The screw and barrel of the injection molding machine a […]
The screw and barrel of the injection molding machine are operated under high pressure, high temperature, high mechanical torque and high friction environment for a long time. The first few elements are required by the process conditions, but the loss caused by friction is inevitable. Generally, the screw has undergone surface nitriding treatment to improve the surface hardness, which 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 operating life of the screw will be greatly reduced.
The following 2 points will introduce the causes of screw wear and the ways to reduce wear
1. Every plastic raw material has an aspirational plasticizing processing temperature range, so the barrel processing temperature should be controlled to make it close to this temperature range. Granular plastics enter the barrel from the hopper and firstly reach the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are not heated and melted unevenly, it is easy to cause increased wear on the inner wall of the barrel and the screw surface; the same, In the compression section and the homogenization section, if the melting of the plastic is disordered and uneven, wear will increase.
2, the speed should be adjusted properly. Because some plastics are added with strengthening agents, such as glass fibers, minerals or other fillers. The friction of these substances on metal raw materials is often much greater than that of molten plastics. When injecting these plastics, if a high speed is used, as the shearing force on the plastic is increased, more torn fibers will occur correspondingly. The torn fibers contain sharp ends and wear. The force is greatly increased. The scraping effect of inorganic minerals is not small when sliding on the metal surface at high speed. Therefore, the speed should not be adjusted too high.