Screw rotating in the barrel, the friction between the material and the two, so that the gradual wear and tear of the screw and the working surface of the barrel: the screw diameter will be reduced friction, the inner diameter of the barrel due to friction increased. As a result, the clearance between the screw and the barrel becomes larger and larger (the surface of the screw is subjected to surface nitriding during working to increase the surface hardness), and the resistance of the head and the manifold in front of the barrel is unchanged, which increases Leakage flow when the material being extruded advances, ie, the flow of material from the diameter gap to the feed direction increases. The result is a decrease in extruder throughput. This leads to the material in the barrel residence time increases, resulting in material decomposition. If the material is polyethylene, the decomposition of hydrogen chloride gas generated to enhance the corrosion of the screw and barrel, forming a vicious circle.

The physical properties of the material: Crushers produce materials such as calcium carbonate and glass fiber filler, these materials tend to be more abrasive metal material than the melting of plastic is much larger. When these plastics are injection molded, higher speeds increase the shearing force on the plastic while producing more shredded fibers. The shredded fibers contain sharp ends that greatly increase the wear force. Therefore, the extruder studio speed should not be adjusted too high.

Material is not plasticized evenly or metal foreign material mixed into the material: This situation leads to a sudden increase in the torque of the screw rotating torque, which exceeds the limit of the screw extruder screw strength, resulting in the screw to exercise, this situation is unconventional damage.

Plasticizing range of different plastics: each plastic has an ideal plasticizing temperature range, granular plastic from the hopper into the barrel, will first reach the feeding section, the feeding section is bound to appear dry friction, when these plastics Insufficient heating, uneven melting, it is easy to cause the cylinder wall and screw surface wear increased. Similarly, in the compression section and the homogenization section, if the molten state of the plastic is uneven, the abrasion may also be increased.