Extrusion & Post
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Uneven wall thickness of low density polyethylene extruded pipes
Fenómeno del problema
Pipe wall thickness is uneven in the circumferential direction, showing eccentric wall phenomenon.
Uneven wall thickness affects pipe pressure resistance; the thin-wall side ruptures first under pressure, seriously affecting pipe use safety.
Análisis de la causa
(1) Die and mandrel not concentric, uneven gap
(2) Uneven melt temperature; large temperature difference around the die circumference
(3) Uneven extruder output, melt pressure fluctuation
(4) Unstable haul-off speed or haul-off center not concentric with the die
(5) Pipe sizing sleeve worn or improperly installed
Solución
(1) Adjust the concentricity of die and mandrel; circumferential gap error not exceeding ±0.05mm
(2) Check die heater band distribution, ensure circumferential temperature difference not exceeding ±3°C (160-220°C range)
(3) Check extruder plasticizing stability, ensure uniform output
(4) Align the haul-off device centerline with the die center
(5) Check the sizing sleeve; replace if severely worn, ensure concentric installation
Conclusión clave
Uneven wall thickness is caused by uneven die gap or uneven temperature; it needs to be solved from mold accuracy and temperature uniformity.
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