Improving flow balance during filling a multi-cavity mold with modified runner systems
Multi-cavity injection molding has been regarded as low cost mass-production method for producing plastic products such as optical elements. However, the flow imbalance during filling a multi-cavity mold using symmetrical runner system is a serious problem. This paper is devoted to improving the flow balance by modifying the runner system design. For this purpose, four eight-cavity molds with four modified symmetrical runner systems are designed, constructed and tested. They are tapering Ç-type runners, pinned H-type runners, curved A runners, and curved B runners. The flow imbalance in each runner system is observed and measured with the aid of short-shot experiments. The experimental results indicate that the tapering H-type runner system can improve flow balance. The pinned H-type runner system fails to improve flow balance. The curved A and B runner system can reverse the imbalance trend, but the stability of the curved systems is poor at high melt temperature.
Huang, TC; Huang, PH; Yang, SY; Ko, TY
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