Molds & Tooling
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LLDPE shrinkage rate 1.5-3%
Problem Phenomenon
Product dimensions deviate, shrinkage differs noticeably among grades of different density, molds are not interchangeable
Cause Analysis
LLDPE shrinkage rate 1.5-3% is lower than LDPE, giving better dimensional stability; but shrinkage still differs within the density range of 0.915-0.935g/cm³; actual shrinkage varies with molding conditions
Solution
①Allow shrinkage allowance of 1.5-3% in the mold; ②recalculate when changing density grade; ③correct shrinkage after mold trial for precision parts; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
LLDPE's low shrinkage is its dimensional advantage; the 1.5-3% range is subdivided by density, giving a basis for mold shrinkage allowance; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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