Causes of screw wear of injection molding machine


The injection molding machine control skills in develop […]

The injection molding machine control skills in developed countries are relatively advanced and sophisticated, which is characterized by the selection of real-time closed-loop control and process monitoring of CRT or LCD display screen. After multiple processing, all or a lot of processing operations are assigned to peripheral equipment to complete, so as to improve the communication ability in the injection molding machine and reduce the load of the main control part. This, to some extent, represents the future direction of injection molding machine control skills.
Injection screw is a long-term operation under high temperature, high pressure, high mechanical torque and high friction environment. The first several factors are required by process conditions, and the loss caused by friction is inevitable. Generally, the screw has been nitrided 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 screw will be greatly reduced.
1. Each kind of plastic has a desired plasticizing temperature scale. The barrel processing temperature should be controlled to make it close to this temperature scale. Granular plastics from the hopper into the barrel, will first arrive at the feeding section, in the feeding section will inevitably show dry friction, when these plastics lack of heat, melting uneven, it is easy to form the barrel wall and screw surface wear increased. In the same way, in the contraction section and homogenization section, if the melting state of the plastic is disorderly and unevenly, the wear will increase.
2. The speed should be adjusted properly. Because some plastics are fortified, such as fiberglass, minerals or other fillers. The friction force of these substances on metal raw materials is often much greater than that of molten plastics. In the injection molding of these plastics, if the high rotational speed is used, the improvement of the shearing force on the plastics will also lead to the corresponding reinforcement of more torn fibers. The torn fibers contain sharp ends, which greatly increase the wear force. The scraping effect of inorganic minerals on metal surface is not small. Therefore, the speed should not be adjusted too high.