Processing Machinery
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PC Degradation from Excessive Barrel Residence Time
Problem Phenomenon
Producing small PC parts on a large machine, products turn yellow and brittle, clearly correlated with the shot volume/machine capacity ratio.
Cause Analysis
A small shot volume makes the melt residence time in the barrel too long, and thermal cumulative degradation occurs after exceeding PC's allowed residence time; PC is sensitive to residence time, and a large machine making small parts is a typical high-risk working condition.
Solution
①Select a suitable machine according to product weight (shot volume 20%~80% of machine capacity); ②Shorten the molding cycle; ③Appropriately reduce the melt temperature; ④Change to a smaller machine if necessary; ⑤Monitor melt residence time to avoid exceeding the limit.
Key Takeaway
PC residence time is a 'hard indicator': machine matching is the premise, a large machine making small parts equals chronic degradation; calculating the residence time when selecting the machine is more effective than adjusting the process afterwards.
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