Extrusion & Post
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Wrinkles in low density polyethylene blown film
Problem Phenomenon
Longitudinal wrinkles appear in the film during haul-off, affecting film flatness and subsequent processing.
Wrinkles become more obvious after winding, and in severe cases cause film scrap.
Cause Analysis
(1) Uneven film thickness; thin areas shrink first producing wrinkles
(2) Uneven haul-off roller pressure
(3) Improper collapsing frame angle or asymmetric included angle
(4) Unstable frost line height
(5) Uneven cooling of film parts causes different shrinkage
Solution
(1) Adjust die gap and air ring, ensure uniform film thickness
(2) Adjust haul-off roller pressure, ensure uniform clamping
(3) Adjust collapsing frame angle symmetrically, generally included angle 30-45°
(4) Stabilize frost line height, fluctuation not exceeding ±50mm
(5) Check air ring cooling uniformity, replace with high-efficiency air ring when necessary
Key Takeaway
Wrinkles are caused by uneven thickness or unbalanced haul-off; they need to be solved from thickness control, haul-off, and collapsing frame adjustment.
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