Plastics & Composites Speeds & Feeds Calculator 2026
Optimized parameters for thermoplastics, PEEK, CFRP, GFRP, and thermosets. Includes heat risk and delamination analysis.
Calculate Plastics Parameters
Plastics & Composites Machining Guide
Machining plastics and composites requires different approaches than metals. The key challenges are heat management, chip evacuation, and for composites - preventing delamination and fiber pullout.
Material Categories
🔵 Thermoplastics
Machinability: Good to Excellent
Soften when heated - can melt if cutting parameters are wrong. Use high feed rates to keep chips moving before they re-weld.
- • ABS: Excellent, very forgiving
- • Delrin/Acetal: Best machinability
- • Acrylic: Brittle, prone to cracking
- • Nylon: Stringy chips, very tough
🟣 High-Performance
Examples: PEEK, Ultem PEI, PTFE
High temperature resistance, higher cutting forces. PEEK requires slower speeds. PTFE is slippery to fixture.
- • PEEK: Aerospace, medical implants
- • Ultem: High-temp electrical
- • PTFE: Seals, chemical equipment
🔴 Fiber-Reinforced (CFRP, GFRP)
⚠️ Very abrasive, requires diamond tools
Carbon and glass fibers rapidly destroy carbide tools. PCD or diamond-coated tools essential. CFRP dust is a health hazard.
- • Use compression routers for edge quality
- • Flood coolant for dust control
- • Backer material prevents delamination
- • Always use dust extraction
🟠 Thermosets (FR4, Phenolic)
Don't melt - produce dust
Formed through irreversible chemical cure. Produce powder/dust rather than chips. Fiberglass versions are very abrasive.
- • FR4/G10: PCB substrates - abrasive
- • Phenolic: Brake pads, electrical
- • Dust extraction required
Speed Reference
| Material | Milling (m/min) | Routing (m/min) | Tool |
|---|---|---|---|
| Delrin/Acetal | 250-600 | 300-700 | Carbide/ZrN |
| ABS | 200-500 | 250-600 | Carbide/ZrN |
| Acrylic (PMMA) | 150-350 | 180-420 | O-Flute, Single Flute |
| PEEK | 100-280 | 130-340 | Carbide Uncoated |
| CFRP | 80-240 | 100-280 | PCD / Diamond ⚠️ |
| FR4/G10 | 100-280 | 120-300 | Diamond Coated ⚠️ |
Best Practices
✓ Do
- • Keep chips moving with high feed rates
- • Use air blast for thermoplastics
- • Use sharp, polished cutting edges
- • Climb mill for better surface finish
- • Use PCD for composites
✗ Don't
- • Don't let chips re-melt onto surface
- • Don't use oil coolant on acrylic/PC
- • Don't dry cut composites
- • Don't use dull tools
- • Don't ignore dust extraction
Frequently Asked Questions
Use high feed rates to keep chips moving (prevents re-cutting), use air blast cooling, keep tools sharp, use proper rake angles (positive geometry), and choose appropriate cutting speeds. Different plastics have different melting points - acetal/Delrin is very forgiving, while acrylic is sensitive.