Reasons for damage to the screw and barrel

Reasons for damage to the screw and barrel

The screw rotates in the barrel, and the friction between the material and the two causes the working surface of the screw and the barrel to gradually wear, the diameter of the screw gradually decreases, and the diameter of the inner hole of the barrel gradually increases. In this way, the matching diameter gap between the screw and the barrel increases little by little with the gradual wear of the two.

Since the resistance of the head and the manifold in front of the barrel has not changed, this increases the leakage flow of the extruded material forward, that is, the flow of the material from the diameter gap to the feeding direction increases. The result is a drop in extruder throughput. This phenomenon increases the residence time of the material in the barrel, resulting in the decomposition of the material. In the case of polyethylene, the hydrogen chloride gas generated by the decomposition enhances the corrosion of the screw and barrel.

TPU film extrusion line

If there are fillers such as calcium carbonate and glass fiber in the material, it can speed up the wear of the screw and barrel.

Because the material is not plasticized evenly, or there is metal foreign matter mixed into the material, the torque of the screw rotation suddenly increases. This torque exceeds the strength limit of the screw, causing the screw to twist and break, which is an unconventional accident damage.

When the screw and barrel are installed, the level, straightness and clearance are not adjusted in place, and the fastening screws are not reinforced. There is friction in the screw barrel when starting up, which accelerates the damage of the screw barrel.

The preheating time before starting the china extruder machine is insufficient, the raw materials accumulated in the screw barrel have not been fully softened, the starting torque is too large, or there are large pieces of unsoftened material, causing the screw barrel to be sprained or broken. and damage the gearbox.

China’s high-quality extruders are generally equipped with overload protection for the main motor of the extruder, which can protect the screw barrel to a certain extent and greatly reduce the occurrence of screw sprains and twist breaks. However, if the screw structure at the stress point is weak or the time is sudden, the screw damage may still occur.