Extrusion & Post
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Random copolymer polypropylene extruded products die lines/lines
Problem Phenomenon
Continuous lines or marks appear on the extrudate surface along the extrusion direction, at fixed positions.
Die lines affect product appearance, especially obvious in transparent products and films.
Cause Analysis
（1）The die inner wall has scratches or damage\
（2）Impurities or carbides accumulate in the die\
（3）The die runner design is unreasonable, with stagnant material zones\
（4）The die joint is uneven\
（5）The breaker plate or filter screen is damaged, impurities pass through
Solution
（1）Disassemble the mold to check the die inner wall, scratches need grinding and polishing repair\
（2）Clean impurities and carbides in the die, use copper tools for cleaning to avoid damage\
（3）Optimize the die runner design, eliminate stagnant material dead corners\
（4）Grind the die joint flat, ensure no steps\
（5）Replace the breaker plate and filter screen, replace regularly to prevent damage
Key Takeaway
Die lines are caused by die inner wall damage or impurities, requiring regular cleaning and inspection of the die condition.
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