Material Machining Views: 7

Notes and tool selection for machining elastomers - rubber, silicone, polyurethane: Characteristics: 1) High elasticity - deflects and springs back: unstable sizes, chamfer size hard to control; 2) High tack - rubber and silicone stick and weld; chips tangle; 3) Very soft - deforms during clamping and cutting; 4) Low or no melt point - vulcanized rubber burns rather than melts; silicone withstands 200-300C; 5) Tears easily - edges tear and fuzz. Which tool: 1) Single-flute countersinks - first choice: low force, good chip removal, less welding - ideal; 2) Very sharp tools - reduce squeezing and tearing; new or freshly sharpened; 3) Carbide or cobalt HSS - both fine; carbide is sharper and more wear-resistant; 4) High-helix tools - better chip removal, less tangling. Parameters: 1) speed - high, 2000-5000rpm: low force, good finish; 2) feed - medium-high, 0.15-0.3mm/rev: less time in the material, less welding and heat; 3) depth - can be large: elastomers are soft, cut in one pass. Notes: 1) prevent deformation - a) light clamping, just enough to hold; b) support - back the part; dedicated fixtures or vacuum chucks; c) measure after spring-back stabilizes; d) freeze before machining (rubber hardens when frozen, easy to cut; elasticity returns after); 2) prevent welding - a) high speed, large feed - less dwell; b) single-flute for chip removal; c) polished tools or DLC coating - less friction; d) compressed air or mist; no cutting fluid (some rubbers corrode or swell); e) clean chips promptly - no tangling; 3) prevent tearing - a) very sharp tools; b) cut from solid toward the edge; c) high speed; d) trim edges with scissors or blades; 4) prevent burning - a) do not dry-cut too long - rubber burns and smokes at high temperature; b) compressed-air cooling; c) no dull tools - friction burns; 5) size control - a) overshoot slightly to compensate spring-back; b) measure after cooling and stabilizing; c) trial cut first; 6) safety - a) fumes and smoke - ventilate; b) some rubber dust is flammable; c) gloves and glasses. Elastomers are hard, but with the right tool (single-flute, very sharp) and parameters (high speed, large feed) plus support, quality chamfers are achievable.