Material Machining Views: 7

Notes for machining plastics, bakelite, nylon, acrylic and other non-metals with countersinks: Characteristics: 1) Low melting point - plastics and acrylic melt at about 100-200C; cutting heat melts the material and causes welding; 2) Low hardness - low cutting force, long tool life; 3) Easily deformed - plastics and nylon are elastic: deflection and spring-back, unstable sizes; 4) Easily chipped - brittle non-metals like acrylic and bakelite chip and crack at edges; 5) Poor thermal conductivity - heat concentrates at the edge, causing melting. Which tool: 1) Standard HSS - usable, cheap, long life; 2) Cobalt HSS (HSS-E) - sharper, for finishing; 3) Carbide - sharpest and most wear-resistant for high volume, but somewhat wasted on soft non-metals; 4) Coating - NOT recommended; non-metals need no coating and coating can add friction; 5) Single-flute - recommended: low cutting force, good chip removal, less welding - ideal for plastics and acrylic. Parameters: 1) speed - high: cobalt HSS 2000-4000rpm, carbide 3000-6000rpm; 2) feed - medium, 0.1-0.2mm/rev; 3) fluid - usually dry-cut, but acrylic and plastics melt easily: use compressed air or light fluid (some plastics corrode with certain fluids); 4) small depth - avoid melting and deformation. Notes: 1) prevent melting - keep speed below the melt-point line speed, use compressed air, sharp tools (dull tools rub and melt); 2) prevent welding - molten plastic sticks: single-flute, high speed, air cooling, clean stuck chips promptly; 3) prevent chipping - brittle materials: cut from solid toward the edge, slow feed, no impact, sharp tool; 4) prevent deformation - elastic materials: light clamping, not too tight, measure after spring-back stabilizes; 5) prevent cracking - anneal or preheat brittle materials (acrylic, glass) to reduce internal stress; 6) surface protection - soft surfaces scratch easily; protect after machining, do not mix with metal parts; 7) safety - chips are powder or strips; some plastic powders are flammable: fire prevention, mask and glasses. Special notes by material: 1) Acrylic (PMMA) - melts and chips easily: single-flute, high speed, air cooling, slow feed, sharp tool; 2) Nylon (PA) - elastic, deflects: light clamping, measure after recovery, fluid cooling OK; 3) Bakelite (phenolic) - brittle with dust: slow feed, prevent chipping, mask, dust extraction; 4) PTFE - soft, sticks: sharp tools, high speed, dry or air-cooled; 5) Carbon fiber composite (CFRP) - hard with delamination: diamond-coated or carbide tools, high speed, small feed, prevent delamination and fuzz. Non-metals are simple to machine, but materials differ greatly - adjust tools and parameters by material. Ask our technical team for the right solution.