Extrusion & Post
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Dimensional fluctuation of low density polyethylene extruded products
Problem Phenomenon
The outer diameter, wall thickness, or width of extruded products fluctuates periodically or randomly in the longitudinal direction.
Dimensional fluctuation affects product fitting accuracy and use performance; common in pipe and profile extrusion.
Cause Analysis
(1) Unstable screw rotation speed, output fluctuation
(2) Unstable haul-off speed, mismatched with extrusion speed
(3) Large barrel temperature fluctuation, melt viscosity changes
(4) Uneven raw material feeding, feeding fluctuation
(5) Cooling water temperature or flow fluctuation
Solution
(1) Check the extruder drive system, stabilize screw rotation speed
(2) Check the haul-off speed control system, ensure stable haul-off speed
(3) Stabilize barrel temperature, control fluctuation within ±3°C (160-220°C range)
(4) Check hopper feeding, ensure continuous and uniform feeding
(5) Stabilize cooling water temperature and flow; add a constant temperature device when necessary
Key Takeaway
Dimensional fluctuation is caused by unstable extrusion or haul-off; all process parameters need to be systematically stabilized.
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