Extrusion & Post
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Bending deformation of linear low-density polyethylene extruded pipes
Problem Phenomenon
The pipe bends after extrusion, with straightness out of tolerance.
Bending deformation affects pipe installation and use, and is especially prominent in long pipe production.
Cause Analysis
(1) Cooling on all sides along the extrusion direction is uneven, causing inconsistent shrinkage
(2) The haul-off device is not concentric with the die
(3) The cooling water tank is installed incorrectly or the water temperature is uneven
(4) Uneven pipe wall thickness causes different shrinkage in all directions
(5) Improper support after extrusion; the pipe's own weight causes bending
Solution
(1) Check the cooling system to ensure uniform cooling on all sides of the pipe
(2) Align the center line of the haul-off device with the die center
(3) Correct the position of the cooling water tank and control uniform water temperature
(4) Adjust the concentricity of the die and mandrel to ensure uniform wall thickness
(5) Add pipe support rollers to reduce self-weight deformation
Key Takeaway
Pipe bending is caused by non-uniform cooling or haul-off eccentricity and needs to be solved from cooling uniformity and equipment alignment.
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