Injection Molding
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LDPE '2079851475616104452 Sink Mark
Problem Phenomenon
Sink marks are obvious in thick-walled areas, and residual depressions remain after holding pressure adjustment
Cause Analysis
LDPE shrinks greatly and thick-walled areas have high feeding compensation requirements; insufficient holding pressure or early gate freeze-off forms sink marks; barrel temperature too high aggravates shrinkage; when troubleshooting on site, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
① Sufficient holding pressure set according to gate freeze-off time; ② appropriately lower the barrel temperature; ③ thin down thick-walled structure design; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
LDPE sink marks are investigated along the three lines of holding pressure, temperature, and structure; lowering temperature to reduce shrinkage is a characteristic measure of polyolefins; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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