Special Considerations and Best Practices for CNC Machining of Engineering Plastics
CNC machining of engineering plastics (e.g. PEEK, PTFE, POM, PMMA, PC, ABS) requires a completely different strategy compared to metals. The main challenges include: poor thermal conductivity (easy to melt or burn), low modulus of elasticity (easy to deform), and dimensional changes due to internal stress release. Best practices for 2026 include: using single- or double-slot tools to facilitate chip removal; using compressed air cooling instead of coolant (to avoid plastic moisture absorption); maintaining sharp tools (dull knives can generate friction heat); and controlling the amount of cutting and feed rate. For PEEK (polyetheretherketone), high-speed milling (10,000-20,000 rpm) and small depth of cut (0.1-0 mm) are recommended, and diamond-coated tools are used. For PTFE (Teflon), sharp turning tools and very low feed rates are required due to its extreme softness and easy deformation. Practical cases show that the surface roughness of engineering plastic parts can be reduced from Ra 3.2 μm to Ra 0.8 μm with no melting marks after using a dedicated plastics machining strategy. In 2026, CNC service providers with engineering plastics expertise will see strong demand in the fields of medical implants (PEEK), semiconductor fixtures (POM, PTFE) and aerospace interiors (ABS, PC).
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Frequently Asked Questions
What are the main challenges when CNC machining engineering plastics like PEEK or PTFE?
The main challenges are poor thermal conductivity, which can cause melting or burning; low modulus of elasticity, leading to easy deformation; and dimensional changes from internal stress release. These require a different machining strategy than metals.
What cutting tools and cooling methods are recommended for plastic CNC machining?
Use single- or double-slot tools for efficient chip removal, and compressed air cooling instead of coolant to prevent moisture absorption. Keep tools sharp to avoid friction heat, and control cutting amount and feed rate. For PEEK, diamond-coated tools are recommended.
What are the recommended parameters for milling PEEK plastic?
For PEEK, high-speed milling at 10,000-20,000 rpm with a small depth of cut (0.1-0 mm) is recommended. Diamond-coated tools are used to handle the material's properties effectively.
What surface roughness can be achieved with a dedicated plastics machining strategy?
Practical cases show surface roughness can be reduced from Ra 3.2 μm to Ra 0.8 μm with no melting marks when using a dedicated plastics machining strategy, ensuring high-quality finishes.
