on 09/21/2016



First Prize in Greater China Region: TYC Brother Industrial Co., Ltd.

CAE Simulation Helps to Eliminate Air Traps in Multi-shot Molded Automotive Light Covers

Industry: Automotive
Team Leader: Nan-Jung Huang
Company/Team Introduction:
TYC Brother Industrial Co., Ltd. is one of the world’s largest manufacturers of automotive, motorcycle, truck and bus lighting products. It is a worldwide supplier of lighting products for all functions to both original equipment manufacturer (OEM) and automotive part replacement markets in North America, Europe, Asia-Pacific, Africa and Middle East.

Story Overview/Challenge:

Multi-shot molding is widely used in manufacturing automotive lighting components. In this case, TYC was tasked with designing an automotive light cover using two-shot molding process. However, the race tracking effect due to variation in part thickness occurred as the molten plastic flowing through the cavity at the second shot, resulting in unnecessary air traps and weld lines at undesired locations and short shots. To add another valve gate for the second shot would be costly, and there was even no enough space to add it. The proper venting locations for the air traps to escape also had to be at the region where the air was not blocked by the part insert injected from the first shot. Therefore, the current air trap locations at the second shot must have been altered to different regions, farther from gate.


To resolve the race-tracking issue, Moldex3D was applied as the tool to evaluate part design revisions on thickness. During the iterative simulations, the thickness of the thinner region of the part from the second shot was gradually increased before finally adding two filling resistance features at each thicker region of the part too. The simulation results showed that the air trap locations could be altered towards the desired locations that could let the air escape. The weld lines could also be minimized at the shifted locations. Equally important, the filling pattern was optimized to achieve balanced filling. More uniform filling temperature inside the part cross section could also be observed in the revised design. In addition, the experimental result and simulation result for the validation of the filling pattern were in a good agreement.


  • Optimized part design
  • Resolved air traps and weld line issues
  • Achieved balanced filling
  • Reduced cost and time spent on mold revisions

Product Used:


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