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