Extrusion & Post
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Die Marks/Lines Appearing on High-Density Polyethylene Extruded Products
Problem Phenomenon
Continuous lines or marks appear on the extrudate surface along the extrusion direction, with fixed positions.
Die marks affect the product appearance and are particularly obvious in transparent products and films.
Cause Analysis
（1）There are scratches or damage on the inner wall of the die
（2）Impurities or carbides accumulate in the die
（3）The die flow channel design is unreasonable, with material retention areas
（4）The die joints are uneven
（5）The breaker plate or filter screen is damaged, and impurities pass through
Solution
（1）Disassemble the mold and check the inner wall of the die; scratches need to be repaired by grinding and polishing
（2）Clean the impurities and carbides in the die, using copper tools to avoid damage
（3）Optimize the die flow channel design to eliminate material retention dead corners
（4）Grind the die joints flat to ensure no steps
（5）Replace the breaker plate and filter screen, and replace them regularly to prevent damage
Key Takeaway
Die marks are caused by damage to the inner wall of the die or impurities, and the die condition needs to be cleaned and checked regularly.
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