Extrusion & Post
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Dimensional fluctuation of linear low-density polyethylene extruded products
Problem Phenomenon
Product outer diameter, wall thickness or width fluctuates periodically or randomly in the longitudinal direction.
Dimensional fluctuation affects product fitting accuracy and service performance and is common in pipe and profile extrusion.
Cause Analysis
(1) Screw speed is unstable and output fluctuates
(2) Haul-off speed is unstable and does not match extrusion speed
(3) Barrel temperature fluctuates greatly and melt viscosity changes
(4) Raw material feeding is uneven and feeding fluctuates
(5) Cooling water temperature or flow fluctuates
Solution
(1) Check the extruder drive system and stabilize screw speed
(2) Check the haul-off machine speed control system to ensure stable haul-off speed
(3) Stabilize barrel temperature, controlling fluctuation within ±3°C (190-250°C range)
(4) Check hopper feeding to ensure continuous and uniform feeding
(5) Stabilize cooling water temperature and flow, and add a constant temperature device if 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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