How to improve the technology of using screws

Update:23 Mar 2019
Summary:

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 feed section where dry friction inevitably occurs. When these plastics are insufficiently heated and the melting is uneven, it is easy to wear the inner wall of the cylinder and the surface of the screw more. Similarly, in the compression section and the homogenization section, if the molten state of the plastic is disordered, the wear will increase.
2, the speed should be adjusted appropriately. Some plastics are supplemented with reinforcing agents such as fiberglass, minerals or other fillers. These materials tend to have a greater friction against metallic materials than molten plastics. When molding these plastics, if they are manufactured at high rotational speeds, the shear forces on the plastic will increase and the reinforcing material will correspondingly produce more fibers. The chopped fibers contain sharp ends and wear. Strength is increasing. When the inorganic mineral slides on the metal surface at a high speed, the scratching effect is not small. Therefore, the speed should not be adjusted too high.
3. Remove debris from the plastic. Generally speaking, the fresh plastic originally purchased has no sundries, but it is possible to mix impurities after transportation, weighing, drying, color mixing, especially after adding recycled materials. Small as metal scrap, heating ring nut paper clip is as big, even a string of warehouse keys, has 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 influence on the wear of the screw surface. If the plastic does not completely remove moisture prior to injection, residual moisture enters the compressed portion of the screw and forms a high pressure pressure "steam particle" that melts in the molten plastic, and the screw advances with the screw. Injection process. From the cross section of the screw to the threaded head, these "vapor particles" are released and expanded during the spraying process, just like the fine impurities of the hard particles, which cause frictional damage to the wall surface. In addition, for certain types of plastics, at high temperatures and pressures, moisture can be a catalyst for cracking plastics, producing harmful impurities that can 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.

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