The following is a descriptive explanation of a part analysis completed by CAE Services. This case study explores the causation of inadequate flow/pack, cooling and warpage.
Objective
Determine the number and location of gates/drops for balanced filling
CAE Services was contracted to determine the number of gates/drops as well as location in order to achieve a balanced filling pattern. additional objectives were to evaluate the cooling uniformity based on the supplied cooling design. Based on the gating design CAE Services was also contracted to provide the amount of warpage occurring in the final part. A recommended set of processing conditions were also to be submitted to the client.
Preliminary Results
First Run Analysis Results
From initial simulation runs, CAE Services’ engineers found several improvements that could be made to the IP Retainer:
- Reduced number of drops from 7 to 6
- Reduced number of knit lines
- Improved fiber orientation
- Reduced warpage
Solution
Flow / Pack
Along with improving part quality, the recommendation to reduce the number of drops resulted in minimal mold construction costs. With each valve-gated drop costing $5000 or more, the savings quickly add up. Determining the best drop/gate locations allowed for favorable fiber orientation, which improved warpage, and reduced overall pressure and clamp tonnage requirements.
Cooling
Initial cooling simulations revealed that the cooling design was not sufficient in cooling several areas of the part. CAE Services’ engineers suggested adding Moldmax inserts in those hot spots to reduce the heat build-up. The simulations showed that the temperatures in those areas would be significantly reduced so that cycle times could be shortened and cooling uniformity could be maintained. A water temperature differential of 20°F was also suggested to control wall temperatures between the core and cavity steel, which would also help control warpage.
Summary
Warpage Solutions
The improvements to the filling pattern in the Flow/Pack analysis were mostly responsible for reducing the predicted warpage in the part. By adding more drops, the warpage was predicted to increase by 55%. Adjustments to the cooling design and processing also played a role in minimizing the warpage of the part.
Providing Answers
Ultimately, CAE Services engineering team were able to provide a solution that improved the part design and moldability in several ways:
- Reduced number of drops from 7 to 6 = reduced mold construction costs
- Improved flow balance
- Favorable fiber orientation
- Reduced number of knit lines
- Reduced fill pressure and clamp force requirements
- Eliminated hot spots
- Reduced cycle time