Extrusion & Post
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Random copolymer polypropylene pipe special material (Nordic standard） extruded pipe uneven wall thickness
Problem Phenomenon
The pipe wall thickness is uneven in the circumferential direction, showing eccentric wall phenomenon.
Uneven wall thickness affects pipe pressure resistance; under pressure the thin-wall side ruptures first, seriously affecting pipe use safety.
Cause Analysis
（1）The die and mandrel are not concentric, the gap is uneven\
（2）Melt temperature uneven, large circumferential temperature difference at the die\
（3）The extruder output is uneven, melt pressure fluctuates\
（4）Haul-off speed unstable or the haul-off center is not concentric with the die\
（5）The pipe sizing sleeve is worn or improperly installed
Solution
（1）Adjust the concentricity of the die and mandrel, circumferential gap error not exceeding ±0.05mm\
（2）Check the die heater band distribution, ensure circumferential temperature difference does not exceed ±3°C (200-220°C range)\
（3）Check the extruder plasticization stability, ensure uniform output\
（4）Adjust the haul-off device centerline to align with the die center\
（5）Check the sizing sleeve, replace if severely worn, ensure concentric installation
Key Takeaway
Uneven wall thickness is caused by uneven die gap or uneven temperature, and needs to be solved from mold precision and temperature uniformity.
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