Use Of Injection Molding Screw Barrel


    Injection Molding Screw Barrel 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 and barrel have undergone surface nitriding treatment to increase the surface hardness, that is, to improve the wear resistance. However, if the causes of wear are ignored and the wear is not reduced, the service life of the screw and barrel will inevitably be greatly reduced.

       1. Every plastic has an ideal plasticizing temperature range. The processing temperature of the barrel should be controlled to be close to this temperature range. The granular plastic enters the barrel from the hopper and reaches the feeding section first. Dry friction will inevitably occur in the feed section. When these plastics are not heated enough and the melting is uneven, it is easy to increase the wear of the inner wall of the barrel and the surface of the screw. Similarly, in the compression section and homogenization section, if the melting state of the plastic is disordered and uneven , It will also cause increased wear.

      2, the speed should be adjusted appropriately. Because some plastics are added with reinforcing agents, such as glass fibers, minerals or other fillers, the friction of these substances on metal materials is often much greater than that of molten plastics. When injection molding these plastics, if high-speed manufacturing is used, while increasing the shearing force to the plastic, it will also cause the reinforcement to produce more broken fibers accordingly. The chopped fiber contains sharp ends, which greatly increase the abrasion force. When inorganic minerals slide on the metal surface at high speed, their scraping effect is not small. Therefore, the speed should not be adjusted too high.

       3. Check the debris in the plastic. Generally speaking, there is no sundries in the fresh plastic originally purchased, but sundries may be mixed in after transportation, weighing, drying, and color mixing, especially after adding recycled materials. Small metal shavings, large heating coil nuts, paper clips, and even a bunch of warehouse keys have been mixed into the barrel. The damage of the screw is self-evident (the barrel will be damaged at the same time), so it needs to be installed. Magnet holder, and strictly manage and monitor the feed.

      4. The water content in the plastic has a certain effect on the wear of the injection screw surface. If the plastic is not completely drained of water before injection, when the remaining water enters the screw compression section, it will form high-temperature and high-pressure "steam particles" pre-melted and mixed in the molten plastic. As the screw advances during the injection process, from the chemical part to the screw head, these "steam particles" release pressure and expand during the injection process, just like tiny hard particles of impurities, causing friction and damage to the wall. In addition, for certain types of plastics, under high temperature and high pressure, moisture may become a catalyst to promote the cracking of the plastic, producing harmful impurities that can attack the metal surface. Therefore, the drying work before injection is not only directly related to the quality of the parts, but also affects the working life of the screw and barrel.

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