Molding Process
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PC Cracking Around Inserts
Problem Phenomenon
PC parts with metal inserts crack around the inserts after cooling, appearing during assembly or use.
Cause Analysis
The shrinkage difference between PC and metal generates hoop stress at the interface, and PC is extremely sensitive to stress; unpreheated inserts and insufficient wall thickness make cracking more likely; interfacial stress concentration is the essence.
Solution
①Preheat the insert to near the mold temperature; ②Ensure sufficient wall thickness around the insert with fillet transitions; ③Reduce holding pressure to reduce additional stress; ④Anneal when necessary to eliminate residual stress; ⑤Reduce the use of inserts.
Key Takeaway
PC insert parts = triple insurance of 'preheating + wall thickness + low stress': PC is most sensitive to stress, and the insert interface is a disaster area; do not use inserts if possible, and if they must be used, do the three things well.
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