Extrusion & Post
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Die marks/lines appearing on linear low-density polyethylene extruded products
Problem Phenomenon
Continuous lines or marks appear on the extrudate surface along the extrusion direction at fixed positions.
Die marks affect product appearance and are especially obvious in transparent products and films.
Cause Analysis
(1) The die inner wall has scratches or damage
(2) Impurities or carbides accumulate inside the die
(3) Unreasonable die flow channel design with stagnation zones
(4) The die joint is uneven
(5) The breaker plate or screen is damaged, allowing impurities to pass through
Solution
(1) Disassemble the mold and check the die inner wall; scratches need to be ground and polished for repair
(2) Clean impurities and carbides inside the die, using copper tools to avoid damage
(3) Optimize die flow channel design to eliminate stagnation dead zones
(4) Grind the die joint flat to ensure no steps
(5) Replace the breaker plate and screen, replacing regularly to prevent damage
Key Takeaway
Die marks are caused by die inner wall damage or impurities; the die condition needs to be regularly cleaned and inspected.
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