Material Machining
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What to note when machining composite materials (carbon fiber, glass fiber, honeycomb)?
Notes and tool selection for machining composites (CFRP carbon fiber, GFRP glass fiber, honeycomb): Characteristics: 1) Anisotropic - strength and hardness differ by direction; cutting force varies; 2) Delamination and fuzz - weak interlayer bonding: delamination, fuzz, burrs; 3) Abrasive wear - carbon and glass fibers are hard: severe abrasive wear, fast tool wear; 4) Heavy dust - carbon fiber dust conducts electricity; glass fiber dust irritates skin; 5) High or no melt point - carbon fiber does not melt; glass softens at high temperature. Which tool: 1) Diamond coating (PCD or CVD diamond) - first choice: extremely hard and wear-resistant, 10-50x carbide life, ideal for carbon and glass fiber; 2) Carbide - usable but wears fast; small quantities; choose ultra-fine-grain; 3) Cobalt HSS - not recommended: wears extremely fast; light glass fiber only. Parameters: 1) speed - high: diamond-coated 3000-8000rpm, carbide 1500-3000rpm; 2) feed - small, 0.03-0.08mm/rev, prevent delamination and fuzz; 3) depth - small, stepped, 0.1-0.3mm per pass. Notes: 1) prevent delamination - a) small feed and depth; b) cut from solid toward the edge; c) sharp tools; d) support - back the part; e) tape the machining area to prevent fuzz; 2) prevent fuzz - a) very sharp tools; b) high speed, small feed; c) final light pass; d) remove fuzz with sandpaper or flame (carbon fiber can be flame-trimmed); 3) dust control - a) dust mask (carbon fiber dust is harmful); b) vacuum or extraction; c) carbon fiber dust conducts - keep it out of electrical equipment; 4) safety - a) carbon fiber dust is flammable; b) glass fiber dust irritates skin and airways - gloves and mask; c) safety glasses; 5) tool choice - prefer diamond coating: expensive but long life and quality - lower total cost; 6) measuring - composites may spring back; measure after stabilizing. Composites are hard mainly due to delamination and fuzz - with the right tool (diamond coating) and parameters (high speed, small feed, small depth) plus support, quality chamfers are achievable.
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