Molding Process
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POM insert preheating
Problem Phenomenon
POM cracks around metal inserts, and the inserts loosen and fall off after thermal cycling
Cause Analysis
POM has low surface energy, so inserts held only by adhesion are unreliable; cold inserts quench the melt at the contact surface, forming a weak interface; differences in expansion coefficients produce stress cracks during thermal cycling
Solution
①Knurl or groove the inserts to provide mechanical interlocking; ②preheat the inserts to 100-120°C; ③the embedding depth of brass inserts shall not be less than 1.5 times the diameter; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
POM inserts rely on mechanical interlocking rather than adhesion; the three elements of knurling, preheating, and embedding depth determine the insert bonding strength; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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