The injection screw is the core component of the injection molding machine, and the screw is operated under high temperature, high pressure, high mechanical torque and high friction environment for a long time, and the wear problem is inevitable. Generally, the screw has been surface nitrided to increase the surface hardness, that is, Improve anti-wear ability.
However, if the cause of wear is neglected, and the wear is not reduced as much as possible, the working life of the screw will be greatly reduced.
1. Temperature setting of injection material: Each plastic has an ideal plasticizing processing temperature range. The barrel processing temperature should be controlled to make it close to this temperature range.
The granular plastic enters the barrel from the hopper, and it will first reach the feed section. Dry friction will inevitably occur in the feed section. When these plastics are insufficiently heated and unevenly melted, 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 melting state of the plastic is disordered, it will also cause increased wear.
2. Setting of screw speed: Because some plastics are added with reinforcement, such as glass fiber, minerals or other fillers. The friction of these substances on metal materials is often much greater than that of molten plastics.
In the injection of these plastics, if the high speed is used, the shear force on the plastic will be increased, and the reinforcement will produce correspondingly more shredded fibers. The shredded fibers contain sharp ends, which cause wear The force is greatly increased. When inorganic minerals glide on the metal surface at high speed, its scraping effect is not small. Therefore, the speed should not be adjusted too high.
3. Debris in plastics: The production of pure raw materials may have a relatively small risk, but now companies are generally doping some raw materials in the raw materials in order to reduce costs. Due to some site management reasons, the raw materials are easy to mix Into some small metal chips, this is very harmful to the screw, so generally install a magnet holder in the barrel, strict management and monitoring of feeding.