Processing Machinery
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Rough inner wall of general-purpose polyethylene extruded products
Problem Phenomenon
The inner wall of the pipe or profile is rough and uneven, with visible stripes or particles.
Rough inner wall affects the fluid resistance and hygienic performance of the pipe, and may breed bacteria in water supply pipes.
Cause Analysis
（1）The mandrel temperature is low, and the melt undergoes stick-slip flow on the mandrel surface
（2）The finish of the mandrel surface is insufficient or worn
（3）The compressed air pressure is insufficient (during internal pressure sizing)
（4）The melt temperature is low, and the flowability is poor
（5）The screw plasticization is insufficient, and there are unmelted particles in the melt
Solution
（1）Appropriately raise the mandrel temperature to match the die temperature (within the range of 160-260°C)
（2）Polish the mandrel surface to Ra≤0.2μm, and chrome plate if necessary
（3）Check the compressed air system to ensure stable pressure
（4）Appropriately raise the barrel temperature to a reasonable value within the range of 160-260°C
（5）Optimize the screw design and speed to ensure sufficient 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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