Extrusion & Post
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Die Marks/Lines on Polypropylene Extruded Products
Problem Phenomenon
Continuous lines or marks appear on the surface of the extrudate along the extrusion direction, with fixed positions.
Die marks affect the appearance of the product, and are especially obvious in transparent products and films.
Cause Analysis
(1) There are scratches or damage on the inner wall of the die
(2) Impurities or carbonized matter accumulate in the die
(3) The die flow channel design is unreasonable, with stagnant material 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 to check the inner wall of the die; scratches need to be ground and polished for repair
(2) Clean the impurities and carbonized matter in the die, using copper tools to avoid damage
(3) Optimize the die flow channel design to eliminate stagnant material 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; the die needs to be cleaned and checked regularly.
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