Designing for Moldability: Seven Rules That Cut Tooling Cost
June 18, 2026 ·
Uniform walls, generous draft and honest tolerances remove more cost from a molded program than any purchasing negotiation.
Most of a molded part's lifetime cost is locked in during the first two weeks of CAD work. Once steel is cut, the cheapest changes available are the ones you already made on screen.
Uniform nominal wall thickness is the single highest-leverage rule. Thick sections cool slowly, shrink unevenly and produce sink marks and internal voids that no process window can fix. Core out heavy sections and support them with ribs at 50-60% of nominal wall.
Draft is not optional. One degree per side is a practical minimum for smooth surfaces; textured surfaces typically need 1.5 degrees per 0.001 inch of texture depth. Insufficient draft shows up as drag marks and shortened tool life.
Finally, apply tight tolerances only where function demands them. Every dimension called at ±0.001 in adds inspection time, scrap risk and tooling refinement cycles. A well-annotated print that separates critical from reference dimensions consistently quotes lower.