Designing Electronic Product Enclosures (eBook)

Tony Serksnis began his career in the drafting room of the Lincoln Electric Company running blueprints in 1964.  He apprenticed as a tool and die designer while attending night school.  After earning a Master's Degree in Mechanical Engineering from the University of Arizona in 1977, he joined the Material Fabrication Group at Lawrence Livermore National Laboratory.  Was a part of the design team that built a precision lathe capable of 0.000001 inch accuracy.  He then moved on to positions at Intel Corporation, Sytek Corporation, and Trimble Navigation.  While at Trimble, he designed products for the Survey and Construction marketplaces.  Later, managed Trimble's Mechanical Engineering Group and was responsible for budgeting, resourcing, prioritization, design and documentation, and project management.

Acknowledgments 5
Pictoglyphs 5
Chapter 1: Successful Design 6
PRD 6
Chapter 2: Building the Design 6
POB 6
Chapter 3: Structural Considerations 6
MOI 6
Chapter 4: Materials and Processes 7
MAT 7
Chapter 5: User Interface 7
EYE 7
Chapter 6: Assembly and Service 7
DFA 7
Chapter 7: Product Environments 8
ENV 8
Chapter 8: Cooling Techniques 8
Q?T 8
Chapter 9: EMC 8
EMC 8
Chapter 10: Safety by Design 9
Chapter 11: Shipping and Packaging 9
RSC 9
Chapter 12: Documentation 10
ECN 10
Chapter 13: Continuous Improvement 10
DNA 10
Presented here is a pictoglyph that shows all of the 3-letter titles of the book chapters: 11
Introduction: Intent of Text 12
Chapter Organization 13
References and Information Access 14
Author’s Credentials 14
Continuing the Dialogue 15
Contents 16
Chapter 1: Successful Design 21
1.1 Design Guide 21
1.2 Defining the Overall Team 22
1.3 Product Requirements 25
1.3.1 Function to Specification 28
1.3.2 Delivery on Time to Project Schedule 30
1.3.3 Delivery at Predicted Costs 31
1.4 Sketching Versus Detailing 31
1.5 Design Reviews 32
1.6 Communication 33
1.6.1 Purpose of Communication 33
1.6.2 Value of Communication 33
1.6.3 Links in the Communication Chain 34
1.7 Engineering Economy 34
Reference 37
Chapter 2: Building the Design 38
2.1 Beginning Point 38
2.2 Defining the Design Boundary: System Description 39
2.3 The Design Process 41
2.3.1 Overall Project Start to Project Finish 41
2.3.2 EPE Designer’s Starting Considerations 42
2.4 Optimal Object Placement 43
2.4.1 Clearance Distance Is a Function Of 45
2.4.2 Object Arrangement 46
2.4.3 Object Arrangement Example (Fig. 2.3) 48
Chapter 3: Structural Considerations 53
3.1 Introduction: Strength of Materials 53
3.2 Design Process for Structures 55
3.2.1 Similar Designs 55
3.2.2 Forces on Part 56
3.2.3 Existing End Conditions 56
3.2.4 Propose Material and Cross Section 56
3.2.4.1 Pine Wood Solution 58
3.2.4.2 Aluminum Solution 59
3.2.5 Combine Function 60
3.2.6 Determine Factor of Safety Needed 61
3.3 Analysis Required 62
3.4 Structural Problems: Static Loads 64
3.4.1 Cantilever Beam Analysis (from Tecknit EMI Shielding Products Manual) 65
3.4.2 Deflection Formulae and Maximum Deflection (from Injection Molding Magazine) 69
3.4.3 Another Deflection Problem, This Time Snap-Fitting Hook (from Mobay Design Manual, Snap-Fit Joints in Plastics) 73
3.5 Dynamic Loads 74
References 75
Again, this chapter has been a review of structural considerations as they relate to structures encountered in the design of electronic enclosures. The reader may have many other sources of information, but the main ones I have used (over the years) are 75
Chapter 4: Materials and Processes 76
4.1 Cost Versus Time Versus Specification 76
4.2 The Designer’s Mind Space 79
4.3 Materials and Process Choice 80
4.4 Finishes and Coatings 85
4.5 Punching and Forming Metals 88
4.6 Molding Plastics 89
4.7 Casting Metals 94
4.8 Dimensioning/Tolerancing 97
4.8.1 Choice of “Nominal Dimension” 97
4.8.2 United States Engineering Units Versus International System of Units 98
4.8.3 The World Before and After CNC-Controlled Machine Tools 99
4.8.4 Overall Size and the Design 100
4.8.5 Theory of Tolerancing: The Need 102
4.8.6 Theory of Tolerancing: Accumulation of Tolerances 104
4.8.7 Inspection Dimensions (Critical Dimensions) 105
4.8.8 True Position Dimensioning 106
4.9 Off-the-Shelf Components 109
4.10 Prototyping 110
Appendix 112
Dimensioning of Sheet Metal on Drawings 112
Dimensioning Bends 112
Minimum Flange Height 113
Minimum Distance Between Bends 114
Location of Holes Adjacent to Bends 114
Location of Holes to Prevent Distortion 115
Punching Holes 116
Bend Relief 117
Corner Construction 119
Beads and Gussets 119
Minimum Bend Radii 119
Grain Direction 122
Temper 122
Recommended Slot Widths 123
Folding 123
Curling 123
Crimping 123
Joggles 124
Dimpling 124
Countersinking 125
Distortion from Bending 126
References 128
Chapter 5: User Interface 129
5.1 Input/Output 129
5.2 Sensors 131
5.2.1 Sight (Vision) 131
5.2.2 Touch (Feel) 132
5.2.3 Hearing (Auditory) 132
5.2.4 Antennae and Receivers 132
5.2.5 More Senses 133
5.3 Power Supplies 133
5.4 Ergonomics 134
5.4.1 Visual Displays 134
5.4.2 Controls 135
5.4.3 Fasteners 135
5.4.4 Physical Response Measurement 136
5.5 Industrial Design 136
5.6 Color 137
References 137
Chapter 6: Assembly and Service 139
6.1 Design for Assembly 139
6.2 Assembly Guidelines 141
6.3 Assembly Tooling 146
6.4 Assembly Testing 146
6.5 Service Considerations 147
Appendix 6 Clearance Holes for Assembly 148
Definitions 148
Notes 148
References 150
Chapter 7: Product Environments 151
7.1 Standards 152
7.2 Testing 155
7.3 Temperature 157
7.4 Vibration 159
7.5 Shock 161
7.6 Water Protection 164
7.6.1 Standards Available 164
7.6.2 IPXX 165
7.6.3 Sealing 166
7.6.4 Water Vapor 166
7.6.5 Other Notes on Sealing from Moisture 168
7.7 Other Design Environments 169
References 170
Chapter 8: Cooling Techniques 171
8.1 Heat Loading and Critical Temperatures 172
8.2 Conduction Mode of Heat Transfer 174
8.3 Natural Convection Mode of Heat Transfer 177
8.4 Forced Convection Mode of Heat Transfer 179
8.5 Radiation Mode of Heat Transfer 181
8.6 Other Cooling Techniques 183
8.7 Thermal Testing 184
References 185
Chapter 9: EMC 186
9.1 EMC Issues 186
9.2 Shielding the Enclosure 190
9.3 EMC Standards 194
9.3.1 Military Standards 194
9.3.2 Commercial Standards 194
References 195
Chapter 10: Safety by Design 196
10.1 Safety Review 196
10.2 Mechanical Issues 197
10.2.1 Temperature of Enclosure Surfaces 198
10.2.2 Physical Stability 198
10.2.3 Mechanical Strength of Enclosures 198
10.2.4 Cable Strain Reliefs 198
10.2.5 Flammability Tests 198
10.2.6 Labeling 199
10.2.7 Batteries 199
10.2.8 Grounding 199
10.2.9 Accessibility 199
10.2.10 Liquid Spills 200
10.2.11 Conductive Coating Adhesion 200
10.3 Approval Process and Safety Standards 200
Reference 201
Chapter 11: Shipping and Packaging 202
11.1 Shipping Environments 203
11.2 Product Fragility 204
11.3 Material Selection 205
11.4 Testing for Transportation 207
References 209
Chapter 12: Documentation 210
12.1 EPE Designer Output 211
12.2 Assemblies/Parts Lists 212
12.3 Part Numbering 212
12.4 Version Control (or Revision Control) 213
12.4.1 Change Visibility 213
12.4.2 Parts Disposition 214
12.4.3 Nimbleness 214
12.4.4 Token Ring 214
12.4.5 Adaptability 215
12.4.6 Implementation 215
12.5 Linkage Between Groups 215
12.5.1 Engineering Deliverables and Needs 216
12.5.2 Long-Term Production Purchases 218
12.6 Engineering Release to Manufacturing 218
Reference 219
Chapter 13: Continuous Improvement 220
13.1 Improvement in Design 220
13.2 Design Review Practices 221
13.3 Existing Improvement Methodologies 222
13.4 Improvement in Processes 223
13.5 Guidelines Versus Procedures 225
Reference 226