Each type of plastic has an ideal plasticizing temperature range, and the barrel processing temperature should be controlled to approach this range. As granular plastic enters the barrel from the hopper, it first reaches the feeding section, where dry friction is inevitable. When these plastics are insufficiently heated and melt unevenly, 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 homogenization section, if the plastic's melting state is disordered and uneven, it will also accelerate wear.
2. The rotational speed should be adjusted properly. Due to the addition of reinforcing agents in some plastics, such as glass fiber, minerals, or other fillers. These materials often have a much higher frictional force against metal than molten plastic. When injecting these plastics, if a high rotational speed is used, it will increase the shearing force on the plastic while also causing the reinforcing materials to produce more shredded fibers. The shredded fibers, with their sharp ends, significantly increase the wear. The abrasive action of inorganic minerals is also considerable when they slide at high speeds across the metal surface. Therefore, the rotational speed should not be adjusted too high.
The screw rotates within the barrel, and the friction between the material and both components gradually wears down the working surfaces of the screw and barrel: the screw diameter gradually decreases, and the inner diameter of the barrel increases. As a result, the clearance between the screw and barrel's mating diameters gradually increases. However, since the resistance from the barrel's front head and分流 plate has not changed, this increases the leakage flow of the extruded material as it advances, meaning the flow of material from the diameter gap towards the feeding direction increases. This leads to a decrease in the production output of the plastic machinery. This phenomenon also increases the material's residence time within the barrel, causing decomposition.
4. The presence of fillers such as calcium carbonate and glass fiber in the material can accelerate the wear of the screw and barrel.
5. Due to uneven plasticization of materials or the presence of metal impurities mixed into the material, the screw rotation torque suddenly increases, exceeding the torque limit of the screw shaft. This results in the screw shaft breaking. This is an atypical accident-related damage.
