Material Drying
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HDPE Bubble Vacuum Void
Problem Phenomenon
Vacuum voids appear inside thick-wall products, with no sink marks on the surface but insufficient strength
Cause Analysis
The surface layer of HDPE thick-wall parts solidifies first to form a hard shell, and insufficient shrinkage compensation at the center forms vacuum voids; the absence of surface sink marks instead conceals internal defects; moisture bubbles need to be distinguished from vacuum voids
Solution
①Strengthen holding pressure compensation to the thick-wall center; ②enlarge the gate to delay freeze-off; ③verify pellet drying first for moisture bubbles; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
HDPE vacuum voids are hidden defects; no sink marks does not mean no problem, and strength sampling inspection is the safety net; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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