It is understood that the injection molding machine screw for a long time in the high temperature, high pressure, high mechanical torque and high friction environment to work, the first few factors are required by the process conditions, and friction caused by the loss is inevitable. The general screw has been subjected to surface nitriding to improve the surface hardness, that is, to improve the wear resistance. But if you ignore the cause of wear and tear, do not try to minimize wear and tear, will greatly reduce the working life of the screw.
The following will focus on the causes of screw wear and reduce the wear and tear of the method:
Each plastic, there is an ideal plastic processing temperature range, should control the barrel processing temperature, so close to this temperature range. Granular plastic from the hopper into the barrel, the first will reach the feeding section, in the feeding section is bound to appear dry friction, when the plastic heat shortage, melting uneven, it is easy to cause the barrel wall and screw surface wear increases. Similarly, in the compression section and the homogenization section, if the plastic state of the molten state is uneven, will cause increased wear
Speed should be adjusted properly. As part of the plastic plus a reinforcing agent, such as glass fiber, mineral or other filler. These materials on the metal material friction is often much larger than the molten plastic. In the injection of these plastics, if the high speed into, then increase the shear force on the plastic at the same time, will also make the corresponding to produce more shredded fiber, the shredded fiber contains sharp ends, so wear Force greatly increased. Inorganic minerals in the metal surface high-speed taxi, the scrapping effect is not small. So the speed should not be transferred too high.
To remove the debris from the plastic. In general, the original purchase of fresh plastic and no debris, but after transport, weighing, drying, color mixing, in particular, to add recycled material, it is possible mixed with debris. Small, such as metal crumbs, large, such as heat pipe nuts back to the needle, and even a string of warehouse keys, mixed into the barrel have occurred, the damage to the screw is self-evident (the barrel of course, will also be damaged ), It is necessary to install the magnet frame, strict feeding management and monitoring.
Plastic contained in the water, the wear of the screw surface have a certain impact. If the plastic does not remove all the water before injection molding, the residual moisture enters the screw compression section, then the formation of melt before mixing in the molten plastic with high temperature pressure of the "steam particles", with the injection material process screw, from the The segment until the screw head, these "steam particles" in the process of loading and unloading pressure expansion, like a trace of fine impurities in the hard particles, the wall produced friction damage. In addition, for certain types of plastics, at high temperature and high pressure, moisture may become a catalyst that promotes plastic cracking, producing harmful impurities that can erode metal surfaces. Therefore, the plastic injection before the drying work, not only on the quality of the workpiece has a direct relationship, but also affect the working life of the screw.