Processing Machinery
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Rough inner wall of low density polyethylene extruded products
Problem Phenomenon
The inner wall of pipes or profiles is rough and uneven, with visible stripes or particles.
Rough inner wall affects pipe fluid resistance and hygienic performance, and may breed bacteria in water supply pipes.
Cause Analysis
(1) Mandrel temperature too low; stick-slip flow of melt on the mandrel surface
(2) Insufficient mandrel surface finish or wear
(3) Insufficient compressed air pressure (during internal pressure sizing)
(4) Melt temperature too low, poor flowability
(5) Insufficient screw plasticization, unmelted particles in the melt
Solution
(1) Appropriately increase mandrel temperature, match with die temperature (160-220°C range)
(2) Polish mandrel surface to Ra≤0.2μm, chrome plating when necessary
(3) Check the compressed air system, ensure stable pressure
(4) Appropriately increase barrel temperature to a reasonable value within the 160-220°C range
(5) Optimize screw design and rotation speed, ensure full plasticization
Key Takeaway
Rough inner wall is caused by low mandrel temperature or poor surface condition; it needs to be solved from temperature control and mold maintenance.
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