Molding Process
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HDPE Sink Mark and Holding Pressure
Problem Phenomenon
Sink marks are obvious on the back of product reinforcing ribs, with depressions at wall thickness intersections
Cause Analysis
HDPE high shrinkage makes thick-wall areas demand large shrinkage compensation; insufficient holding pressure or time forms sink marks; rib backs are high-incidence positions for sink marks, aggravated when rib thickness exceeds 60% of main wall thickness
Solution
①Increase holding pressure and time; ②rib thickness ≤60% of main wall thickness; ③arrange the gate near thick-wall areas; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
HDPE sink mark treatment emphasizes both holding pressure and structure; rib design is the first line of defense against sink marks; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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