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Machining Plastic Parts

Machining Plastic Parts. Luke Kwisnek Patrick Slater Matt Jackson. Objective. Differences between metal and plastic Materials Advantages Disadvantages. Outline. Why Machine Plastics Process Considerations Material Considerations. Why Machine Plastic?. Cost Effective

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Machining Plastic Parts

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  1. Machining Plastic Parts Luke Kwisnek Patrick Slater Matt Jackson

  2. Objective • Differences between metal and plastic • Materials • Advantages • Disadvantages

  3. Outline • Why Machine Plastics • Process Considerations • Material Considerations

  4. Why Machine Plastic? • Cost Effective • Low Volume Production • Secondary Operations • Material Limitations • Thermosets • Composites • Ultra-High Mw Materials

  5. Machining Plastics vs Metals • Ventilation Concerns • Annealing • To Avoid Warpage • Robust Fixturing • Tooling Considerations • Sharper • More Clearance (“Rake”)

  6. Factors Affecting Cutting Action In Plastics • Heat • Thermal Conductivity < Metal • Resists Compressive Fracture • Factors Promoting Tensile Fracture: • Sharp Tools • Large Rake Angles

  7. Factors Affecting Cutting Action In Plastics • Chip Formation • Want Continuous Flow Type • Smooth and Continuous • High Elastic Deformation

  8. Process Specific Considerations

  9. Lathe Cutting • Tooling • Standard Tool Materials • High Rake Angle • Water Soluble Coolants • Close Chucking and Follow Rests • Prevent chatter

  10. Lathe Tool Bit Terminology

  11. Milling • Tooling • Standard Tool Materials • High Clearance • Water Soluble Coolants • Slower Cutting Feeds • Same as Metal Otherwise

  12. Drilling/Reaming • Tooling • Wide, Highly Polished Flutes • Large Helix Angles • Point angles of 60-90° (included) • 120° for PMMA and PVC • Dimensional Concerns • Thermal Expansion • Drill Oversize

  13. Drill Terminology

  14. Reamer Terminology

  15. Tapping/Threading • Tooling • Same Tools as Metal • Blunt Withdrawal Edges • Speeds • 50 ft/min Most Plastics • 25 ft/min Filled Materials

  16. New Cutting Technologies • Water Jet • Ultrasonic • Laser-assisted turning

  17. Material Specific Considerations

  18. Machining Neat Plastics • Teflon, Acetal, Acrylics • Generous Rake • Low Cutting Speeds (< 1m/min) • Nylon • Continuous Chips • Rake, Depth and Speed • Annealing • Standard • Double Anneal (Teflon)

  19. Machining Thermosets • Base Resin Mixtures • Phenolic, Urea, Melamine, Silicone • Most similar to metal • High speeds and feeds • Finishing required

  20. Machining Reinforced Plastics • Fiber-Reinforced Plastics (FRPs) • Base Materials • Polyesters, Polyamides, Expoxy Resins • Matrix (Filler) Materials • Glass, Carbon, Aramid Fibers

  21. Machining Reinforced Plastics cont. • Usage Limitations • Chip/Dust Production • Surface Details • Unique Modes of Failure • Different Fracture Characteristics

  22. Chip Characteristics Powder Ribbon Brush

  23. Fracture Characteristics

  24. Machining Reinforced Plastics cont. • Tooling • Longer Life With K-Carbide • Cutting Speed 38 m/min • Single Crystal Diamond Tooling • Better Life • Cutting Speed 426 m/min

  25. Conclusion • Cost Effective • Low Volume • Difficult to Mold Materials • Promote Tensile Fracture • Continuous Flow Chips • Generous Rake • Sharp Tools • Low Cutting Speeds

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