Workshop

on

Increasing Press Line Efficiency in Mechanical & Hydraulic Presses

INDEX

S.No. Description Page No.

1. Various types of Presses and their Application. Comparison of capabilities and limitations of Mechanical & Hydraulic Presses. 1

2. Introduction to various Sub Assemblies of Mechanical Presses 2

3. Trouble shooting in Hydraulic Circuits 3-4

4. Understanding the capability of Mechanical Presses w.r.t. Force, Energy & Speeds 5-6

5. Health checkup for Mechanical & Hydraulic presses. 7

6. Quick Die Change System 8

7. Servo Driven Mechanical Presses. 9-10

8. Common Press problems and their remedies for Mechanical Presses. 11-12

9. Increasing Efficiency through Automation. 13

10. Operation, maintenance and trouble shooting in Hydraulic Clutch & Brake Units 14-16

11. Lubrication & Pneumatic System for Mechanical Presses 17

12. Electrical System Press Safety & Interlocks for Mechanical & Hydraulic Presses. 18

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Various Types of Presses & their Application

A. Classification of presses is based on following parameters: 1. Motive Power

a) Hydraulic Press-Load Generation through motor drive hydraulic pumps. b) Mechanical Press- Load generation through motor Flywheel gears & transmission

through connecting rods. c) Servo Press-Load generation through Servo Motor, Gears and transmission through

connecting rods.

2. Construction/Frame/Position type a) Gap Frame b) 4 Pillar c) H Frame d) Link Frame

3. Number of Dies used

a) Single Die Station- Stand alone Hydraulic & Mechanical Press, Tandem Press line b) Multi Die Station c) Progressive Dies – Multiple operations like Punching , Blanking & notching are done

at high production rates d) Transfer Presses- Multiple operations are done using specially designed transfer dies

and suitable transfer system as per requirement.

4. Application based presses a) Forming, Draw & Deep draw b) Hot Forming c) Blanking & Trimming d) Die Spotting & Tryout presses e) Hemming Press f) Rubber Pad Forming g) Decorative Laminates h) Close Die Forming i) Composite SMC Moulding j) Straightening Presses k) Wheel & Axle Press for Railways

B. Limitations of presses based on motive power

1. Hydraulic Presses 2. Mechanical Presses 3. Servo presses

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Sub-Assemblies in a Mechanical Press

A. Crown Assembly 1. Eccentric Gear Assembly

a) Eccentric Gear type b) Eccentric Pin type c) Link Drive type d) Crank Shaft type e) Eccentric Shaft type

2. Intermediate Gear Assembly

a) With Integrated Pinion on Intermediate Shaft b) With Removable Pinion on Intermediate Shaft

3. Drive Shaft Assembly

a) Flywheel with Bearings b) Pinion, Keys & Drive Shaft c) Clutch Brake Unit with Rotary Union

B. Slide Assembly

1. Slide adjustment assembly

a) Ball type b) Plunger type c) Pin type

2. Gib Assembly

a) 8-Point Guided b) 6-Point Guided c) 4-Point Guided

3. Hydraulic Over Load valve Assembly

a) Variable Tonnage b) Fixed Tonnage

C. Die Cushion Assembly

1. Die Cushion with fixed stroke 2. Die Cushion with variable stroke 3. Single Stage Die Cushion 4. Two Stage Die Cushion 5. Die Cushion Adjustment & Damper Assembly

D. Moving Bolster Assembly

1. Centre to Front / Rear 2. Centre to Left / Right 3. T-Track type

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2

Troubleshooting in Hydraulic Circuits

A. Troubleshooting is a very important aspect of any maintenance team. Trouble shooting in hydraulic circuits can only be done by trained maintenance personal. This requires the training on the following aspects before actually working on the machines. 1. Understanding of hydraulic symbols 2. Understanding of construction of the various elements used in the hydraulic circuits. 3. Understanding of working of hydraulic circuits.

B. This programme has been designed considering that the people attending the programme

have basic knowledge of understanding of hydraulic symbols. During the workshop, discussion on working of few important valves used in hydraulic circuits of hydraulic presses, working of hydraulic circuits of presses and finally some of the problems encountered during the working of hydraulic presses will be discussed. Before actually working on the trouble shooting part, one must understand the basic principles of hydraulics. While attending the problem one must answer the following questions:

1. What is the function of Hydraulic Pump? 2. What happens to the Pressure when it acts in a closed chamber? 3. What happens when there is a resistance to Flow? 4. Actuator speed is determined by what? 5. Oil under Pressure Takes what path in the hydraulic system? 6. What happens when oil moves from the area of high pressure to the area of low

pressure without performing any work? C. All the above questions relates to one or the other problem we come across while working in

hydraulic presses. Hence understanding of the problem is must. Always start with the basics and easy things first. The common problems encountered in the hydraulic presses are:

1. No pressure build up. 2. Pressure build up time high. 3. Slide going up with very low speed. 4. Machine going down but not coming up. 5. Machine coming up but not building pressure during pressing 6. Jerk during fast approach to pressing change over. 7. Creep in the press. 8. Oil temperature going high 9. Leakage from the joints 10. Recurring hydraulic seal failure in the cylinder

D. There are 3 types of valves used in hydraulic circuits. Conventional valves, logic elements and

proportional and servo valves. We have different hydraulic circuits for hydraulic presses according to flow and control requirements. Manual setting of valves as well as setting of valves thru operator panel is provided. We will discuss these circuits.

E. You must keep the following DO’s and Don’ts in your mind as maintenance personal. 1. Don’t Jump To The Solution. 2. Observe Think And Brain Storm. 3. Establish Probable Causes. 4. Differentiate The Causes As Electrical Or Mechanical Or Hydraulic 5. Start With The Simplest Solution (Easy Things First) 6. Never Disturb Any Settings. 7. Conduct Failure Analysis.

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8. Always Release The Pressure Before Opening Any Valve And Keep The Slide On Some Positive Stop.

9. Check Oil Properties and filtration level At Regular Intervals. Never try to reuse paper filter elements

10. Take Care Of Air Breathers. They should never be kept Open.

F. Most important part in any hydraulic system is hydraulic oil. That is generally overlooked by maintenance team. Use of proper oil, maintaining the oil level and oil temperature in the oil tank and checking of oil cleanliness at regular interval is a must. Oil cleanliness level required is mentioned in the hydraulic circuits as well as in the operator manuals. There are some valves and pumps which are very sensitive to contamination. Instructions regarding the contamination level are to be followed in spirit and in totality to avoid a major breakdown. If you find anything abnormal, establish the probable cause first. It is our experience that your 60% to 70% problems will be over, if you are taking ‘CARE’ of hydraulic oil.

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Understanding the Capability of Mechanical Press

A. Classification of Mechanical Presses (on the basis of drive mechanism)

1. Eccentric/Crank Drive Press

a) Mechanism i) Based on Slider Crank Mechanism

b) Advantages

i) Cheaper ii) Higher Rigidity of Linkage System iii) Supports High Speed Operations iv) Works for all general Stamping Operations

c) Slide Motion Analysis i) Sinusoidal (FBOS v/s Crank Angle)

d) Press Force Analysis

2. Link-Drive Press

a) Mechanism i) Multiple Linkages System to obtain desired slide motion

b) Advantages

i) Suitable for Draw Operations ii) Better Product Quality iii) Increased Die Life iv) Lower Vibrations

c) Slide Motion Analysis

i) More Useful Time : Less Slide Speed from TDC to BDC ii) Lesser Idle Time : Higher Slide Speed from BDC to TDC

d) Press Force Analysis

B. Comparison between Eccentric Drive Press and Link Drive Press

C. Work / Energy

1. Definition a) Work done (per stroke) = Press Force applied x Draw/Shear distance

2. Understanding the use of Work/Energy concept in presses

a) In presses, energy is stored in the rotating mass of flywheel

3. Specific Deformation Work (analysis based on different materials)

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D. Production Processes

1. Metal Forming

a) Classification of various Metal Forming processes

i) Bulk Deformation Processes : Rolling, Forging, Extrusion, Drawing ii) Sheet Metal Working Processes : Deep Drawing, Bending, Shearing

b) Understanding the process requirements and suitable presses

2. Metal Parting

a) Classification of various Metal Forming processes i) Blanking, Shearing, Punching, Bite Cutting

b) Understanding the process requirements and suitable presses

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Health Check up for Mechanical Presses & Hydraulic Presses

A. Parameters for Health check up for Mechanical Presses: 1. Overall clearance. 2. Accuracy i.e. Flatness, Parallelism, Perpendicularity & leveling. 3. Jib clearance & condition. 4. Vibration 5. Lubrication , Hydraulic & Pneumatic systems 6. Oil condition & Make up rate. 7. Clutch & Brake system & Brake angle. 8. Hydraulic overload & slide adjustment system. 9. Gear condition 10. Die cushion working & snubbing action. 11. Electrical system, working of safety equipment & interlocks.

B. Parameters for health heck up for Hydraulic presses:

1. Accuracy i.e. flatness, Parallelism, Perpendicularity & leveling. 2. Jib clearance & condition. 3. Pump condition , hydraulic & pneumatic systems 4. Oil condition & make up rate . 5. System leakages internal & external. 6. Cylinder & ram condition. 7. Electrical system. 8. Die cushion 9. Working of dampers (if fitted) 10. Accumulators pre-charge & condition. 11. Working of safety equipment & interlocks. 12. Vibration level

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Quick Die Change System & Auto Die Change System

A. Why Quick Die Change System

1. Faster response for changing production schedules. 2. Reduce inventory 3. Reduce change over time- Increase equipment utilisation 4. Reduces cost per unit 5. Improve repeatability 6. Improve flexibility 7. Easier to train new operators 8. Increase operator safety

B. Elements of Quick Die Change System

1. Die Clamps

a) Selection of Die Clamps b) Type of Die Clamps based on application of Force c) Type of Die Clamps based on Mode of Positioning

2. Die Lifters a) Selection of Die lifters

3. Pre-rollers / die changing arms

a) Selection of Die change arms

4. Die Carts / Die Change Tables 5. Dedicated Push Pull unit 6. Moving Bolsters

C. Auto Die Change System

1. Need 2. Requirements

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Servo Driven Mechanical Presses: Advantages & Trends

A. Overview

1. No Clutch-Brake, No Flywheel, No dual Solenoid Valve. B. Concept

1. Tailor made Slide Motion 2. Suitable for Progressive Die Application 3. Link Drive Servo presses suitable for high energy

C. Tangible Benefits

1. Less power consumption 2. Better Productivity 3. Less number of operators 4. Less maintenance Cost 5. Reduced number of rejections and less work 6. Improved Die Life 7. Reduced inventory ( No WIP) 8. Low Capital cost

D. Intangible Benefits

1. Better quality of final product 2. Low environment pollution 3. Reduce noise 4. Reduce handling

E. Customer Benefits

1. Flexibility 2. Optimum adaptation to different forming processes 3. Reverse stroke motion 4. Try-out mode 5. Reduction in maintenance cost 6. Better energy balance

F. Composition

1. Servo Motor 2. Power and other drives 3. Numeric control 4. Servo amplifiers 5. Capacitor Bank 6. Brake

G. Application in various stamping process

1. Blanking 2. Sheet Forming 3. Draw Operation 4. Transfer Press Applications 5. Progressive

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H. Comparison of various types of presses 1. Productivity vs formability : Link Press, Crank Press, Hydraulic Press and Servo Press 2. Drawing :Pressure vs time ( Pneumatic Cushion) ;Conventional Press vs Servo Press 3. Drawing :Pressure vs time (Hydraulic Cushion) ; Conventional Press vs Servo Press 4. Blanking : Pressure vs time ( Pneumatic Cushion) ;Conventional Press vs Servo Press

I. Key Features to suit process requirement

1. Adjustment of Stroke Length and Operating Speed 2. Programmable Slide Motion 3. Slide Dwell for benefit of Complex Jobs 4. Optimized Press Stroke for Automation Cycle 5. Crank Motion 6. Knuckle Motion 7. Programmable Dwell at BDC 8. Multiple Dwell

J. Energy Buffer/Regeneration

1. Energy BUFFER using Flywheel 2. Energy BUFFER using Capacitor Bank.

K. Capacitive Energy Buffering

L. Isgec References

1. 400T Servo Press installed at Brandl, Romania

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Common Problems in Mechanical Presses related to various Sub-Assemblies

A. Hydraulic Over Load Assembly 1. It is used to protect the dies & press from overloading in most of the cases. 2. It is very large size fast acting relief valve to drain the oil in-case of development of high

pressure in the system due to high load. 3. Most common problem in the overload system & their remedies are

S.No. Problem Cause Remedy

a) Charging time very high

i) Air pressure low ii) Rolling diaphragm worn

out/punctured

i) Correct the same. ii) Replace the same.

b) Over load dumping without actual overload

i) Air pressure low ii) Rolling diaphragm worn

out/punctured iii) Missing electrical signal

i) Correct the same ii) Replace the same iii) Correct the signal

c) Haskel pump pumping continuously

i) Leakage from main cartridge

ii) Rolling diaphragm worn out/punctured

iii) Leakage from ball seat iv) Haskel pump faulty

i) Clean the cartridge & reassemble

ii) Replace the rolling diaphragm

iii) Check the ball seat iv) Service it or replace it

d) Over load not charging at all

i) Precondition not ok ii) Oil level low iii) Air entrapped in the system iv) Rolling diaphragm worn

out/punctured v) Leakage from the cylinder

i) Correct as per HMI ii) Check & fill correct grade

of oil iii) Bleed the air iv) Replace the same v) Chances of leakage from

main cylinder/seal are less so the system must be checked before seal replacement

B. Slide Adjustment Assembly

1. It is used to accommodate different die heights on the press. 2. The basic components of the slide adjustment assembly are worm, worm wheel, nut &

screw.

S.No. Problem Cause Remedy

a) Jamming of slide adjustment

i) Failure of coupling ii) Jamming of worm wheel &

worm shaft

i) Replace the same ii) Correct the same.

b) Motor tripping & high current

i) Wrong setting of MPCB ii) Jamming of adjustment

i) Correct the same as per relevant circuit.

ii) Correct the same

c) Variation in actual & displayed value

Failure of encoder coupling Replace the encoder

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S.No. Problem Cause Remedy

d) Over travel of slide

Adjustment motor brake not working

Rectify the same

e) Abnormal sound during the slide adjustment

i) Brake not release properly ii) Worm wheel/bearing worn

out iii) Fan cover fouling

i) Check & correct ii) Check & replace if

required iii) Correct the same

f) Torque Coupling failure /Slippage.

Loosen of key/bore worn out. Correct the bore size/ fitment.

C. Die Cushion Assembly

1. Die cushion is used to provide counter force during the draw operations. 2. It can be single stage, double stage with fixed stroke or with adjustable stoke. 3. Snubber & delayed return are the other features

S.No. Problem Cause Remedy

a) Die cushion not coming up Check precondition

Check precondition Correct the same as per HMI

b) Die cushion movement non parallel

Uneven clearance Correct the same in the presence / supervision of Isgec engineer.

c) Height of die cushion not equal to the reading

i) Encoder coupling failure ii) Counter meter cable broken

i) Replace the coupling ii) Replace the cable

d) No Snubbing Action

Oil level low Fill the correct grade of oil

e) Die Cushion adjustment jammed.

Jamming in worm shaft & worm wheel

Correct the same.

D. Moving Bolster

Moving bolsters are used to change the dies quickly & safely, the next die change set up can be made ready off line while present part is under production. We can achieve less 10 minutes die change, when the press is equipped with two moving bolsters.

S.No. Problem Cause Remedy

a) Moving bolster not lifting

i) Precondition not ok ii) Pump not built up the

pressure

i) Check the precondition as per HMI

ii) Check the pump & replace if required

b) Moving bolster not seating properly

i) Non alignment ii) Foreign particle entrapped

between bolster & bed area

i) Correct the alignment ii) Remove the foreign

particle.

c) No movement or erratic movement

Non alignment Correct the alignment

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Increasing efficiency through Automation

A. Press Automation 1. Why Press Automation?

2. Type of press automation

a) Die Automation & Pneumatic Ejection b) Robotic Automation – Pick & Place c) Transfer bar for inter station transfer d) Cross Bar Transfer (single and double) e) Robot Beam Transfer

3. Productivity Measurement

4. Compact robotic automation B. Robotic Tandem Press Line

1. Elements of Robotic Automation

a) Front of Line Equipment b) Robot for Press Linking c) Automation tooling (grippers and fingers) d) End of Line Equipment

C. Transfer Presses with Automation

1. Front of Line Equipment

2. Transfer bar for Inter Station Transfer and Grippers & Tooling for components

3. End of Line Equipment

D. Important features of Isgec Transfer Presses

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Clutch and Brakes

A. Principle of Operation B. Types:

1. Mechanical 2. Electromagnetic 3. Pneumatic 4. Hydraulic

C. Cooling types:

1. Dry 2. Wet

D. Mechanical Press Drive E. Hydraulically actuated clutches and spring-applied brakes F. Hydraulic Clutch & Brakes G. Clutch Brake Liners H. Construction I. Clutching Operation

Hydraulic oil moves the piston against the force of the springs, which release the brake plates and bring the friction clutch plates together which activates the clutch.

J. Braking Operation

Springs press piston in the cylinder to bring the friction brake plates together which activates the brake.

K. Fitment

1. Clutch/Brake Combined Unit 2. Housing 3. Rotary Unit 4. Flexible Hose 5. Throttle 6. Press safety valve 7. Check valve 8. Accumulator 9. Pressure gauge 10. Stopcock 11. Hydraulic unit

L. Advantages

1. Hydraulically engaged, spring-released multi-plate Clutches combined with the hydraulically released spring-applied multi-plate Brakes require small space and have low moment of inertia of the rotating parts.

2. Permitted for the high application frequencies. 3. To a large extent they require no maintenance. 4. Cylinder and piston are protected against rust.

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M. Conventional Hydraulic Circuit N. Fast Engagement with Accumulator O. Modified Hydraulic Circuit P. Hydraulic Module Q. Single Brake R. Double Brake S. Checking for wear prior to Dismantling

T. Parts – Single Brake

U. Parts – Double Brake

V. Enemy of Clutch – Slip

Reasons of Slip: 1. High Torque 2. Poor Friction

a) Moisture b) Contamination

3. Insufficient Force a) Low Pressure b) Internal leakage

4. High rpm

W. Fault finding

Fault Reason Remedy

Clutch Slips

Oil pressure too low Set the working pressure to the required figure: 63 bar

Fault in the hydraulic system (dirt, leaks)

Repair hydraulic system

Friction linings worn down (max. permissible size of the air gap reached)

Get customer service to change the plates

Reason cannot be established

Obtain technical service

Brake slip (braking angle increased)

Friction linings worn down (max. permissible size of the air gap reached)

Get customer service to change the plates

Reason cannot be established Obtain technical service

X. Oil Inlet

Y. Oil Inlet With Encoder

Z. Oil Inlet - Construction

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AA. Slip Control

1. Machine Controller (PLC) 2. Sensor Pads on Flywheel

AB. Braking Angle

AC. Pneumatic Clutch & Brake AD. Mounting Types AE. Pneumatic Clutch & Brake Fitment AF. Pneumatic Clutch & Brake Circuit AG. Mounting on Shaft AH. Pneumatic Clutch & Brake Construction AI. Air Inlet AJ. Wet Clutch & Brake

1. Application of the brake 2. Engagement of the clutch

AK. Version with key AL. Version with locking assemblies AM. Applications

1. Machine Tools 2. Construction Machines 3. Marine Transmission 4. Vehicles 5. Textile Machine 6. Paper Industry

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Lubrication & Pneumatic System for Mechanical Presses Construction & Working principles of Various Elements

A. Oil lubrication System for Mechanical Presses. 1. Various Bearings, bushes, gears in the press crown and slide-guides needs lubrication oil

at different quantities based on speeds and area. 2. Lubrication system ensures lubricant supply to all the points. 3. Lubrication system mainly consists of hydraulic pump, filter and progressive distributors. 4. The oil is collected back in the tank through inbuilt trap for contamination and re-

circulated through filters to ensure clean oil supply. 5. Progressive distributor ensures a metered quantity of oil at every point. The working of

progressive feeder is monitored with inbuilt proximity switch and press PLC. 6. Normally gear oil of viscosity grade 150 is recommended for mechanical presses.

B. Grease Lubrication System.

1. Generally die-cushion guides (liners) in the press-bed are lubricated with grease.

2. Grease pump operated with pneumatic solenoid valve forces greases to progressive block which delivers metered quantity of grease at pre-defined interval.

C. Pneumatic System for Counter Balance Cylinder and Die-Cushion 1. Variety in upper die-weights need different air pressure settings based on the pressure

v/s weight chart displayed on the machine. 2. There may be a manual or automatic pressure setting. 3. Automatic pressure data can be fed in tool data and the circuit ensures to maintain the

pressure as per specified data. 4. Similar system is taken for various pressure settings for die-cushion.

D. Air Saving Valve:

1. Air saving valve saves the compressed air of die-cushion reservoir from draining when

the cushion cylinder is drained for a die change.

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Electrical Systems

A. Electrical Systems- Safeties & Interlocks in Presses 1. Safeties & Interlocks

a) Mode Selection b) Emergency & Immediate Stops c) Two Hand d) Light Curtain e) Cam box System f) PSV actuation & feedback monitoring g) Hydraulic Module Sensor Monitoring

B. Electrical Systems- Machine Parameter Settings

1. Mechanical Presses

a) Parameter settings b) Tuning c) Diagnosis

2. Hydraulic Presses

a) Parameter settings, b) Tuning c) Diagnosis

C. Electrical Systems- VFD (Working & Parameterization)

1. VFD a) Components Working, b) Parameter settings c) Tuning d) Diagnosis

D. Electrical Systems- Troubleshooting in Electrical System

1. Control & Power circuit

a) Architecture, Diagnosis

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