Extrusion & Post
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Metallocene linear low density polyethylene blown film wrinkles（Variant: Color/Material Change Scenario）
Problem Phenomenon
Longitudinal wrinkles appear in the film during hauling, affecting film flatness and subsequent processing.
The wrinkles become more obvious after winding, and in severe cases cause the film to be scrapped.In particular, when changing materials or colors, this problem is more prominent and requires key attention.
Cause Analysis
（1） Film thickness uneven, thin parts shrink first producing wrinkles\
（2） Haul-off roll pressure uneven\
（3） Collapsing frame angle improper or the included angle asymmetric\
（4） Cooling line height unstable\
（5） Uneven cooling at various parts of the film causes different shrinkage\
（6） When changing materials or colors, process parameter fluctuations or equipment status changes aggravate this problem
Solution
（1） Adjust the die gap and air ring, ensure uniform film thickness\
（2） Adjust the haul-off roll pressure, ensure uniform clamping\
（3） Adjust the collapsing frame angle symmetrically, generally an included angle of 30-45°\
（4） Stabilize the cooling line height, fluctuation not exceeding ±50mm\
（5） Check the air ring cooling uniformity, replace with a high-efficiency air ring if necessary\
（6） And do well in cleaning the transition material, paying special attention to parameter stability when changing materials or colors
Key Takeaway
Wrinkles are caused by uneven thickness or unbalanced hauling, and need to be solved from thickness control, hauling and collapsing frame adjustment.Targeted preventive measures need to be taken in different production scenarios.
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