Injection Mold Design Guide Guide

Before building the mold, a good mold maker will return a DFM report showing how they intend to split the core/cavity, where the gates are, and what concerns they have. Never skip the DFM. It is cheaper to change a 3D model than to weld up a block of steel.

| Requirement | Why it matters | |-------------|----------------| | (0.5–4 mm typical) | Prevents sink, warpage, and fill imbalances | | Draft angle – 0.5° to 2° (per side) | Allows part release without drag marks | | Radii at corners – 0.25–0.5 × wall thickness | Reduces stress concentration and improves flow | | Nominal wall progression – gradual changes only | Avoids flow hesitation and freeze-off | injection mold design guide

He turned the page. A crude drawing showed a fortress wall—thick at the base, thin at the battlements. The caption read: “Uneven walls create ghosts: voids, sinks, and residual stress.” Before building the mold, a good mold maker