How to improve the technique of using screws


1. Each plastic has an ideal plasticizing processing te […]

1. Each plastic has an ideal plasticizing processing temperature range, and the barrel processing temperature should be controlled to be close to this temperature range. When the granular plastic enters the barrel from the hopper, it will first reach the feeding section, where dry friction inevitably occurs. When these plastics are not fully heated and melted unevenly, the inner wall of the cylinder and the surface of the screw tend to wear more. Similarly, in the compression section and the homogenization section, if the molten state of the plastic is disordered, wear will increase.

2. The speed should be adjusted appropriately. Some plastics are supplemented with reinforcing agents, such as glass fibers, minerals or other fillers. Compared with molten plastics, these materials tend to have greater friction on metal materials. When molding these plastics, if they are manufactured at high rotational speeds, the shear force on the plastic will increase, and the reinforcing material will correspondingly produce more fibers.
Screw cap The chopped fiber contains sharp ends and frays. Strength is increasing. When inorganic minerals slide on the metal surface at high speed, the scratching effect is not small. Therefore, the speed should not be adjusted too high.

3. Remove the debris in the plastic. Generally speaking, the fresh plastic originally purchased has no debris, but it may be mixed with impurities during transportation, weighing, drying, and color mixing, especially after adding recycled materials. Small as metal scrap, as big as a heating ring nut paper clip, and even a bunch of warehouse keys have been mixed into the barrel. The damage to the screw is self-evident (the cylinder will also be damaged at the same time). Therefore, the magnet bracket must be installed to be strict Manage and monitor materials.

4. The moisture contained in the plastic has a certain effect on the wear of the screw surface. If the plastic is not completely removed of moisture before injection, the residual moisture enters the compressed part of the screw and forms high-pressure pressure "steam particles" melted in the molten plastic, and the screw advances with the screw. Injection process. From the cross section of the screw to the thread head, these "steam particles" are released and expanded during the injection process, just like the fine impurities of hard particles, which will cause frictional damage to the wall surface. In addition, for certain types of plastics, under high temperature and high pressure, moisture may become a catalyst for breaking the plastic, producing harmful impurities that may attack the metal surface. Therefore, the drying work before injection molding is not only directly related to the quality of the parts, but also affects the service life of the screw.