Extrusion & Post
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Longitudinal stripes on PVA extruded film
Problem Phenomenon
Continuous stripes 1-3mm wide along the extrusion direction on the surface of PVA extruded film
Cause Analysis
Local damage or uneven gap of die lips; melt residence zone in the die producing unstable flow; pressure fluctuation at the screw front end
Solution
1) Check die lip flatness and gap uniformity ±0.01mm; 2) Clean the die interior to remove carbonized matter in the residence zone; 3) Install gear pump on the extruder to stabilize melt pressure; 4) Polish die lips to Ra<0.1μm
Key Takeaway
Longitudinal stripes are caused by die defects and pressure fluctuation; die maintenance and pressure stability are key
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