Heinz Tschaetsch

Metal Forming Practise

Heinz Tschaetsch

Metal FormingPractiseProcesses – Machines – Tools

Translated by Anne Koth

123

Author:

Professor Dr.-Ing. e. h. Heinz TschaetschPaul-Gerhardt-Str. 2501309 Dresden, Germany

andKaiserplatz 2a83435 Bad Reichenhall, Germany

Translator:

Anne KothAllsprach-ÜbersetzungsbüroWilthener Str. 6a01324 Dresden, Germany

Originally German edition published by Vieweg Verlag, Wiesbaden 2005

Library of Congress Control Number: 2006926219

ISBN-10 3-540-33216-2 Springer Berlin Heidelberg New YorkISBN-13 978-3-540-33216-9 Springer Berlin Heidelberg New York

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Preface

The book “Metal Forming”, a translation of the eighth revised edition of “Umformtechnik” in German, describes the latest technology in the sector of metal forming. Part I covers metal forming and shearing processes. It describes the main features of these processes, the tooling required and fields of application. Practical examples show how to cal-culate the forces involved in forming and the strain energy. Part II describes forming machines and shows how to calculate their parameters. This section also introduces flexible manufacturing systems in metal forming and the handling systems required for automation (automatic tool changing and workpiece conveyor systems). Part III includes tables and flow diagrams with figures needed to calculate forming forces and strain energy. These production units are automated as much as possible using modern CNC engineering to reduce non-productive time and changeover time, and thus also manufacturing costs. Along-side these economic advantages, however, another important reason for using metal working processes is their technical advantages, such as:

material savings optimal grain direction work hardening with cold forming.

This book runs through all the main metal forming and shearing processes and the tooling and machines they involve. Incremental sheet forming was recently added in Chapter 15.4.

For engineers on the shop floor, this book is intended as an easily-navigable reference work. Students can use this book for reference, saving them time making notes in the lecture theatre so that they can pay better attention to the lecture.

I would particularly like to thank my colleague, Prof. Jochen Dietrich, Ph.D.eng. h.c., lecturer in production processes and CNC engineering at Dresden University of Applied Sciences, Germany (Hochschule für Technik und Wirtschaft), for his involvement as co-author from the 6th edition.

Thanks also to Dr. Mauerman of the Fraunhofer Institute for Machine Tools and Forming Technology, Chemnitz, Germany (Institut für Werkzeugmaschinen und Umformtechink), for his collaboration on the 7th edition of the book.

Bad Reichenhall and Dresden, November 2005 Heinz Tschätsch

Contents

Preface ................................................................................................................................ V

Terms, symbols and units ................................................................................................. 1

Part I Metal forming and shearing processes ................................................................. 3

1 Types of production processes .............................................................................. 5

2 Terms and parameters of metal forming ............................................................. 72.1 Plastic (permanent) deformation ............................................................................... 7 2.2 Flow stress ................................................................................................................ 82.3 Deformation resistance.............................................................................................. 102.4 Deformability ............................................................................................................ 112.5 Degree of deformation and principal strain .............................................................. 11 2.6 Strain rate .................................................................................................................. 14 2.7 Exercise..................................................................................................................... 14

3 Surface treatment ................................................................................................... 153.1 Cold bulk forming..................................................................................................... 15 3.2 Cold sheet forming.................................................................................................... 16 3.3 Hot forming............................................................................................................... 173.4 Exercise..................................................................................................................... 17

4 Upset forging .......................................................................................................... 184.1 Definition .................................................................................................................. 18 4.2 Application................................................................................................................ 18 4.3 Starting stock ............................................................................................................ 184.4 Permissible deformations .......................................................................................... 19 4.5 Upsetting force.......................................................................................................... 234.6 Upsetting work.......................................................................................................... 234.7 Upsetting tooling....................................................................................................... 244.8 Achievable precision................................................................................................. 26 4.9 Defects in upset forging ............................................................................................ 27 4.10 Example calculations ................................................................................................ 27 4.11 Exercise..................................................................................................................... 32

5 Extrusion ................................................................................................................. 33 5.1 Definition .................................................................................................................. 33 5.2 Application of the process......................................................................................... 33 5.3 Types of extrusion process........................................................................................ 34 5.4 Starting stock ............................................................................................................ 355.5 Principal strain .......................................................................................................... 355.6 Calculation of force and mechanical work................................................................ 36 5.7 Extrusion tooling....................................................................................................... 385.8 Reinforcement calculation for single-reinforced dies.................................................... 39 5.9 Achievable precision ................................................................................................ 42 5.10 Defects during extrusion .......................................................................................... 43

VIII Contents

5.11 Sequence of operations diagram .............................................................................. 43 5.12 Example calculations ................................................................................................ 44 5.13 Shape classification .................................................................................................. 495.14 Exercise ..................................................................................................................... 55

6 Thread and gear rolling ......................................................................................... 56 6.1 Types of process ....................................................................................................... 566.2 Application of the processes .................................................................................... 58 6.3 Advantages of thread rolling .................................................................................... 59 6.4 Establishing the initial diameter ............................................................................... 60 6.5 Rolling speeds with cylindrical dies ......................................................................... 61 6.6 Rolling dies .............................................................................................................. 61 6.7 Example..................................................................................................................... 63 6.8 Thread rolling machines ........................................................................................... 64 6.9 Exercise ..................................................................................................................... 68 6.10 Processes and machines for rolling gears ................................................................. 69

7 Cold hubbing .......................................................................................................... 77 7.1 Definition ................................................................................................................. 77 7.2 Application of the process ........................................................................................ 77 7.3 Permissible deformations ......................................................................................... 78 7.4 Calculation of force and mechanical work ............................................................... 78 7.5 Materials which can be hubbed ................................................................................ 79 7.6 Hubbing speed .......................................................................................................... 807.7 Lubrication during hubbing ...................................................................................... 80 7.8 Characteristics of the workpieces to be hubbed ....................................................... 80 7.9 Hubbing tooling ....................................................................................................... 81 7.10 Advantages of cold hubbing ..................................................................................... 82 7.11 Defects during cold hubbing .................................................................................... 83 7.12 Machines for cold hubbing ....................................................................................... 83 7.13 Example calculations ................................................................................................ 84 7.14 Exercise ..................................................................................................................... 85

8 Coining (stamping) ................................................................................................. 86 8.1 Definition ................................................................................................................. 86 8.2 Types and applications of coining processes ........................................................... 86 8.3 Calculation of force and mechanical work ............................................................... 87 8.4 Tooling ..................................................................................................................... 88 8.5 Defects during coining ............................................................................................. 89 8.6 Example .................................................................................................................... 89 8.7 Exercise .................................................................................................................... 90

9 Ironing (wall ironing) ............................................................................................. 91 9.1 Definition ................................................................................................................. 91 9.2 Application of the process ........................................................................................ 91 9.3 Starting stock ............................................................................................................ 91 9.4 Principal strain ......................................................................................................... 919.5 Calculation of force and mechanical work ............................................................... 93 9.6 Example .................................................................................................................... 93 9.7 Exercise ..................................................................................................................... 94

Contents IX

10 Wire drawing .......................................................................................................... 95 10.1 Definition ................................................................................................................. 95 10.2 Application ............................................................................................................... 95 10.3 Starting stock ........................................................................................................... 96 10.4 Principal strain ......................................................................................................... 96 10.5 Permissible deformations ......................................................................................... 96 10.6 Drawing force .......................................................................................................... 9710.7 Drawing speeds ........................................................................................................ 9710.8 Drive power ............................................................................................................. 9910.9 Drawing tooling ....................................................................................................... 10010.10 Example ................................................................................................................... 102 10.11 Exercise..................................................................................................................... 104

11 Tube drawing .......................................................................................................... 105 11.1 Definition ................................................................................................................. 105 11.2 Tube drawing processes ........................................................................................... 105 11.3 Principal strain and drawing force ........................................................................... 106 11.4 Drawing tooling ....................................................................................................... 10711.5 Example ................................................................................................................... 108 11.6 Exercise..................................................................................................................... 108

12 Extrusion ................................................................................................................. 109 12.1 Definition ................................................................................................................. 109 12.2 Application ............................................................................................................... 109 12.3 Starting stock ........................................................................................................... 110 12.4 The extrusion process ............................................................................................... 110 12.5 Principal strain ......................................................................................................... 113 12.6 Strain rates during extrusion .................................................................................... 113 12.7 Extrusion force ......................................................................................................... 11412.8 Mechanical work ...................................................................................................... 11612.9 Tooling ..................................................................................................................... 118 12.10 Extrusion presses ..................................................................................................... 12012.11 Example ................................................................................................................... 121 12.12 Exercise..................................................................................................................... 122

13 Impression-die forging (closed-die forging) ......................................................... 123 13.1 Definition ................................................................................................................. 123 13.2 Starting stock ........................................................................................................... 123 13.3 Types and application of the process ....................................................................... 124 13.4 Processes in the forging die ..................................................................................... 126 13.5 Calculation of force and mechanical work ............................................................... 127 13.6 Tooling ..................................................................................................................... 132 13.7 Design of impression-die forgings ........................................................................... 136 13.8 Achievable precision ................................................................................................ 137 13.9 Example ................................................................................................................... 137 13.10 Exercise..................................................................................................................... 139

14 Deep drawing .......................................................................................................... 141 14.1 Definition ................................................................................................................. 141 14.2 Application of the process ........................................................................................ 141

X Contents

14.3 Forming process and stress distribution ................................................................... 142 14.4 Starting stock ............................................................................................................ 143 14.5 Permissible deformation ........................................................................................... 150 14.6 Deep drawing steps .................................................................................................. 152 14.7 Calculating the drawing force .................................................................................. 154 14.8 Blank holder force .................................................................................................... 15514.9 Drawing work .......................................................................................................... 15614.10 Drawing tooling ....................................................................................................... 15814.11 Achievable precision ................................................................................................ 16614.12 Defects during deep drawing ................................................................................... 167 14.13 Example .................................................................................................................... 169 14.14 Hydromechanical deep drawing ............................................................................... 172 14.15 Sheet hydroforming .................................................................................................. 17414.16 Tube hydroforming .................................................................................................. 179 14.17 Exercise ..................................................................................................................... 184

15 Deep drawing without a blank holder; metal spinning ....................................... 185 15.1 Deep drawing without a blank holder ...................................................................... 185 15.2 Metal spinning .......................................................................................................... 18615.3 Exercise ..................................................................................................................... 192 15.4 Incremental sheet forming ........................................................................................ 193

16 Bending ................................................................................................................... 194 16.1 Definition ................................................................................................................. 194 16.2 Application of the process ........................................................................................ 194 16.3 The bending process ................................................................................................. 194 16.4 Limits of bending deformation ................................................................................. 195 16.5 Spring-back .............................................................................................................. 197 16.6 Determining the blank length ................................................................................... 198 16.7 Bending force ........................................................................................................... 19916.8 Bending work ........................................................................................................... 20116.9 Bending tooling ........................................................................................................ 20316.10 Bending defects ........................................................................................................ 20416.11 Example .................................................................................................................... 204 16.12 Bending machines .................................................................................................... 20516.13 Exercise ..................................................................................................................... 211

17 Embossing ............................................................................................................... 212 17.1 Definition ................................................................................................................. 212 17.2 Application of the process ........................................................................................ 212 17.3 Calculation of force and mechanical work ............................................................... 213 17.4 Embossing tooling .................................................................................................... 21617.5 Embossing defects .................................................................................................... 21717.6 Example .................................................................................................................... 217 17.7 Exercise ..................................................................................................................... 217

18 Shearing .................................................................................................................. 218 18.1 Definition ................................................................................................................. 218 18.2 Shearing process flow .............................................................................................. 218 18.3 Types of shearing process ........................................................................................ 219

Contents XI

18.4 Permissible deformation ........................................................................................... 220 18.5 Calculation of force and mechanical work ............................................................... 220 18.6 Resultant line of action ............................................................................................ 222 18.7 Break clearance ........................................................................................................ 22518.8 Web and rim thickness ............................................................................................. 227 18.9 Achievable precision ................................................................................................ 228 18.10 Shearing tooling ....................................................................................................... 22918.11 Example ................................................................................................................... 238 18.12 Exercise..................................................................................................................... 240

19 Fine blanking (precision blanking) ....................................................................... 241 19.1 Definition ................................................................................................................. 241 19.2 Fields of application ................................................................................................. 24119.3 Shearing process flow .............................................................................................. 241 19.4 Fine blanking tooling design .................................................................................... 242 19.5 Break clearance ........................................................................................................ 24219.6 Forces during fine blanking ..................................................................................... 243 19.7 Fine blanking presses ............................................................................................... 244 19.8 Exercise..................................................................................................................... 246 19.9 Laser cutters ............................................................................................................. 247

20 Joining by forming ................................................................................................. 249 20.1 Clinching .................................................................................................................. 250 20.2 Punch riveting .......................................................................................................... 25420.3 Self-piercing riveting with semi-tubular rivets ........................................................ 257

Part II Presses

21 Types of press ......................................................................................................... 262 21.1 Presses controlled by work ...................................................................................... 262 21.2 Presses controlled by the ram path ........................................................................... 262 21.3 Presses controlled by force ...................................................................................... 263 21.4 Exercise..................................................................................................................... 263

22 Hammers ................................................................................................................. 264 22.1 Columns and frames ................................................................................................. 264 22.2 Types of hammer ..................................................................................................... 264 22.3 Constructional design and calculation of impact energy .......................................... 266 22.4 Fields of application for hammers ............................................................................ 273 22.5 Example ................................................................................................................... 274 22.6 Exercise..................................................................................................................... 274

23 Screw presses .......................................................................................................... 275 23.1 Forms of structural design ........................................................................................ 275 23.2 Functions of the individual styles of construction ................................................... 276 23.3 Calculating the parameters for screw presses .......................................................... 287 23.4 Advantages of screw presses ............................................................................................ 29123.5 Typical fields of application of screw presses ......................................................... 291 23.6 Examples .................................................................................................................. 292 23.7 Exercise..................................................................................................................... 294

XII Contents

24 Eccentric and crank presses .................................................................................. 295 24.1 Types of these presses .............................................................................................. 295 24.2 Press frame materials ............................................................................................... 298 24.3 Frame deflection and deflection energy ................................................................... 299 24.4 Eccentric and crank press drives .............................................................................. 300 24.5 Calculating the parameters ....................................................................................... 306 24.6 Example .................................................................................................................... 310 24.7 Application of eccentric and crank presses .............................................................. 312 24.8 Exercise ..................................................................................................................... 312

25 Knuckle-joint and toggle presses .......................................................................... 313 25.1 Single-point knuckle-joint presses ........................................................................... 313 25.2 Toggle presses – modified knuckle-joint presses ..................................................... 314 25.3 Horizontal knuckle-joint and toggle presses ............................................................ 317 25.4 Exercise ..................................................................................................................... 317

26 Hydraulic presses ................................................................................................... 318 26.1 Hydraulic press drives .............................................................................................. 318 26.2 Example..................................................................................................................... 320 26.3 Advantages of hydraulic presses .............................................................................. 321 26.4 Practical application of hydraulic presses ................................................................ 321 26.5 Exercise ..................................................................................................................... 324

27 Special-purpose presses ......................................................................................... 325 27.1 Deep drawing transfer presses ................................................................................. 325 27.2 Transfer presses for bulk forming ............................................................................ 331 27.3 Automatic punching presses ..................................................................................... 339 27.4 Exercise ..................................................................................................................... 344

28 Workpiece and stock feed systems ........................................................................ 345 28.1 Feed devices for piercing or blanking operations .................................................... 345 28.2 Transport devices in deep drawing transfer presses ................................................. 346 28.3 Transport devices for transfer presses for bulk forming .......................................... 347 28.4 Feed devices to supply round blanks ........................................................................ 348 28.5 Feed devices to convey single workpieces in steps .................................................. 348 28.6 Feed devices to supply forging presses .................................................................... 349 28.7 Exercise ..................................................................................................................... 349

29 Future developments in metal forming presses and tool changing systems ...... 351 29.1 Flexible manufacturing systems ............................................................................... 351 29.2 Automatic tool change systems ................................................................................ 362

Part III Tables ................................................................................................................... 367

Bibliography ....................................................................................................................... 401

Index ................................................................................................................................... 403

Terms, symbols and units

Term Symbol Unit (selection)

Work, mechanical W Nm

Force (force of pressure) F N

Drawing force Fdr N

Blank holder force FBH N

Velocity m/s, m/min

Strain rate s–1

Pressure p Pa, bar

Shear stress N/mm2

Tensile stress R, N/mm2

Tensile strength Rm N/mm2

Yield strength Re N/mm2

Elastic limit RP0.2 N/mm2

Elongation m/m, %

Flow stress kstr N/mm2

Flow stress before forming (cold forming) kstr0 N/mm2

Flow stress after forming (cold forming) kstr1 N/mm2

Resistance to flow pfl N/mm2

Deformation resistance kr N/mm2

Modulus of elasticity E N/mm2

Density t/m3, kg/dm3, g/cm3

Blank length before forming h0, l0 m, mm

Blank length after forming h1, l1 m, mm

Area A m2, mm2

Area before forming A0 m2, mm2

Area after forming A1 m2, mm2

Volume V m3, mm3

Forming temperature T K, ºC

Coefficient of friction –

Efficiency –

2 Terms, symbols and units

Term Symbol Unit (selection)

Deformation efficiency F –

Impact effect (with hammers) i –

Power P Nm/s, W

Acceleration a, g m/s2

Press strokes per minute n min–1, s–1

Stroke length H, h m, mm

Mass moment of inertia Id, kgm2

Mass m kg

Angular velocity s–1

Moment M Nm, J

Tangential force (with crank presses) Tp N

Crank angle (with crank presses) º