1. Each kind of plastic has an ideal plasticizing processing temperature range. The processing temperature of the barrel should be controlled to make it close to this temperature range. Granular plastics enter the barrel from the hopper and first reach the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are not heated enough and melt unevenly, it is easy to cause the wear of the inner wall of the barrel and the surface of the screw to increase. Similarly, in the compression section and the homogenization section, if the melting state of the plastic is disordered and uneven, it will also cause wear to increase.
2. The speed should be adjusted properly. Because some plastics are reinforced, such as glass fibers, minerals or other fillers. The friction force of these substances on the metal material is often much greater than that of the molten plastic. When injection molding these plastics, if a high speed is used, the shear force on the plastic will be improved at the same time, and the strengthening will correspondingly produce more shredded fibers. The shredded fibers contain sharp ends, which greatly increases the wear force. When inorganic minerals slide on the metal surface at high speed, their scraping effect is not small, so the speed should not be adjusted too high.
3. The screw rotates in the barrel, and the friction between the material and the two makes the working surface of the screw and the barrel 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 gap between the matching diameter of the screw and the barrel increases little by little with the gradual wear of the two. However, since the resistance of the machine head and the shunt plate in front of the barrel does not change, this increases the leakage flow of the extruded material when it advances, that is, the flow of the material from the diameter gap to the feeding direction increases. As a result, the production volume of plastic machinery decreases. This phenomenon increases the residence time of the material in the barrel, causing the material to decompose. If it is polyvinyl chloride, the hydrogen chloride gas generated by the decomposition strengthens the corrosion of the screw and barrel.
4. 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.
5. Because the material is not plasticized evenly, or there are metal foreign objects mixed into the material, the screw rotation torque force suddenly increases. This torque exceeds the strength limit of the screw and makes the screw twist. This is an unconventional accident damage.
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