How to improve screw usage technology

1. Each type of plastic has an ideal plasticizing processing temperature range, and the processing temperature of the barrel should be controlled to approach this temperature range. Granular plastic enters the material barrel from the hopper and first reaches the feeding section, where dry friction is inevitable. When these plastics are not heated enough and melted 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 and homogenization stages, if the melting state of the plastic is disordered and uneven, it can also cause increased wear.

2. The speed should be adjusted properly. Due to the addition of reinforcing agents such as fiberglass, minerals, or other fillers to some plastics. These substances often have much greater friction on metal materials than on molten plastics. When injecting these plastics, if a high rotational speed is used, it will increase the shear force on the plastic and correspondingly produce more shredded fibers, which contain sharp ends and greatly increase the wear force. When inorganic minerals slide at high speed on metal surfaces, their scraping effect is also significant. So the speed should not be set too high.

3. To remove debris from the plastic. Generally speaking, fresh plastic purchased in its original packaging does not contain any impurities, but after transportation, weighing, drying, color mixing, and especially adding recycled materials, there may be impurities mixed in. Small as metal shavings, large as heating ring nuts, paper clips, and even strings of warehouse keys have all been mixed into the material barrel, and the damage to the screw is self-evident (the material barrel will also be damaged at the same time). Therefore, it is necessary to install a magnetic iron frame and strictly manage and monitor the feeding process.

4. The moisture content in plastic has a certain impact on the wear of the screw surface. If the plastic is not completely drained of moisture before injection molding, the residual moisture will enter the screw compression section and form “steam particles” with high temperature and pressure that are previously melted and mixed in the molten plastic. As the injection material progresses, these “steam particles” will expand during the injection process from the homogenization section to the screw head, like fine impurities and hard particles, causing friction and damage to the wall surface. In addition, for certain types of plastics, under high temperature and pressure, moisture may become a catalyst that promotes plastic cracking, producing harmful impurities that can corrode metal surfaces. Therefore, the drying work before plastic injection molding is not only directly related to the quality of the parts, but also affects the working life of the screw.