Common Injection Molding Design Mistakes

Many injection molding problems — sink, warp, sticking, cosmetic defects — trace back to a handful of design mistakes made before the mold was ever built. Uneven walls, missing draft, overly thick sections, and designing without the molding process in mind top the list. The good news is that knowing them means you can design around them.

Uneven Wall Thickness

Walls that vary a lot in thickness cool and shrink unevenly, inviting sink marks and warpage. Keeping wall thickness as uniform as possible is one of the most important molding-friendly design habits.

Not Enough Draft

Walls without adequate draft make parts hard to eject and prone to drag marks and mold wear. Draft is easy to design in early and painful to add late — so it belongs in the design from the start.

Thick Sections and Heavy Features

Thick bosses, ribs, and heavy sections cool slowly and unevenly, causing sink and stress. Thinning and coring out thick features helps parts cool predictably.

Designing Without the Process in Mind

Perhaps the biggest one: designing the part as if it will appear by magic, rather than be molded. Draft, wall thickness, and material behavior all need to be considered together — which is what design for manufacturing is about.

Other Ones Worth Avoiding

A Good Next Step

A short conversation can help you catch molding design issues in your part before the mold is made — where they're cheap to fix.

Please keep your question general — no confidential product details are needed for the introductory consultation. If confidential review is needed later, an NDA can be arranged before a longer engagement.