Analysis of the causes of screw wear by dispensing machine m
Release date：2021-08-24 09:59 Views：
Each kind of plastic has an ideal plasticizing 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 the hopper and reach the feeding part first, dry grinding will inevitably occur. When these plastics are not heated sufficiently and melt unevenly, it is easy to increase the wear of the inner wall of the barrel and the surface of the screw. Similarly, in the compression section and homogenization section, if the melting state of the plastic is uneven, it will also cause increased wear. Dispenser manufacturer
The vehicle speed should be adjusted appropriately. Because some plastics contain fortifiers, such as glass fiber, minerals or other fillers. Compared with molten plastics, these substances usually wear metal materials more. During injection molding, if high-speed rotation is adopted, it will not only improve the shear force on the plastic, but also make the reinforcement produce more shredded fibers accordingly. The shredded fibers contain sharp ends, which greatly increases the wear force. When the metal surface slides at high speed, the scraping effect of inorganic minerals is not small. Therefore, the speed cannot be adjusted too high.
The screw rotates in the barrel, and the friction between the material and the two causes the surface of the screw and the barrel to wear gradually: the diameter of the screw decreases gradually, and the diameter of the inner hole of the barrel increases gradually. In this way, the fit diameter gap between the screw and the barrel gradually increases with the gradual wear of the two. However, since the resistance of the head in front of the barrel and the splitter plate does not change, this increases the leakage flow when the extrusion material moves forward, that is, the amount of material flowing from the diameter gap to the feeding direction increases. As a result, the output of plastic machinery decreased. This phenomenon also prolongs the residence time of materials in the cylinder and causes the decomposition of materials. In polyethylene, hydrogen chloride gas produced by decomposition will aggravate the corrosion of screw and barrel. Dispenser manufacturer
If there are fillers such as calcium carbonate and glass fiber in the material, the wear of screw and barrel can be accelerated. Due to the uneven plasticization of materials or the mixing of metal foreign matters, the rotating torque of the screw suddenly increases, which exceeds the strength limit of the screw and breaks the screw. It is an unconventional accidental injury.