Machining Composites – Carbon Fiber, G10, and Fiberglass in CNC
Composite materials like carbon fiber, G10 (garolite), and fiberglass are lightweight, strong, and increasingly used in aerospace, electronics, and sporting goods. However, they are extremely abrasive, dust-generating, and prone to delamination.
In this guide, you’ll learn how to machine composites effectively without ruining tools, machines, or your health.
🧱 Composite Material Overview
| Material | Composition | Characteristics |
|---|---|---|
| Carbon Fiber | Epoxy + carbon weaves | Strong, brittle, conductive |
| G10 | Epoxy + fiberglass | Tough, insulative, stable |
| Fiberglass | Glass fibers + resin | Cheap, abrasive, non-conductive |
🛠 Tool Selection for Composites
- Diamond-coated carbide tools highly recommended
- Use downcut, burr-style, or compression end mills to prevent fraying
- For drilling, use brad-point or diamond-ground bits
- Avoid HSS or standard carbide – wears out too quickly
⚙️ Feeds and Speeds (General Guidelines)
| Material | RPM | Feed (mm/min) | DOC |
|---|---|---|---|
| Carbon Fiber | 10000–18000 | 1000–2500 | 0.5–1 mm |
| G10 | 8000–14000 | 1200–2200 | 1–2 mm |
| Fiberglass | 6000–12000 | 1000–1800 | 0.5–1.5 mm |
📌 Use high RPM, light depth, and conservative feed to minimize delamination.
🌬 Dust Control & Safety
- Always use vacuum extraction or sealed enclosures
- Wear N95 or P100 respirators — composite dust is hazardous
- Protect linear guides and electronics from fiber dust
- Never use compressed air to blow composite chips
🧠 Techniques to Reduce Delamination
- Use sacrificial backers during drilling
- Pre-drill with pilot holes if possible
- Use step-down passes in profiling
- Apply entry/exit support tabs on thin parts
🧪 Surface Finish Expectations
| Material | Machined Finish | Notes |
|---|---|---|
| Carbon Fiber | Matte, sharp edges | May require edge sealing |
| G10 | Clean, stable | Often sanded post-machining |
| Fiberglass | Slight fuzz | Use post-process sanding |
🛡 Tool Life Tips
- Limit tool exposure — change often
- Use minimum tool stick-out
- Monitor tool wear under magnification
- Use coolant mist sparingly — dry machining is standard
⚠️ Health & Machine Precautions
- Install dust separators or HEPA filters
- Avoid machining in enclosed non-ventilated areas
- Protect CNC rails with bellows or covers
- Clean the shop daily when machining composites
📦 Applications of Composites
| Industry | Application |
|---|---|
| Aerospace | UAV frames, panels |
| Electronics | G10 circuit boards, housings |
| Sports | Bike parts, snowboards, drones |
| Marine | Structural reinforcements, fairings |
✅ Summary Tips for Composites
- Always wear protective gear
- Use abrasion-resistant tools
- Keep feed light, RPM high
- Extract dust efficiently
- Avoid deep plunges or aggressive passes
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