Injection Molding
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POM weld line low strength
Problem Phenomenon
A fine line is visible at the product weld line in appearance, stress tests fracture at this location, and the strength is significantly lower than the body.
Cause Analysis
The fronts of the two melt streams have low temperature and fuse poorly when meeting; low melt temperature or mold temperature and slow injection speed all weaken the molecular chain diffusion bonding at the weld line.
Solution
①Appropriately increase the melt temperature within the 230℃ upper limit; ②increase mold temperature; ③adjust the gate position to improve the meeting angle; ④increase the injection speed in the meeting area.
Key Takeaway
POM weld line strength depends on front temperature and meeting conditions; temperature and speed adjustments are constrained by the decomposition upper limit, and gate design should be used to avoid critical stressed areas when necessary.
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