Molds & Tooling
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PP Weak Weld Line Strength
Problem Phenomenon
Weld lines behind holes of PP parts are obvious, cracking along the weld line under load.
Cause Analysis
PP crystallizes fast; if the temperature at the melt front meeting point is insufficient, the crystalline interface bonds weakly; with poor venting, the weld line is more obvious.
Solution
①Raise melt temperature and injection speed; ②open vent grooves at the meeting point; ③adjust gate position to avoid stressed areas; ④appropriately raise mold temperature to delay front crystallization.
Key Takeaway
PP weld lines must complete entanglement before crystallization.
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