Production & Quality
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HDPE holding pressure shrinkage compensation management
Problem Phenomenon
Shrinkage cavities appear inside thick-walled products, and surface sink marks are obvious when the holding pressure is insufficient
Cause Analysis
HDPE's high shrinkage requires sufficient holding pressure for shrinkage compensation; 2-5 seconds of holding pressure for thin-walled parts, proportionally extended for thick-walled parts; insufficient holding pressure causes sink marks, and excessive holding pressure increases internal stress
Solution
①Holding pressure is set at 60-80% of the injection pressure; ②hold 2-5 seconds for thin walls and extend for thick walls; ③optimize the holding pressure according to the gate freeze-off time; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
HDPE holding pressure is graded by wall thickness; gate freeze-off analysis is the scientific method to determine the holding time; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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