Technology of Thermoforming
1st Edition
Published on 18. March 2013
882 pages
978-3-446-40247-8 (ISBN)
Description
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
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James L. Throne
Technology of Thermoforming
Book
07/1996
1st Edition
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€249.99
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Content
- Intro
- Preface
- Contents
- 1 Thermoforming-Definitions,History,Methods and Equipment
- 1.1 Introduction
- 1.2 History
- 1.3 Markets
- 1.4 Some Definitions
- Gage
- Clamping of Thin-Gage Sheet
- Clamping of Heavy-Gage Sheet
- Heating of Thin-Gage Sheet
- Heating Heavy-Gage Sheet
- Shaping Thin-Gage Sheet
- Shaping Heavy-Gage Sheet
- Trimming the Thin-Gage Sheet
- Trimming the Heavy-Gage Sheet
- Depth-of-Draw
- 1.5 Methods of Forming
- One-Step Forming
- Two-Step Forming with Prestretching
- Multi-Step Forming
- Other Variations
- 1.6 Thermoforming Machinery
- Heating Source
- Forming Platform
- Vacuum System
- Pressure System
- Process Control
- Trimming and Cut Parts Handling
- 1.7 Heavy-Gage Thermoforming Machinery Specifics
- 1.8 Thin-Gage Thermoforming Machinery Specifics
- 1.9 References
- 2 Polymeric Materials
- 2.1 Introduction
- 2.2 Network Nature of Polymers
- 2.3 Addition and Condensation Polymerization
- 2.4 Aromatic and Aliphatic Polymers
- 2.5 Molecular Weight and Molecular Weight Distribution
- 2.6 Molecular Weight and Properties
- 2.7 Morphology and Properties
- 2.8 Molecular Orientation
- 2.9 Chain Mobility and Polymer Stiffness
- 2.10 Stress-Crack Resistance
- 2.11 Gas Permeation
- 2.12 Copolymerization
- 2.13 Blends
- 2.14 Adducts
- Plasticizers
- Other Additives
- Fillers and Reinforcing Fibers
- 2.15 Laminates
- 2.16 Stress-Strain Behavior of Plastics
- 2.17 Thermal Properties
- Heat Capacity
- Thermal Conductivity
- Thermal Diffusivity
- Thermal Expansion Coefficient
- 2.18 Infrared Spectra
- 2.19 Summary
- 2.20 References
- 3 Heating the Sheet
- 3.1 Introduction
- 3.2 Energy Absorption by Sheet
- 3.3 Heat Transfer Modes
- 3.4 Incorporating Formability and Time-Dependent Heating
- 3.5 Conduction
- 3.6 Convection Heat Transfer Coefficient
- The Biot Number
- Effective Radiation Heat Transfer Coefficient
- Constant Heat Flux
- 3.7 Radiation Heating
- Black Body Radiation
- Gray Body-Emissivity
- Radiant Heater Efficiency-Constant Heat Flux Application
- 3.8 Real Heaters-Efficiencies
- Radiative Heat Transfer Coefficient
- Convection and the Heat Transfer Coefficient
- Rod Heaters
- 3.9 Long-Term Radiant Heater Efficiencies
- 3.10 Edge Losses-View Factor
- Local Energy Input
- Pattern Heating
- Zone, Zoned or Zonal Heating
- Heater to Sheet Distance
- 3.11 Thin-Gage Sheet-Approximate Heating Rates
- Constant Environmental Temperature Approximation
- Constant Heat Flux Approximation
- Thin-Gage Approximations-Comments
- 3.12 Heavy-Gage Sheet-Internal Temperature Control
- Constant Environmental Temperature
- The Constant Heat Flux Case
- The Thickness Effect
- Summary
- 3.13 Equilibration
- Convection Heating
- Constant Heat Flux
- Computed Equilibration Times
- The W-L-F Equation
- The Arrhenius Equation
- Relating Shift Factors to Sheet Thickness
- 3.14 Infrared-Transparent Polymers
- 3.15 Computer-Aided Prediction of Sheet Temperature
- The Radiant Boundary Condition
- 3.16 Guidelines for Determining Heating Cycles
- The Biot Number
- Thin-Gage Guidelines
- Heavy-Gage Guidelines
- Intermediate-Gage Guidelines
- 3.17 References
- 4 Stretching the Sheet
- 4.1 Introduction
- 4.2 The Stretching Concept
- 4.3 Polymer Hot Strength
- Standard Tensile Tests
- Hot Tensile Tests
- Hot Creep Tests
- Other Stretching Tests
- Temperature-Dependent Viscosity for Amorphous Polymers
- Dynamic Mechanical Testing
- 4.4 Stress-Strain-Rate of Strain-Theory
- Elasticity-A Rationalization
- Strain Energy Function
- The Rivlin Form for the Strain Energy Function
- The Ogden Form for the Strain Energy Function
- Viscoelastic Models
- 4.5 Available Stress-Strain Data
- Sensitivity of Models
- 4.6 The Importance of Polymer Material Properties
- 4.7 Practical Aspects of Stretching
- Funnel Test
- 4.8 Bursting Conditions
- 4.9 Sheet Sag
- Initial Sag
- Tensile Sag
- The Catenary Sag
- Parabolic Sag
- Relating Sag to Hot Sheet Strength
- Sag-A Comment
- 4.10 References
- Appendix 4.1 Biaxial Stretching of an Elastic Membrane
- 5 Cooling and Trimming the Part
- 5.1 Introduction
- 5.2 Overall Cooling Heat Balance
- 5.3 Cooling the Formed Shape
- 5.4 Steady State Heat Balance
- Interfacial Resistance
- Shape Factor
- Convection Heat Transfer Coefficient
- 5.5 Cyclic Heat Balance
- Cooling the Free Surface of the Sheet
- Cooling Thin Sheet in Ambient Air
- Transient Heat Removal From the Sheet
- Quiescent Ambient Air
- Moving Ambient Air
- Cooling on Nonmetallic Molds
- 5.6 Transient Heat Transfer During Sheet Cooling on the Mold Surface-Computer Models
- Interfacial Air
- 5.7 Shrinkage
- Unconstrained Shrinkage
- Constrained Shrinkage
- 5.8 Trimming
- Trimming Heavy-Gage Parts
- Trimming Thin-Gage Parts
- 5.9 Mechanics of Cutting
- The Trim Region
- Registering the Trim Site
- The Nature of the Cut
- Fracture Mechanics
- Mechanical Chipping
- Multiple-Edged Tool or Toothed Saw Performance
- Abrasive Cut-Off Wheel
- Toothless or Shear and Compression Cutting
- Fracture Mechanics in Trimming
- Nibbling
- Brittleness, Orientation and Trim Temperature
- 5.10 Steel Rule Die
- Resharpening
- Tabbing and Notching
- 5.11 Punch and Die Trimming
- Forged and Machined Dies
- 5.12 Drilling
- 5.13 Other Cutting Techniques
- Thermal Cutting
- Water Jet Cutting
- 5.14 Trimming-A Summary
- 5.15 References
- 6 Thermoforming Molds
- 6.1 Introduction
- 6.2 Prototype Molds
- Wood
- Fiberboard
- Plaster
- Plastic
- White Metal
- Nickel
- 6.3 Production Molds
- Aluminum
- Steel
- Other Metals
- 6.4 Mold Coolant Channels
- Mold Channel Flow
- Expansion
- Contraction
- Sharp-Edged Orifice
- 6.5 Vent Holes
- Sizing Vacuum Systems-Steady State
- Sizing Vacuum Systems-Dynamic
- Solenoid Valve Flow Resistance
- Vent Hole Resistance to Flow
- Vent Hole Diameter
- Other Types of Vents
- Vent Hole Placement
- 6.6 Surface Treatments
- Surface Texture
- 6.7 Plug Design Considerations
- Plug Materials
- Wood Plugs
- Plastic Plugs
- Metal Plugs
- Plug Design Concepts
- 6.8 Sheet Clamping
- 6.9 Sag Bands and Sheet Supports
- 6.10 Other Aspects of Mold Design
- Undercuts
- Encapsulation
- Moving Elements
- Stripper Plates/Bars
- Mold Releases
- Web Breakers, Catchers and Chasers
- Moats, Dams and Double Steps
- Chamfers and Radii
- Prestretching Restraints
- 6.11 Efficient Use of Sheet
- Heavy-Gage Sheet
- Thin-Gage Sheet
- 6.12 References
- 7 Parts Design
- 7.1 Introduction
- 7.2 Elements of Parts Design
- Material Testing and Its Relevance to Part Performance
- Philosophy of Parts Design
- Minimizing the Amount of Sheet to be Reground
- Rules for Part Layout on Heavy-Gage
- Rules for Multiple Part Layout on Thin-Gage
- Economics of Buying Sheet of Specific Size
- 7.3 Prototyping as a Justification for Thermoforming
- 7.4 Draw Ratio
- Linear Draw Ratio
- H:D
- Rim and Lip Sheet for Female Cavities
- Draw Ratio Usage-A Rationale
- Mechanical Assists-Some Design Features
- Preblowing or Inflation-Comments
- Plug Assist-Comments
- 7.5 Computer-Aided Design in Thermoforming
- 7.6 Wall Thickness Prediction-A Justification
- Geometric Element Analysis or GEA
- Finite Element Analysis
- General Comments on Plug Design
- Plug Assist Analysis
- Plug Design"Geometric Element Analysis
- Plug Design"Finite Element Analysis
- 7.7 Regrind
- Material Property Deterioration on Regrind
- Property Value Loss-Experiment and Protocol
- Cascading 100% Regrind
- 7.8 General Guidelines for Part Design
- General Tips
- Process Tips
- Mold Tips
- Prestretch Tips
- Part Design Tips
- Rim and Edge Designs
- Design-A Comment
- 7.9 References
- Appendix 7.I Draw Ratios for Truncated Cone
- Appendix 7.II Mechanical Property Loss in Regrind
- 8 Producing Sheet and Film
- 8.1 Introduction
- 8.2 Forming Thin Films
- 8.3 Forming Sheet
- Single-Screw Extrusion
- Filtering the Polymer
- Flow Improvement Devices
- Pressure and Temperature in an Extruder
- Sheet Die Concepts
- Gage Thickness Monitoring and Control
- Twin-Screw Extrusion
- 8.4 Roll Stacks
- 8.5 Sheet Trimming
- 8.6 Take-OfT and Take-Up Rolls
- 8.7 Residence Time and Residence Time Distribution Through Extruder and Die
- 8.8 Drying
- 8.9 Producing Biaxially Oriented Sheet
- 8.10 Multilayer Sheet Formation
- Coextrusion
- Lamination
- 8.11 Sheet Quality and Quality Control
- Sheet Dimensions
- Orientation
- Sheet Squareness and Flatness
- Moisture
- Sheet Appearance
- Annoyance Factors
- Lamination
- 8.12 References
- 9 Newer Thermoforming Technologies
- 9.1 Introduction
- 9.2 Thermoforming Crystallizing Polyethylene Terephthalate
- PET Crystallinity
- CPET Patents
- Characterizing Polyethylene Terephthalate
- The Effect of Temperature on Crystallization During Sheet Extrusion
- Cooling CPET on Chill Rolls
- Heating CPET in Roll-Fed Thermoformers
- Forming the CPET Sheet
- Cooling the CPET Formed Part
- Trimming Parts from Web
- Troubleshooting CPET Forming
- 9.3 Pressure Forming
- Thin Gage
- Heavy Gage
- 9.4 Forming Filled and Reinforced Polymers
- 9.5 Laminated Sheet Thermoforming
- Heating Multilayer Sheet
- Forming Multilayer Sheet
- 9.6 Twin-Sheet Thermoforming
- Simultaneous Twin-Sheet Forming
- Sequential Twin-Sheet Forming
- Seal Area-Adhesion
- Seal Area-Compressive Form
- Seal Area-Design
- 9.7 Polypropylene Thermoforming
- Sag Test
- Modified Polypropylenes
- 9.8 Thermoforming Foam Sheet
- Cell Architecture-Actual v. Ideal
- Radiant Energy Transmission
- Internal Cell Gas Pressure
- Forming Window for Foam
- The Forming Equipment
- 9.9 Other Forming Technologies
- Interdigitation
- Sealed Air Cushion/Dunnage
- 9.10 References
- 10 Set-Up Protocols, Troubleshooting, and the Economics of Thermoforming
- 10.1 Introduction
- 10.2 Setting Up a Thermoforming Machine-Protocols
- A New Polymer
- Setting Up a New Mold
- Setting the Mold Stops
- Dry-Cycling the Mold
- Checking the Vacuum
- Attaching Cooling to the Mold
- The Sheet Delivery System
- Setting the Oven Conditions
- Forming Step-Simple Vacuum Forming
- Changing Temperature Conditions
- Activating the Assists
- Pressure Boxes
- General Objectives
- 10.3 Troubleshooting the Forming Process
- 10.4 Energy and Materials Cost
- The Energy Audit
- Cost of Extrusion
- Cost of Regrind
- Competitive Costs of Polymers
- 10.5 General Processing Economics
- Rules of Thumb
- Global Production Costs
- Manufacturing Efficiencies
- The Learning Curve
- 10.6 Isolated Venture Costs
- 10.7 New Venture Economics
- Entrepreneurial Risks
- 10.8 The Incremental Operation
- 10.9 Comparative Process Economics
- 10.10 References
- Appendix A Abbreviations for Thermoformable Polymers Referred to in Text
- Appendix B Typical Conversion Factors Used in Thermoforming (US Customary to Metric,Metric to US Customary)
- Appendix C Glossary of Thermoforming Terms
- Author Index
- Subject Index
