The screw of the injection molding machine works under high pressure, high temperature, high mechanical torque and high friction environment for a long time. The first few factors are required by the process conditions, but the loss caused by friction is inevitable. Generally, the screw has been subjected to surface nitriding treatment to improve the surface hardness, that is, to improve the wear resistance. However, if the cause of wear is neglected, and the wear is not reduced as much as possible, the working life of the screw will be greatly reduced.
The following 2 points introduce the causes of screw wear and methods to reduce wear
1. Each plastic raw material has an ideal plasticizing processing temperature range, so the barrel processing temperature should be controlled to make it close to this temperature range. When the granular plastic enters the barrel from the hopper, it will first reach the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are insufficiently heated and unevenly melted, it is easy to cause increased wear on the inner wall of the barrel and the surface of the screw; In the compression section and homogenization section, if the molten state of the plastic is disordered, it will also cause increased wear.
2. The speed should be adjusted properly. Because some plastics are added with reinforcing agents, such as fiberglass, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastics. In the injection of these plastics, if the high speed is used, the shear force on the plastic will be increased, and the reinforcement will correspondingly produce more shredded fibers. The shredded fibers contain sharp ends, which cause wear The force is greatly increased. When inorganic minerals glide on the metal surface at high speed, its scraping effect is not small. So the speed should not be adjusted too high