Causes of screw wear of vertical injection molding machine

The injection system of the vertical injection molding machine is composed of a plasticizing device and a power transmission device. The injection screw plasticizing device is mainly composed of a feeding device, a barrel, a screw, and a nozzle. The power transmission device includes an injection cylinder, an injection seat moving cylinder and a screw Drive device.

The injection screw is operated for a long time under high temperature, high pressure, high mechanical torque and high friction environment. The first few factors are required by the process conditions, and the wear caused by friction is inevitable. Generally, the screw has been exposed to surface nitrogen. Chemical treatment to increase the surface hardness, that is, to improve the wear resistance, but if the causes of wear are ignored and the wear is not tried to reduce as much as possible, the working life of the screw will inevitably be greatly reduce.

The following explains the reasons for the wear of the injection screw and the methods to reduce the wear
1. Each plastic has an ideal processing temperature range for plasticization. The processing temperature of the barrel should be controlled to be close to this temperature range. The granular plastic enters the barrel from the hopper, and will first reach the feeding section, and dry friction will inevitably occur in the feeding section. When these plastics are not heated enough and the melting is uneven, it is easy to cause increased wear on the inner wall of the barrel and the surface of the screw. Similarly, in the compression section and the homogenization section. If the molten state of the plastic is disordered and uneven, it will also cause increased wear.

2, the speed should be adjusted properly. Because some plastics are added with reinforcing agents, such as glass fibers, minerals or other fillers, the friction of these substances on metal materials is often much greater than that of molten plastics. When injection molding these plastics, if they are made with a high rotation speed, it will increase the shearing force to the plastic, and at the same time, the reinforcement will produce more shredded fibers. The shredded fibers contain sharp ends, causing wear The force is greatly increased, and the scraping effect of inorganic minerals when sliding on the metal surface at high speed is not small, so the speed should not be adjusted too high.

How to improve the life of injection screw
The injection screw can work for a long time under high temperature, high pressure, high mechanical torque and high friction environment. Process conditions require these factors, and losses caused by friction are inevitable. Generally, injection screws have been surface nitriding treatment to increase surface hardness, that is, to improve wear resistance. However, if the cause of wear is ignored and the wear is not minimized, the service life of the injection screw will be greatly shortened. The reasons for the wear of the injection screw and the methods to reduce wear are described below.

1.Every plastic has an ideal plasticizing temperature range. The processing temperature of the barrel should be controlled close to this temperature range. Granular plastic enters the barrel from the hopper and first reaches the feeding area. Dry friction will inevitably occur in the feed zone. If these plastics are not fully heated and melted unevenly, they will easily cause greater wear on the inner wall of the barrel and the surface of the injection screw. Similarly, in the compression section and the homogenization section, if the molten state of the plastic is chaotic and uneven, it will also cause increased wear of the injection screw.
2. The speed should be adjusted appropriately. Because some plastics are added with reinforcing agents, such as glass fibers, minerals or other fillers. The friction of these substances on metal materials is usually much greater than that of molten plastic. When these plastics are injection molded, if they are made at high rotation speeds, and at the same time increase the shear force on the plastic, it will also cause the reinforcement to produce more chopped fibers. The chopped fiber contains sharp ends, which can cause wear on the injection screw. When inorganic minerals slide on the metal surface at high speed, the scraping effect is not small, and it will also cause wear of the injection screw. Therefore, the speed should not be adjusted too high.

Basics of Injection Molding Process
Temperature, pressure, speed and cooling control purposes, operation and results how the adjustment of injection molding machine settings affects process and quality optimization screw control settings multi-stage filling and multi-stage packing control; Effects of crystallization, non-crystallization and molecular/fiber alignment on process and quality internal stress, cooling rate, plastic shrinkage on plastic parts quality plastic rheology: how plastic flows, aligns and changes viscosity, the relationship between shearing and molecular/fiber alignment. The relationship between pouring system, cooling system, mold structure and injection process

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