The injection molding screw works under high temperatur […]
The injection molding screw works under high temperature, high pressure, high mechanical torque and high friction environment for a long time. The first few factors are required by the process conditions, and the loss caused by friction is inevitable. Generally, the screw has undergone surface nitriding treatment to improve the surface hardness, that is, to improve the wear resistance. However, if the cause of wear is ignored and the wear is not minimized, the working life of the screw will be greatly reduced.
The following explains the causes of screw wear and the methods to reduce wear
1. Each plastic has an ideal plasticizing temperature range, and the barrel processing temperature should be controlled to make it close to this temperature range. Granular plastic enters the barrel from the hopper, and will first reach the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are insufficiently heated and melt unevenly, it is easy to cause increased wear on the inner wall of the barrel and the surface of the screw. Similarly, in the compression section and the homogenization section, if the molten state of the plastic is turbulent, it will also cause increased wear.
2. The speed should be adjusted properly. Because some plastics are added with reinforcing agents, such as glass fibers, minerals or other fillers. These substances tend to be much more abrasive to metal than molten plastic. When these plastics are injection molded, if the high rotational speed is used, the shear force on the plastic will be increased, and at the same time, more shredded fibers will be generated accordingly. The shredded fibers contain sharp ends, which will cause wear and tear. Power is greatly increased. When inorganic minerals slide at high speed on the metal surface, their scraping effect is not small. So the speed should not be adjusted too high.