Injection Mold Design Guide Jun 2026

Every resin shrinks as it cools. You cannot cut a mold to the nominal part dimension.

The following best practices should be followed when designing an injection mold: injection mold design guide

If you design a vertical wall (0° draft), the part will weld itself to the steel. As plastic cools, it shrinks onto the core. Without draft, ejector pins will push through the part (ejector pin push-through) or the mold will seize. Every resin shrinks as it cools

A standard two-plate injection mold consists of two primary halves: As plastic cools, it shrinks onto the core

End your design process by conducting a comprehensive review alongside your mold maker. Catching geometry flaws on a computer screen is virtually free; fixing them once tool steel has been cut costs thousands of dollars and weeks of production time.

: Maximum rib height should not exceed 3 times the nominal wall thickness to avoid filling issues and thin steel sections in the mold.