Material Analysis
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COC and Metal Insert Bonding Water Leakage
Problem Phenomenon
COC insert-molded fluid parts leak at the interface during pressure testing, the leakage rate rises after thermal cycling, and the insert pull-out test is unqualified.
Cause Analysis
The thermal expansion coefficients of COC and metal differ greatly, and micro-gaps are generated at the interface after cooling shrinkage; the insert surface finish is too high and lacks mechanical anchoring; the insert temperature is low during molding, and the melt is quenched, resulting in weak bonding.
Solution
①Preheat the insert to close to the mold temperature; ②knurl or groove the insert bonding surface for mechanical interlocking; ③optimize the holding pressure curve for interfacial compaction; ④dual verification by thermal cycling and pressure testing.
Key Takeaway
The interfacial sealing of COC insert parts relies on mechanical interlocking rather than material adhesion; preheating and structural design are the two pillars; verification must cover temperature cycling conditions.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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