(Parte 1 de 5)

Product Design for Manufacture and Assembly

Third Edition

AND MATERIALS PROCESSING A Series ofReference Books and Textbooks

Geoffrey Boothroyd

Boothroyd Dewhurst, Inc. Wakefield, Rhode Island

1.Computers in Manufacturing, U. Rembold, M. Seth, and J. S. Weinstein 2.Cold Rolling of Steel, William L. Roberts 3.Strengthening of Ceramics: Treatments, Tests, and Design Applications,

Harry P. Kirchner 4.Metal Forming: The Application of Limit Analysis, Betzalel Avitzur 5.Improving Productivity by Classification, Coding, and Data Base Standardization: The Key to Maximizing CAD/CAM and Group Technology, William F. Hyde 6.Automatic Assembly, Geoffrey Boothroyd, Corrado Poli, and Laurence E. Murch 7.Manufacturing Engineering Processes, Leo Alting 8.Modern Ceramic Engineering: Properties, Processing, and Use in Design,

David W. Richerson 9.Interface Technology for Computer-Controlled Manufacturing Processes,

Ulrich Rembold, Karl Armbruster, and Wolfgang Ülzmann 10.Hot Rolling of Steel, William L. Roberts 1.Adhesives in Manufacturing, edited by Gerald L. Schneberger 12.Understanding the Manufacturing Process: Key to Successful CAD/CAM

Implementation, Joseph Harrington, Jr. 13.Industrial Materials Science and Engineering, edited by Lawrence E. Murr 14.Lubricants and Lubrication in Metalworking Operations, Elliot S. Nachtman and Serope Kalpakjian 15.Manufacturing Engineering: An Introduction to the Basic Functions,

John P. Tanner 16.Computer-Integrated Manufacturing Technology and Systems,

Ulrich Rembold, Christian Blume, and Ruediger Dillman 17.Connections in Electronic Assemblies, Anthony J. Bilotta 18.Automation for Press Feed Operations: Applications and Economics,

Edward Walker 19.Nontraditional Manufacturing Processes, Gary F. Benedict 20.Programmable Controllers for Factory Automation, David G. Johnson 21.Printed Circuit Assembly Manufacturing, Fred W. Kear 2.Manufacturing High Technology Handbook, edited by Donatas Tijunelis and Keith E. McKee 23.Factory Information Systems: Design and Implementation for CIM

Management and Control, John Gaylord 24.Flat Processing of Steel, William L. Roberts 25.Soldering for Electronic Assemblies, Leo P. Lambert 26.Flexible Manufacturing Systems in Practice: Applications, Design, and

Simulation, Joseph Talavage and Roger G. Hannam 27.Flexible Manufacturing Systems: Benefits for the Low Inventory Factory, John E. Lenz

28.Fundamentals of Machining and Machine Tools: Second Edition,

Geoffrey Boothroyd and Winston A. Knight 29.Computer-Automated Process Planning for World-Class Manufacturing,

James Nolen 30.Steel-Rolling Technology: Theory and Practice, Vladimir B. Ginzburg 31.Computer Integrated Electronics Manufacturing and Testing, Jack Arabian 32.In-Process Measurement and Control, Stephan D. Murphy 3.Assembly Line Design: Methodology and Applications, We-Min Chow 34.Robot Technology and Applications, edited by Ulrich Rembold 35.Mechanical Deburring and Surface Finishing Technology, Alfred F. Scheider 36.Manufacturing Engineering: An Introduction to the Basic Functions,

Second Edition, Revised and Expanded, John P. Tanner 37.Assembly Automation and Product Design, Geoffrey Boothroyd 38.Hybrid Assemblies and Multichip Modules, Fred W. Kear 39.High-Quality Steel Rolling: Theory and Practice, Vladimir B. Ginzburg 40.Manufacturing Engineering Processes: Second Edition, Revised and Expanded, Leo Alting 41.Metalworking Fluids, edited by Jerry P. Byers 42.Coordinate Measuring Machines and Systems, edited by John A. Bosch 43.Arc Welding Automation, Howard B. Cary 4.Facilities Planning and Materials Handling: Methods and Requirements,

Vijay S. Sheth 45.Continuous Flow Manufacturing: Quality in Design and Processes,

Pierre C. Guerindon 46.Laser Materials Processing, edited by Leonard Migliore 47.Re-Engineering the Manufacturing System: Applying the Theory of

Constraints, Robert E. Stein 48.Handbook of Manufacturing Engineering, edited by Jack M. Walker 49.Metal Cutting Theory and Practice, David A. Stephenson and John S. Agapiou 50.Manufacturing Process Design and Optimization, Robert F. Rhyder 51.Statistical Process Control in Manufacturing Practice, Fred W. Kear 52.Measurement of Geometric Tolerances in Manufacturing, James D. Meadows 53.Machining of Ceramics and Composites, edited by Said Jahanmir,

M. Ramulu, and Philip Koshy 54.Introduction to Manufacturing Processes and Materials, Robert C. Creese 5.Computer-Aided Fixture Design, Yiming (Kevin) Rong and Yaoxiang (Stephens) Zhu 56.Understanding and Applying Machine Vision: Second Edition, Revised and Expanded, Nello Zuech 57.Flat Rolling Fundamentals, Vladimir B. Ginzburg and Robert Ballas 58.Product Design for Manufacture and Assembly: Second Edition, Revised and Expanded, Geoffrey Boothroyd, Peter Dewhurst, and Winston A. Knight 59.Process Modeling in Composites Manufacturing, edited by Suresh G. Advani and E. Murat Sozer 60.Integrated Product Design and Manufacturing Using Geometric

Dimensioning and Tolerancing, Robert Campbell 61.Handbook of Induction Heating, edited by Valery I. Rudnev, Don Loveless,

Raymond Cook, and Micah Black 62.Re-Engineering the Manufacturing System: Applying the Theory of

Constraints, Second Edition, Robert Stein 63.Manufacturing: Design, Production, Automation, and Integration,

Beno Benhabib 64.Rod and Bar Rolling: Theory and Applications, Youngseog Lee 65.Metallurgical Design of Flat Rolled Steels, Vladimir B. Ginzburg 6.Assembly Automation and Product Design: Second Edition, Geoffrey Boothroyd

67.Roll Forming Handbook, edited by George T. Halmos 68.Metal Cutting Theory and Practice: Second Edition, David A. Stephenson and John S. Agapiou 69.Fundamentals of Machining and Machine Tools: Third Edition,

Geoffrey Boothroyd and Winston A. Knight 70.Manufacturing Optimization Through Intelligent Techniques, R. Saravanan 71.Metalworking Fluids: Second Edition, Jerry P. Byers 72.Handbook of Machining with Grinding Wheels,

Ioan D. Marinescu, Mike Hitchiner, Eckart Uhlmann, W. Brian Rowe, and Ichiro Inasaki 73.Handbook of Lapping and Polishing, edited by Ioan D. Marinescu,

Eckart Uhlmann, and Toshiro K. Doi 74.Product Design for Manufacture and Assembly, Third Edition, edited by Geoffrey Boothroyd, Peter Dewhurst, and Winston A. Knight

Geoffrey Boothroyd

Peter Dewhurst Winston A.Knight

CRC Press is an imprint of the Taylor & Francis Group, an informa business

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Product Design for Manufacture and Assembly

Third Edition

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Prefacexix
Preface to the Second Editionxxi
Preface to the First Editionxi
Authorsxxv
Nomenclaturexxvii
1. Introduction1
1.1 What Is Design for Manufacture and Assembly?1
1.2 History1
1.3 Implementation of Design for Assembly4
1.4 Design for Manufacture5
1.5 Producibility Guidelines5
1.6 How Does DFMA Work?8
1.7 Falsely Claimed Reasons for Not Implementing DFMA15
1.7.1 No Time15
1.7.2 Not Invented Here15
1.7.3 Ugly Baby Syndrome15
1.7.4 Low Assembly Costs15
1.7.5 Low Volume17
1.7.6 We Have Been Doing It for Years17
1.7.7 It Is Only Value Analysis17
1.7.8 DFMA Is Only One among Many Techniques17
1.7.9 DFMA Leads to Products that are more Difficult to Service18
1.7.10 I Prefer Design Rules18
1.7.1 I Refuse to Use DFMA18
1.8 What Are the Advantages of Applying DFMA during Product Design?19
1.9 Overall Impact of DFMA on U.S. Industry2
1.10 Conclusions23
References26
2. Selection of Materials and Processes29
2.1 Introduction29
2.2 General Requirements for Early Materials and Process Selection29
2.2.1 Relationship to Process and Operations Planning31
2.3 Selection of Manufacturing Processes31
2.4 Process Capabilities34
2.4.1 General Shape Attributes34
2.4.2 DFA Compatibility Attributes35
2.5 Selection of Materials35
2.5.1 Grouping of Materials into Process Compatible Classes35
2.5.2 Material Selection by Membership Function Modification41
2.5.3 Material Selection by Dimensionless Ranking43
2.6 Primary Process/Material Selection52

Contents 2.7 Systematic Selection of Processes and Materials ....................................................57

2.7.1 Computer-Based Primary Process/Material Selection57
2.7.2 Expert Processing Sequence Selector57
2.7.3 Economic Ranking of Processes61
References70
3. Product Design for Manual Assembly73
3.1 Introduction73
3.2 General Design Guidelines for Manual Assembly74
3.2.1 Design Guidelines for Part Handling74
3.2.2 Design Guidelines for Insertion and Fastening74
3.3 Development of the Systematic Design for Assembly Methodology79
3.4 Assembly Efficiency81
3.5 Classification Systems82
3.6 Effect of Part Symmetry on Handling Time85
3.7 Effect of Part Thickness and Size on Handling Time8
3.8 Effect of Weight on Handling Time89
3.9 Parts Requiring Two Hands for Manipulation90
3.10 Effects of Combinations of Factors90
May Require Tweezers for Grasping and Manipulation90
3.12 Effect of Chamfer Design on Insertion Operations91
3.13 Estimation of Insertion Time94
3.14 Avoiding Jams during Assembly95
3.15 Reducing Disc-Assembly Problems97
of Threaded Fasteners of Various Designs98
Operations9
3.18 Effects of Holding Down100
3.19 Manual Assembly Database and Design Data Sheets103
3.20 Application of the DFA Methodology104
3.20.1 Results of the Analysis107
3.21 Further Design Guidelines110
3.2 Large Assemblies113
3.23 Types of Manual Assembly Methods114
3.24 Effect of Assembly Layout on Acquisition Times118
3.25 Assembly Quality121
3.26 Applying Learning Curves to the DFA Times123
References131
4. Electrical Connections and Wire Harness Assembly133
4.1 Introduction133
4.2 Wire or Cable Harness Assembly135
4.3 Types of Electrical Connections138
4.3.1 Solder Connections139
4.3.2 Low-Pressure Connections139
4.3.3 High-Pressure Connections141
4.4 Types of Wires and Cables143

viii Contents 3.1 Effect of Symmetry for Parts That Severely Nest or Tangle and 3.16 Effects of Obstructed Access and Restricted Vision on Insertion 3.17 Effects of Obstructed Access and Restricted Vision on Pop-Riveting 4.5 Preparation and Assembly Times ........................................................................... 144

4.5.1 Preparation144
4.5.2 Assembly and Installation150
4.5.3 Securing155
4.5.4 Attachment158
4.6 Analysis Method162
4.6.1 Procedure163
4.6.2 Case Study165
References184
5. Design for High-Speed Automatic Assembly and Robot Assembly185
5.1 Introduction185
5.2 Design of Parts for High-Speed Feeding and Orienting186
5.3 Example189
5.4 Additional Feeding Difficulties193
5.5 High-Speed Automatic Insertion193
5.6 Example197
5.7 Analysis of an Assembly198
5.8 General Rules for Product Design for Automation198
5.9 Design of Parts for Feeding and Orienting203
5.10 Summary of Design Rules for High-Speed Automatic Assembly206
5.10.1 Rules for Product Design206
5.10.2 Rules for the Design of Parts206
5.1 Product Design for Robot Assembly206
5.1.1 Summary of Design Rules for Robot Assembly212
References218
6. Printed Circuit Board Design for Manufacture and Assembly219
6.1 Introduction219
6.2 Design Sequence for Printed Circuit Boards219
6.3 Types of Printed Circuit Boards220
6.3.1 Number of Sides220
6.3.2 Number of Layers221
6.3.3 Board Materials221
6.3.4 Device Types2
6.3.5 Copper Weight2
6.4 Bare Board Manufacture2
6.4.1 Basic Bare Board Costs223
6.4.2 Number of Boards per Panel225
6.4.3 Hole Drilling226
6.4.4 Optional Bare Board Processes226
6.4.5 Bare Board Testing227
6.5 Terminology227
6.6 Assembly of Printed Circuit Boards228
6.6.1 Assembly Operations for Through-Hole Printed Circuit Boards229
6.6.1.1 Automatic Dual Inline Package Insertion230
6.6.1.2 Automatic Axial (VCD) Insertion232
6.6.1.3 Automatic Single Inline Package Insertion234
6.6.1.4 Automatic Radial Component Insertion234

Contents ix 6.6.1.5 Semiautomatic Insertion .............................................................235

6.6.1.6 Manual Insertion235
6.6.1.7 Robot Insertion236
6.6.1.8 Inspection and Rework236
6.6.2 Assembly of Surface-Mounted Devices236
6.6.3 Soldering Processes238
6.6.3.1 Wave Soldering238
6.6.3.2 Reflow Soldering238
6.6.4 Other Assembly Processes239
6.6.4.1 Cleaning239
6.6.4.2 Rework239
6.6.4.3 Board Testing240
6.6.5 Assembly Sequences for Printed Circuit Boards240
6.7 Estimation of PCB Assembly Costs242
6.7.1 Component Insertion Costs243
6.7.1.1 Insertion Cost244
6.7.1.2 Setup Cost246
6.7.1.3 Rework Cost247
6.7.1.4 Programming Cost247
6.7.2 Worksheet for Printed Circuit Board Assembly Costs248
6.7.3 Example248
6.8 Case Studies in PCB Assembly250
6.8.1 Measuring Instrument Connector Board250
6.8.2 Power Supply254
6.9 Glossary of Terms256
References260
7. Design for Machining261
7.1 Introduction261
7.2 Machining Using Single-Point Cutting Tools261
7.3 Machining Using Multipoint Tools266
7.4 Machining Using Abrasive Wheels275
7.5 Standardization281
7.6 Choice of Work Material282
7.7 Shape of Work Material284
7.8 Machining Basic Component Shapes284
7.8.1 Disc-Shaped Rotational Components (L/D ≤ 0.5)284
7.8.2 Short, Cylindrical Components (0.5 < L/D < 3)288
7.8.3 Long, Cylindrical Rotational Components (L/D ≥ 3)288
7.8.4 Nonrotational Components (A/B ≤ 3, A/C ≥ 4)291
7.8.5 Long, Nonrotational Components (A/B > 3)293
7.8.6 Cubic, Nonrotational Components (A/B < 3, A/C < 4)293
7.9 Assembly of Components296
7.10 Accuracy and Surface Finish297
7.1 Summary of Design Guidelines300
7.12 Cost Estimating for Machined Components301
7.12.1 Material Cost302
7.12.2 Machine Loading and Unloading303

x Contents 7.12.3 Other Nonproductive Costs .......................................................................303

7.12.4 Handling between Machines303
7.12.5 Material Type305
7.12.6 Machining Costs305
7.12.7 Tool Replacement Costs307
7.12.8 Machining Data308
7.12.9 Rough Grinding310
7.12.10 Finish Grinding313
7.12.1 Allowance for Grinding Wheel Wear313
7.12.12 Allowance for Spark-Out315
7.12.13 Examples315
7.12.14 Machining Cost Estimating Worksheet317
7.12.15 Approximate Cost Models for Machined Components321
References329
8. Design for Injection Molding331
8.1 Introduction331
8.2 Injection Molding Materials331
8.3 Molding Cycle332
8.3.1 Injection or Filling Stage3
8.3.2 Cooling or Freezing Stage334
8.3.3 Ejection and Resetting Stage334
8.4 Injection Molding Systems334
8.4.1 Injection Unit335
8.4.2 Clamp Unit335
8.5 Injection Molds336
8.5.1 Mold Construction and Operation336
8.5.2 Mold Types338
8.5.3 Sprue, Runner, and Gates340
8.6 Molding Machine Size340
8.7 Molding Cycle Time343
8.7.1 Injection Time343
8.7.2 Cooling Time344
8.7.3 Mold Resetting347
8.8 Mold Cost Estimation349
8.8.1 Mold Base Costs349
8.8.2 Cavity and Core Manufacturing Costs351
8.9 Mold Cost Point System357
8.10 Estimation of the Optimum Number of Cavities360
8.1 Design Example363
8.12 Insert Molding364
8.13 Design Guidelines365
8.14 Assembly Techniques366
References372
9. Design for Sheet Metalworking375
9.1 Introduction375
9.2 Dedicated Dies and Pressworking376

Contents xi 9.2.1 Individual Dies for Profile Shearing .........................................................377

9.2.2 Cost of Individual Shearing Dies381
9.2.3 Individual Dies for Piercing Operations387
9.2.4 Individual Dies for Bending Operations389
9.2.5 Individual Dies for Deep Drawing392
9.2.6 Miscellaneous Features398
9.2.7 Progressive Dies399
9.3 Press Selection400
9.3.1 Cycle Times405
9.4 Turret Pressworking407
9.5 Press Brake Operations410
9.6 Design Rules413
References421
10. Design for Die Casting423
10.1 Introduction423
10.2 Die-Casting Alloys423
10.3 Die-Casting Cycle425
10.4 Die-Casting Machines425
10.4.1 Die-Mounting and Clamping Systems425
10.4.2 Metal-Pumping and Injection Systems426
10.4.3 Hot-Chamber Machines426
10.4.4 Cold-Chamber Machines427
10.5 Die-Casting Dies428
10.5.1 Trimming Dies429
10.6 Finishing429
10.7 Auxiliary Equipment for Automation431
10.8 Determination of the Optimum Number of Cavities431
10.9 Determination of Appropriate Machine Size436
10.9.1 Required Machine Clamp Force436
10.9.2 Shot Volume and Material Cost per Part438
10.9.3 Dimensional Machine Constraints439
10.10 Die Casting Cycle Time Estimation441
10.10.1 Ladling of Molten Metal441
10.10.2 Metal Injection441
10.10.3 Metal Cooling442
10.10.4 Part Extraction and Die Lubrication446
10.10.5 Trimming Cycle Time448
10.1 Die Cost Estimation449
10.1.1 Die Set Costs449
10.1.2 Cavity and Core Costs450
10.1.3 Trim Die Costs451
10.12 Assembly Techniques453
10.13 Design Principles455
References458
1. Design for Powder Metal Processing461
1.1 Introduction461
1.2 Main Stages in the Powder Metallurgy Process462

xii Contents 1.2.1 Mixing ...........................................................................................................463

1.2.2 Compaction463
1.2.3 Sintering464
1.3 Secondary Manufacturing Stages464
1.3.1 Repressing and Resintering464
1.3.2 Sizing and Coining464
1.3.3 Infiltration464
1.3.4 Impregnation465
1.3.5 Resin Impregnation465
1.3.6 Heat Treatment466
1.3.7 Machining466
1.3.8 Tumbling and Deburring466
1.3.9 Plating and Other Surface Treatments466
1.3.10 Steam Treating466
1.3.1 Assembly Processes466
1.4 Compaction Characteristics of Powders467
1.4.1 Powder Compaction Mechanics468
1.4.2 Compression Characteristics of Metal Powders470
1.4.3 Powder Compression Ratio473
1.5 Tooling for Powder Compaction473
1.5.1 Compaction Dies474
1.5.2 Punches for Compaction475
1.5.3 Core Rods for Through Holes475
1.5.4 Die Accessories476
1.6 Presses for Powder Compaction476
1.6.1 Factors in Choosing the Appropriate Press476
1.6.1.1 Punch Motions476
1.6.1.2 Load Required477
1.6.1.3 Fill Height477
1.6.1.4 Ejection Stroke478
1.6.1.5 Maximum Die Diameter478
1.6.2 Presses for Coining, Sizing, and Repressing478
1.7 Form of Powder Metal Parts479
1.7.1 Profile Complexity480
1.8 Sintering Equipment Characteristics481
1.8.1 Sintering Equipment481
1.8.1.1 Continuous-Flow Furnaces482
1.8.1.2 Batch Furnaces484
1.9 Materials for Powder Metal Processing484
1.10 Contributions to Basic Powder Metallurgy Manufacturing Costs486
1.10.1 Material Costs486
1.10.2 Compacting Costs492
1.10.2.1 Press Selection492
1.10.2.2 Setup Cost494
1.10.3 Compaction Tooling Costs495
1.10.3.1 Initial Tooling Costs495
1.10.3.2 Tool Material Costs495
1.10.3.3 Tool Manufacturing Costs497
1.10.3.4 Dies497

Contents xiii 1.10.3.5 Punches ...................................................................................... 498

1.10.3.6 Core Rods500
1.10.3.7 Total Tool Manufacturing Costs501
1.10.4 Tool Accessory Costs501
1.10.5 Tool Replacement Costs502
1.10.6 Validation of the Tool Cost-Estimating Procedure503
1.10.7 Sintering Costs503
1.10.7.1 Continuous-Flow Furnaces504
1.10.7.2 Batch Furnaces505
1.10.8 Repressing, Coining, and Sizing506
1.1 Modifications for Infiltrated Materials506
1.1.1 Material Costs506
1.1.2 Compaction Costs507
1.1.3 Sintering Costs507
and Other Surface Treatments507
1.12.1 Processing Costs507
1.12.2 Additional Material Costs507
1.12.2.1 Self-Lubricating Bearing Materials508
1.12.2.2 Materials Impregnated with Oil or Polymer508
1.13 Some Design Guidelines for Powder Metal Parts509
1.14 Powder Injection Molding510
1.14.1 Feedstock Preparation and Pelletization51
1.14.2 Molding512
1.14.3 Debinding512
1.14.4 Sintering514
1.14.5 Secondary Operations515
1.14.6 Feedstock Characteristics515
1.14.7 Material Costs519
1.14.8 Mold Cavity Geometry521
1.14.9 Molding Costs521
References525
12. Design for Sand Casting527
12.1 Introduction527
12.2 Sand Casting Alloys528
12.3 Basic Characteristics and Mold Preparation529
12.3.1 Sand Preparation529
12.3.2 Gating System529
12.3.3 Mold Risers and Chills530
12.3.4 Pattern Types531
12.3.5 Sand Compaction Methods532
12.4 Sand Cores533
12.5 Melting and Pouring of Metal533
12.6 Cleaning of Castings534
12.7 Cost Estimating535
12.7.1 Metal Cost535
12.7.2 Sand Costs538

xiv Contents 1.12 Impregnation, Heat Treatment, Tumbling, Steam Treatment, 12.7.3 Tooling Costs ................................................................................................ 539

12.7.4 Processing Costs542
12.8 Design Rules for Sand Castings545
12.8.1 Avoid Sharp Angles and Multiple-Section Joints545
12.8.2 Design Sections of Uniform Thickness546
12.8.3 Proportion Inner Wall Thickness547
12.8.4 Consider Metal Shrinkage in the Design547
12.8.5 Use a Simple Parting Line547
12.8.6 Define Appropriate Machining Allowances548
12.8.7 Use Economical Tolerances548
12.9 Example Calculations549
References556
13. Design for Investment Casting559
13.1 Introduction559
13.2 Process Overview559
13.3 Pattern Materials561
13.4 Pattern Injection Machines561
13.5 Pattern Molds563
13.6 Pattern and Cluster Assembly563
13.7 Ceramic Shell Mold563
13.8 Ceramic Cores564
13.9 Pattern Meltout565
13.10 Pattern Burnout and Mold Firing565
13.1 Knockout and Cleaning565
13.12 Cutoff and Finishing566
13.13 Pattern and Core Material Cost566
13.14 Wax Pattern Injection Cost568
13.15 Fill Time570
13.16 Cooling Time570
13.17 Ejection and Reset Time571
13.18 Process Cost per Pattern or Core573
13.19 Estimating Core Injection Cost574
13.20 Pattern and Core Mold Cost575
13.21 Core Mold Cost579
13.2 Pattern and Cluster Assembly Cost579
13.23 Number of Parts per Cluster581
13.24 Pattern Piece Cost582
13.25 Cleaning and Etching583
13.26 Shell Mold Material Cost583
13.27 Investing the Pattern Cluster584
13.28 Pattern Meltout585
13.29 Burnout, Sinter, and Preheat585
13.30 Total Shell Mold Cost585
13.31 Cost for Melting Metal586
13.32 Raw Base Metal Cost590
13.3 Ready-to-Pour Liquid Metal Cost590
13.34 Pouring Cost590

Contents xv 13.35 Final Material Cost .................................................................................................... 591

13.36 Breakout592
13.37 Cleaning593
13.38 Cutoff593
13.39 Design Guidelines596
References597
14. Design for Hot Forging599
14.1 Introduction599
14.2 Characteristics of the Forging Process599
14.2.1 Types of Forging Processes599
14.3 Role of Flash in Forging600
14.3.1 Determination of the Flash Land Geometry601
14.3.2 Amount of Flash603
14.3.3 Webs in Forgings605
14.4 Forging Allowances605
14.5 Preforming during Forging606
14.5.1 Die Layout611
14.6 Flash Removal613
14.7 Classification of Forgings614
14.7.1 Forging Complexity616
14.7.1.1 Shape Complexity Factor616
14.7.1.2 Number of Surface Patches in the Part617
14.8 Forging Equipment617
14.8.1 Gravity Drop Hammers617
14.8.2 Double Acting or Power Hammers618
14.8.3 Vertical Counterblow Hammers618
14.8.4 Horizontal Counterblow Hammers619
14.8.5 Mechanical Presses619
14.8.6 Screw Presses620
14.8.7 Hydraulic Presses620
14.8.8 Choice of Forging Machine Type620
14.8.9 Comparisons of Forging Equipment621
14.9 Classification of Materials621
14.10 Forging Costs624
14.10.1 Material Costs626
14.10.2 Equipment Operating Costs627
14.10.3 Examples of Equipment Selection629
14.10.4 Forging Processing Costs630
14.10.5 Forging Machine Setup Costs632
14.1 Forging Die Costs633
14.1.1 Initial Die Costs633
14.1.2 Estimation of Costs for Multi-Impression Forging Dies634
14.1.2.1 Die Material Costs634
14.1.2.2 Multi-Impression Die Manufacturing Costs636
14.12 Die Life and Tool Replacement Costs638
14.13 Costs of Flash Removal640
14.13.1 Flash Removal Processing Costs640

xvi Contents 14.13.2 Tooling Costs for Flash Removal ...............................................................641

14.14 Other Forging Costs642
14.14.1 Billet Preparation642
14.14.2 Billet Heating Costs643
References646

Contents xvii Index ............................................................................................................................................. 649 xix

Preface

This third edition of Product Design for Manufacture and Assembly includes updating of the data in all chapters of the book. In addition, a comprehensive set of problems and student assignments have been added to each chapter. This is because the book has been used in the past as the assigned text for university-level courses and the addition of these problem sets has made the new edition substantially more useful as a text book. The overall aim is to provide a text that can not only serve as a reference text for design and manufacturing engineers in industry, but will also serve as a basic text for courses in product design and design for manufacture. A comprehensive coverage of the factors that influence the ease of assembly and manufacture of products for a wide range of the basic processes used in industry is provided.

The introductory chapter has been updated to include more recent case studies of the application of design for manufacture and assembly (DFMA) techniques in industry, while still illustrating the effect that DFMA has had on U.S. industry as a whole. In Chapters 3 and 5, the extended versions of the classification schemes of the features of products that influence the difficulty of handling and insertion for manual, high-speed automatic and robot assembly have been added. This allows realistic student assignments to be added to these chapters. The chapter on printed circuit board assembly (Chapter 6) has been updated to reflect the changes in industry that have taken place since the previous edition, in particular the increased emphasis on the use of surface-mounted devices.

The remaining chapters on basic manufacturing processes have been updated with more recent data and comprehensive sets of problems and assignments added to each chapter. In Chapter 1 on design for powder metal processing, a discussion on design for powder injection molding has been added, as this technique has become more widely used in industry.

Each chapter includes some cost information on materials, labor, and machine operations. This information is representative of typical costs at the time of publication and does not necessarily indicate costs applicable at the current time. Costs obviously fluctuate over a period of time. The relative costs indicated in these data are probably suitable for a reasonable comparison between product designs and processing methods to be made.

As for the previous editions, we thank the various companies that have supported research on DFMA at the University of Rhode Island and the graduate students who have contributed to the research. The techniques developed from this research have become widely used in industry and have had a significant influence on the development of more competitive products that are both simpler in configuration and easier to manufacture with reduced overall costs.

Geoffrey Boothroyd

Peter Dewhurst Winston A. Knight xxi

Preface to the Second Edition

This second edition of Product Design for Manufacture and Assembly includes three new chapters, describing the processes of sand casting, investment casting, and hot forging. These chapters, combined with the chapters describing design for machining, injection molding, sheet metalworking, die casting, and powder metals, cover a wide range of the most basic forming processes used in industry.

In addition, substantial material has been added to the introductory chapter illustrating the effects that the application of design for manufacture and assembly (DFMA) has had on U.S. industry as a whole. Chapter 2, dealing with the selection of materials and processes for manufacture, now includes further material describing material selection specifically and the economic ranking of processes using a new software tool.

Chapter 3, dealing with product design for manual assembly, includes an updated special section dealing with the effect of design on product quality. Finally, additional material has been added to Chapter 15 discussing links between computer-aided design (CAD) solid models and design analysis tools.

As for the previous edition, we thank the various companies who have supported research on DFMA at the University of Rhode Island and the graduate students who have contributed to the research. We particularly acknowledge the help of Allyn Mackay, on whose work the new chapter on investment casting is largely based.

Finally, thanks are due to Shirley Boothroyd for typing much of the new material and to Kenneth Fournier for preparing some of the additional artwork.

Geoffrey Boothroyd

Peter Dewhurst Winston A. Knight

Preface to the First Edition

We have been working in the area of product design for manufacture and assembly (DFMA) for over 20 years. The methods that have been developed have found wide application in industry—particularly U.S. industry. In fact, it can be said that the availability of these methods has created a revolution in the product design business and has helped to break down the barriers between design and manufacture; it has also allowed the development of concurrent or simultaneous engineering.

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