The screw is rotated inside the barrel, and the material is friction with the two. The working surface of the screw and the cylinder is gradually worn down: the diameter of the screw is reduced, and the diameter of the inner hole of the cylinder is increased by friction.So the screw and barrel with diameter clearance will be more and more big (work when the screw is made surface nitriding treatment, in order to improve the surface hardness), because of the barrel in front of the nose and shunt plate resistance has not changed, this increases the progress was extruded material leakage flow, the material feeding direction from diameter clearance flow has increased.The result is a decrease in the production of extruder.This causes the material to stay in the barrel to increase in time, resulting in the decomposition of the material.If the material is polyethylene, the decomposition of hydrogen chloride gas enhances the corrosion of the screw and the cylinder, forming a vicious circle.

Physical properties of materials: materials such as calcium carbonate and glass fiber are used in crushers, which are often much more abrasive to metal materials than molten plastic.When these plastic injection molding, if high speed in the increase of plastic shear force at the same time, also correspondingly to produce more fiber is torn, torn fiber containing sharp end, the wear and tear strength increased greatly.Therefore, the speed of the extruder studio should not be adjusted too high.
Material plasticizing uniform or metal foreign body with no material: this situation is causing the screw rotation torque force suddenly increases, the torque beyond the strength of the screw extruder screw limit, caused the screw exercise, this situation is abnormal damage.
Various plastic plasticizing range: each plastic has an ideal plasticizing processing temperature range, granular plastic from the hopper into the cylinder, will first reach the feeding section, the charging period of inevitable dry friction, when the plastic is heated, fused inequality, very easy to cause the inner wall of the cylinder and the screw surface wear.Similarly, in the compression and homogenization sections, if the plastic melts, it will also increase wear and tear.