Skip to content

Fathom is hiring for multiple positions across our nationwide sites! To see all open positions, click here

Field Note:
Inconsistent Wall Thickness Can Cause Defects

Avoid these problems when designing parts for injection molding

Problem

Inconsistent wall thicknesses often drive uneven cooling, which can cause a variety of defects in injection molded parts:

  • Thicker sections cool slower, leading to sink marks, voids and warping

  • Sink marks are especially common near ribs, bosses and reinforced corners

  • Voids may be caused by the center of the part cooling too slowly. This can affect the part’s structural integrity.

  • Thick walls use more material and require longer cycle times. Both factors result in higher per-part costs.

  • Thinner wall sections cool faster, resulting in short shots where parts are only partially formed.

  • Thin areas can also act as weak points in the parts, reducing their structural integrity

sink-mark-chatgpt

Solution

Try these tips to solve the underlying problems that tend to cause sink marks:

  • Maintain consistent, nominal wall thickness throughout the part

  • If the wall thickness must change, use gradual, tapered transitions instead of abrupt steps

  • Consider replacing thick wall sections with reinforcing ribs, which use much less material and will cool faster

  • Place gates near thicker sections to ensure proper packing and reduce sink marks

  • Material flow characteristics have a direct impact on achievable wall thickness. Select materials that are consistent with your desired wall thickness

InjectionMolding_Step3 (1)

Key Learnings

Proper wall design reduces material costs, shortens cycle times and helps ensure consistent part quality.

To ensure that your part design doesn’t cause this common cosmetic problem, request a consultation today.