How to improve the service life of injection molding machine screw?
Generally, the screw of injection molding machine has been nitrided to improve the surface hardness, that is, to improve the anti-wear ability. However, if it is neglected, the screw of the injection molding machine works for a long time under high temperature, high pressure, high mechanical torque and high friction environment. The process conditions of the first few factors are required, and the loss caused by friction is unavoidable. The cause of wear and tear, if you do not try to reduce the wear as much as possible, will inevitably greatly reduce the life of the screw. In order to ensure the safe and stable production of the screw of the injection molding machine and prolong its service life, it is necessary to strengthen the maintenance of the screw of the injection molding machine. The basic contents are as follows:
(1) Each plastic has an ideal processing temperature range for plasticization. The processing temperature of the barrel should be controlled to make it close to this temperature range. The granular plastic enters the barrel from the hopper, and will first reach the feeding section, and then the feeding section. Dry friction is bound to occur. When these plastics are insufficiently heated 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 section and the homogenization section, if the melting state of the plastic is chaotic and uneven. , will also cause increased wear.
(2) The speed should be adjusted properly. Due to some plastic refueling enhancers, such as fiberglass, minerals or other fillers. These substances tend to be much more abrasive than molten plastic. When injection molding these plastics, if a high rotational speed is used, while increasing the shear force on the plastic, the reinforcing agent will also produce more shredded fibers correspondingly. The shredded fibers contain sharp ends, so that the The wear force is greatly increased. When the electrodeless minerals glide at high speed on the metal surface, it also has a lot of scraping effect. Therefore, the speed should not be adjusted too high.
(3) To check the debris in the plastic. Generally speaking, there is no debris in the original purchased plastic, but after transportation, weighing, drying, color mixing, especially adding recycled materials, there may be debris. Small as metal shavings, as big as hot-ring nut paper clips, and even strings of warehouse keys have precedents that have been mixed into the barrel, which is indescribable damage to the screw (the barrel is of course also damaged at the same time), so , must strictly manage and monitor the feeding.
(4) The moisture contained in the plastic has a certain influence on the wear of the screw surface. If the plastic does not remove all the water before injection, the residual water will be transformed into "steam particles" with high temperature and high pressure melted into the molten plastic when the residual water enters the screw compression section. From the chemical section to the head of the screw, these "steam particles" unload and expand during the injection process, like fine impurity particles, which cause friction and damage to the wall surface.
In addition, with certain types of plastics, at high temperatures and pressures, moisture can become a catalyst for cracking the plastic, creating harmful impurities that can attack metal surfaces. Therefore, the drying work before plastic injection molding not only has a direct relationship with the quality of the parts, but also affects the working life of the screw. As mentioned above, in order to prolong the working life of the screw, flame hardening and nitriding treatment are usually used. However, due to the common daily use of filled plastics and reinforced (glass fiber reinforced) plastics, and the corrosiveness or strong wear of individual plastics, the life of these treated screws is still too short. In recent years, some new ones have been developed. High-tech processing methods have greatly improved the situation.
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