brought to the output chute. During the ma-chining operation, the swivel arm moves to a place where it will not be in theway, such as the setdown position. Swivel arms have the fundamental advantagethat they require only a narrow handling channel and can remove themselvesquickly a long distance from the actual operations zone.

A typical feature of machine tools is that a new blank workpiece can be inputonly after the previous finished workpiece has been removed. The times takenfor these operations add up if the handling device is of single-arm design anddoes not have a double gripper. Idle motions can be avoided by using a double-arm system. An example is shown in Fig. 4-26. Only the clamping device of themachine tool is visible. After clamping by their end faces, workpieces aremachined on both sides by rotary tools, for example in facing, centring andcountersinking operations. The two gripper units are mounted on a commonslide separated by a distance A. There is no need for a pick-and-place device topick up the blank workpiece – this function can be provided by the gripper,which has one fixed finger and one moving finger.

Fig. 4-25:

Rotary loader

1 Centring gripper

2 Machine tool

3 Feed magazine

4 Blank workpiece

5 Arm

6 Rotary unit

7 Lifting unit

8 Output chute

9 Finished workpiece

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77

By the way, roller conveyor magazines should be given a multi-stage configur-ation as shown in Fig. 4-27. The moving workpieces are slightly braked at eachstage and are able to align themselves. This prevents misalignment which couldlead to malfunctions.

In the case of machines with continuous throughput, the problem is occasionallyencountered that a pick-and-place device is not able to deliver the required per-formance. One way out would be alternate feed from 2 magazines (Fig. 4-28).The machine tool has an infeed conveyor belt onto which the workpieces needto be placed. This method, too, avoids idle motions, since while one workpieceis being set down, the other vertical unit operates in parallel to prepare the nextworkpiece. The cost of motion units is however modest - just 3 linear units are

4 Use of pick-and-place devices

Fig. 4-26:

Loading device on a counter-

sinking and centring machine

1 Slide

2 Linear unit

3 Vertical unit

4 Gripper

5 Machine tool clamping

device

6 Roller outfeed conveyor

7 Finished workpiece

8 Blank workpiece

9 Feed zone

Fig. 4-27:

Multi-stage roller conveyor

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78 4 Use of pick-and-place devices

required. With larger workpieces, the distances and thus the linear strokes arealso larger. The use of a Smart Soft Stop linear axis for the horizontal motioncould then bring further time savings.

Several arms are also used in the feed concept shown in Fig. 4-29. The main aimhere is, however, not to save time but to find a way of feeding the presses at all.The space available in presses for feed devices is limited due to the fact that therest position of the upper press tool is directly above the lower press tool. A feedchannel thus cannot be used for gantry units. In the example, therefore, the feedoperation is divided between 2 handling devices.

Fig. 4-28:

Feeding a machine

from 2 magazines

1 Lifting unit

2 Slide

3 Smart Soft Stop linear unit

4 Workpiece

5 Infeed conveyor belt

6 Magazine

Fig. 4-29:

Press feed with distributed

handling actions

1 Lifting unit

2 Gantry unit with rodless

pneumatic cylinder

3 Shaping tool

4 Rotary unit

5 Double gripper

6 Gripper

7 Swivel arm

8 Swivel/lifting unit

9 Workpiece carrier

magazine for blank

and finished workpieces

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79

The tool is fed by a swivel-arm pick-and-place device. A gantry unit brings theworkpiece to this device from the magazine. The finished workpiece is now retur-ned to the double gripper, which swivels through 180° and immediately feedsthe next blank workpiece. During the shaping operation, the gantry unit runs tothe magazine, sets down the finished workpiece and picks up a new blank work-piece. The two pick-and-place units thus work “hand in hand”.

Removal devices are used in the main with injection-moulding and die-castingmachines. The workpiece to be removed is created inside the machine and willoften require careful handling - it may even be necessary to ensure that it is setdown in a way which prevents distortion as the workpiece cools. There is alsothe occasional need to set workpiece down within moulding turning devices.Workpieces of this are generally removed using simple handling devices, whichmay be gantry variants made up of standard modules, removal arms integratedinto machines or specially-designed handling devices. Fig. 4-30 shows anexample.

It can be seen that 2 actuators are sufficient to remove the workpieces. Thenumber of motion axes is reduced to the absolute minimum necessary. A two-axis device does not of course provide a three-dimensional working area butonly a two-dimensional working surface. In this example, this is a double-curvature surface on which both the pickup and setdown positions must belocated.

The ejector shown in Fig. 4-31 is of equally simple design. An ejector yoke is setin motion once the slide with the lower tool has travelled out of the operationszone. A pneumatic swivel/lifting module is used here as a compact drive unit.

4 Use of pick-and-place devices

4.3.2 Reaching into themachine

Fig. 4-30:

Removal device for mouldings

1 Injection moulding

2 Gripper

3 Rotary unit

4 Swivel arm

5 Frame

6 Pneumatic cylinder

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80 4 Use of pick-and-place devices

Machining operations often involve work on both ends of turned components.This means unclamping the workpiece, turning it round and re-clamping it. Thereare of course grippers which can use specially-designed (rotary) jaws to turn aworkpiece, but in machining cells peripheral turning stations are generally used.These can be used for different-sized workpieces without conversion. Fig. 4-32shows an example of this, using pneumatic drives .

The robot first sets the workpiece down on a platform, where it is clamped. The platform then lowers away and the workpiece can be turned. Following this,the platform returns and the clamp jaws retract. The workpiece is now freelyaccessible and can be picked up again.

Fig. 4-31:

Workpiece ejector

1 Ejector yoke

2 Sliding lower tool

3 Guide

4 Swivel/lifting module

5 Slide

6 Workpiece

7 Gravity chute

Fig. 4-32:

180° turning station

1 Swivel/lifting module

2 Workpiece

3 Rotatable clamp jaws

4 Pneumatic cylinder

5 Clamping jaws

6 Short-stroke cylinder

I to IV Turning operations

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5

Gripper technology

5.1 Grippers and grippedobjects as a system

81

Grippers are the technical equivalent of human hands and are used to automatethe production, assembly, testing and packing of components. Efficient grippersare very important, in fact crucial. Since grippers produce an effect, they can bereferred to as effectors – and since they are installed at the end of a mechanicalstructure, they are also called end effectors.

Automation in modern production means that there is less and less manualwork. Human hands, able with their intricate joints to execute well over 1,000different gripping motions, are for example no longer suitable for micro-assemb-ly operations. The trend towards the miniaturisation of products, componentsand handling devices is plain for everyone to see. Standard suction cups, forexample, start with a diameter of 1.2 mm and a length of 1.6 mm. These developa holding force of 0.03 N. This is of course very low. Mechanical grippers areaccordingly also being miniaturised.

The design of grippers is governed by the load required to achieve a secure hol-ding function. The forces and torque values during a handling sequence mayvary as a function of location, direction of motion and time. Vibration may alsobe involved. Grippers and gripped objects must therefore always be consideredas systems. Force transmission is governed by the following factors:

– Physical arrangement of the gripper in relation to the handling device– Resulting force, influenced by mass, inertia and centrifugal force, among other

things– Geometry of gripped object or gripping areas– Design of gripper jaws with regard to the force components absorbed by posi-

tive-locking and force-locking connections– Surface properties of workpieces and gripper jaws – Environmental influences such as dust, drilling emulsion, temperature and

vibration.

Fig. 5-1 shows a number of gripping situations in schematic form. The degree offreedom F is specified in terms of the rotary and thrust axes secured by force-locking connections. Workpieces can shift only in these directions and only if theforces operative during handling exceed the capacity of the frictional pairings atthe gripper jaws.

5 Gripper technology

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82 5 Gripper technology

It should be noted that it is not automatically possible to increase clamping for-ces, since this may lead to damage to sensitive and thin-walled workpieces. Weshould accordingly use positive locking to hold workpieces in the direction inwhich the highest force is operative. Workpieces made of brittle material cannottolerate edge pressure and must be gripped over large surfaces (Fig. 5-2). Lightflat workpieces can even be held without direct contact, using for examplemicroscopic water droplets to form a layer of ice which holds the workpieces.The resulting holding force is 50 to 100 times greater than with comparable suc-tion cups. Another solution is to use the aerodynamic paradox (right of Fig. 5-2).An air-jet gripper of this kind is very simple and contains no moving parts.Outflowing air creates a slight vacuum between the gripper plate and the upperface of the workpiece.

Fig. 5-1:

Positive locking or force-

locking? – Some examples

of combinations

1 Gripper jaw

2 Workpiece

F Degree of freedom

Fig. 5-2:

Gripping discs (examples)

1 Workpiece

2 Gripper jaw

3 Parallel-jaw gripper

p Compressed air

Point contact Area contact Contactless

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83

5.2 Precision and specialgrippers

Fig. 5-3:

Miniature precision gripper

(Festo)

1 Gripper jaw

2 Roller guide

3 Driver pin

4 Slide

5 Sealing ring

6 Piston

7 Pinion

8 Pressure spring

9 Gripper housing

D Piston diameter (12, 16 or

20 mm)

H Total stroke (5, 10 or 15

mm depending on size)

L Operating distance

Fig. 5-4:

Forces acting on a miniature

precision gripper (Festo)

1 Gripper jaw

2 Workpiece

3 Pneumatic piston

4 Pressure spring

FG Gripping force

FF Spring force

FP Piston pressure force

Especially in assembly systems, grippers are required which close precisely evenif the fingers are long and whose guides allow gripper jaws to move with therequired smoothness. Precision grippers of this kind have backlash-free rollerguides. Fig. 5-3 shows a simplified view of a gripper of this kind. The jaws of theparallel gripper are driven by pneumatic pistons. To ensure that the jaws closeprecisely centrally, the two pistons are linked by a rack-and-pinion mechanism.The gripping force can be adjusted via the operating pressure. In practical opera-tion, with 6 bar operating pressure and a piston diameter of 12 mm, this force isapproximately 56 N (with L = 20 mm). Built-in pressure springs provide a certainback-up function for the gripping force in the case of a supply pressure drop orfailure.

The gripping forces which are developed depend on the mode of operation(single- or double-acting) and the gripping method (internal or external). Fig. 5-4shows the superposition of the individual effective forces as a function of thetype of application.

5 Gripper technology

Page 85: Pneumatic Pickplace

Fig. 5-5:

Gripper system for large

folded cartons

1 Gripper frame

2 Pneumatic cylinder

3 Cut corrugated cardboard

4 Vacuum line

5 Swivel suction cup

6 Suction cup

7 Erected cardboard carton

8 Base plate with rotary joint

84 5 Gripper technology

There are a number of special grippers which have been designed for specialhandling objects and processes. Attempts are also often made to combine grip-ping operations with other actions. Fig. 5-5, for example, shows the design prin-ciple of a vacuum gripper system for corrugated-paper cartons. The flat cutworkpieces are picked up from a stack by suction cups. The outer cups then swi-vel inwards, folding the 4 sides into a carton. Swivel suction cups are installedfor this purpose on all 4 sides of the base plate. The sequence is as follows:

– Separation of a flat cut workpieces from the stack– Folding-up of all 4 sides– Setdown of folded carton in a carrier on the packing line.

Here is another example: Fast cyclical handling of narrow strip material can beachieved by using 2 gripper units. Fig. 5-6 shows the configuration for this. Whileone gripper unit advances the material, the other unit returns with its gripperopen. This sequence is particularly useful with large feed distances and shortcycle times. The diagram shows that each motion of a gripper unit is a mirrorimage of the motion of the other unit. In order to prevent slippage, the gripperjaws can be provided with an anti-slip coating, for example an elastomer grippercushion with a nap pattern, or else the gripper surface can be roughened bymicro-grooves. Gripper cushions are vital particularly with strip material with asensitive surface. In comparison, with steel, these cushions give a coefficient offriction of roughly 0.5, which is a very good value.

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85

In metal forming, presses are used which produce a workpiece in several stages.This requires workpieces to be transported from one tool to the next. Largemulti-stage presses incorporate a transfer gripper device. In the case of smallerpresses or special solutions, a multiple gripper device can be created by usingstandard pneumatic components, as shown in Fig. 5-7. In this case, several indi-vidual grippers have been mounted on a transfer rail. It is occasionally possibleto do without the lateral lifting axis if wide-opening angled grippers are used.The individual press tools are designed to present a continuous even surfaceafter the working stroke, which means that it will not generally be necessary tolift the workpieces. If, however, this were required, it would be necessary toinstall a vertical lifting axis as axis 1.

5 Gripper technology

Fig. 5-6:

Pneumatically-driven strip

feed device

a) Overall layout

b) Cyclical feed diagram

1 Strip

2 Gripper

3 Lateral guide roller

4 Base plate

G Gripper

L Linear unit

t Time

Fig. 5-7:

Two-axis transfer gripper

device

1 Press

2 Workpiece

3 Lower part of tool

4 Gripper

5 Transfer rail

6 Linear unit

7 Short-stroke unit

b)a)

OpenClosed

Adv.Return

OpenClosed

Adv.Return

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86 5 Gripper technology

Miniature grippers are used in electrical engineering, electronics, precisionengineering, laboratory automation, the optical industry and in the constructionof medical equipment. In a survey 10 years ago to find out why robots were notbeing used in the electrical engineering/electronic industries, grippers were the2nd most commonly cited reason - in other words, the grippers available at thattime were largely unsuitable for automatic handling tasks. In the meantime, inline with the general trend, many products and components have become smal-ler, which has not made them any easier to handle. Very small workpieces,however, behave in a different way to large ones. Properties become importantwhich with larger workpieces would be of no consequence. Electrostatic charges,for example, can make a workpiece “stick” to a gripper. This has allowed newtypes of grippers to be developed, operating for example on the principle ofadhesion. Mechanical grippers, however, have also advanced into the miniatureworld. Fig. 5-8 shows the design of a miniature angled gripper. Gripping force isproduced by a single-acting pneumatic piston and a wedge device.

With an operating pressure of 6 bar, gripping forces of around 5.5 N are produ-ced with a piston diameter of 8 mm. As a comparison: A vacuum suction cupwith a diameter of 11 mm develops a holding force of approx. 1.2 N. There arevarious supplementary components to allow mounting of the small grippers asshown in Fig. 5-9b. These comprise mounting flanges and locking nuts. This alsoallows turret grippers to be created easily for assembly applications (Fig. 5-9a).A height compensator with a certain degree of compliance in the longitudinaldirection of the gripper is integrated into mounting flange and provides 5 mmcompensation in the case of a gripper with 8 mm piston diameter.

5.3 Miniature grippers

Fig. 5-8:

Miniature angled gripper

(Festo)

a) Section through gripper

b) Mounting variant

1 Housing

2 Piston with 8 mm diameter

3 Gripper jaw

4 Cylindrical pin

5 Pressure spring

6 Gripper finger

7 Workpiece

8 Plastic jaw guide

9 Mounting flange with inte-

gral pressure spring

H Height compensator

Page 88: Pneumatic Pickplace

Fig. 5-9:

Configuration variants for

miniature angled grippers

(Festo)

a) Turret gripper

b) Gripper variants

1 Gripper finger

2 Gripper jaw

3 Gripper housing

4 Mounting flange

5 Disk turret

6 Mounting bracket

7 Rotary unit

Fig. 5-10:

Gripper with remote drive

1 Pneumatic cylinder

2 Return spring

3 Coupling

4 Thrust rod

5 Gripper jaw

6 Gripper finger

7 Workpiece

p Compressed air

5.4 Magnetic grippers

87

Significantly higher gripper forces can be achieved with micro grippers if thegripper and finger drive are separate. The drive can then be installed remotelyand can be of suitable size. The gripper is then driven not by a small piston butby a thrust rod with a tapered end. A configuration of this kind is shown in Fig. 5-10. The thrust rod can, by the way, also be routed through the hollowpiston rod of a small linear unit. The suction cup can also in this case have a dia-meter of, for example, 12 mm.

Magnetic grippers are of very simple design and are a popular choice for thehandling of ferromagnetic materials, particularly flat sheet-metal workpieces. Apush-off force is, however, generally required in order to detach workpieces fromthe magnet. A further possible disadvantage is that workpieces may “stick” dueto residual magnetism. Without a push-off force, the only possibility is for theworkpiece fed by the magnetic gripper to be accepted immediately by a clamp-ing device and “torn off” the magnet (an in-line tear-off will require a greaterforce than a lateral displacement). In order to avoid the need for this, there arevarious possible solutions which have the aim of shifting the magnetic field. Thiscan be achieved by changing the position of the magnet relative to the work-

5 Gripper technology

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88 5 Gripper technology

piece, which is of course the same as increasing the air gap. The ideal way toachieve this shift motion is by using a pneumatic cylinder. Fig. 5-11 shows apossible configuration. It is possible to assist the detachment of the workpiecefrom the gripper even further by providing air jets in the base of the cylinder (Fig. 5-11c). If there is no objecting to the workpiece “jumping” as the gripperapproaches (which leads to a loss of positioning accuracy), then there is no needfor the cylinder to be double-acting. The downwards stroke of the piston canthen be produced by spring force in this case. The magnetic gripper illustratedshows that pneumatics can form the basis for a very simple technical solution.

Another possibility would be a derivative which uses an electromagnet in placeof a permanent magnet. As the piston fitted with an electromagnetic coil movesdownwards, the coil docks against electric base contacts; only then is it activa-ted. This allows the holding force to be varied by electrical means, almost com-pletely avoiding the problem of residual magnetism.

Fig. 5-11:

Magnetic gripper with pneu-

matic magnetic field shift

a) Section through magnetic

gripper

b) Cylinder base as shaped

carrier

c) Shift of magnet combined

with simultaneous air jet

d) Handling sequence

1 Piston

2 Permanent magnet

3 Cylinder base

4 Workpiece

5 Shaped cylinder base

6 Jet bore

p Compressed air supply

p

1

2

3

4

p

p

p

p4

2

1

4

5 6

a) b) c)

d)

Anfahren Halten Bewegen Positionieren Lösen

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89

The basis for all decisions is an assessment of solution variants, designs andcomponents. Not everything which can be combined to form a handling unit isactually worthwhile. On the other hand, we know from the principle of synergythat the whole can be greater than the sum of the parts. What makes mattersdifficult is that there are several solutions to most tasks. This last chapter willtherefore concentrate on combination, assessment and selection.

The advantages of a combination method were first recognised by Archimedes(approx. 287-212 BC). In order to arrive at new designs of war machines moreeasily, he made up some concentric wooden discs on which the names of groupsof design features were written (Fig. 6-1). By turning the discs around relative toeach other, the features could be combined in different ways, generating ideasfor new approaches.

In the case of present-day modular handling systems, manufacturers also gene-rally offer aids which indicate the compatibility of the modular components.Recommendations are also given as to which interface adapters are available.Adapters also in principle allow components from different modular systems tobe combined. This is, however, not done very often in practice. In order to avoiderrors during combination work, a graphic combination diagram or similar showbe prepared. A common way of solving technical problems is the morphologicalmethod. Fig. 6-2 shows a simplified example based on a two-dimensional mor-phological system for a pick-and-place device. Attempts should be made for theproblem elements to find and include as many solution elements as possible.Taking into account compatibility factors, we can then define solutions by linkingsolution elements from top to bottom. This example is intended only as an illust-ration of a systematic problem-solving method. There are of course many othermethods, such as solution trees, solution catalogues or combination tables. Theresult will generally be several different solutions. It is therefore necessary as anext step to assess the variants.

6 Criteria, code numbers and components

6 Criteria, code numbersand components

6.1 Don’t just dream –combine!

Fig. 6-1:

Combination discs made by

Archimedes of Syracuse

Vertic

alsup

port

Hor

izontal support Inclined

supportSupportframe

Bie

r

2-wheeled 4-wheeled

Skid

RollerYokeslin

g

Twistedrope

Te

nsioned rope

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The target variant can be found through systematic study of equipment-specificfeatures, particularly kinematic and dynamic behaviour. The selection processconcludes with a comparison of requirement and performance profiles. To dothis, we need assessment criteria for alternative solutions. It is not easy to findthe right solutions. These must be independent of each other, complete, asquantitative as possible and always formulated positively, for example not as“Noise generation” but rather “Silent operation” if this is what we mean. The criterion groups are:

– Physical/technical function– Feasibility of manufacture– Cost-effectiveness– Man/machine relationships.

6 Criteria, code numbers and components90

Fig. 6-2:

Demonstration example

of a two-dimensional morpho-

logical system

6.2 Assessment and selection

Solution elements

Solution

Pro

ble

m e

lem

en

ts Pushing

Coupling

Turning

Couplin

Gripping

Testing

Spindle Piston Belt

Bracket Pulley Plate Adapater

Croiwn whee Adapter Arm Bracket

Sheats

Parallel gripper

Suction Double gripper

Light Magnet Air jet Induction

Piston Pinion Rotary vane

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6 Criteria, code numbers and components

The assessment process is the totality of all the steps in which assessment

criteria are used to select the most suitable of a number of solution variants.

Table 6-1 shows a number of the factors, features and criteria which are im-portant for the assessment process. Depending on the application in question,suitable criteria will be selected or additional ones formulated.

Acceptable installation-position errorAccessoriesAdjustment and programmingfacilitiesAvailability of softwareAvailable size stepsController linksConvertabilityCorrosion protectionCost-effectivenessDocumentationEase of adjustmentEase of installationEase of operationElectromagnetic compatibilityFacilities for fitting sensorsFacility for fitting valvesFacility for user adjustment of backlashFreedom from driftFreedom from maintenanceGuidance accuracy

and characteristicsInnovation potentialIntegratabilityInterchangeabilityManufacturer certificationOverload resistancePerformance parameters

Quality standardResistance to vibrationRigiditySafety standardSealingSilent operationSuitability for clean roomsSurface protectionSystem reservesTemperature resistanceTestabilityTorque handling capacityTroubleshooting programmeWorking life, service life

Performance parameters

AccelerationCushioningDead weightDeformationEfficiencyFailure rateForces and momentsFriction

Interfaces-Control technology-Electrical-Mechanical-Pneumatic

Load capacityMaintenance cyclePosition deviation

Price/performanceparametersRange of inversionRequired workingspace/area, strokeSpeedSpeed profileStart/stop charac-teristicsThrust

91

Table 6-1:

Some factors and criteria for

the assessment of solutions

and components

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In the assessment process, it is not possible to make a clear division betweentechnical and economic factors, since many of the latter which relate to the pro-duction costs must be described in technical terms. One possibility (out ofmany) is a graphic representation of the technical/economic comparison in an sgraph. Fig. 6-3 shows the method involved.

The economic value is a composite value for the qualities of the economicfeatures, while the technical value is a composite of the technical features,particularly those relating to function, control and operation. The “strength” s ofa solution variant i is identified by the point si. The best components (solutions)will therefore be located at top right of the graph. A healthy development ofalternative solutions will run close to the ideal line and will come closer to theideal value sideal in steps. Important technical factors include deformation,oscillatory characteristics and guide properties.

A number of errors may result from the elasticity of mechanical components.Mechanical assemblies, handling devices and axis modules are subject duringuse to static and dynamic forces and moments. These may be external, such asprocess forces and variable working loads, or internal, such as dead weight orthe effects of temperature. These produce deformations which are opposed by acertain resistance. This resistance is referred to as rigidity.

Deformations lead to a shift in the gripping point (tool centre point TCP), whichimpairs positioning accuracy. Accurate positioning therefore demands handlingunits with high rigidity. Deformation depends in particular on load, the distancebetween supports or cantilever distance, and the cross-section of the guide pro-file. Fig. 4 illustrates deformations through the examples of loaded and un-loaded handling devices. The representation is simplified, since, even without aweight load, weight forces are present which can cause deformations.Deformations may occur on one or more axes to different degrees, depending onthe configuration of the assembly. Gantry axes behave differently from less-rigidtelescopically-advancing designs. In the case of gantry axes, the distance bet-ween supports is a decisive factor.

6 Criteria, code numbers and components92

Fig. 6-3:

The s graph can help with the

selection of components.

1 Ideal line

2 Development line

(assumed progression)

si Strength of problem

solution as overall value

Technical value

Econ

omic

val

ue

sideal

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6 Criteria, code numbers and components

In order to assess the achievable cycle time, we must also study the oscillatorycharacteristics. In most cases, free vibration will be present. After strong retarda-tion, this will cease after a short time due to bearing friction and internal friction.The amplitude and frequency of the vibration will depend on the speed, load andcantilever extension involved.

In order to characterise oscillatory behaviour, amplitude and settling time arecombined and considered as “overshoot behaviour”. If a target position isapproached with a high rate of retardation, oscillation will be induced in thesystem and the target will be overshot (Fig. 6-5). The overshoot amplitude OA isthe greatest deviation of the gripper in a certain direction when approaching atarget position. The settling time T is a component of the function executiontime. This is the time which the handling device requires until the amplitude ofthe gripper oscillations after the target position is reached no longer exceeds adefined amount, the permissible position spread P. These remarks also applyanalogously to rotary units.

93

Fig. 6-4:

Deformations cause a shift in

the tool centre point TCP with

linear units

a) Telescopic advance

b) Travelling on gantry beam

Fig. 6-5:

Overshoot behaviour in a

displacement/time graph

unloaded unloaded

loaded loaded

TCPTCP

Travel time with rated load

Time

Tra

vel

dis

tan

ce

Page 95: Pneumatic Pickplace

A linear unit consists of a guide, a slide, a drive, a transducer (optional) and acontroller. All these components should be perfectly matched to each other.Users expect modules of this kind to deliver a service life of 100 million motioncycles. For handling systems, a repetition accuracy of ±0.5 to ±0.1 mm is gener-ally sufficient with stroke lengths of 100 to 1000 mm. Automated assembly oper-ations may have more stringent requirements. The differences in the prices oflinear units are due to the various types of positioning (fixed end stops, end andintermediate stops, free positioning) and the quality of the guide system used(Fig. 6-6). The “performance” in the graph means a combination of load capacity,rigidity and guide accuracy.

The technical requirements placed on linear motions vary widely according towhether the applications in question involve:

– Handling axes– Machine tools or production machinery– High-precision systems.

In view of the very wide range of attachments and fittings use in handlingsystems, we must pay special attention to the permissible axis-specific force andmoment loads. The rigidity of a linear guide depends on the design of the sup-porting body, the support rail, the bearings (type, number, contact points) andthe initial stress of the system. Regarding the choice of guides with ball or rollerbearings, we should note the following: Ball bearings are suitable for low to medium loads where only medium systemrigidity is required. These bearings are low-friction and can thus achieve highspeeds, which is very useful in handling systems. Roller-bearing guides, on theother hand, provide high precision, rigidity and load capacity. They are thusespecially suitable for use in machine tools and special machinery.

6 Criteria, code numbers and components94

6.3 Guides and smooth-ness of operation

Fig. 6-6:

Trend of price/performance

ratio for linear guides

1 Linear ball bearing

2 Profile rail guide

3 Precision guide

Performance

Pri

ce

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6 Criteria, code numbers and components

Handling technology has been the subject of enormous development in the last30 years. Modular devices and industrial robots have replaced human beings atmany points in the production process, and there is no sign that this develop-ment is about to come to halt. In the field of pick-and-place technology, a largenumber of manufacturers are currently offering a total of 3,500 linear units,together with around 900 rotary units and over 650 grippers. The market forhandling components is growing faster than the market for industrial robots.What is the reason for this astonishing development?

We find the following explanations:

– Modular handling units do not include any unwanted functions.– Modular devices offer the performance of a special machine but with the

reliability of standard units.– Handling components are series-produced and are thus cheaper, thoroughly

tested and of high quality.– Most modules are available from stock with no waiting.– Many modular systems are now so extensive that they can provide even highly

complex assemblies.– A wide choice of size steps means that components can be selected to match

given loads.– CAD-compatible files are available to save time in planning work. – Handling modules can be re-used if a particular application is no longer

required.– The integration of electronic components makes it easier to link handling

systems to controllers.

There are also disadvantages, which are however less important. These includethe following:

– Every connection between components represents a spring/mass system andmakes the assembly “soft”.

– Interfaces are not standardised, which makes it difficult to combine compo-nents from different systems.

– The very large number of different systems and variants is confusing for users.

Notwithstanding this, pick-and-place technology has a great future ahead of it.New and improved automation components will appear and help to further auto-mate workpiece manufacture, assembly and other related areas.

95

6.4 And, finally...

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96 Literature

Literature

Ameling, W.; Backe, W. et alia: Flexible Handhabungsgeräte im Maschinenbau(Flexible Handling Devices in Mechanical Engineering). Published by VCH,Weinheim 1996

Deppert, W.; Stoll, K.: Pneumatik-Anwendungen (Pneumatic Applications).Published by Vogel Verlag, Würzburg 1990

Gerhard, E.: Entwickeln und Konstruieren mit System (Systematic DevelopmentAnd Design). Published by expert Verlag, Renningen 1998

Hesse, S.: Greiferanwendungen (Gripper Applications). From the series "BlueDigest on Automation” published by Festo Esslingen 1997

Hesse, S.: Lexikon Greifertechnik (Lexicon of Gripper Technology). Published byFesto Esslingen, 1997

Hesse, S.: Greifer-Praxis (Grippers in Practice). Published by Vogel Verlag,Würzburg 1991

Hesse, S.: Montagemaschinen (Assembly Machines). Published by Vogel Verlag,Würzburg 1993

Hesse, S.: Handhabungsmaschinen (Handling Machines). Published by VogelVerlag, Würzburg 1993

Hesse, S.: Praxiswissen Handhabungstechnik in 36 Lektionen (Practical HandlingTechnology In 36 Lessons). Published by expert Verlag, Renningen 1996

Hesse, S.; Schmidt, H.: Rationalisieren mit Balancern und Hubeinheiten(Rationalization Using Balancers And Lifting Units). Published by expert verlag,Renningen 1998.

Hesse, S.; Nörthemann, K.-H.; Krahn, H.; Strzys, P.: Vorrichtungen zurHerstellung von Gußstücken und Spritzgußteilen (Equipment For The ProductionOf Castings And Injection Mouldings). Published by expert verlag, Renningen1998.

Hesse, S.: Industrieroboterpraxis - Automatisierte Handhabung in der Fertigung(Industrial Robots In Practice - Automated Handling In Production Processes).Published by Vieweg Verlag, Wiesbaden 1998

Hesse, S.: Atlas der modernen Handhabungstechnik (Atlas of Modern HandlingTechnology). Published by Vieweg Verlag, Wiesbaden 1993

Hesse, S.: Industrieroboterpraxis - Automatisierte Handhabung in der Fertigung(Industrial Robot Practice: Automated Handling in Production Facilities).Published in German by Vieweg Verlag, Wiesbaden 1998

Page 98: Pneumatic Pickplace

Literature

Krahn, H.; Nörthemann, K.-H.; Hesse, S.; Eh, D.: Konstruktionselemente 3 -Beispielsammlung für die Montage- und Zuführtechnik (Design Elements 3 - AnAnthology Of Examples For Assembly And Feed Systems). Published by VogelVerlag, Würzburg, 1999

Linde, H.; Hill, B.: Erfolgreich erfinden - WiderspruchsorientierteInnovationsstrategie für Entwickler und Konstrukteure (Successful Invention - AContradiction-Oriented Innovation Strategy For Developers And Designers).Published by Hoppenstedt Verlag, Darmstadt, 1993

Lotter, B.: Wirtschaftliche Montage (Economic Assembly). Published by VDIVerlag, Düsseldorf 1992

Nist, G.; et alia: Steuern und Regeln im Maschinenbau (Open- And Closed-LoopControl In Mechanical Engineering). Published by Verlag Europa-Lehrmittel,Haan-Gruiten 1989

Seegräber, L.: Greifsysteme für Montage, Handhabung und Industrieroboter(Gripper Systems For Assembly, Handling And Industrial Robots). Published byexpert Verlag, Ehningen 1993

Seitz, G.; Hesse, S.: Robotik - Grundwissen für die berufliche Bildung (Robotics-Fundamentals For Vocational Training). Published by Vieweg Verlag, Wiesbaden1996

97

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98 Glossary of technical terms

4-position drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244-position rotary drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

A Air-jet gripper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Alternate feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Assessment criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91Auxiliary process time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

B Basic units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Belt distributor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Blank workpiece handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Boom-type design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

C Cam/roller system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Cascade control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Centring bars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Clamping unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Closed-loop control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Code rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Combination slide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Combination variants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44Compact device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Conductive-plastic potentiometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Conduit system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Control cams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13, 68Cross-gantry configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Cushioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Cycle time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

D Deceleration force curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Degree of freedom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Degree of freedom of the transmission system . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Destacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Directness of pneumatic drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Distributor slides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Double distributor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Double-arm loader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Double-arm system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Dovetail clamp systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Drum stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

E Ejector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79End effectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81End-position controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51End-position cushioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Glossary

of technical terms

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99

F Feed device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Finished workpiece handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Fluidic muscle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Force cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Force locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39Freedom from backlash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

G Guide system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

H Handling cycle time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Handling function diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70Handling modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Home position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

I Incremental encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Industrial shock absorbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Installation components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Intermediate stop system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Intermediate stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22, 33

K Kinematic chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

L Lift/turn loader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Lifting-piston suction cup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Linear guides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Linear positioner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Linear units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Loading device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77Locking device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

M Machine feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Magazine feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Magnetic grippers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Magnetostrictive distance measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55Mass moment of inertia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Miniature angled gripper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Miniature grippers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Morphological system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89Motion patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23, 43Multiple gripper device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Multi-position drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Multi-stage roller conveyor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

O One-way flow control valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Over-determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Overhead swivel motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75Overshoot amplitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Glossary of technical terms

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100 Glossary of technical terms

P Parallel gripper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Parallelogram arm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Performance profiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Periphery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27, 28Pick-and-place cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Pick-and-place devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Positioning axes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Positioning system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Positive locking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Potentiometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Precision gripper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Press feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78Profile connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Prosthetic arm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

R Rebound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Removal devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Resolver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53Rigidity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Rotary arm unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Rotary cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Rotary loader . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Rotary unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34, 60Rotary vane motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Rotary-vane module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Rotary-vane type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Rotor position encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

S Select shock absorbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50Separation operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73Servopneumatic axes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Servopneumatic position control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Settling time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93S-graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92Shock absorber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Slot-nut connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40Smart Soft Stop system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51, 70Spindle drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Standard cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Steiner method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Stepping motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52Stop system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31Stopper cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67Strip feed device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Strip material feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65Suction-cup spider . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Swivel arm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62Swivel stop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Swivel/linear drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

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Swivel-arm pick-and-place device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79Synchronisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

T Tension/compression components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68Three-finger gripper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72Toothed piston system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Toothed-belt drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Transfer device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66Transfer gripper device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Transfer unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70Turning station . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80Turret gripper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Twin unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Twin-piston rotary drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Two-dimensional patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

W Workpiece carrier magazine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Workpiece ejector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80Workpiece handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Glossary of technical terms

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Appendix102

1

13

12

11

16

17

18

10

8

9

7

4

3

6

15

14

5

2

19

Appendix:Typical configurationsof pick-and-placedevices produced withFesto’s modular system

Pick-and-place device

of boom-arm design

(HMP/HMP/DRQD/HGR)

1 Adapter kits

2 Profile column

3 Adapter kits

4 Adapter kits

5 Accessories

6 Cover cap

7 Linear modules

8 Adapter kits

9 Linear modules

10 Adapter kits

11 Rotary drive

12 Adapter kits

13 Radial gripper

14 Distribution box

15 Conduit

16 Fitting

17 Lock nut

18 Adapter plate

19 Multiple distributor for

inputs and outputs

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Appendix 103

10

9

8

7

6

5

4

3

2

1

Pick-and-place device

of boom-arm design

1 Adapter kits

2 Profile column

3 Cover cap

4 Adapter bracket/base

bracket, adapter kits

5 Adapter kits

6 Linear module

7 Adapter kits

8 Mini slide

9 Adapter kits

10 Parallel gripper

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Appendix104

4

5

3

68

7

2

1

12

11

10

9

Pick-and-place device

of gantry design

1 Adapter kits

2 Profile column

3 Adapter kits

4 Profile column

5 Cover cap

6 Adapter kits

7 Linear drive

8 Guide axis

9 Adapter kits

10 Linear modules

11 Adapter kits

12 Parallel gripper

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Appendix 105

1

2

3

5

4

8

9

10

11

Pick-and-place device

of gantry design

1 Adapter kits

2 Profile column

3 Cover cap

4 Adapter kits

5 Linear drive

6 Shock absorber

7 (Shock absorber bracket)

8 Adapter plate

9 Mini slide

10 Adapter kits

11 Parallel gripper

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