Extrusion & Post
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Wrinkles Appearing in High-Density Polyethylene Blown Film
Problem Phenomenon
Longitudinal wrinkles appear in the film during the haul-off process, affecting the film flatness and subsequent processing.
Wrinkles are more obvious after winding, and in severe cases cause the film to be scrapped.
Cause Analysis
（1）The film thickness is uneven, and the thin parts shrink first to produce wrinkles
（2）The haul-off roller pressure is uneven
（3）The tent frame angle is improper or the included angle is asymmetric
（4）The cooling line height is unstable
（5）Uneven cooling of various parts of the film causes different shrinkage
Solution
（1）Adjust the die gap and air ring to ensure uniform film thickness
（2）Adjust the haul-off roller pressure to ensure uniform clamping
（3）Adjust the tent frame angle to be symmetric, generally with an included angle of 30-45°
（4）Stabilize the cooling line height, with the fluctuation not exceeding ±50mm
（5）Check the air ring cooling uniformity, and replace with a high-efficiency air ring when necessary
Key Takeaway
Wrinkles are caused by uneven thickness or unbalanced haul-off, and need to be solved from thickness control, haul-off, and tent frame adjustment.
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