Processing Machinery
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Rough inner wall of linear low-density polyethylene extruded products
Problem Phenomenon
The inner wall of the pipe or profile is rough and uneven, with visible streaks or particles.
A rough inner wall affects pipe fluid resistance and hygiene performance and may breed bacteria in water supply pipes.
Cause Analysis
(1) Mandrel temperature is on the low side, and the melt undergoes stick-slip flow on the mandrel surface
(2) The mandrel surface finish is insufficient or worn
(3) Compressed air pressure is insufficient (during internal pressure sizing)
(4) Melt temperature is on the low side and fluidity is poor
(5) Screw plasticization is insufficient, and there are unmelted particles in the melt
Solution
(1) Appropriately increase mandrel temperature to match die temperature (190-250°C range)
(2) Polish the mandrel surface to Ra≤0.2μm, with chrome plating if necessary
(3) Check the compressed air system to ensure stable pressure
(4) Appropriately increase barrel temperature to a reasonable value within the 190-250°C range
(5) Optimize screw design and speed to ensure full plasticization
Key Takeaway
Rough inner wall is caused by low mandrel temperature or poor surface condition and needs to be solved from temperature control and mold maintenance.
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