| Parameter | Formula / rule | |-----------|----------------| | Projected area | Part + runner area on parting line | | Clamp force (tons) | (Projected area in cm² × injection pressure in tons/cm²) × safety factor (1.2–1.5) | | Ejector pin stress | F_push / (n × pin_cross_section) < 300 MPa for steel | | Cooling time estimate | (thickness² × constant) / thermal diffusivity (empirical) | | Shrinkage compensation | Multiply part dims by (1 + shrinkage %) – use moldflow to refine |
Remember: Every hour spent refining the mold design saves ten hours on the production floor. injection mold design guide
Air trapped in the mold compresses as the plastic fills. Compressed air heats up, burning the plastic at the weld lines (diesel effect). A mold without vents will fail. A mold without vents will fail