Extrusion & Post
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LLDPE die gap
Problem Phenomenon
LLDPE blown film produced per the LDPE die gap, bubble unstable and severe sharkskin.
Cause Analysis
LLDPE melt viscosity is high and shear-sensitive, requiring a larger die gap (0.060-0.100 inches) to reduce shear; During on-site troubleshooting, verify item by item according to this mechanism, avoiding blindly adjusting the machine based only on experience.
Solution
LLDPE die gap configured at 1.5-2.5mm; insufficient gap aggravates shear heat and melt fracture; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
LLDPE die gap must be larger than LDPE; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a reference for troubleshooting similar problems in the future.
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