Material Drying
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Rough inner and outer walls of low density polyethylene pipes
Problem Phenomenon
The inner or outer wall surface of the pipe is rough, with visible stripes or particles.
Rough pipe wall increases fluid resistance, affects conveying efficiency, and may affect hygienic performance in water supply pipes.
Cause Analysis
(1) Die or mandrel temperature too low, rough melt surface
(2) Insufficient die or mandrel surface finish
(3) Sizing sleeve worn or rough surface
(4) Melt temperature too low, poor flowability
(5) High moisture content in compressed air affecting the inner wall
Solution
(1) Appropriately increase die and mandrel temperature to the higher value within the 160-220°C range
(2) Polish die and mandrel to Ra≤0.2μm, chrome plating treatment
(3) Check the sizing sleeve; replace if worn or rough
(4) Appropriately increase barrel temperature to a reasonable value within the 160-220°C range
(5) Add drying and filtering devices to compressed air
Key Takeaway
Rough pipe wall is caused by low mold temperature or poor surface condition; it needs to be solved from temperature control and mold maintenance.
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