Throne Technology of Thermoforming
1. Auflage 2013
ISBN: 978-3-446-40247-8
Verlag: Carl Hanser
Format: PDF
Kopierschutz: 1 - PDF Watermark
E-Book, Englisch, 882 Seiten
ISBN: 978-3-446-40247-8
Verlag: Carl Hanser
Format: PDF
Kopierschutz: 1 - PDF Watermark
This thorough text covers thermoforming processes and products. It moves from a relatively simple approach to more technical in-depth consideration, featuring examples and guidelines to illustrate all technical aspects.
Contents:
- Definitions, History, Methods, and Equipment
- Polymeric Materials
- Heating the Sheet
- Stretching the Sheet
- Cooling and Trimming the Part
- Molds
- Parts Design
- Producing Sheet and Film
- Latest Technologies
- Set-Up Protocols, Trouble-shooting, and the Economics of Thermoforming
Autoren/Hrsg.
Fachgebiete
Weitere Infos & Material
1;Preface;6
2;Contents;10
3;1 Thermoforming—Definitions,History,Methods and Equipment;18
3.1;1.1 Introduction;19
3.2;1.2 History;20
3.3;1.3 Markets;21
3.4;1.4 Some Definitions;28
3.4.1;Gage;29
3.4.2;Clamping of Thin-Gage Sheet;29
3.4.3;Clamping of Heavy-Gage Sheet;30
3.4.4;Heating of Thin-Gage Sheet;30
3.4.5;Heating Heavy-Gage Sheet;31
3.4.6;Shaping Thin-Gage Sheet;31
3.4.7;Shaping Heavy-Gage Sheet;31
3.4.8;Trimming the Thin-Gage Sheet;32
3.4.9;Trimming the Heavy-Gage Sheet;32
3.4.10;Depth-of-Draw;32
3.5;1.5 Methods of Forming;33
3.5.1;One-Step Forming;34
3.5.2;Two-Step Forming with Prestretching;36
3.5.3;Multi-Step Forming;39
3.5.4;Other Variations;42
3.6;1.6 Thermoforming Machinery;46
3.6.1;Heating Source;46
3.6.2;Forming Platform;48
3.6.3;Vacuum System;49
3.6.4;Pressure System;53
3.6.5;Process Control;53
3.6.6;Trimming and Cut Parts Handling;55
3.7;1.7 Heavy-Gage Thermoforming Machinery Specifics;55
3.8;1.8 Thin-Gage Thermoforming Machinery Specifics;63
3.9;1.9 References;69
4;2 Polymeric Materials;71
4.1;2.1 Introduction;72
4.2;2.2 Network Nature of Polymers;72
4.3;2.3 Addition and Condensation Polymerization;74
4.4;2.4 Aromatic and Aliphatic Polymers;75
4.5;2.5 Molecular Weight and Molecular Weight Distribution;75
4.6;2.6 Molecular Weight and Properties;78
4.7;2.7 Morphology and Properties;80
4.8;2.8 Molecular Orientation;87
4.9;2.9 Chain Mobility and Polymer Stiffness;87
4.10;2.10 Stress-Crack Resistance;89
4.11;2.11 Gas Permeation;89
4.12;2.12 Copolymerization;90
4.13;2.13 Blends;91
4.14;2.14 Adducts;91
4.14.1;Plasticizers;91
4.14.2;Other Additives;93
4.14.3;Fillers and Reinforcing Fibers;94
4.15;2.15 Laminates;95
4.16;2.16 Stress-Strain Behavior of Plastics;95
4.17;2.17 Thermal Properties;99
4.17.1;Heat Capacity;99
4.17.2;Thermal Conductivity;101
4.17.3;Thermal Diffusivity;101
4.17.4;Thermal Expansion Coefficient;104
4.18;2.18 Infrared Spectra;104
4.19;2.19 Summary;113
4.20;2.20 References;120
5;3 Heating the Sheet;122
5.1;3.1 Introduction;123
5.2;3.2 Energy Absorption by Sheet;123
5.3;3.3 Heat Transfer Modes;127
5.4;3.4 Incorporating Formability and Time-Dependent Heating;132
5.5;3.5 Conduction;138
5.6;3.6 Convection Heat Transfer Coefficient;141
5.6.1;The Biot Number;142
5.6.2;Effective Radiation Heat Transfer Coefficient;143
5.6.3;Constant Heat Flux;144
5.7;3.7 Radiation Heating;145
5.7.1;Black Body Radiation;146
5.7.2;Gray Body—Emissivity;151
5.7.3;Radiant Heater Efficiency—Constant Heat Flux Application;155
5.8;3.8 Real Heaters—Efficiencies;157
5.8.1;Radiative Heat Transfer Coefficient;161
5.8.2;Convection and the Heat Transfer Coefficient;162
5.8.3;Rod Heaters;167
5.9;3.9 Long-Term Radiant Heater Efficiencies;168
5.10;3.10 Edge Losses—View Factor;169
5.10.1;Local Energy Input;172
5.10.2;Pattern Heating;176
5.10.3;Zone, Zoned or Zonal Heating;178
5.10.4;Heater to Sheet Distance;179
5.11;3.11 Thin-Gage Sheet—Approximate Heating Rates;181
5.11.1;Constant Environmental Temperature Approximation;181
5.11.2;Constant Heat Flux Approximation;184
5.11.3;Thin-Gage Approximations—Comments;184
5.12;3.12 Heavy-Gage Sheet—Internal Temperature Control;185
5.12.1;Constant Environmental Temperature;185
5.12.2;The Constant Heat Flux Case;189
5.12.3;The Thickness Effect;191
5.12.4;Summary;192
5.13;3.13 Equilibration;193
5.13.1;Convection Heating;194
5.13.2;Constant Heat Flux;196
5.13.3;Computed Equilibration Times;197
5.13.4;The W-L-F Equation;198
5.13.5;The Arrhenius Equation;199
5.13.6;Relating Shift Factors to Sheet Thickness;199
5.14;3.14 Infrared-Transparent Polymers;199
5.15;3.15 Computer-Aided Prediction of Sheet Temperature;205
5.15.1;The Radiant Boundary Condition;209
5.16;3.16 Guidelines for Determining Heating Cycles;209
5.16.1;The Biot Number;210
5.16.2;Thin-Gage Guidelines;210
5.16.3;Heavy-Gage Guidelines;210
5.16.4;Intermediate-Gage Guidelines;211
5.17;3.17 References;211
6;4 Stretching the Sheet;214
6.1;4.1 Introduction;215
6.2;4.2 The Stretching Concept;219
6.3;4.3 Polymer Hot Strength;225
6.3.1;Standard Tensile Tests;225
6.3.2;Hot Tensile Tests;229
6.3.3;Hot Creep Tests;230
6.3.4;Other Stretching Tests;232
6.3.5;Temperature-Dependent Viscosity for Amorphous Polymers;233
6.3.6;Dynamic Mechanical Testing;239
6.4;4.4 Stress-Strain-Rate of Strain—Theory;243
6.4.1;Elasticity—A Rationalization;250
6.4.2;Strain Energy Function;252
6.4.3;The Rivlin Form for the Strain Energy Function;253
6.4.4;The Ogden Form for the Strain Energy Function;256
6.4.5;Viscoelastic Models;257
6.5;4.5 Available Stress-Strain Data;259
6.5.1;Sensitivity of Models;264
6.6;4.6 The Importance of Polymer Material Properties;265
6.7;4.7 Practical Aspects of Stretching;274
6.7.1;Funnel Test;277
6.8;4.8 Bursting Conditions;281
6.9;4.9 Sheet Sag;283
6.9.1;Initial Sag;284
6.9.2;Tensile Sag;285
6.9.3;The Catenary Sag;286
6.9.4;Parabolic Sag;287
6.9.5;Relating Sag to Hot Sheet Strength;288
6.9.6;Sag—A Comment;293
6.10;4.10 References;294
6.11;Appendix 4.1 Biaxial Stretching of an Elastic Membrane;299
7;5 Cooling and Trimming the Part;301
7.1;5.1 Introduction;302
7.2;5.2 Overall Cooling Heat Balance;302
7.3;5.3 Cooling the Formed Shape;304
7.4;5.4 Steady State Heat Balance;305
7.4.1;Interfacial Resistance;306
7.4.2;Shape Factor;308
7.4.3;Convection Heat Transfer Coefficient;310
7.5;5.5 Cyclic Heat Balance;319
7.5.1;Cooling the Free Surface of the Sheet;320
7.5.2;Cooling Thin Sheet in Ambient Air;320
7.5.3;Transient Heat Removal From the Sheet;322
7.5.4;Quiescent Ambient Air;322
7.5.5;Moving Ambient Air;324
7.5.6;Cooling on Nonmetallic Molds;326
7.6;5.6 Transient Heat Transfer During Sheet Cooling on the Mold Surface—Computer Models;331
7.6.1;Interfacial Air;335
7.7;5.7 Shrinkage;337
7.7.1;Unconstrained Shrinkage;338
7.7.2;Constrained Shrinkage;342
7.8;5.8 Trimming;346
7.8.1;Trimming Heavy-Gage Parts;348
7.8.2;Trimming Thin-Gage Parts;350
7.9;5.9 Mechanics of Cutting;351
7.9.1;The Trim Region;353
7.9.2;Registering the Trim Site;354
7.9.3;The Nature of the Cut;355
7.9.4;Fracture Mechanics;357
7.9.5;Mechanical Chipping;357
7.9.6;Multiple-Edged Tool or Toothed Saw Performance;359
7.9.7;Abrasive Cut-Off Wheel;361
7.9.8;Toothless or Shear and Compression Cutting;364
7.9.9;Fracture Mechanics in Trimming;364
7.9.10;Nibbling;372
7.9.11;Brittleness, Orientation and Trim Temperature;375
7.10;5.10 Steel Rule Die;376
7.10.1;Resharpening;379
7.10.2;Tabbing and Notching;380
7.11;5.11 Punch and Die Trimming;381
7.11.1;Forged and Machined Dies;384
7.12;5.12 Drilling;384
7.13;5.13 Other Cutting Techniques;389
7.13.1;Thermal Cutting;389
7.13.2;Water Jet Cutting;391
7.14;5.14 Trimming—A Summary;393
7.15;5.15 References;396
8;6 Thermoforming Molds;399
8.1;6.1 Introduction;400
8.2;6.2 Prototype Molds;401
8.2.1;Wood;402
8.2.2;Fiberboard;403
8.2.3;Plaster;404
8.2.4;Plastic;406
8.2.5;White Metal;414
8.2.6;Nickel;417
8.3;6.3 Production Molds;417
8.3.1;Aluminum;418
8.3.2;Steel;419
8.3.3;Other Metals;420
8.4;6.4 Mold Coolant Channels;421
8.4.1;Mold Channel Flow;422
8.4.2;Expansion;423
8.4.3;Contraction;423
8.4.4;Sharp-Edged Orifice;423
8.5;6.5 Vent Holes;428
8.5.1;Sizing Vacuum Systems—Steady State;430
8.5.2;Sizing Vacuum Systems—Dynamic;431
8.5.3;Solenoid Valve Flow Resistance;433
8.5.4;Vent Hole Resistance to Flow;434
8.5.5;Vent Hole Diameter;440
8.5.6;Other Types of Vents;444
8.5.7;Vent Hole Placement;447
8.6;6.6 Surface Treatments;450
8.6.1;Surface Texture;453
8.7;6.7 Plug Design Considerations;456
8.7.1;Plug Materials;456
8.7.2;Wood Plugs;458
8.7.3;Plastic Plugs;458
8.7.4;Metal Plugs;458
8.7.5;Plug Design Concepts;462
8.8;6.8 Sheet Clamping;465
8.9;6.9 Sag Bands and Sheet Supports;468
8.10;6.10 Other Aspects of Mold Design;468
8.10.1;Undercuts;469
8.10.2;Encapsulation;470
8.10.3;Moving Elements;471
8.10.4;Stripper Plates/Bars;472
8.10.5;Mold Releases;473
8.10.6;Web Breakers, Catchers and Chasers;474
8.10.7;Moats, Dams and Double Steps;475
8.10.8;Chamfers and Radii;476
8.10.9;Prestretching Restraints;478
8.11;6.11 Efficient Use of Sheet;478
8.11.1;Heavy-Gage Sheet;478
8.11.2;Thin-Gage Sheet;480
8.12;6.12 References;484
9;7 Parts Design;487
9.1;7.1 Introduction;488
9.2;7.2 Elements of Parts Design;488
9.2.1;Material Testing and Its Relevance to Part Performance;490
9.2.2;Philosophy of Parts Design;493
9.2.3;Minimizing the Amount of Sheet to be Reground;495
9.2.4;Rules for Part Layout on Heavy-Gage;496
9.2.5;Rules for Multiple Part Layout on Thin-Gage;498
9.2.6;Economics of Buying Sheet of Specific Size;500
9.3;7.3 Prototyping as a Justification for Thermoforming;503
9.4;7.4 Draw Ratio;505
9.4.2;Linear Draw Ratio;511
9.4.3;H:D;513
9.4.4;Rim and Lip Sheet for Female Cavities;516
9.4.5;Draw Ratio Usage—A Rationale;520
9.4.6;Mechanical Assists—Some Design Features;520
9.4.7;Preblowing or Inflation—Comments;520
9.4.8;Plug Assist—Comments;524
9.5;7.5 Computer-Aided Design in Thermoforming;524
9.6;7.6 Wall Thickness Prediction—A Justification;527
9.6.1;Geometric Element Analysis or GEA;530
9.6.2;Finite Element Analysis;538
9.6.3;General Comments on Plug Design;544
9.6.4;Plug Assist Analysis;550
9.6.5;Plug Design„Geometric Element Analysis;553
9.6.6;Plug Design„Finite Element Analysis;556
9.7;7.7 Regrind;561
9.7.1;Material Property Deterioration on Regrind;562
9.7.2;Property Value Loss—Experiment and Protocol;566
9.7.3;Cascading 100% Regrind;570
9.8;7.8 General Guidelines for Part Design;572
9.8.1;General Tips;572
9.8.2;Process Tips;573
9.8.3;Mold Tips;574
9.8.4;Prestretch Tips;576
9.8.5;Part Design Tips;578
9.8.6;Rim and Edge Designs;586
9.8.7;Design—A Comment;590
9.9;7.9 References;591
9.10;Appendix 7.I Draw Ratios for Truncated Cone;594
9.11;Appendix 7.II Mechanical Property Loss in Regrind;596
10;8 Producing Sheet and Film;599
10.1;8.1 Introduction;600
10.2;8.2 Forming Thin Films;601
10.3;8.3 Forming Sheet;604
10.3.1;Single-Screw Extrusion;605
10.3.2;Filtering the Polymer;608
10.3.3;Flow Improvement Devices;611
10.3.4;Pressure and Temperature in an Extruder;613
10.3.5;Sheet Die Concepts;615
10.3.6;Gage Thickness Monitoring and Control;619
10.3.7;Twin-Screw Extrusion;621
10.4;8.4 Roll Stacks;624
10.5;8.5 Sheet Trimming;627
10.6;8.6 Take-OfT and Take-Up Rolls;628
10.7;8.7 Residence Time and Residence Time Distribution Through Extruder and Die;631
10.8;8.8 Drying;634
10.9;8.9 Producing Biaxially Oriented Sheet;637
10.10;8.10 Multilayer Sheet Formation;640
10.10.1;Coextrusion;641
10.10.2;Lamination;645
10.11;8.11 Sheet Quality and Quality Control;649
10.11.1;Sheet Dimensions;654
10.11.2;Orientation;654
10.11.3;Sheet Squareness and Flatness;656
10.11.4;Moisture;657
10.11.5;Sheet Appearance;658
10.11.6;Annoyance Factors;659
10.11.7;Lamination;660
10.12;8.12 References;661
11;9 Newer Thermoforming Technologies;665
11.1;9.1 Introduction;666
11.2;9.2 Thermoforming Crystallizing Polyethylene Terephthalate;669
11.2.1;PET Crystallinity;667
11.2.2;CPET Patents;669
11.2.3;Characterizing Polyethylene Terephthalate;669
11.2.4;The Effect of Temperature on Crystallization During Sheet Extrusion;676
11.2.5;Cooling CPET on Chill Rolls;679
11.2.6;Heating CPET in Roll-Fed Thermoformers;683
11.2.7;Forming the CPET Sheet;683
11.2.8;Cooling the CPET Formed Part;685
11.2.9;Trimming Parts from Web;687
11.2.10;Troubleshooting CPET Forming;687
11.3;9.3 Pressure Forming;687
11.3.1;Thin Gage;692
11.3.2;Heavy Gage;694
11.4;9.4 Forming Filled and Reinforced Polymers;696
11.5;9.5 Laminated Sheet Thermoforming;704
11.5.1;Heating Multilayer Sheet;704
11.5.2;Forming Multilayer Sheet;708
11.6;9.6 Twin-Sheet Thermoforming;713
11.6.1;Simultaneous Twin-Sheet Forming;718
11.6.2;Sequential Twin-Sheet Forming;719
11.6.3;Seal Area—Adhesion;721
11.6.4;Seal Area—Compressive Form;723
11.6.5;Seal Area—Design;724
11.7;9.7 Polypropylene Thermoforming;727
11.7.1;Sag Test;728
11.7.2;Modified Polypropylenes;734
11.8;9.8 Thermoforming Foam Sheet;739
11.8.1;Cell Architecture—Actual v. Ideal;739
11.8.2;Radiant Energy Transmission;743
11.8.3;Internal Cell Gas Pressure;748
11.8.4;Forming Window for Foam;750
11.8.5;The Forming Equipment;753
11.9;9.9 Other Forming Technologies;755
11.9.1;Interdigitation;755
11.9.2;Sealed Air Cushion/Dunnage;757
11.10;9.10 References;758
12;10 Set-Up Protocols, Troubleshooting, and the Economics of Thermoforming;765
12.1;10.1 Introduction;766
12.2;10.2 Setting Up a Thermoforming Machine—Protocols;770
12.2.1;A New Polymer;770
12.2.2;Setting Up a New Mold;775
12.2.3;Setting the Mold Stops;778
12.2.4;Dry-Cycling the Mold;778
12.2.5;Checking the Vacuum;779
12.2.6;Attaching Cooling to the Mold;780
12.2.7;The Sheet Delivery System;781
12.2.8;Setting the Oven Conditions;782
12.2.9;Forming Step—Simple Vacuum Forming;783
12.2.10;Changing Temperature Conditions;784
12.2.11;Activating the Assists;784
12.2.12;Pressure Boxes;785
12.2.13;General Objectives;785
12.3;10.3 Troubleshooting the Forming Process;786
12.4;10.4 Energy and Materials Cost;800
12.4.1;The Energy Audit;800
12.4.2;Cost of Extrusion;808
12.4.3;Cost of Regrind;810
12.4.4;Competitive Costs of Polymers;810
12.5;10.5 General Processing Economics;811
12.5.1;Rules of Thumb;813
12.5.2;Global Production Costs;815
12.5.3;Manufacturing Efficiencies;818
12.5.4;The Learning Curve;823
12.6;10.6 Isolated Venture Costs;825
12.7;10.7 New Venture Economics;836
12.7.1;Entrepreneurial Risks;842
12.8;10.8 The Incremental Operation;848
12.9;10.9 Comparative Process Economics;850
12.10;10.10 References;860
13;Appendix A Abbreviations for Thermoformable Polymers Referred to in Text;861
14;Appendix B Typical Conversion Factors Used in Thermoforming (US Customary to Metric,Metric to US Customary);864
15;Appendix C Glossary of Thermoforming Terms;866
16;Author Index;872
17;Subject Index;879
