A Practical Guide to Design for Additive Manufacturing (eBook)

Acknowledgements 6
About This Book 7
Contents 9
About the Authors 15
Acronyms 17
1 Introduction to Additive Manufacturing 21
1.1 What Is Additive Manufacturing? 21
1.2 The Additive Manufacturing Process Chain 24
1.3 Current Usage of Additive Manufacturing 27
1.4 The Advantages of Additive Manufacturing 28
1.4.1 Part Complexity 28
1.4.2 Instant Assemblies 31
1.4.3 Part Consolidation 32
1.4.4 Mass Customization 33
1.4.5 Freedom of Design 33
1.4.6 Light-Weighting 34
1.4.7 On-Demand Manufacturing 36
2 Additive Manufacturing Technologies 38
2.1 Material Extrusion 38
2.2 Material Jetting 42
2.3 Binder Jetting 44
2.4 Sheet Lamination 47
2.5 Vat Photopolymerisation 49
2.6 Powder Bed Fusion 52
2.7 Direct Energy Deposition 54
2.8 Hybrid AM 56
2.9 AM Technology Readiness Level for Part Production 57
3 DfAM Strategic Design Considerations 59
3.1 Introduction to Design for Additive Manufacturing 59
3.2 Using AM to Add Value to Products 61
3.3 General Guidelines for Designing AM Parts 61
3.3.1 The #1 Rule of Design for AM 61
3.3.2 The #2 Rule of Design for AM 62
3.3.3 The #3 Rule of Design for AM 63
3.3.4 The #4 Rule of Design for AM 63
3.3.5 The #5 Rule of Design for AM 63
3.3.6 The #6 Rule of Design for AM 64
3.3.7 The #7 Rule of Design for AM 65
3.4 Design to Avoid Anisotropy 65
3.5 The Economics of Additive Manufacturing 66
3.5.1 Time Factors That Are Not Affected by Design 69
3.6 Design to Minimize Print Time 70
3.7 Design to Minimize Post-processing 74
3.8 Take Advantage of Design Complexity 82
3.9 Function First, Materials Second 84
3.10 Use Topology Optimisation or Lattice Structures 85
4 Computational Tools for Design Analysis and Optimisation of AM Parts 89
4.1 Aims of Using Design Analysis for AM 89
4.2 Special Considerations for Analysis of AM Parts 89
4.2.1 Material Data 89
4.2.2 Surface Finish 90
4.2.3 Geometry 90
4.2.4 Simplifying Geometry 90
4.2.5 Mesh-Based Versus Parametric Models 91
4.2.6 Geometry Distortion 91
4.3 Mesh 91
4.3.1 Parametric Models 91
4.3.2 Mesh-Based Models 92
4.4 Boundary Conditions 92
4.5 Optimisation 92
4.6 Topology Optimisation 92
4.6.1 Objective and Constraints 93
4.6.2 Common Settings 93
4.6.3 Post-processing and Interpreting Results 93
4.7 Parametric or Size Optimisation 94
4.8 Build Process Simulation 94
4.8.1 Layer-by-Layer Simulation 95
4.8.2 Scan Pattern Simulation 95
4.8.3 Limitations 95
5 Guidelines for Part Consolidation 96
5.1 Design for Function 97
5.2 Material Considerations 98
5.3 Number of Fasteners 98
5.4 Use Knowledge from Conventional DFM/DFA 99
5.5 Assembly Considerations 100
5.6 Moving Parts 100
5.7 Common Sense 101
6 Guidelines for AM Tooling Design 102
6.1 Mounting Fixtures and Guides 102
6.2 Conformal Cooling 103
6.3 Coolant Flow Strategies 105
6.4 Coolant Channel Shape 106
6.5 Coolant Channel Spacing 107
6.6 A Hybrid Approach to AM Tooling 107
6.7 Minimise Print Time in Tooling 108
7 Design for Polymer AM 110
7.1 Anisotropy 110
7.2 Wall Thicknesses 111
7.3 Overhangs and Support Material 112
7.4 Holes 113
7.5 Ribs 114
7.6 Avoiding Superfluous Material 115
7.7 Font Sizes and Small Details 117
7.7.1 Small Details 117
7.7.2 Font Sizes 117
8 Polymer Design Guidelines 119
8.1 Designing for Material Extrusion 119
8.1.1 Material Extrusion Accuracy and Tolerances 119
8.1.2 Layer Thickness 120
8.1.3 Support Material 120
8.1.4 Fill Style 121
8.1.5 Other Considerations 122
8.1.6 Feature Type: Vertical Wall Thickness 123
8.1.7 Feature Type: Horizontal Walls 123
8.1.8 Feature Type: Support Material Overhang Angles 123
8.1.9 Feature Type: Clearances Between Moving Parts with Soluble Supports 124
8.1.10 Feature Type: Clearance Between Moving Parts with Break-Away Support Material 124
8.1.11 Feature Type: Vertical Circular Holes 125
8.1.12 Feature Type: Circular Pins 125
8.1.13 Feature Type: Built-in Screw Threads 126
8.2 Designing for Polymer Powder Bed Fusion 126
8.2.1 Powder Bed Fusion Accuracy and Tolerances 127
8.2.2 Layer Thickness 127
8.2.3 Avoiding Large Masses of Material 127
8.2.4 Powder Age and Refresh Rate 128
8.2.5 Feature Type: Wall Thickness 128
8.2.6 Feature Type: Clearance Between Moving Parts 129
8.2.7 Feature Type: Circular Profile Through Holes 129
8.2.8 Feature Type: Square Profile Through Holes 130
8.2.9 Feature Type: Circular Pins 130
8.2.10 Feature Type: Hole Proximity to Wall Edge 131
8.3 Designing for Vat Photopolymerisation 131
8.3.1 Resolution 131
8.3.2 Print Orientation 132
8.3.3 Support Material 132
8.3.4 Overhangs 132
8.3.5 Isotropy 133
8.3.6 Hollowing Parts and Resin Removal 133
8.3.7 Details 134
8.3.8 Horizontal Bridges 134
8.3.9 Connections 134
8.3.10 Feature Type: Wall Thickness 134
8.3.11 Feature Type: Circular Holes 135
9 Design for Metal AM 136
9.1 Designing for Metal Powder Bed Fusion 136
9.2 The Basics of Powder Bed Fusion 137
9.3 Metal Powder Production 137
9.4 Powder Morphology (Ideal Powder Shape) 139
9.5 Powder Size Distribution 139
9.6 Other Powder Considerations 140
9.7 Metal AM Material Characteristics 140
9.8 Potential Defects in AM Materials 141
9.9 The Metal AM Process 143
9.9.1 Energy Density 145
9.10 Controlled Chaos 147
9.11 The Reality of Metal AM 147
9.12 Topology Optimisation 148
9.13 Lattice Structures 149
9.13.1 Lattice Structure Strut Diameters 152
9.14 Overhangs and Support Material 153
9.14.1 Printing Parts with Large Horizontal Surfaces 154
9.14.2 Angle for Support Material 156
9.14.3 Unsupported Angles, Overhangs, and Bridges 156
9.15 Residual Stress 158
9.15.1 Designing to Reduce Residual Stress 159
9.15.2 Designing to Minimize Residual Stress Example 160
9.16 Stress Concentrations 164
9.16.1 Designing to Reduce Stress Concentrations 164
9.17 Horizontal Holes 165
9.18 Setting up a Metal AM Print Job 166
9.18.1 General Part Positioning Guidelines 167
10 Metal AM Guidelines 171
10.1 Design for Laser Powder Bed Fusion 171
10.1.1 Feature Type: Wall Thickness 171
10.1.2 Feature Type: Overhang Angle 172
10.1.3 Feature Type: Clearance Between Moving Parts 172
10.1.4 Feature Type: Vertical Slots and Circular Holes 173
10.1.5 Feature Type: Vertical Bosses and Circular Pins 173
10.1.6 Feature Type: Built-In External Screw Threads 173
10.2 Design for Electron Beam Melting 174
10.2.1 Post Processing 175
10.2.2 Design Guidelines 176
10.2.3 Feature Type: Wall Thickness 178
10.2.4 Feature Type: Vertical Slots and Circular Holes 178
10.2.5 Feature Type: Clearances to Remove Powder 179
10.2.6 Feature Type: Screw and Threads 179
10.3 Designing for Metal Binder Jetting 180
10.3.1 Shrinkage 180
10.3.2 Part Density 181
10.3.3 The Most Important Design Rule for Metal Binder Jetting 182
10.3.4 Feature Type: Wall Thicknesses 185
10.3.5 Feature Type: Overhang 186
10.3.6 Feature Type: Holes 186
10.3.7 Feature Type: Salt-Shaker Holes 187
11 Other AM Considerations 188
11.1 Designer Machine Operator Cooperation 188
11.2 Health and Safety 189
11.2.1 Material Exposure 189
11.2.2 Gas Monitoring 189
11.2.3 Gas Exhaust 190
11.2.4 Material Handling 190
11.2.5 Risk of Explosion 190
11.3 AM Part Certification 190
11.3.1 What Needs to Be Certified? 191
12 Post-processing 193
12.1 Support Material Removal 194
12.1.1 Polymer 194
12.1.2 Metal 199
12.2 Polymer Surface Treatments 203
12.2.1 Vapour Smoothing 203
12.2.2 Tumbling 206
12.2.3 Dying 207
12.2.4 Painting 208
12.2.5 Using Textures 208
12.2.6 Sand Blasting 209
12.2.7 Machining 209
12.2.8 Metalizing 210
12.2.9 Wrapping 210
12.2.10 Hydrographics 211
12.3 Metal Surface Treatments 211
12.3.1 Shot-Peening 212
12.3.2 Plasma Cleaning and Ion Beam Cleaning 212
12.3.3 Machining and Grinding 213
12.3.4 Abrasive Flow Machining 213
12.3.5 Anodizing 214
12.3.6 Plasma Spraying 214
12.3.7 Plating and PVD 214
12.3.8 Painting 215
12.4 Gluing and Welding AM Parts 216
12.5 Heat Treatment and Aging 216
12.5.1 Residual Stress Relief 216
12.5.2 Hot Isostatic Pressing (HIP) 217
12.5.3 Case Hardening and Gas Nitride Treatment 218
13 The Future of Additive Manufacturing 220
13.1 Functionally Graded Materials 220
13.2 Bioprinting 221
13.3 Construction Applications 222
13.4 Printed Electronics 223
13.5 Nano Printing 225
13.6 Food Printers 225
14 Concluding Remarks 228
Glossary of Terms 230
References and Further Reading 235
Further Reading 235
References 235