How to Prevent Injection Molding Air Traps with SOLIDWORKS Plastics

Article by Aditya Chandurkar updated December 7, 2015


Injection Molding Air Traps occur when a bubble of air is trapped as plastic flow fronts coincide.  The air bubble, or air trap, can cause various defects in a plastic part such as blemishes on the surface, incomplete filling and packing.

Common Air Trap Causes

  • Race Track Effect
  • Hesitation
  • Lack of Ventilation

Air Trap Detection

Using SOLIDWORKS Plastics simulation functionality, defects such as air traps can be detected during the design process. Easy to use simulation setup and post processing tools indicated the exact location of the air bubbles/air traps in the part.  

Injection Molding Air Traps

Air Trap Detection

The Image below depicts an air trap location detected early during the development stages of the part design process using SOLIDWORKS Plastics.

SOLIDWORKS Plastics Air Trap Analysis Results

SOLIDWORKS Plastics Air Trap Analysis Results

Race Track effect

The Race Track effect occurs when the injected material races through the thick section of the mold cavity before the thin section is filled. Using SOLIDWORKS 3D CAD software the part geometry can be modified in the same real estate and the differences in wall thickness can be reduced which will eliminate the race track effect.


During the filling process, sometimes the plastic material will tend to fill the thick section of the mold cavity over the thin sections due to lower resistance of the flow. One of the techniques to avoid hesitation can be changing the injection location point in the mold cavity. This can be done by modifying the boundary conditions for the simulation setup in SOLIDWORKS Plastics. Modifying model geometry can also eliminate hesitation.

Injection Location

Injection Location Setup Tool

Learn More

SOLIDWORKS Plastics brings easy-to-use injection molding simulation directly to the designers of plastic parts and injection molds, as well as advanced CAE analysis.  You can quickly evaluate manufacturability while you design, to eliminate costly mold rework, improve part quality, and accelerate time to market. View our product page to learn more »

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Aditya Chandurkar