Extrusion & Post
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Uneven wall thickness of heat-resistant polyethylene extruded pipes
Problem Phenomenon
The wall thickness of the pipe is uneven in the circumferential direction, showing eccentric wall phenomenon.
Uneven wall thickness affects the pressure resistance of the pipe; the thin-walled side ruptures first under pressure, seriously affecting the safety of pipe use.
Cause Analysis
(1) Die and mandrel not concentric, gap uneven
(2) Melt temperature uneven, large circumferential temperature difference at the die
(3) Extruder output uneven, melt pressure fluctuates
(4) Haul-off speed unstable or haul-off center not concentric with the die
(5) Pipe sizing sleeve worn or improperly installed
Solution
(1) Adjust the concentricity of die and mandrel, circumferential gap error not exceeding ±0.05mm
(2) Check die heating ring distribution, ensure circumferential temperature difference not exceeding ±3°C (190-230°C range)
(3) Check extruder plasticizing stability to ensure uniform output
(4) Adjust the center line of the haul-off device 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 accuracy and temperature uniformity.
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