PVC screw barrel to check the plastic guess of the debr […]
PVC screw barrel to check the plastic guess of the debris. Generally speaking, there are no sundries in the original purchased fresh plastic, but through transportation, weighing, boring, color mixing, and especially adding recycled materials, there may be mixed impurities. As small as metal dust, as big as heating ring nuts, paper clips, and even a series of warehouse keys, mixed into the barrel have occurred, which is obvious to the screw damage of injection molding machine (the barrel of course will also be damaged together), so it is necessary to install magnetic iron frame, strict handling and monitoring of feeding.
The moisture content in PVC screw barrel has certain influence on the wear of screw surface. If the water in the plastic is not completely removed before injection, when the residual water enters into the screw tightening section, it will form the "steam particles" with high temperature and pressure mixed in the molten plastic before injection. With the push of the screw in the injection process, from the homogenization section to the head of the screw, these "steam particles" will expand during the injection process, like fine impurities hard particles, which will grind the wall surface Rub damage effect. In addition, for some kinds of plastics, under high temperature and high pressure, water may become a catalyst to promote the cracking of plastics, resulting in harmful impurities that can corrode the metal surface. Therefore, the drying operation before plastic injection not only has a direct relationship with the quality of the parts, but also affects the working life of the screw.
The rotational speed of PVC screw barrel 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.