plastic part design guidelines

Most mold problems are not molding problems. They are mold design decisions that were locked in before the first steel chip was cut — a draft angle that is too shallow for the texture, a gate placed on a visible surface, a cooling circuit that chills one side of the part faster than the other. Once the tool exists, every one of those choices becomes an EDM job, a weld, a re-qualification, and weeks of delay. Mold design fundamentals come down to four linked decisions: draft, gating, the runner system and cooling. A steeper draft reduces the ejection force the cooling layout must resist; a thicker runner shifts fill pressure, which changes what gate size you can get away with. This article walks through each decision in the order a mold designer faces it, with the numbers you should expect...