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012 Better Plastics Part Design

Peter J. Rucinski Senior Product Manager

Mathieu Fourcade Product Marketing Manager

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012

AMORPHOUS CRYSTALLINE Polycarbonate (PC) High-Density Polyethylene (HDPE)

Acrylic (PMMA) Low-Density Polyethylene (LDPE)

Polystyrene (PS) Polypropylene (PP)

Polyvinyl Chloride (PVC) Nylon (PA6, PA6/6, PA12)

Acrylonitrile Butadiene Styrene (ABS)

Acetal (POM)

Polysulfone (PSO) Polyester (PET, PBT)

Polyetherimide (PEI)

Polyethersulfone (PES)

Common Plastics

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Amorphous vs. Crystalline Plastics PROPERTY AMORPHOUS CRYSTALLINE

Optical Transparent Opaque/Translucent

Light Transmission Excellent Poor

Chemical Resistance Limited Good-Excellent

Shrinkage Low High

Coefficient of Friction High Low

Tough/Brittle Brittle/Tough Tough

Stiff/Flexible Stiff/Flexible Flexible/Stiff

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Fillers and Additives Added in concentrations of PPM to 50%+ by weight…

Colorants Fillers

UV Stabilizers Reinforcements Anti-oxidants Anti-static Agents

Flame Retardants Anti-microbial Agents

External Lubricants Fragrances

Foaming Agents Plasticizers

Other Plastics (blends) Compatibilizing Agents

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• Different plastics have different properties and they process differently

• Within a class of material, properties and processability can vary drastically, for example: • Polycarbonate – DVD’s to bullet-proof glass • PVC – Rain coats to rigid pipe

• Fillers, Additives & Reinforcements affect all of the above

Why is this Important?

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012 Advantages/Benefits

• Produce complex geometry in “net” shape • High-volume – 100’s of thousands to millions of parts/year • Fast – typical cycle times ~3-60 seconds • Low cost/part – typically pennies • Plastics light, chemically resistant, good strength/weight ratio, etc.

Injection Molding Overview

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…for Injection Molding

Best Practices in Plastic Part Design…

• Maintain Uniform Wall Thickness • Follow Rib Design Guidelines • Gate from Thick to Thin • Minimize Weld Lines

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Typical Wall Thicknesses:

Maintain Uniform Wall Thickness

• ~2 mm to 4 mm (0.080 inch to 0.160 inch).

• Thin-wall ~0.5 mm (0.020 inch). • Minimum limit ~.25mm (0.010

inch)

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012 • Promotes uniform filling and

packing • Avoids flow hesitation • Reduces cooling time and

maintains uniform cooling • Reduces material usage –

lowers part cost

Maintain Uniform Wall Thickness

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• Rib thickness should be between 50-70% of nominal wall thickness.

• Rib height should be 2.5 - 3X nominal wall thickness.

• Ribs should have 0.5 - 1.5 degrees of draft (for ejection).

• Rib base radii should be 0.25 - 0.4Xnominal wall thickness.

• Distance between two ribs should be 2 – 3X times nominal wall thickness.

Rib Design Guidelines

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Rib Design – Sink Marks

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Internal View

Rib Design – Sink Marks

External View

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80% 2.0mm Ribs

100% 2.5mm Ribs

Rib Design – Sink Marks

50% 1.25mm Ribs

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Gate from Thick to Thin

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012 Also called:

• Knit Lines • Meld Lines Can cause: • Structural weakness • Cosmetic defects Recommendations: • Minimize # of gates • Control position

Minimize Weld Lines

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Using SW Plastics Simulation to Avoid Just One Round of Mold

Rework can result in a Positive ROI

Introducing SolidWorks Plastics • Predict and avoid manufacturing defects • Eliminate costly mold rework • Improve part quality • Decrease time to market Value Proposition • >80% of plastic parts are injection molded • Injection molding is a complex mix of time,

temperature, pressure, material & tooling variables

• Injection molds range in cost from >$10K to $1M+ and mold rework is costly and time-consuming

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DEMO

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Best practices in plastics part design…

• Maintain Uniform Wall Thickness • Follow Rib Design Guidelines • Gate from Thick to Thin • Minimize Weld Lines

Summary

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Using SolidWorks Plastics during the earliest stages of part and mold design helps you:

• Predict and avoid injection molding manufacturing defects

• Eliminate costly mold rework • Improve part quality • Decrease time to market

Summary

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Questions?