Design Solutions
`Guide
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 1 of 86
`
`

`

`Page 2 of 86
`
`AMT Exhibit 2005
`CORPAKv. AMT IPR2007-01990
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 2 of 86
`
`

`

`Table of
`Contents
`
`Topic
`
`Part/Page
`
`Welcome! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I
`Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–2
`BASF Product Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–2
`Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`Design Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`CAD/CAE Capabilities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`Design Considerations for Injection Molded Parts. . . . . . . . . . . . II
`Parting Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–2
`Draft Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–3
`Wall Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–3
`Fillets and Radii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–3
`Bosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–4
`Ribs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–4
`Openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–5
`Shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–5
`Gating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–5
`Vents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–6
`Potential Knit Lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–6
`Structural Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III
`Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–2
`Stress-Strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–2
`Normal Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–3
`Shear Stress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–3
`Torsional Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–4
`Bending Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–5
`Section Properties of Various Cross-Sections . . . . . . . . . . . . . . . . . . . . III–6
`Explanation of Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–6
`Beam Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–6
`Formulas for Common Beams in Bending . . . . . . . . . . . . . . . . . . . . . . . III–7
`Formulas for Torsional Deformation and Stress . . . . . . . . . . . . . . . . . . . III–8
`I, T and L Sections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–9
`Formulas for Flat Plates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–10
`Flat Plate Equations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–10
`Pressure Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–11
`Thermal Expansion and Stress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–12
`Impact Stresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–13
`Stress Concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–14
`Rib Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–15
`Design for Equivalent Stiffness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–18
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 3 of 86
`
`

`

`Topic
`
`Part/Page
`
`Design Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IV
`Cruise Control Bracket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IV–2
`Cover Cap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IV–4
`Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V
`Snap-Fit Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V–2
`Snap-Fit Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V–2
`Cantilever vs. Cylindrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–2
`Tapered Cantilever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–2
`Short Cantilever Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–3
`New Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–4
`Snap-Fit Design Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–4
`Press-Fit Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–5
`Adhesive Bonding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–6
`Bolts, Nuts, and Machine Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–8
`Molded-in Threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–9
`Self-Tapping Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–10
`Inserts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–11
`Ultrasonic Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–12
`Shear Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–12
`Energy Director . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–13
`Vibration Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–14
`Other Assembly Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–15
`Thermoplastic Staking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–15
`Spin Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–15
`Electromagnetic Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .V–16
`Plastic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VI
`Classification of Plastic Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VI–2
`Molecular Weight Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VI–4
`Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VI–5
`Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VI–5
`Thermal Expansion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VI–5
`Thermal Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VI–6
`Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII
`The Mechanical Properties of Plastics . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–2
`Short-Term Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–2
`Notches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–2
`Rate of Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–2
`Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–4
`Thermal Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–4
`Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–5
`Dimensional Considerations (Moisture Absorption) . . . . . . . . . . . . . . . .VII–6
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 4 of 86
`
`

`

`Topic
`
`Part/Page
`
`Effects of Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–6
`Dimensional Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–6
`Accelerated Moisture Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–6
`Process Induced Property Variations . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–7
`Additives (Color) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–8
`Ultraviolet (UV) Light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–8
`Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–8
`Long-Term Properties–Creep, Stress Relaxation and Service Life . . . .VII–9
`Coefficient of Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VII–11
`Design Considerations for Gas Assist Molding . . . . . . . . . . . . . . .VIII
`Hollow Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VIII–2
`Short Shot Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VIII–3
`Full Shot Molding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .VIII–3
`Finishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IX
`Electroplating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IX–2
`Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IX–2
`Printing/Hot Stamping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IX–2
`Machining . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IX–3
`Surface Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .IX -3
`Appendix I: Physical Properties and Terminology . . . . . . . . . . . . .A1
`Anisotropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Brittleness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Ductility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Elasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Friction and Wear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Hardness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Isotropy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Lubricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–2
`Mold Shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–3
`Notch Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–3
`Plasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–3
`Specific Gravity (Relative Density) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–3
`Toughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–3
`Warpage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–3
`Water Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A1–3
`Appendix II: ISO and ASTM Test Methods . . . . . . . . . . . . . . . . . . .A2
`A2–2
`Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B1
`B1–2
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 5 of 86
`
`

`

`Part I
`
`Welcome!
`
`Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–2
`BASF Product Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–2
`Recycling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`Design Assistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`CAD/CAE Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I–3
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 6 of 86
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`

`

`WELCOME!
`
`Part I: Welcome!
`
`As part of our customer-driven philosophy
`
`of doing business, we have prepared this
`
`guide to give you a general product design
`
`Overview
`Proper design strategy includes:
`a) a concern for safety and performance
`
`b) appropriate material selection and preparation
`for processing to achieve the ultimate functional
`design goal
`
`c) maximum functionality
`
`overview with a focus on plastic part design.
`
`d) minimum material usage
`
`It is our goal to provide all our customers with
`
`the optimum level of technical and design
`
`support during their product development
`
`process.
`
`Our intent in developing this Design Solutions Guide is to
`supply general information for the customer on a variety of
`applications as a precursor to the more narrowly focused
`information which will appear in subsequent manuals.
`Manuals on specific applications will expand upon this
`general guide and address those precise topics. Your
`design success is our primary concern.
`
`Recycling
`Recycling is part of an all-important global drive toward
`reducing contamination, landfill volume and saving natural
`resources. Recycling is good business too, since
`in many cases, it results in reduced product lifestyle
`costs. Recycled plastic materials can often be specified into
`less-demanding applications.
`
`There are some design implications which should be
`considered when using recycled products:
`
`• One should use the same material in assembly
`applications where parts are permanently affixed to
`one another. Mixing material types is acceptable
`for mechanically assembled units which can be
`disassembled.
`
`• Color availability is generally limited.
`
`• Cadmium-free colors are available.
`
`I-2
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 7 of 86
`
`

`

`WELCOME!
`
`Safety
`When designing parts, a factor of safety should be used to
`manage the risk of catastrophic, premature and short-term
`failures. The factor is contingent upon numerous
`conditions, including type of application, temperature, lack
`of material homogeneity, unforeseen overloads,
`unknowns, etc.
`
`Having predetermined load conditions, the introduction of
`a factor will extend the service life of the product
`depending on the value used. The value used for the
`factor is based on the criticality of the function.
`Engineering handbooks cover this subject in more detail.
`
`Nylon has some unique characteristics. For instance,
`in the presence of moisture, it changes its physical
`properties. Strength, stiffness, surface hardness and
`brittleness will decrease while elongation, ductility, impact
`resistance, dimensions and creep will increase. These
`characteristics need to be tempered with the safety factor
`during design. These are reasons for designing with
`information not found on data sheets which are readily
`issued by material suppliers.
`
`Data sheet information is point data only.
`
`We trust you will find this and our other manuals of
`great value. We are always available to assist when
`needed.
`
`I-3
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 8 of 86
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`

`

`Part II
`
`Design Considerations for Injection
`Molded Parts
`
`Parting Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–2
`Draft Angles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–3
`Wall Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–3
`Fillets and Radii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–3
`Bosses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–4
`Ribs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–4
`Openings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–5
`Shrinkage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–5
`Gating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–5
`Vents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–6
`Potential Knit Lines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II–6
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 9 of 86
`
`

`

`Design Considerations for Injection Molded Parts
`
`Part II: Design Considerations for Injection Molded Parts
`
`The injection molding process is the most common
`process for producing economical and automated
`thermoplastic parts. It commonly requires the use of steel
`molds, injection molding machinery and auxiliary
`equipment.
`
`To injection mold a part, there are numerous design
`aspects which should be addressed. They are:
`
`Parting Lines
`Parting line consideration depends upon shape and the
`function of the part. If a shaft diameter is used as a bearing
`surface and is going to be injection molded, it cannot
`tolerate a conventional parting line. In this situation,
`incorporating small flats on the shaft at the parting line will
`avoid mismatch and minimal flash conditions (see Figure II-
`2).
`
`1. Parting Lines
`2. Draft Angles
`3. Wall Thickness
`4. Fillets and Radii
`5. Bosses
`6. Ribs
`7. Opening Formations
`8. Shrinkage
`9. Gating
`10. Vents
`11. Potential Knit Lines
`
`Mold Clamp
`System
`
`Nozzle
`
`Heater
`Bands
`
`Hopper
`
`Screw
`
`Motor
`
`Injection
`Piston
`
`Mold
`
`Back Flow
`Check Valve
`
`Screw Travel
`Limit Switches
`
`Motors, Pumps, Valves, Oil Tank,
`Heat Exchangers, etc.
`
`Controls
`
`Parting Line
`
`.005
`
`.005
`
`Figure II-2. Free Running Shaft
`
`The parting line depends on the shape of the part. Figure
`II-3 illustrates an irregular parting line. When
`a parting line involves two mating halves with close
`tolerances, the mold mating steel parts should be
`interlocked for good positioning or take in an allowance for
`possible mismatches. The allowance should be in the
`0.005 in to 0.010 in range relative to the finished dimension.
`
`Figure II-1. Schematic of Reciprocating Screw
`Injection Molding Machine
`
`Parting line
`
`Figure II-3. Irregular Parting Line
`
`II-2
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 10 of 86
`
`

`

`Design Considerations for Injection Molded Parts
`
`Fillets and Radii
`Sharp corners should be avoided. They are the number
`one cause of part failure, stress concentrations, poor flow
`patterns and increased tool wear (see Figure II-5).
`
`Indicate radii at all inside and outside corners to the
`maximum which a design will allow.
`
`Draft Angles
`Draft is necessary for the ejection of the parts from the
`mold. Always design with draft angles. Recommended
`draft angle is normally 1° with 1/2° on ribs. Some draft
`angle is better than none and more draft is desirable if the
`design permits. Where minimum draft is desired, good
`polishing is recommended and feature depth should not
`exceed .5in.
`
`Wall Thickness
`The number one rule for designing plastic parts is uniform
`wall thickness. Uniform walls aid in material flow in the
`mold, reduce the risk of sink marks, molded-in stresses
`and differential shrinkage.
`
`For non-uniform walls, the change in thickness should not
`exceed 15% of the nominal wall (see Figure II-4) and
`should transition gradually.
`
`Corners should always be designed with a minimum fillet
`radius of 50% of the wall thickness and an outer radius of
`150% of the wall thickness to maintain a uniform wall
`thickness (see Figure II-4).
`
`NOT RECOMMENDED
`
`RECOMMENDED
`
`Z
`
`Figure II-4
`
`3Z
`Min.
`
`NOT RECOMMENDED
`
`RECOMMENDED
`
`R = .5T Min.
`
`T
`
`R = 1.5T Min.
`
`Figure II-4
`
`II-3
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 11 of 86
`
`

`

`Design Considerations for Injection Molded Parts
`
`Bosses
`Bosses are usually designed to accept inserts, self-tapping
`screws, drive pins, etc., for use in assembling or mounting
`parts.
`
`Avoid stand-alone bosses wherever possible. Bosses
`should be attached to walls or ribs by means of ribs or
`gussets for structural stability (see Figures II-5 & 6).
`
`NOT RECOMMENDED
`
`RECOMMENDED
`.5T AT BASE
`
`Ribs
`Ribs should be used when needed for stiffness and
`strength or to assist in filling difficult areas.
`
`In structural parts where sink marks are of no concern, rib
`base thickness (t) can be 75–85% of the adjoining wall
`thickness (T).
`
`For appearance parts, where sink marks are objectionable,
`rib base thickness (t) should not exceed 50% of the
`adjoining wall thickness (T) if the outside surface is textured
`and 30% if not textured. Sink marks are also dependent
`on the material.
`
`Figure II-5
`
`T
`
`Rib height should be at least 2.5–3.0 times the wall
`thickness (T) for effective strength.
`Draft should be 1/2° per side nominal.
`
`The O.D. of the boss should ideally be 2.5 times the screw
`diameter for self-tapping screw applications. Thick-walled
`bosses with bases greater than 50% of the wall could form
`visible sink marks. To overcome this condition, a thinner-
`walled boss of 2.0 times screw diameter or less can have
`multiple ribs (see Figure II-6).
`
`NOT RECOMMENDED
`
`RECOMMENDED
`
`Fillets at the base of the rib should be .020 in minimum.
`
`Multiple ribs should be spaced at least 2 times the wall
`thickness apart to reduce molded in stress and problems
`in cooling of the mold (See Figure II-7).
`
`°
`1/2
`
`Min.
`
`2 T Min.
`
`t
`
`Figure II-7
`
`R = .020in
`
`T
`
`SINK
`MARK
`
`.5T
`
`R = .25T
`
`Figure II-6
`
`.7 T
`
`T
`
`2.5-3.0 T Min.
`
`The thickness at the base of the ribs and gussets used to
`stabilize bosses should not exceed 50% of the thickness
`of the adjoining wall.
`
`Boss inside and outside diameters should have 1/2° draft
`per side. See Part V of this guide for additional information
`on bosses for press fits and self-tapping screws.
`
`II-4
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 12 of 86
`
`

`

`Design Considerations for Injection Molded Parts
`
`Openings
`When an opening is desired in a part (such as to
`accommodate a snap-fit) and is to be formed without
`core pulls, a 5° angle mating of the core and cavity is
`required (see Figure II-8).
`
`Gating
`The gate connects the part to the runner system. It is
`usually the thinnest cross-section in the entire system. The
`design of the gate is dependent on tool design, part
`geometry and the material selection.
`
`Gate location, size, type and number must also be
`addressed.
`
`• Gates should be located away from high stress or
`impact areas.
`
`• Gate configuration and location should minimally
`affect part appearance.
`
`• Gate design and location should eliminate secondary
`degating operations, if possible.
`
`• The gate should be located to best fill the part;
`position flow for advantageous glass fiber orientation, if
`present, and locate knit lines in
`low-stress areas.
`
`Refer to the BASF Injection Molding Processing Guide for
`more details.
`
`MOLD
` PULL
`
`5° Min.
`
`“Kissoff” between
`two pieces of steel
`
`Figure II-8
`
`Shrinkage
`Shrinkage is a characteristic of resin which occurs
`during molding. Different resins have different mold
`shrinkages. Crystalline and semi-crystalline materials
`exhibit higher shrinkage than amorphous materials.
`Unreinforced plastics have higher shrinkage than
`reinforced grades. It is important that the grade of material
`be selected before the mold is constructed
`and that the proper mold shrinkage be specified. Basic
`shrinkage data is obtained from ASTM tests or ISO tests.
`
`Material shrinkage can vary with part and tool design:
`thick walls will have higher shrinkage rates than thin,
`variation in section thickness can cause differential
`shrinkage and warpage; flow direction will effect shrinkage,
`particularly with glass fiber-reinforced grades (more when
`perpendicular to flow and less when parallel to flow; see
`Figure VII-14).
`
`Shrinkage is also influenced by process conditions.
`As cavity pressure increases, shrinkage typically
`will decrease. The mold and melt temperature will
`also influence shrinkage. Cooler molds will reduce
`shrinkage while hotter melt temperatures will increase
`shrinkage especially with semi-crystalline materials.
`
`Contact BASF Technical Services for shrinkage
`recommendations on any of our products.
`
`II-5
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 13 of 86
`
`

`

`Design Considerations for Injection Molded Parts
`
`Vents
`Vents are regions in the mold where clearance is used to
`permit trapped air and gases to escape. Lack of proper
`venting can cause excessive injection pressure, short
`shots, burn marks and splay. A cavity can be considered
`adequately vented when plastic can be injected at high
`rates without showing signs of burn marks.
`
`There are many ways to vent a mold. Typically, this is
`done by machining numerous shallow channels at the
`parting line. The dimensions of the channels are
`dependent on the material injected. Contact BASF
`Technical Services for this information. Other ways
`to vent a mold are ejector pins, vent pins and runners.
`Flow analysis can identify areas needing specific venting for
`best results.
`
`Potential Knit Lines
`Knit lines are areas in the molded part where two or more
`flow fronts converge. This area generally has lower strength
`than the other areas of the part. One should anticipate knit
`lines, which show up well in flow analysis programs, and
`direct them away from anticipated high stress areas of the
`part where possible. Knit lines generally form on the
`opposite side of obstacles which are in the way of the
`normal flow path, such as pins that form holes in the part or
`bosses designed to accept inserts.
`
`II-6
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 14 of 86
`
`

`

`Part III
`
`Structural Design
`
`Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–2
`Stress-Strain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–2
`Normal Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–3
`Shear Stress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–3
`Torsional Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–4
`Bending Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–5
`Section Properties of Various Cross-Sections. . . . . . . . . . III–6
`Explanation of Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–6
`Beam Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–6
`Formulas for Common Beams in Bending . . . . . . . . . . . . . III–7
`Formulas for Torsional Deformation and Stress . . . . . . . . . III–8
`I, T and L Sections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–9
`Formulas for Flat Plates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–10
`Flat Plate Equations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–10
`Pressure Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–11
`Thermal Expansion and Stress. . . . . . . . . . . . . . . . . . . . . . . III–12
`Impact Stresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–13
`Stress Concentrations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–14
`Rib Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . III–15
`Design for Equivalent Stiffness . . . . . . . . . . . . . . . . . . . . . . . III–18
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 15 of 86
`
`

`

`Hooke’s Law is the relationship between stress and strain,
`such that strain is proportional to stress and
`the modulus of elasticity (E) or Young’s Modulus is
`the constant of proportionality:
`σ−ε
`E =
`. All plastic materials have a characteristic stress-strain
`curve (see Figure III-2).
`
`Typical Metal
`
`Brittle Plastic
`
`Ductile Plastic
`
`STRESS
`
`Figure III-2. Stress vs. Strain
`
`In order to obtain a stress-strain curve for a resin, a tensile
`test is performed at room temperature. The part is axially
`loaded with the force directed away from the part. The
`stress-strain curve describes the resin’s response to a
`force applied at a predetermined rate (.2–.5in/min).
`The yield point (deviation from the straight line) is
`dependent upon the temperature at which it is measured.
`Plastic materials do not have a distinct
`linear response like that of metals. Temperature and
`humidity can change these curves. Higher temperatures
`and humidity generally reduce stress carrying ability and
`increase strain (deflection).
`
`When a plastic part is subjected to a high enough external
`force, it will exceed its elastic limit (the straight line portion
`of the curve in Figure III-2). Its original size and shape will
`no longer remain constant. The material behaves linearly
`as long as the stress is kept well below the yield point.
`Once the yield point is reached, the material at that point is
`in its plastic (non-linear) range. Exceeding the linear range
`results in some permanent deformation of the material. It
`is only when the part
`has not been stressed beyond its elastic limit that
`Hooke’s Law applies. There are many types of stresses:
`Normal, Shear, Torsional, and Bending. Each will be
`discussed in detail.
`
`Structural Design
`
`Part III: Structural Design
`
`Stress
`
`Stress-Strain
`When a force is applied to a part, the result is a deformed
`part which is both stressed and strained. The stress (σ) in a
`part is determined by the load (F) applied per unit area.
`σ= F_
`A
`Strain (ε) is a change in the part’s length over its original
`length (see Figure III-1).
`
`∆L
`ε =
`L
`Figure III-1. Strain
`
`F
`
`A
`
`F
`
`L
`
`∆L
`
`III-2
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 16 of 86
`
`

`

`Shear Stress
`Shear Stress (τ), like tensile and compressive stress, is
`also expressed as the force applied over a cross-sectional
`area (A).
`
`τ= F_
`A
`
`The difference is that the result of the force being applied is
`a stress which is parallel to the cross-section (see Figure
`III-5).
`
`F
`
`C
`
`F
`
`F
`
`C
`
`F
`
`A
`
`Figure III-5. Shear Stress
`
`Illustration credit: Beer & Johnson, Mechanical Materials.
`
`Structural Design
`
`Normal Stress
`Normal stress (σ) is the ratio of the force applied over a
`given cross-sectional area (A):
`σ= F_
`A
`
`When a load is applied perpendicular (normal) to
`the plane of a surface, it results in a stress normal to
`the cross-section. A normal stress is either tensile or
`compressive, depending on the direction of the force
`applied. When the force is directed away from the part,
`the stress is tensile (see Figure III-3), and when the force is
`directed toward the part, the stress is compressive
`(see Figure III-4).
`
`A
`
`F
`
`F
`
`Figure III-3. Tensile Stress
`
`A
`
`F
`
`F
`
`Figure III-4. Compressive Stress
`
`III-3
`
`AMT Exhibit 2005
`CORPAK v. AMT IPR2007-01990
`Page 17 of 86
`
`

`

`Example for solid circular shaft:
`
`A 5in long solid circular shaft of .5in diameter, is subjected
`to a torque of 8 in–lb. Calculate the shear stress and angle
`of twist.
`
`Using Ultramid•
` 8267 resin (40% mineral/glas