Additive manufacturing technologies  3d printing, rapid prototyping, and direct digital manufacturing

Ian Gibson • David Rosen • Brent StuckerAdditive Manufacturing Technologies 3D Printing, Rapid Prototyping, and Direct Digital Manufacturing Second Edition... In a product development co

Additive Manufacturing Technologies

Ian Gibson • David Rosen • Brent Stucker

Additive Manufacturing Technologies

3D Printing, Rapid Prototyping,

and Direct Digital Manufacturing

Second Edition

Georgia Institute of TechnologyAtlanta, GA USA

Springer New York Heidelberg Dordrecht London

Library of Congress Control Number: 2014953293

# Springer Science+Business Media New York 2010, 2015

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Thank you for taking the time to read this book on Additive Manufacturing (AM)

We hope you benefit from the time and effort it has taken putting it together and thatyou think it was a worthwhile undertaking It all started as a discussion at aconference in Portugal when we realized that we were putting together bookswith similar aims and objectives Since we are friends as well as colleagues, itseemed sensible that we join forces rather than compete; sharing the load andplaying to each other’s strengths undoubtedly means a better all-round effort andresult

We wrote this book because we have all been working in the field of AM formany years Although none of us like to be called “old,” we do seem to have

60 years of experience, collectively, and have each established reputations aseducators and researchers in this field We have each seen the technologiesdescribed in this book take shape and develop into serious commercial tools, withtens of thousands of users and many millions of parts being made by AM machineseach year AM is now being incorporated into curricula in many schools,polytechnics, and universities around the world More and more students arebecoming aware of these technologies and yet, as we saw it, there was no singletext adequate for such curricula We believe that the first edition of this bookprovided such a text, and based upon the updated information in this 2nd edition,

we hope we’ve improved upon that start

Additive Manufacturing is defined by a range of technologies that are capable oftranslating virtual solid model data into physical models in a quick and easyprocess The data are broken down into a series of 2D cross-sections of a finitethickness These cross-sections are fed into AM machines so that they can becombined, adding them together in a layer-by-layer sequence to form the physicalpart The geometry of the part is therefore clearly reproduced in the AM machinewithout having to adjust for manufacturing processes, like attention to tooling,undercuts, draft angles, or other features We can say therefore that the AMmachine is a What You See Is What You Build (WYSIWYB) process that isparticularly valuable the more complex the geometry is This basic principle drivesnearly all AM machines, with variations in each technology in terms of thetechniques used for creating layers and in bonding them together Further variations

v

include speed, layer thickness, range of materials, accuracy, and of course cost.With so many variables, it is clear to see why this book must be so long anddetailed Having said that, we still feel there is much more we could have writtenabout.

The first three chapters of this book provide a basic overview of AM processes.Without fully describing each technology, we provide an appreciation for why AM

is so important to many branches of industry We outline the rapid development ofthis technology from humble beginnings that showed promise but still requiringmuch development, to one that is now maturing and showing real benefit to productdevelopment organizations In reading these chapters, we hope you can learn thebasics of how AM works

The next nine chapters (Chaps.4 12) take each group of technologies in turn anddescribe them in detail The fundamentals of each technology are dealt with interms of the basic process, whether it involves photopolymer curing, sintering,melting, etc., so that the reader can appreciate what is needed in order to under-stand, develop, and optimize each technology Most technologies discussed in thisbook have been commercialized by at least one company; and these machines aredescribed along with discussion on how to get the best out of them The last chapter

in this group focused on inexpensive processes and machines, which overlaps some

of the material in earlier chapters, but we felt that the exponentially increasinginterest in these low-cost machines justified the special treatment

The final chapters deal with how to apply AM technology in different settings.Firstly, we look at selection methods for sorting through the many optionsconcerning the type of machine you should buy in relation to your applicationand provide guidelines on how to select the right technology for your purpose.Since all AM machines depend on input from 3D CAD software, we go on todiscuss how this process takes place We follow this with a discussion of post-processing methods and technologies so that if your selected machine and materialcannot produce exactly what you want, you have the means for improving the part’sproperties and appearance A chapter on software issues in AM completes thisgroup of chapters

AM technologies have improved to the extent that many manufacturers are using

AM machine output for end-product use Called Direct Digital Manufacturing, thisopens the door to many exciting and novel applications considered impossible,infeasible, or uneconomic in the past We can now consider the possibility of masscustomization, where a product can be produced according to the tastes of anindividual consumer but at a cost-effective price Then, we look at how the use ofthis technology has affected the design process considering how we might improveour designs because of the WYSIWYB approach This moves us on nicely to thesubjects of applications of AM, including tooling and products in the medical,aerospace, and automotive industries We complete the book with a chapter on thebusiness, or enterprise-level, aspects of AM, investigating how these systems

enable creative businesses and entrepreneurs to invent new products, and where

AM will likely develop in the future

This book is primarily aimed at students and educators studying AdditiveManufacturing, either as a self-contained course or as a module within a largercourse on manufacturing technology There is sufficient depth for an undergraduate

or graduate-level course, with many references to point the student further along thepath Each chapter also has a number of exercise questions designed to test thereader’s knowledge and to expand their thinking A companion instructor’s guide isbeing developed as part of the 2nd edition to include additional exercises and theirsolutions, to aid educators Researchers into AM may also find this text useful inhelping them understand the state of the art and the opportunities for furtherresearch

We have made a wide range of changes in moving from the first edition,completed in 2009, to this new edition As well as bringing everything as up todate as is possible in this rapidly changing field, we have added in a number of newsections and chapters The chapter on medical applications has been extended toinclude discussion on automotive and aerospace There is a new chapter on rapidtooling as well as one that discusses the recent movements in the low-cost AMsector We have inserted a range of recent technological innovations, includingdiscussion on the new Additive Manufacturing File Format as well as otherinclusions surrounding the standardization of AM with ASTM and ISO We havealso updated the terminology in the text to conform to terminology developed bythe ASTM F42 committee, which has also been adopted as an ISO internationalstandard In this 2nd edition we have edited the text to, as much as possible, removereferences to company-specific technologies and instead focus more on technolog-ical principles and general understanding We split the original chapter on printingprocesses into two chapters on material jetting and on binder jetting to reflect thestandard terminology and the evolution of these processes in different directions

As a result of these many additions and changes, we feel that this edition is nowsignificantly more comprehensive than the first one

Although we have worked hard to make this book as comprehensive as possible,

we recognize that a book about such rapidly changing technology will not be date for very long With this in mind, and to help educators and students betterutilize this book, we will update our course website athttp://www.springer.com/978-1-4419-1119-3, with additional homework exercises and other aids foreducators If you have comments, questions, or suggestions for improvement,they are welcome We anticipate updating this book in the future, and we lookforward to hearing how you have used these materials and how we might improvethis book

As mentioned earlier, each author is an established expert in AdditiveManufacturing with many years of research experience In addition, in manyways, this book is only possible due to the many students and colleagues withwhom we have collaborated over the years To introduce you to the authors andsome of the others who have made this book possible, we will end this preface withbrief author biographies and acknowledgements.

Dr Brent Stucker thanks Utah State and VTT Technical Research Center ofFinland, which provided time to work on the first edition of this book while onsabbatical in Helsinki; and more recently the University of Louisville for providingthe academic freedom and environment needed to complete the 2nd edition.Additionally, much of this book would not have been possible without the manygraduate students and postdoctoral researchers who have worked with Dr Stuckerover the years In particular, he would like to thank Dr G.D Janaki Ram of theIndian Institute of Technology Madras, whose coauthoring of the “Layer-BasedAdditive Manufacturing Technologies” chapter in theCRC Materials ProcessingHandbook helped lead to the organization of this book Additionally, the followingstudents’ work led to one or more things mentioned in this book and in theaccompanying solution manual: Muni Malhotra, Xiuzhi Qu, Carson Esplin, AdamSmith, Joshua George, Christopher Robinson, Yanzhe Yang, Matthew Swank, JohnObielodan, Kai Zeng, Haijun Gong, Xiaodong Xing, Hengfeng Gu, Md Anam,Nachiket Patil, and Deepankar Pal Special thanks are due to Dr Stucker’s wifeGail, and their children: Tristie, Andrew, Megan, and Emma, who patientlysupported many days and evenings on this book

Prof David W Rosen acknowledges support from Georgia Tech and the manygraduate students and postdocs who contributed technically to the content in thisbook In particular, he thanks Drs Fei Ding, Amit Jariwala, Scott Johnston, AmeyaLimaye, J Mark Meacham, Benay Sager, L Angela Tse, Hongqing Wang, ChrisWilliams, Yong Yang, and Wenchao Zhou, as well as Lauren Margolin and XiayunZhao A special thanks goes out to his wife Joan and children Erik and Krista fortheir patience while he worked on this book

Prof Ian Gibson would like to acknowledge the support of Deakin University inproviding sufficient time for him to work on this book L.K Anand also helped inpreparing many of the drawings and images for his chapters Finally, he wishes tothank his lovely wife, Lina, for her patience, love, and understanding during thelong hours preparing the material and writing the chapters He also dedicates thisbook to his late father, Robert Ervin Gibson, and hopes he would be proud of thiswonderful achievement

ix

1 Introduction and Basic Principles 1

1.1 What Is Additive Manufacturing? 1

1.2 What Are AM Parts Used for? 3

1.3 The Generic AM Process 4

1.3.1 Step 1: CAD 4

1.3.2 Step 2: Conversion to STL 4

1.3.3 Step 3: Transfer to AM Machine and STL File Manipulation 5

1.3.4 Step 4: Machine Setup 5

1.3.5 Step 5: Build 5

1.3.6 Step 6: Removal 6

1.3.7 Step 7: Post-processing 6

1.3.8 Step 8: Application 6

1.4 Why Use the Term Additive Manufacturing? 7

1.4.1 Automated Fabrication (Autofab) 7

1.4.2 Freeform Fabrication or Solid Freeform Fabrication 7

1.4.3 Additive Manufacturing or Layer-Based Manufacturing 7

1.4.4 Stereolithography or 3D Printing 8

1.4.5 Rapid Prototyping 8

1.5 The Benefits of AM 9

1.6 Distinction Between AM and CNC Machining 10

1.6.1 Material 10

1.6.2 Speed 10

1.6.3 Complexity 11

1.6.4 Accuracy 11

1.6.5 Geometry 12

1.6.6 Programming 12

1.7 Example AM Parts 12

1.8 Other Related Technologies 14

1.8.1 Reverse Engineering Technology 14

1.8.2 Computer-Aided Engineering 15

xi

1.8.3 Haptic-Based CAD 16

1.9 About this Book 17

1.10 Exercises 17

References 18

2 Development of Additive Manufacturing Technology 19

2.1 Introduction 19

2.2 Computers 20

2.3 Computer-Aided Design Technology 22

2.4 Other Associated Technologies 26

2.4.1 Lasers 26

2.4.2 Printing Technologies 26

2.4.3 Programmable Logic Controllers 27

2.4.4 Materials 27

2.4.5 Computer Numerically Controlled Machining 28

2.5 The Use of Layers 28

2.6 Classification of AM Processes 30

2.6.1 Liquid Polymer Systems 31

2.6.2 Discrete Particle Systems 32

2.6.3 Molten Material Systems 33

2.6.4 Solid Sheet Systems 34

2.6.5 New AM Classification Schemes 34

2.7 Metal Systems 35

2.8 Hybrid Systems 36

2.9 Milestones in AM Development 37

2.10 AM Around the World 39

2.11 The Future? Rapid Prototyping Develops into Direct Digital Manufacturing 40

2.12 Exercises 41

References 41

3 Generalized Additive Manufacturing Process Chain 43

3.1 Introduction 43

3.2 The Eight Steps in Additive Manufacture 44

3.2.1 Step 1: Conceptualization and CAD 44

3.2.2 Step 2: Conversion to STL/AMF 45

3.2.3 Step 3: Transfer to AM Machine and STL File Manipulation 47

3.2.4 Step 4: Machine Setup 47

3.2.5 Step 5: Build 48

3.2.6 Step 6: Removal and Cleanup 48

3.2.7 Step 7: Post-Processing 49

3.2.8 Step 8: Application 49

3.3 Variations from One AM Machine to Another 50

3.3.1 Photopolymer-Based Systems 51

3.3.2 Powder-Based Systems 51

3.3.3 Molten Material Systems 51

3.3.4 Solid Sheets 52

3.4 Metal Systems 52

3.4.1 The Use of Substrates 53

3.4.2 Energy Density 53

3.4.3 Weight 53

3.4.4 Accuracy 53

3.4.5 Speed 54

3.5 Maintenance of Equipment 54

3.6 Materials Handling Issues 54

3.7 Design for AM 55

3.7.1 Part Orientation 55

3.7.2 Removal of Supports 56

3.7.3 Hollowing Out Parts 57

3.7.4 Inclusion of Undercuts and Other Manufacturing Constraining Features 57

3.7.5 Interlocking Features 57

3.7.6 Reduction of Part Count in an Assembly 58

3.7.7 Identification Markings/Numbers 58

3.8 Application Areas That Don’t Involve Conventional CAD Modeling 59

3.8.1 Medical Modeling 59

3.8.2 Reverse Engineering Data 59

3.8.3 Architectural Modeling 60

3.9 Further Discussion 60

3.9.1 Exercises 61

References 61

4 Vat Photopolymerization Processes 63

4.1 Introduction 63

4.2 Vat Photopolymerization Materials 65

4.2.1 UV-Curable Photopolymers 66

4.2.2 Overview of Photopolymer Chemistry 67

4.2.3 Resin Formulations and Reaction Mechanisms 70

4.3 Reaction Rates 73

4.4 Laser Scan Vat Photopolymerization 74

4.5 Photopolymerization Process Modeling 74

4.5.1 Irradiance and Exposure 75

4.5.2 Laser–Resin Interaction 78

4.5.3 Photospeed 80

4.5.4 Time Scales 81

4.6 Vector Scan VP Machines 82

4.7 Scan Patterns 84

4.7.1 Layer-Based Build Phenomena and Errors 84

4.7.2 WEAVE 86

4.7.3 STAR-WEAVE 88

4.7.4 ACES Scan Pattern 90

4.8 Vector Scan Micro-Vat Photopolymerization 94

4.9 Mask Projection VP Technologies and Processes 95

4.9.1 Mask Projection VP Technology 95

4.9.2 Commercial MPVP Systems 96

4.9.3 MPVP Modeling 98

4.10 Two-Photon Vat Photopolymerization 99

4.11 Process Benefits and Drawbacks 101

4.12 Summary 102

4.13 Exercises 102

References 103

5 Powder Bed Fusion Processes 107

5.1 Introduction 107

5.2 Materials 109

5.2.1 Polymers and Composites 109

5.2.2 Metals and Composites 110

5.2.3 Ceramics and Ceramic Composites 112

5.3 Powder Fusion Mechanisms 112

5.3.1 Solid-State Sintering 112

5.3.2 Chemically Induced Sintering 115

5.3.3 LPS and Partial Melting 116

5.3.4 Full Melting 120

5.3.5 Part Fabrication 121

5.4 Process Parameters and Modeling 122

5.4.1 Process Parameters 123

5.4.2 Applied Energy Correlations and Scan Patterns 125

5.5 Powder Handling 127

5.5.1 Powder Handling Challenges 127

5.5.2 Powder Handling Systems 128

5.5.3 Powder Recycling 129

5.6 PBF Process Variants and Commercial Machines 131

5.6.1 Polymer Laser Sintering 131

5.6.2 Laser-Based Systems for Metals and Ceramics 134

5.6.3 Electron Beam Melting 136

5.6.4 Line-Wise and Layer-Wise PBF Processes for Polymers 140

5.7 Process Benefits and Drawbacks 143

5.8 Conclusions 144

5.9 Exercises 144

References 145

6 Extrusion-Based Systems 147

6.1 Introduction 147

6.2 Basic Principles 148

6.2.1 Material Loading 149

6.2.2 Liquification 149

6.2.3 Extrusion 149

6.2.4 Solidification 153

6.2.5 Positional Control 154

6.2.6 Bonding 155

6.2.7 Support Generation 156

6.3 Plotting and Path Control 157

6.4 Fused Deposition Modeling from Stratasys 160

6.4.1 FDM Machine Types 161

6.5 Materials 163

6.6 Limitations of FDM 164

6.7 Bioextrusion 166

6.7.1 Gel Formation 166

6.7.2 Melt Extrusion 166

6.7.3 Scaffold Architectures 168

6.8 Other Systems 168

6.8.1 Contour Crafting 169

6.8.2 Nonplanar Systems 169

6.8.3 FDM of Ceramics 171

6.8.4 Reprap and Fab@home 171

6.9 Exercises 172

References 173

7 Material Jetting 175

7.1 Evolution of Printing as an Additive Manufacturing Process 175

7.2 Materials for Material Jetting 176

7.2.1 Polymers 177

7.2.2 Ceramics 180

7.2.3 Metals 181

7.2.4 Solution- and Dispersion-Based Deposition 183

7.3 Material Processing Fundamentals 184

7.3.1 Technical Challenges of MJ 184

7.3.2 Droplet Formation Technologies 186

7.3.3 Continuous Mode 187

7.3.4 DOD Mode 188

7.3.5 Other Droplet Formation Methods 190

7.4 MJ Process Modeling 191

7.5 Material Jetting Machines 195

7.6 Process Benefits and Drawbacks 198

7.7 Summary 198

7.8 Exercises 199

References 200

8 Binder Jetting 205

8.1 Introduction 205

8.2 Materials 207

8.2.1 Commercially Available Materials 207

8.2.2 Ceramic Materials in Research 208

8.3 Process Variations 210

8.4 BJ Machines 212

8.5 Process Benefits and Drawbacks 216

8.6 Summary 217

8.7 Exercises 217

References 218

9 Sheet Lamination Processes 219

9.1 Introduction 219

9.1.1 Gluing or Adhesive Bonding 219

9.1.2 Bond-Then-Form Processes 220

9.1.3 Form-Then-Bond Processes 222

9.2 Materials 224

9.3 Material Processing Fundamentals 225

9.3.1 Thermal Bonding 226

9.3.2 Sheet Metal Clamping 227

9.4 Ultrasonic Additive Manufacturing 228

9.4.1 UAM Bond Quality 229

9.4.2 Ultrasonic Metal Welding Process Fundamentals 230

9.4.3 UAM Process Parameters and Process Optimization 233

9.4.4 Microstructures and Mechanical Properties of UAM Parts 235

9.4.5 UAM Applications 239

9.5 Conclusions 242

9.6 Exercises 243

References 243

10 Directed Energy Deposition Processes 245

10.1 Introduction 245

10.2 General DED Process Description 247

10.3 Material Delivery 249

10.3.1 Powder Feeding 249

10.3.2 Wire Feeding 251

10.4 DED Systems 252

10.4.1 Laser Based Metal Deposition Processes 252

10.4.2 Electron Beam Based Metal Deposition Processes 256

10.4.3 Other DED Processes 257

10.5 Process Parameters 257

10.6 Typical Materials and Microstructure 258

10.7 Processing–Structure–Properties Relationships 261

10.8 DED Benefits and Drawbacks 266

10.9 Exercises 267

References 268

11 Direct Write Technologies 269

11.1 Direct Write Technologies 269

11.2 Background 269

11.3 Ink-Based DW 270

11.3.1 Nozzle Dispensing Processes 271

11.3.2 Quill-Type Processes 273

11.3.3 Inkjet Printing Processes 275

11.3.4 Aerosol DW 276

11.4 Laser Transfer DW 277

11.5 Thermal Spray DW 280

11.6 Beam Deposition DW 282

11.6.1 Laser CVD 282

11.6.2 Focused Ion Beam CVD 284

11.6.3 Electron Beam CVD 284

11.7 Liquid-Phase Direct Deposition 285

11.8 Beam Tracing Approaches to Additive/Subtractive DW 286

11.8.1 Electron Beam Tracing 286

11.8.2 Focused Ion Beam Tracing 287

11.8.3 Laser Beam Tracing 287

11.9 Hybrid Technologies 287

11.10 Applications of Direct Write Technologies 288

11.10.1 Exercises 290

References 290

12 The Impact of Low-Cost AM Systems 293

12.1 Introduction 293

12.2 Intellectual Property 294

12.3 Disruptive Innovation 296

12.3.1 Disruptive Business Opportunities 296

12.3.2 Media Attention 297

12.4 The Maker Movement 299

12.5 The Future of Low-Cost AM 301

12.6 Exercises 301

References 301

13 Guidelines for Process Selection 303

13.1 Introduction 303

13.2 Selection Methods for a Part 304

13.2.1 Decision Theory 304

13.2.2 Approaches to Determining Feasibility 305

13.2.3 Approaches to Selection 307

13.2.4 Selection Example 310

13.3 Challenges of Selection 312

13.4 Example System for Preliminary Selection 316

13.5 Production Planning and Control 321

13.5.1 Production Planning 322

13.5.2 Pre-processing 323

13.5.3 Part Build 323

13.5.4 Post-processing 324

13.5.5 Summary 324

13.6 Open Problems 325

13.7 Exercises 326

References 326

14 Post-processing 329

14.1 Introduction 329

14.2 Support Material Removal 329

14.2.1 Natural Support Post-processing 330

14.2.2 Synthetic Support Removal 331

14.3 Surface Texture Improvements 334

14.4 Accuracy Improvements 334

14.4.1 Sources of Inaccuracy 335

14.4.2 Model Pre-processing to Compensate for Inaccuracy 335

14.4.3 Machining Strategy 337

14.5 Aesthetic Improvements 341

14.6 Preparation for Use as a Pattern 342

14.6.1 Investment Casting Patterns 342

14.6.2 Sand Casting Patterns 343

14.6.3 Other Pattern Replication Methods 344

14.7 Property Enhancements Using Non-thermal Techniques 345

14.8 Property Enhancements Using Thermal Techniques 346

14.9 Conclusions 349

14.10 Exercises 349

References 350

15 Software Issues for Additive Manufacturing 351

15.1 Introduction 351

15.2 Preparation of CAD Models: The STL File 352

15.2.1 STL File Format, Binary/ASCII 352

15.2.2 Creating STL Files from a CAD System 354

15.2.3 Calculation of Each Slice Profile 355

15.2.4 Technology-Specific Elements 359

15.3 Problems with STL Files 361

15.4 STL File Manipulation 364

15.4.1 Viewers 365

15.4.2 STL Manipulation on the AM Machine 365

15.5 Beyond the STL File 367

15.5.1 Direct Slicing of the CAD Model 367

15.5.2 Color Models 368

15.5.3 Multiple Materials 368

15.5.4 Use of STL for Machining 368

15.6 Additional Software to Assist AM 369

15.6.1 Survey of Software Functions 370

15.6.2 AM Process Simulations Using Finite Element Analysis 371

15.7 The Additive Manufacturing File Format 372

15.8 Exercises 373

References 374

16 Direct Digital Manufacturing 375

16.1 Align Technology 375

16.2 Siemens and Phonak 377

16.3 Custom Footwear and Other DDM Examples 380

16.4 DDM Drivers 383

16.5 Manufacturing Versus Prototyping 385

16.6 Cost Estimation 387

16.6.1 Cost Model 387

16.6.2 Build Time Model 389

16.6.3 Laser Scanning Vat Photopolymerization Example 392

16.7 Life-Cycle Costing 393

16.8 Future of DDM 395

16.9 Exercises 396

References 397

17 Design for Additive Manufacturing 399

17.1 Motivation 400

17.2 Design for Manufacturing and Assembly 401

17.3 AM Unique Capabilities 404

17.3.1 Shape Complexity 404

17.3.2 Hierarchical Complexity 405

17.3.3 Functional Complexity 407

17.3.4 Material Complexity 409

17.4 Core DFAM Concepts and Objectives 411

17.4.1 Complex Geometry 411

17.4.2 Integrated Assemblies 412

17.4.3 Customized Geometry 412

17.4.4 Multifunctional Designs 412

17.4.5 Elimination of Conventional DFM Constraints 413

17.5 Exploring Design Freedoms 413

17.5.1 Part Consolidation and Redesign 414

17.5.2 Hierarchical Structures 415

17.5.3 Industrial Design Applications 417

17.6 CAD Tools for AM 418

17.6.1 Challenges for CAD 418

17.6.2 Solid-Modeling CAD Systems 420

17.6.3 Promising CAD Technologies 422

17.7 Synthesis Methods 426

17.7.1 Theoretically Optimal Lightweight Structures 426

17.7.2 Optimization Methods 427

17.7.3 Topology Optimization 428

17.8 Summary 433

17.9 Exercises 434

References 434

18 Rapid Tooling 437

18.1 Introduction 437

18.2 Direct AM Production of Injection Molding Inserts 439

18.3 EDM Electrodes 443

18.4 Investment Casting 444

18.5 Other Systems 445

18.5.1 Vacuum Forming Tools 445

18.5.2 Paper Pulp Molding Tools 446

18.5.3 Formwork for Composite Manufacture 446

18.5.4 Assembly Tools and Metrology Registration Rigs 446

18.6 Exercises 448

References 448

19 Applications for Additive Manufacture 451

19.1 Introduction 451

19.2 Historical Developments 452

19.2.1 Value of Physical Models 453

19.2.2 Functional Testing 453

19.2.3 Rapid Tooling 454

19.3 The Use of AM to Support Medical Applications 455

19.3.1 Surgical and Diagnostic Aids 457

19.3.2 Prosthetics Development 458

19.3.3 Manufacturing 460

19.3.4 Tissue Engineering and Organ Printing 460

19.4 Software Support for Medical Applications 461

19.5 Limitations of AM for Medical Applications 46319.5.1 Speed 46419.5.2 Cost 46419.5.3 Accuracy 46519.5.4 Materials 46519.5.5 Ease of Use 46619.6 Further Development of Medical AM Applications 46619.6.1 Approvals 46619.6.2 Insurance 46719.6.3 Engineering Training 46719.6.4 Location of the Technology 46819.6.5 Service Bureaus 46819.7 Aerospace Applications 46819.7.1 Characteristics Favoring AM 46919.7.2 Production Manufacture 46919.8 Automotive Applications 47219.9 Exercises 473References 474

20 Business Opportunities and Future Directions 47520.1 Introduction 47520.2 What Could Be New? 47720.2.1 New Types of Products 47720.2.2 New Types of Organizations 47920.2.3 New Types of Employment 48020.3 Digiproneurship 48120.4 Exercises 485References 486Index 487

Introduction and Basic Principles 1

Additive manufacturing is the formalized term for what used to be called rapidprototyping and what is popularly called 3D Printing The term rapid prototyping(RP) is used in a variety of industries to describe a process for rapidly creating asystem or part representation before final release or commercialization In otherwords, the emphasis is on creating something quickly and that the output is aprototype or basis model from which further models and eventually the finalproduct will be derived Management consultants and software engineers bothalso use the term rapid prototyping to describe a process of developing businessand software solutions in a piecewise fashion that allows clients and otherstakeholders to test ideas and provide feedback during the development process

In a product development context, the term rapid prototyping was used widely to

# Springer Science+Business Media New York 2015

I Gibson et al., Additive Manufacturing Technologies,

DOI 10.1007/978-1-4939-2113-3_1

1

describe technologies which created physical prototypes directly from digitalmodel data This text is about these latter technologies, first developed forprototyping, but now used for many more purposes.

Users of RP technology have come to realize that this term is inadequate and inparticular does not effectively describe more recent applications of the technology.Improvements in the quality of the output from these machines have meant thatthere is often a much closer link to the final product Many parts are in fact nowdirectly manufactured in these machines, so it is not possible for us to label them as

“prototypes.” The term rapid prototyping also overlooks the basic principle of thesetechnologies in that they all fabricate parts using an additive approach A recentlyformed Technical Committee within ASTM International agreed that new termi-nology should be adopted While this is still under debate, recently adopted ASTMconsensus standards now use the term additive manufacturing [1]

Referred to in short as AM, the basic principle of this technology is that a model,initially generated using a three-dimensional Computer-Aided Design (3D CAD)system, can be fabricated directly without the need for process planning Althoughthis is not in reality as simple as it first sounds, AM technology certainly signifi-cantly simplifies the process of producing complex 3D objects directly from CADdata Other manufacturing processes require a careful and detailed analysis of thepart geometry to determine things like the order in which different features can befabricated, what tools and processes must be used, and what additional fixtures may

be required to complete the part In contrast, AM needs only some basic sional details and a small amount of understanding as to how the AM machineworks and the materials that are used to build the part

dimen-The key to how AM works is that parts are made by adding material in layers;each layer is a thin cross-section of the part derived from the original CAD data.Obviously in the physical world, each layer must have a finite thickness to it and sothe resulting part will be an approximation of the original data, as illustrated byFig.1.1 The thinner each layer is, the closer the final part will be to the original Allcommercialized AM machines to date use a layer-based approach, and the majorways that they differ are in the materials that can be used, how the layers arecreated, and how the layers are bonded to each other Such differences willdetermine factors like the accuracy of the final part plus its material propertiesand mechanical properties They will also determine factors like how quickly thepart can be made, how much post-processing is required, the size of the AMmachine used, and the overall cost of the machine and process

This chapter will introduce the basic concepts of additive manufacturing anddescribe a generic AM process from design to application It will go on to discussthe implications of AM on design and manufacturing and attempt to help inunderstanding how it has changed the entire product development process Since

AM is an increasingly important tool for product development, the chapter endswith a discussion of some related tools in the product development process

1.2 What Are AM Parts Used for?

Throughout this book you will find a wide variety of applications for AM You willalso realize that the number of applications is increasing as the processes developand improve Initially, AM was used specifically to create visualization models forproducts as they were being developed It is widely known that models can be muchmore helpful than drawings or renderings in fully understanding the intent of thedesigner when presenting the conceptual design While drawings are quicker andeasier to create, models are nearly always required in the end to fully validate thedesign

Following this initial purpose of simple model making, AM technology hasdeveloped over time as materials, accuracy, and the overall quality of the outputimproved Models were quickly employed to supply information about what isknown as the “3 Fs” of Form, Fit, and Function The initial models were used tohelp fully appreciate the shape and general purpose of a design (Form) Improvedaccuracy in the process meant that components were capable of being built to thetolerances required for assembly purposes (Fit) Improved material propertiesmeant that parts could be properly handled so that they could be assessed according

to how they would eventually work (Function)

Fig 1.1 CAD image of a teacup with further images showing the effects of building using different layer thicknesses

To say that AM technology is only useful for making models, though, would beinaccurate and undervaluing the technology AM, when used in conjunction withother technologies to form process chains, can be used to significantly shortenproduct development times and costs More recently, some of these technologieshave been developed to the extent that the output is suitable for end use Thisexplains why the terminology has essentially evolved from rapid prototyping toadditive manufacturing Furthermore, use of high-power laser technology hasmeant that parts can now also be directly made in a variety of metals, thus extendingthe application range even further.

AM involves a number of steps that move from the virtual CAD description to thephysical resultant part Different products will involve AM in different ways and todifferent degrees Small, relatively simple products may only make use of AM forvisualization models, while larger, more complex products with greater engineeringcontent may involve AM during numerous stages and iterations throughout thedevelopment process Furthermore, early stages of the product development pro-cess may only require rough parts, with AM being used because of the speed atwhich they can be fabricated At later stages of the process, parts may requirecareful cleaning and post-processing (including sanding, surface preparation, andpainting) before they are used, with AM being useful here because of the complex-ity of form that can be created without having to consider tooling Later on, we willinvestigate thoroughly the different stages of the AM process, but to summarize,most AM processes involve, to some degree at least, the following eight steps(as illustrated in Fig.1.2)

1.3.1 Step 1: CAD

All AM parts must start from a software model that fully describes the externalgeometry This can involve the use of almost any professional CAD solid modelingsoftware, but the output must be a 3D solid or surface representation Reverseengineering equipment (e.g., laser and optical scanning) can also be used to createthis representation

1.3.2 Step 2: Conversion to STL

Nearly every AM machine accepts the STL file format, which has become a defacto standard, and nowadays nearly every CAD system can output such a fileformat This file describes the external closed surfaces of the original CAD modeland forms the basis for calculation of the slices

1.3.3 Step 3: Transfer to AM Machine and STL File ManipulationThe STL file describing the part must be transferred to the AM machine Here, theremay be some general manipulation of the file so that it is the correct size, position,and orientation for building.

1.3.4 Step 4: Machine Setup

The AM machine must be properly set up prior to the build process Such settingswould relate to the build parameters like the material constraints, energy source,layer thickness, timings, etc

1.3.5 Step 5: Build

Building the part is mainly an automated process and the machine can largely carry

on without supervision Only superficial monitoring of the machine needs to takeplace at this time to ensure no errors have taken place like running out of material,power or software glitches, etc

Fig 1.2 Generic process of CAD to part, showing all eight stages

1.3.6 Step 6: Removal

Once the AM machine has completed the build, the parts must be removed Thismay require interaction with the machine, which may have safety interlocks toensure for example that the operating temperatures are sufficiently low or that thereare no actively moving parts

1.3.7 Step 7: Post-processing

Once removed from the machine, parts may require an amount of additionalcleaning up before they are ready for use Parts may be weak at this stage or theymay have supporting features that must be removed This therefore often requirestime and careful, experienced manual manipulation

1.3.8 Step 8: Application

Parts may now be ready to be used However, they may also require additionaltreatment before they are acceptable for use For example, they may requirepriming and painting to give an acceptable surface texture and finish Treatmentsmay be laborious and lengthy if the finishing requirements are very demanding.They may also be required to be assembled together with other mechanical orelectronic components to form a final model or product

While the numerous stages in the AM process have now been discussed, it isimportant to realize that many AM machines require careful maintenance Many

AM machines use fragile laser or printer technology that must be carefully tored and that should preferably not be used in a dirty or noisy environment Whilemachines are generally designed to operate unattended, it is important to includeregular checks in the maintenance schedule, and that different technologies requiredifferent levels of maintenance It is also important to note that AM processes falloutside of most materials and process standards; explaining the recent interest in theASTM F42 Technical Committee on Additive Manufacturing Technologies, which

moni-is working to address and overcome thmoni-is problem [1] However, many machinevendors recommend and provide test patterns that can be used periodically toconfirm that the machines are operating within acceptable limits

In addition to the machinery, materials may also require careful handling Theraw materials used in some AM processes have limited shelf-life and may also berequired to be kept in conditions that prevent them from unwanted chemicalreactions Exposure to moisture, excess light, and other contaminants should also

be avoided Most processes use materials that can be reused for more than onebuild However, it may be that reuse could degrade the properties if performedmany times over, and therefore a procedure for maintaining consistent materialquality through recycling should also be observed

1.4 Why Use the Term Additive Manufacturing?

By now, you should realize that the technology we are referring to is primarily theuse of additive processes, combining materials layer by layer The term additivemanufacturing, or AM, seems to describe this quite well, but there are many otherterms which are in use This section discusses other terms that have been used todescribe this technology as a way of explaining the overall purpose and benefits ofthe technology for product development

1.4.1 Automated Fabrication (Autofab)

This term was popularized by Marshall Burns in his book of the same name, whichwas one of the first texts to cover this technology in the early 1990s [2] Theemphasis here is on the use of automation to manufacture products, thus implyingthe simplification or removal of manual tasks from the process Computers andmicrocontrollers are used to control the actuators and to monitor the systemvariables This term can also be used to describe other forms of Computer Numeri-cal Controlled (CNC) machining centers since there is no direct reference as to howparts are built or the number of stages it would take to build them, although Burnsdoes primarily focus on the technologies also covered by this book Some keytechnologies are however omitted since they arose after the book was written

1.4.2 Freeform Fabrication or Solid Freeform Fabrication

The emphasis here is in the capability of the processes to fabricate complexgeometric shapes Sometimes the advantage of these technologies is described interms of providing “complexity for free,” implying that it doesn’t particularlymatter what the shape of the input object actually is A simple cube or cylinderwould take almost as much time and effort to fabricate within the machine as acomplex anatomical structure with the same enclosing volume The reference to

“Freeform” relates to the independence of form from the manufacturing process.This is very different from most conventional manufacturing processes that becomemuch more involved as the geometric complexity increases

1.4.3 Additive Manufacturing or Layer-Based ManufacturingThese descriptions relate to the way the processes fabricate parts by adding material

in layers This is in contrast to machining technology that removes, or subtractsmaterial from a block of raw material It should be noted that some of the processesare not purely additive, in that they may add material at one point but also usesubtractive processes at some stage as well Currently, every commercial processworks in a layer-wise fashion However, there is nothing to suggest that this is an

essential approach to use and that future systems may add material in other waysand yet still come under a broad classification that is appropriate to this text Aslight variation on this, Additive Fabrication, is a term that was popularized byTerry Wohlers, a well-known industry consultant in this field and who compiles awidely regarded annual industry report on the state of this industry [3] However,many professionals prefer the term “manufacturing” to “fabrication” since “fabri-cation” has some negative connotations that infer the part may still be a “prototype”rather than a finished article Additionally, in some regions of the world the termfabrication is associated with sheet metal bending and related processes, and thusprofessionals from these regions often object to the use of the word fabrication forthis industry Additive manufacturing is, therefore, starting to become widely used,and has also been adopted by Wohlers in his most recent publications andpresentations.

1.4.4 Stereolithography or 3D Printing

These two terms were initially used to describe specific machines.Stereolithography (SL) was termed by the US company 3D Systems [4, 5] and3D Printing (3DP) was widely used by researchers at MIT [6] who invented anink-jet printing-based technology Both terms allude to the use of 2D processes(lithography and printing) and extending them into the third dimension Since mostpeople are very familiar with printing technology, the idea of printing a physicalthree-dimensional object should make sense Many consider that eventually theterm 3D Printing will become the most commonly used wording to describe AMtechnologies Recent media interest in the technology has proven this to be true andthe general public is much more likely to know the term 3D Printing than any otherterm mentioned in this book

1.4.5 Rapid Prototyping

Rapid prototyping was termed because of the process this technology was designed

to enhance or replace Manufacturers and product developers used to findprototyping a complex, tedious, and expensive process that often impeded thedevelopmental and creative phases during the introduction of a new product RPwas found to significantly speed up this process and thus the term was adopted.However, users and developers of this technology now realize that AM technologycan be used for much more than just prototyping

Significant improvements in accuracy and material properties have seen thistechnology catapulted into testing, tooling, manufacturing, and other realms that areoutside the “prototyping” definition However, it can also be seen that most of theother terms described above are also flawed in some way One possibility is thatmany will continue to use the term RP without specifically restricting it to themanufacture of prototypes, much in the way that IBM makes things other than

business machines and that 3M manufactures products outside of the miningindustry It will be interesting to watch how terminology develops in the future.Where possible, we have used additive manufacturing or its abbreviation AMthroughout this book as the generic term for the suite of technologies covered bythis book It should be noted that, in the literature, most of the terms introducedabove are interchangeable; but different terminology may emphasize the approachused in a particular instance Thus, both in this book and while searching for orreading other literature, the reader must consider the context to best understandwhat each of these terms means.

Many people have described this technology as revolutionizing product ment and manufacturing Some have even gone on to say that manufacturing, as weknow it today, may not exist if we follow AM to its ultimate conclusion and that weare experiencing a new industrial revolution AM is now frequently referred to asone of a series of disruptive technologies that are changing the way we designproducts and set up new businesses We might, therefore, like to ask “why is this thecase?” What is it about AM that enthuses and inspires some to make these kinds ofstatements?

develop-First, let’s consider the “rapid” character of this technology The speed tage is not just in terms of the time it takes to build parts The speeding up of thewhole product development process relies much on the fact that we are usingcomputers throughout Since 3D CAD is being used as the starting point and thetransfer to AM is relatively seamless, there is much less concern over data conver-sion or interpretation of the design intent Just as 3D CAD is becoming What YouSee Is What You Get (WYSIWYG), so it is the same with AM and we might just aseasily say that What You See Is What You Build (WYSIWYB)

advan-The seamlessness can also be seen in terms of the reduction in process steps.Regardless of the complexity of parts to be built, building within an AM machine isgenerally performed in a single step Most other manufacturing processes wouldrequire multiple and iterative stages to be carried out As you include more features

in a design, the number of these stages may increase dramatically Even a relativelysimple change in the design may result in a significant increase in the time required

to build using conventional methods AM can, therefore, be seen as a way to moreeffectively predict the amount of time to fabricate models, regardless of whatchanges may be implemented during this formative stage of the productdevelopment

Similarly, the number of processes and resources required can be significantlyreduced when using AM If a skilled craftsman was requested to build a prototypeaccording to a set of CAD drawings, he may find that he must manufacture the part

in a number of stages This may be because he must employ a variety of tion methods, ranging from hand carving, through molding and forming techniques,

construc-to CNC machining Hand carving and similar operations are tedious, difficult, and

prone to error Molding technology can be messy and obviously requires thebuilding of one or more molds CNC machining requires careful planning and asequential approach that may also require construction of fixtures before the partitself can be made All this of course presupposes that these technologies are withinthe repertoire of the craftsman and readily available.

AM can be used to remove or at least simplify many of these multistageprocesses With the addition of some supporting technologies like silicone-rubbermolding, drills, polishers, grinders, etc it can be possible to manufacture a vastrange of different parts with different characteristics Workshops which adopt AMtechnology can be much cleaner, more streamlined, and more versatile than before

As mentioned in the discussion on Automated Fabrication, AM shares some of itsDNA with CNC machining technology CNC is also a computer-based technologythat is used to manufacture products CNC differs mainly in that it is primarily asubtractive rather than additive process, requiring a block of material that must be atleast as big as the part that is to be made This section discusses a range of topicswhere comparisons between CNC machining and AM can be made The purpose isnot really to influence choice of one technology over another rather than to establishhow they may be implemented for different stages in the product developmentprocess, or for different types of product

1.6.1 Material

AM technology was originally developed around polymeric materials, waxes, andpaper laminates Subsequently, there has been introduction of composites, metals,and ceramics CNC machining can be used for soft materials, like medium-densityfiberboard (MDF), machinable foams, machinable waxes, and even some polymers.However, use of CNC to shape softer materials is focused on preparing these partsfor use in a multistage process like casting When using CNC machining to makefinal products, it works particularly well for hard, relatively brittle materials likesteels and other metal alloys to produce high accuracy parts with well-definedproperties Some AM parts, in contrast, may have voids or anisotropy that are afunction of part orientation, process parameters or how the design was input to themachine, whereas CNC parts will normally be more homogeneous and predictable

picture, as AM technology can be used to produce a part in a single stage CNCmachines require considerable setup and process planning, particularly as partsbecome more complex in their geometry Speed must therefore be considered interms of the whole process rather than just the physical interaction of the partmaterial CNC is likely to be a multistage manufacturing process, requiringrepositioning or relocation of parts within one machine or use of more than onemachine To make a part in an AM machine, it may only take a few hours; and infact multiple parts are often batched together inside a single AM build Finishingmay take a few days if the requirement is for high quality Using CNC machining,even 5-axis high-speed machining, this same process may take weeks with consid-erably more uncertainty over the completion time.

1.6.3 Complexity

As mentioned above, the higher the geometric complexity, the greater the tage AM has over CNC If CNC is being used to create a part directly in a singlepiece, then there may be some geometric features that cannot be fabricated Since amachining tool must be carried in a spindle, there may be certain accessibilityconstraints or clashes preventing the tool from being located on the machiningsurface of a part AM processes are not constrained in the same way and undercutsand internal features can be easily built without specific process planning Certainparts cannot be fabricated by CNC unless they are broken up into components andreassembled at a later stage Consider, for example, the possibility of machining aship inside a bottle How would you machine the ship while it is still inside thebottle? Most likely you would machine both elements separately and work out away to combine them together as an assembly and/or joining process With AM youcan build the ship and the bottle all at once An expert in machining must thereforeanalyze each part prior to it being built to ensure that it indeed can be built and todetermine what methods need to be used While it is still possible that some partscannot be built with AM, the likelihood is much lower and there are generally ways

advan-in which this may be overcome without too much difficulty

1.6.4 Accuracy

AM machines generally operate with a resolution of a few tens of microns It iscommon for AM machines to also have different resolution along different orthog-onal axes Typically, the vertical build axis corresponds to layer thickness and thiswould be of a lower resolution compared with the two axes in the build plane.Accuracy in the build plane is determined by the positioning of the build mecha-nism, which will normally involve gearboxes and motors of some kind Thismechanism may also determine the minimum feature size as well For example,

SL uses a laser as part of the build mechanism that will normally be positionedusing galvanometric mirror drives The resolution of the galvanometers would

determine the overall dimensions of parts built, while the diameter of the laser beamwould determine the minimum wall thickness The accuracy of CNC machines onthe other hand is mainly determined by a similar positioning resolution along allthree orthogonal axes and by the diameter of the rotary cutting tools There arefactors that are defined by the tool geometry, like the radius of internal corners, butwall thickness can be thinner than the tool diameter since it is a subtractive process.

In both cases very fine detail will also be a function of the desired geometry andproperties of the build material

if these features are beyond a certain limit Consider, for example, the featuresrepresented in the part in Fig.1.3 Many of them would be very difficult to machinewithout manipulation of the part at various stages

1.6.6 Programming

Determining the program sequence for a CNC machine can be very involved,including tool selection, machine speed settings, approach position and angle, etc.Many AM machines also have options that must be selected, but the range,complexity, and implications surrounding their choice are minimal in comparison.The worst that is likely to happen in most AM machines is that the part will not bebuilt very well if the programming is not done properly Incorrect programming of aCNC machine could result in severe damage to the machine and may even be ahuman safety risk

Figure1.4shows a montage of parts fabricated using some of the common AMprocesses Part a was fabricated using a stereolithography machine and depicts asimplified fuselage for an unmanned aerial vehicle where the skin is reinforced with

a conformal lattice structure (see Chap.4for more information about the process) Amore complete description of this part is included in the Design for AdditiveManufacturing chapter Parts b and c were fabricated using material jetting(Chap 7) Part b demonstrates the capability of depositing multiple materialssimultaneously, where one set of nozzles deposited the clear material, while another

The cavity here may be too deep to machine

The undercut here cannot be

performed without more than

3 axis machining

Base cannot be machined since machine must hold using a fixture

Sharp internal features cannot be machined without a tool radius

Fig 1.3 Features that represent problems using CNC machining

Fig 1.4 Montage of AM parts

set deposited the black material for the lines and the Objet name Part c is a section

of chain Both parts b and c have working revolute joints that were fabricated usingclearances for the joints and dissolvable support structure Part d is a metal part thatwas fabricated in a metal powder bed fusion machine using an electron beam as itsenergy source (Chap 5) The part is a model of a facial implant Part e wasfabricated in an Mcor Technologies sheet lamination machine that has ink-jetprinting capability for the multiple colors (Chap.9) Parts f and g were fabricatedusing material extrusion (Chap.6) Part f is a ratchet mechanism that was fabricated

in a single build in an industrial machine Again, the working mechanism is achievedthrough proper joint designs and dissolvable support structure Part g was fabricated

in a low-cost, personal machine (that one of the authors has at home) Parts h and

i were fabricated using polymer powder bed fusion Part h is the well-known “braingear” model of a three-dimensional gear train When one gear is rotated, all othergears rotate as well Since parts fabricated in polymer PBF do not need supports,working revolute and gear joints can be created by managing clearances andremoving the loose powder from the joint regions Part i is another conformal latticestructure showing the shape complexity capability of AM technologies

The most common input method for AM technology is to accept a file convertedinto the STL file format originally built within a conventional 3D CAD system.There are, however, other ways in which the STL files can be generated and othertechnologies that can be used in conjunction with AM technology This section willdescribe a few of these

1.8.1 Reverse Engineering Technology

More and more models are being built from data generated using reverse ing (RE) 3D imaging equipment and software In this context, RE is the process ofcapturing geometric data from another object These data are usually initiallyavailable in what is termed “point cloud” form, meaning an unconnected set ofpoints representing the object surfaces These points need to be connected togetherusing RE software like Geomagic [7], which may also be used to combine pointclouds from different scans and to perform other functions like hole-filling andsmoothing In many cases, the data will not be entirely complete Samples may, forexample, need to be placed in a holding fixture and thus the surfaces adjacent to thisfixture may not be scanned In addition, some surfaces may obscure others, likewith deep crevices and internal features; so that the representation may not turn outexactly how the object is in reality Recently there have been huge improvements inscanning technology An adapted handphone using its inbuilt camera can nowproduce a high-quality 3D scan for just a few hundred dollars that even just a few

years ago would have required an expensive laser-scanning or stereoscopic camerasystem costing $100,000 or more.

Engineered objects would normally be scanned using laser-scanning or probe technology Objects that have complex internal features or anatomicalmodels may make use of Computerized Tomography (CT), which was initiallydeveloped for medical imaging but is also available for scanning industriallyproduced objects This technique essentially works in a similar way to AM, byscanning layer by layer and using software to join these layers and identify thesurface boundaries Boundaries from adjacent layers are then connected together toform surfaces The advantage of CT technology is that internal features can also begenerated High-energy X-rays are used in industrial technology to create high-resolution images of around 1μm Another approach that can help digitize objects

touch-is the Capture Geometry Inside [8] technology that also works very much like areverse of AM technology, where 2D imaging is used to capture cross-sections of apart as it is machined away layer by layer Obviously this is a destructive approach

to geometry capture so it cannot be used for every type of product

AM can be used to reproduce the articles that were scanned, which essentiallywould form a kind of 3D facsimile (3D Fax) process More likely, however, the datawill be modified and/or combined with other data to form complex, freeformartifacts that are taking advantage of the “complexity for free” feature of thetechnology An example may be where individual patient data are combined with

an engineering design to form a customized medical implant This is something thatwill be discussed in much more detail later on in this book

1.8.2 Computer-Aided Engineering

3D CAD is an extremely valuable resource for product design and development.One major benefit to using software-based design is the ability to implement changeeasily and cheaply If we are able to keep the design primarily in a software formatfor a larger proportion of the product development cycle, we can ensure that anydesign changes are performed virtually on the software description rather thanphysically on the product itself The more we know about how the product isgoing to perform before it is built, the more effective that product is going to

be This is also the most cost-effective way to deal with product development Ifproblems are only noticed after parts are physically manufactured, this can be verycostly 3D CAD can make use of AM to help visualize and perform basic tests oncandidate designs prior to full-scale commitment to manufacturing However, themore complex and performance-related the design, the less likely we are to gainsufficient insight using these methods However, 3D CAD is also commonly linked

to other software packages, often using techniques like finite element method(FEM) to calculate the mechanical properties of a design, collectively known asComputer-Aided Engineering (CAE) software Forces, dynamics, stresses, flow,and other properties can be calculated to determine how well a design will performunder certain conditions While such software cannot easily predict the exact

behavior of a part, for analysis of critical parts a combination of CAE, backed upwith AM-based experimental analysis, may be a useful solution Further, with theadvent of Direct Digital Manufacture, where AM can be used to directly producefinal products, there is an increasing need for CAE tools to evaluate how these partswould perform prior to AM so that we can build these products right first time as aform of Design for Additive Manufacturing (D for AM).

1.8.3 Haptic-Based CAD

3D CAD systems are generally built on the principle that models are constructedfrom basic geometric shapes that are then combined in different ways to make morecomplex forms This works very well for the engineered products we are familiarwith, but may not be so effective for more unusual designs Many consumerproducts are developed from ideas generated by artists and designers rather thanengineers We also note that AM has provided a mechanism for greater freedom ofexpression AM is in fact now becoming a popular tool for artists and sculptors,like, for example, Bathsheba Grossman [9] who takes advantage of the geometricfreedom to create visually exciting sculptures One problem we face today is thatsome computer-based design tools constrain or restrict the creative processes andthat there is scope for a CAD system that provides greater freedom Haptic-basedCAD modeling systems like the experimental system shown in Fig.1.5[10], work

in a similar way to the commercially available Freeform [11] modeling system toprovide a design environment that is more intuitive than other standard CADsystems They often use a robotic haptic feedback device called the Phantom to

Fig 1.5 Freeform modeling system

provide force feedback relating to the virtual modeling environment An object can

be seen on-screen, but also felt in 3D space using the Phantom The modelingenvironment includes what is known as Virtual Clay that deforms under forceapplied using the haptic cursor This provides a mechanism for direct interactionwith the modeling material, much like how a sculptor interacts with actual clay Theresults using this system are generally much more organic and freeform surfacesthat can be incorporated into product designs by using additional engineering CADtools As consumers become more demanding and discerning we can see that CADtools for non-engineers like designers, sculptors, and even members of the generalpublic are likely to become much more commonplace

There have been a number of texts describing additive manufacturing processes,either as dedicated books or as sections in other books So far, however, there havebeen no texts dedicated to teaching this technology in a comprehensive way within

a university setting Recently, universities have been incorporating additivemanufacturing into various curricula This has varied from segments of singlemodules to complete postgraduate courses This text is aimed at supporting thesecurricula with a comprehensive coverage of as many aspects of this technology aspossible The authors of this text have all been involved in setting up programs intheir home universities and have written this book because they feel that there are

no books to date that cover the required material in sufficient breadth and depth.Furthermore, with the increasing interest in 3D Printing, we believe that this textcan also provide a comprehensive understanding of the technologies involved.Despite the increased popularity, it is clear that there is a significant lack of basicunderstanding by many of the breadth that AM has to offer

Early chapters in this book discuss general aspects of AM, followed by chapterswhich focus on specific AM technologies The final chapters focus more on genericprocesses and applications It is anticipated that the reader will be familiar with 3Dsolid modeling CAD technology and have at least a small amount of knowledgeabout product design, development, and manufacturing The majority of readerswould be expected to have an engineering or design background, more specificallyproduct design, or mechanical, materials or manufacturing engineering Since AMtechnology also involves significant electronic and information technologycomponents, readers with a background in computer applications and mechatronicsmay also find this text beneficial

1 Find three other definitions for rapid prototyping other than that of additivemanufacturing as covered by this book

2 From the web, find different examples of applications of AM that illustrate theiruse for “Form,” “Fit,” and “Function.”

3 What functions can be carried out on point cloud data using Reverse Engineeringsoftware? How do these tools differ from conventional 3D CAD software?

4 What is your favorite term (AM, Freeform Fabrication, RP, etc.) for describingthis technology and why?

5 Create a web link list of videos showing operation of different AM technologiesand representative process chains

6 Make a list of different characteristics of AM technologies as a means tocompare with CNC machining Under what circumstances do AM have theadvantage and under what would CNC?

7 How does the Phantom desktop haptic device work and why might it be moreuseful for creating freeform models than conventional 3D CAD?

4 Jacobs PF (1995) Stereolithography and other RP and M technologies: from rapid prototyping

to rapid tooling SME, New York

5 3D Systems http://www.3dsystems.com

6 Sachs EM, Cima MJ, Williams P, Brancazio D, Cornie J (1992) Three dimensional printing: rapid tooling and prototypes directly from a CAD model J Eng Ind 114(4):481–488

7 Geomagic Reverse Engineering software http://www.geomagic.com

8 CGI Capture geometry inside http://www.cgiinspection.com