Injection Molding
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POM Insert Cracking
Problem Phenomenon
Cracks around inserts in POM metal-insert molded parts
Cause Analysis
POM shrinks greatly, generating high hoop stress on inserts during cooling; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience; this mechanism has been repeatedly verified by industry literature and should be confirmed first during troubleshooting
Solution
Preheat inserts to 100-120℃; sufficient wall thickness around inserts; anneal after molding; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Key Takeaway
Insert parts need triple protection of preheating plus wall thickness plus annealing; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for subsequent similar problems
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