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Summary
Summary
Since the dawn of civilization, mankind has been engaged in the conception and manufacture of discrete products to serve the functional needs of local customers and the tools (technology) needed by other craftsmen. In fact, much of the progress in civilization can be attributed to progress in discrete product manufacture. The functionality of a discrete object depends on two entities: form, and material composition. For instance, the aesthetic appearance of a sculpture depends upon its form whereas its durability depends upon the material composition. An ideal manufacturing process is one that is able to automatically generate any form (freeform) in any material. However, unfortunately, most traditional manufacturing processes are severely constrained on all these counts. There are three basic ways of creating form: conservative, subtractive, and additive. In the first approach, we take a material and apply the needed forces to deform it to the required shape, without either adding or removing material, i. e. , we conserve material. Many industrial processes such as forging, casting, sheet metal forming and extrusion emulate this approach. A problem with many of these approaches is that they focus on form generation without explicitly providing any means for controlling material composition. In fact, even form is not created directly. They merely duplicate the external form embedded in external tooling such as dies and molds and the internal form embedded in cores, etc. Till recently, we have had to resort to the 'subtractive' approach to create the form of the tooling.
Table of Contents
Preface | p. xi |
Acknowledgments | p. xvii |
1. Introduction | p. 1 |
1.1 The Importance of Being Rapid | p. 1 |
1.2 The Nature of RP/T | p. 6 |
1.3 History of RP | p. 13 |
1.4 The State of RP/T Industry | p. 21 |
2. Materials Basics | p. 25 |
2.1 Atomic Structure and Bonding | p. 25 |
2.2 Ceramics | p. 31 |
2.3 Polymers | p. 33 |
2.3.1 Nature of Polymers | p. 33 |
2.3.2 Free Radical Polymerization | p. 36 |
2.3.3 Cationic Polymerization | p. 38 |
2.3.4 Thermoplastic and Thermosetting Polymers | p. 39 |
2.3.5 Polymer Structures | p. 41 |
2.3.6 Properties of Polymers | p. 42 |
2.3.7 Degradation of Polymers | p. 47 |
2.4 Powdered Materials | p. 48 |
2.4.1 Types of Powders | p. 48 |
2.4.2 Compaction and Sintering of Powders | p. 49 |
2.5 Composites | p. 52 |
3. Lasers for RP | p. 57 |
3.1 The Principle of Laser | p. 57 |
3.1.1 The Nature of Light | p. 57 |
3.1.2 Emission Radiation | p. 59 |
3.1.3 Light Amplification by Stimulated Emission Radiation | p. 60 |
3.2 Laser System | p. 63 |
3.3 Laser Beam Characteristics | p. 65 |
3.4 Laser Beam Control | p. 69 |
3.5 Types of Lasers Used in RP | p. 71 |
4. Reverse Engineering and Cad Modeling | p. 75 |
4.1 Basic Concept of Reverse Engineering | p. 75 |
4.2 Digitizing Techniques for Reverse Engineering | p. 78 |
4.2.1 Mechanical Contact Digitizing | p. 79 |
4.2.2 Optical Non-Contact Measurement | p. 81 |
4.2.3 CT Scanning Method | p. 91 |
4.2.4 Data Pre-processing for Surface Reconstruction | p. 96 |
4.3 Model Representation | p. 98 |
4.3.1 Basic Geometric Features | p. 98 |
4.3.2 General Algebraic Surfaces | p. 98 |
4.3.3 Parametric Surfaces | p. 99 |
4.3.4 Subdivision Surfaces | p. 101 |
4.3.5 Other Approaches and Recommendations | p. 102 |
4.4 B-Spline Based Model Reconstruction | p. 103 |
4.4.1 Parametrization of Measured Points | p. 103 |
4.4.2 Knots Allocation | p. 105 |
4.4.3 Least Squares Fitting | p. 107 |
4.5 Nurbs Based Model Reconstruction | p. 110 |
4.5.1 A Two-Step Linear Approach | p. 112 |
4.5.2 Numerical Algorithms for Weights Identification | p. 115 |
4.6 Other Approaches for Model Reconstruction | p. 119 |
4.6.1 Basic Geometric Features | p. 119 |
4.6.2 General Algebraic Surfaces | p. 119 |
4.6.3 Subdivision Surface Fitting | p. 120 |
4.7 Surface Local Updating | p. 121 |
4.7.1 Related Work and General Strategies | p. 122 |
4.7.2 Pre-Processing Steps for Surface Local Updating | p. 123 |
4.7.3 Computing Updated Control Points | p. 124 |
4.8 Examples on Model Reconstruction | p. 125 |
4.8.1 Parametrization for Surface Reconstruction | p. 126 |
4.8.2 B-Spline Surfaces | p. 127 |
4.8.3 NURBS Surfaces | p. 129 |
4.8.4 Subdivision Surfaces | p. 130 |
4.8.5 Surface Local Updating | p. 132 |
5. Data Processing for Rapid Prototyping | p. 135 |
5.1 Introduction | p. 135 |
5.2 Cad Model Preparation | p. 140 |
5.3 Data Interfacing for Rapid Prototyping | p. 144 |
5.3.1 STL Interface Specification | p. 144 |
5.3.2 STL Data Generation | p. 147 |
5.3.3 STL Data Manipulation | p. 149 |
5.3.4 Alternative RP interfaces | p. 151 |
5.4 Part Orientation and Support Generation | p. 152 |
5.4.1 Factors Affecting Part Orientation | p. 152 |
5.4.2 Various Models for Part Orientation Determination | p. 153 |
5.4.3 The Functions of Part Supports | p. 158 |
5.4.4 Support Structure Design | p. 159 |
5.4.5 Automatic Support Structure Generation | p. 162 |
5.5 Model Slicing and Contour Data Organization | p. 165 |
5.5.1 Model Slicing and Skin Contour Determination | p. 165 |
5.5.2 Identification of Internal and External Contours | p. 169 |
5.5.3 Contour Data Organization | p. 171 |
5.6 Direct and Adaptive Slicing | p. 173 |
5.6.1 Identification of Peak Features | p. 174 |
5.6.2 Adaptive Layer Thickness Determination | p. 178 |
5.6.3 Skin Contours Computation | p. 180 |
5.7 A Selective Hatching Strategy for RP | p. 185 |
5.8 Tool Path Generation | p. 188 |
6. Stereolithography (SL) | p. 195 |
6.1 The Stereolithography (SL) Process | p. 195 |
6.1.1 Part Building Using SL | p. 195 |
6.1.2 Post-build Processes | p. 197 |
6.1.3 Pre-build Processes | p. 198 |
6.2 Photo-Polymerization of SL Resins | p. 199 |
6.2.1 SL Polymers | p. 199 |
6.2.2 Radical Photo-polymerization | p. 200 |
6.2.3 Cationic Polymerization | p. 204 |
6.2.4 Vinylethers and Epoxies | p. 204 |
6.2.5 Developments in SL Resins | p. 205 |
6.3 Absorption of Laser Radiation by the Resin | p. 207 |
6.3.1 Beam Size and Positioning over the Resin Surface | p. 207 |
6.3.2 Laser Scanning Patterns | p. 208 |
6.3.3 Total Exposure from a Single Laser Scan | p. 208 |
6.3.4 Total Exposure of Interior Resin Layers | p. 210 |
6.3.5 Shape of a Cured Strand | p. 211 |
6.3.6 Cure Depth and Width | p. 212 |
6.3.7 Multi-layer Part Building, Overcure, and Undercure | p. 214 |
6.4 Recoating Issues | p. 216 |
6.4.1 Recoating Cycle | p. 216 |
6.4.2 Resin Level Control | p. 220 |
6.4.3 Gap Control | p. 221 |
6.5 Curing and Its Implications | p. 222 |
6.5.1 Degree of Curing and 'Green Strength' | p. 222 |
6.5.2 Effects During Post-curing | p. 225 |
6.6 Part Quality and Pocess Planning | p. 227 |
6.6.1 Shrinkage, Swelling, Curl and Distortion | p. 227 |
6.6.2 Surface Deviation and Accuracy | p. 231 |
6.6.3 Build Styles and Decisions | p. 235 |
6.6.4 Build-time and Build-cost | p. 238 |
6.6.5 Functional Prototyping using SL | p. 240 |
6.7 Other Laser Lithography Systems | p. 242 |
7. Selective Laser Sintering (SLS) | p. 245 |
7.1 The Principle of SLS | p. 245 |
7.2 Indirect and Direct SLS | p. 249 |
7.2.1 Powder Structures | p. 249 |
7.2.2 Indirect SLS using Coated Powders | p. 250 |
7.2.3 Direct SLS using Mixed Powders and LPS | p. 254 |
7.3 Modeling of SLS | p. 258 |
7.3.1 Modeling of Material Properties | p. 258 |
7.3.2 Energy Input Sub-model | p. 263 |
7.3.3 Heat Transfer Sub-model | p. 266 |
7.3.4 Sintering Sub-model and Solution | p. 268 |
7.4 Post-Processing | p. 272 |
7.5 Process Accuracy | p. 275 |
8. Other RP Systems | p. 279 |
8.1 Selective Laser Cladding (SLC) | p. 279 |
8.2 Laminated Object Manufacturing (LOM) | p. 281 |
8.3 Fused Deposition Modeling (FDM) | p. 288 |
8.4 3D Printing and Desktop Processes | p. 294 |
8.5 Shape Deposition Manufacturing (SDM) | p. 300 |
8.6 Vacuum Casting | p. 303 |
8.7 Electroforming | p. 304 |
8.8 Freeze Casting | p. 305 |
8.9 Contour Crafting | p. 306 |
8.10 3D Welding | p. 307 |
8.11 CNC Machining and Hybrid Systems | p. 308 |
9. Rapid Tooling | p. 311 |
9.1 Classification of RT Routes | p. 312 |
9.2 RP of Patterns | p. 313 |
9.3 Indirect RT | p. 316 |
9.3.1 Indirect Methods for Soft and Bridge Tooling | p. 316 |
9.3.2 Indirect Methods for Production Tooling | p. 322 |
9.3.3 Direct RT Methods for Soft and Bridge Tooling | p. 324 |
9.3.4 Direct RT Methods for Production Tooling | p. 325 |
9.4 Other RT Approaches | p. 327 |
10. Applications of RP | p. 329 |
10.1 Heterogeneous Objects | p. 330 |
10.2 Assemblies | p. 332 |
10.3 Mems and Other Small Objects | p. 333 |
10.4 Medicine | p. 337 |
10.5 Miscellaneous Areas Involving Art | p. 340 |
References | p. 345 |
Index | p. 377 |