Injection molding.
DFM rules.
Mold-friendly design.
Injection molding design fundamentals. Wall thickness, draft, fillets, ribs, gating, ejection. Designed-for-molding parts cost 50% less than poorly-designed.
Key principles.
Uniform
Uniform walls prevent sink marks, warping. 1-3.5 mm typical.
1-2° standard
Draft for mold release. 1-2° smooth, 3-5° textured.
Generous
All inside corners filleted. Prevents stress concentration.
60% wall thick
Ribs 60% of base wall. Prevents sink marks.
Material flow
Gate placement affects flow patterns, weld lines, sink marks.
Pin placement
Plan ejector pin locations on non-cosmetic surfaces.
FAQ
Wall thickness range?
1-3.5 mm typical. Thinner: warps. Thicker: sink marks. Uniform critical.
Draft angle minimum?
1° absolute minimum smooth surfaces. 2-5° for textured.
Fillet sizes?
Internal: 1/3 wall thickness. External: 1.5× wall thickness. No sharp corners.
Mold flow analysis?
For complex parts, mold flow simulation predicts issues before tooling. Premium service.
Material selection?
ABS workhorse. PP cheap. PC high-strength. Nylon engineering. Per cost/performance.
Tooling cost?
$10K-200K depending on cavities, complexity. Aluminum bridge $10-30K, steel production $50-200K.
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