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