Extrusion & Post
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Uneven wall thickness of general-purpose polyethylene extruded pipes
Fenómeno do problema
The wall thickness of the pipe in the circumferential direction is uneven, and eccentric wall appears.
Uneven wall thickness affects the pressure resistance of the pipe, and the thin-walled side breaks first when under pressure, seriously affecting the use safety of the pipe.
Análise das causas
（1）The die and the mandrel are not concentric, and the gap is uneven
（2）The melt temperature is uneven, and the temperature difference in the circumferential direction of the die is large
（3）The extruder output is uneven, and the melt pressure fluctuates
（4）The haul-off speed is unstable or the haul-off center is not concentric with the die
（5）The pipe sizing sleeve is worn or installed incorrectly
Solução
（1）Adjust the concentricity of the die and the mandrel, and the circumferential gap error should not exceed ±0.05mm
（2）Check the distribution of the die heater bands to ensure that the circumferential temperature difference does not exceed ±3°C (within the range of 160-260°C)
（3）Check the plasticizing stability of the extruder to ensure uniform output
（4）Adjust the center line of the haul-off device to align with the center of the die
（5）Check the sizing sleeve, replace it if it is severely worn, and ensure concentricity when installing
Conclusão principal
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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