Screw is an important part of injection molding machine. Its function is transporting, compacting, melting, stirring and pressing plastic.
1. Each kind of plastic has an ideal processing temperature range. The processing temperature of the barrel should be controlled to make it close to this temperature range. When granular plastics enter the barrel from hopper, they will first reach the feeding section. Dry friction will inevitably occur in the feeding section. When these plastics are not heated enough and melt unevenly, it is easy to cause wear and tear on the inner wall of the barrel and the surface of the screw. Similarly, in the compression and homogenization stages, if the melting state of plastics is not uniform, the wear will also increase.
Screw head group
2, the speed should be adjusted properly. Some plastics are reinforced with fortifier, such as glass fiber, mineral or other filler. The friction force of these materials on metal materials is often much larger than that of molten plastics. In injection moulding of these plastics, if high-speed conversion is used, the shear force on the plastics will be increased, and the corresponding reinforcement will produce more torn fibers. The torn fibers contain sharp ends, which greatly increases the wear force. When inorganic minerals move on metal surface at high speed, their scraping effect is not small. So the speed should not be adjusted too high.
3, check out plastic waste. Generally speaking, there is no impurity in the fresh plastic purchased in the original, but after transportation, weighing, drying, mixing, especially adding recycled recycled recycled materials, it is possible to mix colored, especially adding recycled recycled recycled recycled materials, it is possible to mix impurities.
Spring nozzle
4. Moisture content in plastic has certain effect on the wear of screw surface. If the plastic has not completely removed the moisture before injection, when the residual water enters the screw compression section, the steam particles with high temperature and pressure which are mixed in the melt plastic before injection will be formed. With the advance of the screw during injection process, from homogenization section to screw head, these “steam particles” will expand in the process of injection, as in the case of pressure relief. The fine particles of hard particles can cause friction and damage to the wall. In addition, for some kinds of plastics, under high temperature and high pressure, water may become a catalyst for the cracking of plastics, resulting in harmful impurities that can erode the metal surface. Therefore, the drying work before plastic injection is not only directly related to the quality of the parts, but also affects the working life of the screw.
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