Extrusion & Post
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Wrinkles Appearing in Polypropylene Blown Film
Fenómeno del problema
Longitudinal wrinkles appear in the film during haul-off, affecting the film flatness and subsequent processing.
The wrinkles are more obvious after winding, and in severe cases cause the film to be scrapped.
Análisis de la causa
(1) The film thickness is uneven, and the thin parts shrink first, producing wrinkles
(2) The pressure of the haul-off rollers is uneven
(3) The angle of the collapsing frame 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
Solución
(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 collapsing frame angle to be symmetric, generally with an included angle of 30-45°
(4) Stabilize the cooling line height, with fluctuation not exceeding ±50mm
(5) Check the cooling uniformity of the air ring, and replace it with a high-efficiency air ring when necessary
Conclusión clave
Wrinkles are caused by uneven thickness or unbalanced haul-off, and need to be solved from thickness control, haul-off, and collapsing frame adjustment.
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