The Top Plastic Materials for CNC Machining in Prototyping & Low-Volume Production

Why Plastics Dominate Prototype & Low-Volume CNC

CNC machining bridges the gap between design validation and full-scale production. For prototypes and batches of 10–500 units, plastics provide:

• Cost Efficiency: Lower material costs vs. metals; minimal setup investment.

• Design Flexibility: Rapid iterations for complex geometries without tooling delays.

• Functional Testing: Simulates end-use performance (e.g., chemical resistance, load-bearing).

• Weight Savings: Critical for automotive, aerospace, and medical devices.

Top 8 CNC Plastics: Properties, Applications & Machining Insights

1. ABS (Acrylonitrile Butadiene Styrene)

• Key Properties: Impact resistance, machinability, low cost. Tensile strength: 29–43 MPa; hardness: Shore D 100.

• Best For: Automotive housings, consumer electronics prototypes, functional snap-fit joints.

• Machining Tips:

  • Use sharp carbide tools to prevent melting.

  • Optimize feeds/speeds to avoid delamination (e.g., 0.1–0.3 mm/rev feed).

• Limitations: Poor UV/weather resistance; avoid for outdoor applications.

2. POM (Polyoxymethylene / Acetal)

• Key Properties: High stiffness, low friction, exceptional dimensional stability. Tensile strength: 53 MPa (Delrin 570).

• Best For: Gears, bearings, medical device components requiring precision.

• Machining Tips:

  • Ideal for tight tolerances (±0.05 mm).

  • Minimize heat buildup with compressed air cooling.

• Limitations: Prone to cracking under high stress; avoid acidic environments.

3. Polycarbonate (PC)

• Key Properties: Optical clarity, impact resistance, heat tolerance (up to 135°C). Tensile strength: 55–77 MPa.

• Best For: Transparent prototypes (lighting covers, safety visors), EMI shields.

• Machining Tips:

  • Prevent scratching with polished diamond tools.

  • Use low RPM to reduce internal stresses.

• Limitations: Vulnerable to UV degradation and solvents like acetone.

4. Nylon (PA 6/66)

• Key Properties: High wear resistance, flexibility, and fatigue strength. Tensile strength: 76 MPa (PA 66).

• Best For: Bushings, pulleys, and parts requiring repeated motion.

• Machining Tips:

  • Pre-dry material (4 hrs at 80°C) to prevent moisture-induced swelling.

  • Glass-filled grades (PA 30% GF) boost strength but increase tool wear.

• Limitations: High water absorption (up to 8%) affects dimensional stability.

5. PEEK (Polyetheretherketone)

• Key Properties: Aerospace-grade thermal/chemical resistance. Tensile strength: 93 MPa; continuous service: 260°C.

• Best For: Sterilizable medical implants, high-temperature engine components.

• Machining Tips:

  • Requires rigid setups and sharp tools (uncoated carbide).

  • Use high-pressure coolant to manage heat.

• Limitations: High cost (~5× ABS); complex machining raises part expenses.

6. PTFE (Teflon)

• Key Properties: Lowest friction coefficient (0.04), chemical inertness, non-stick surface.

• Best For: Seals, gaskets, lab equipment liners for corrosive fluids.

• Machining Tips:

  • Avoid deformation with light clamping forces and support structures.

  • Glass-filled PTFE improves creep resistance for load-bearing parts.

• Limitations: Low strength (9–30 MPa); prone to creep under load.

7. Acrylic (PMMA)

• Key Properties: Optical clarity (92% light transmission), weather resistance.

• Best For: Light pipes, display prototypes, cosmetic housings.

• Machining Tips:

  • Polish edges with flame or solvent (e.g., acetone vapor) for optical clarity.

  • Use low feed rates to prevent chipping.

• Limitations: Brittle; unsuitable for high-impact applications.

8. Polypropylene (PP)

• Key Properties: Chemical resistance, flexibility, and low density (0.9 g/cm³).

• Best For: Fluid-handling components, living hinges, disposable medical parts.

• Machining Tips:

  • High RPM tools reduce material “gumming.”

  • Minimize stresses to avoid warping.

• Limitations: Poor UV resistance; difficult to bond/paint.

Material Selection Guide for Prototypes & Low Volumes

Use this decision framework to match materials with project goals: