Material Drying
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Rough Inner and Outer Walls of High-Density Polyethylene Pipes
Problem Phenomenon
The inner or outer wall surface of the pipe is rough, with visible stripes or particles.
Rough pipe walls increase fluid resistance and affect conveying efficiency, and may affect hygiene performance in water supply pipes.
Cause Analysis
（1）The die or mandrel temperature is low, and the melt surface is rough
（2）The surface finish of the die or mandrel is insufficient
（3）The sizing sleeve is worn or the surface is rough
（4）The melt temperature is low, and the flowability is poor
（5）The compressed air has a high water content, affecting the inner wall
Solution
（1）Appropriately increase the die and mandrel temperatures to higher values within the 180-260°C range
（2）Polish the die and mandrel to Ra≤0.2μm and perform chrome plating
（3）Check the sizing sleeve, and replace it if worn or rough
（4）Appropriately increase the barrel temperature to a reasonable value within the 180-260°C range
（5）Add a drying and filtering device to the compressed air
Key Takeaway
Rough pipe walls are caused by low mold temperature or poor surface condition, and need to be solved from temperature control and mold maintenance.
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