Design Tips: 9 Mistakes to Avoid When Designing Injection Molded Parts

Whether you're prototyping with a partner like Formioo or working with custom molding specialists such as https://www.hollyplasticparts.com/plastic-injection-molding/ , avoiding these mistakes can save time, cost, and hassle.

Let’s break them down:

1. Uneven Wall Thickness

Inconsistent walls cause warping and shrink marks. Keep them uniform where possible and use gradual transitions.

2. Sharp Thickness Changes

Sudden shifts in thickness create stress points. Smooth out the geometry to help material flow better and avoid defects.

3. C-Shaped Designs Without Support

Open "C" shapes often warp or deform. Use ribs or redesign to improve strength, especially when using glass-filled materials.

4. Overusing Chamfers

Too many chamfers can hurt both function and tooling. Use them only where needed, for assembly or aesthetics.

5. Poor Parting Line Placement

Bad placement can lead to flash and defects. Work with your molder to align parting lines with clean edges.

6. No Draft Angles

Without a draft, parts stick in the mold. Add 1–2° draft to vertical walls to ensure smooth ejection.

7. CAD File Issues

Sending improper CAD formats leads to delays. Use standard formats like STEP or Parasolid to avoid compatibility issues.

These design missteps are easy to make, but also easy to avoid if you plan ahead.