Processing Machinery
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Rough inner wall of random copolymer polypropylene pipe special material extruded products (Variant: mass production scenario)
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.
In particular, in continuous mass production, this problem is more prominent and needs key attention.
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
（6）In continuous mass production, process parameter fluctuations or equipment status changes have aggravated this problem
Solution
（1）Appropriately raise the mandrel temperature to match the die temperature (within the range of 200-220°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 200-220°C
（5）Optimize the screw design and speed to ensure sufficient plasticization
（6）And establish standardized work instructions, with special attention to parameter stability in continuous mass production
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.
In different production scenarios, targeted preventive measures need to be taken.
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