Blow Molding
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LDPE Die Gap Comparison
Problem Phenomenon
Processing LLDPE with the LDPE die gap results in high back pressure, low output, and melt fracture.
Cause Analysis
LDPE die gap is 0.024-0.040 inches, LLDPE needs 0.060-0.10 inches; LLDPE's high viscosity under a small gap causes high back pressure, strong shear, and melt fracture.
Solution
①Set the die gap by material type; ②LLDPE gap is 2-3 times that of LDPE; ③Switch die parameters synchronously when changing material for production; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
The die gap is the equipment watershed between LDPE and LLDPE; the 2-3 times difference must be reflected in the material change procedure; After confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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