The flat double barrel rotates in the cylinder, and the working surfaces of the screw and the cylinder are gradually worn due to the friction between the material and the two. The diameter of the flat double barrel is reduced due to friction, and the diameter of the inner hole of the cylinder block is enlarged due to friction. Therefore, the gap between the fitting diameter of the flat double barrel and the cylinder body is getting larger and larger, and the flat double barrel is subjected to surface nitriding treatment in order to improve the surface hardness during operation. Since the resistance of the cylinder head and the manifold in front of the cylinder does not change, the leakage flow rate when the extruded material advances, that is, the flow rate from the diameter gap to the material supply direction increases. As a result, the output of the extruder decreased. As a result, the residence time of the material in the cylinder increases, and the material is decomposed. When the material is polyethylene, the gas generated by the decomposition strengthens the corrosion of the screw and the cylinder, forming a vicious circle. Then, let's take a look at the reasons why the flat double barrel is easily damaged!
Physical properties of flat double barrel material: When the material produced by the crusher contains filler materials such as calcium carbonate and glass fiber, the friction force of these substances on metal materials is often much greater than that of molten plastics. When injection molding these plastics, the high rotational speed increases the shear force on the plastic, which in turn produces more chopped fibers, which contain sharp ends and greatly increase the wear force. So the speed of the extruder studio should not be too high.
Corrosion-resistant, abrasion-resistant, high-temperature resins with flat double barrels may unknowingly damage the screw and cylinder. For example, some engineering materials, thermoplastic elastomers, and biopolymers create corrosive environments. In addition, reinforcing materials (eg, glass fibers, glass balls, etc.), some fillers, and additives have abrasive properties.
In order not to compromise production efficiency and product quality, processors must closely monitor equipment hazards from these materials. In order to maintain high machining standards, it is necessary to establish a preventive maintenance program (hereinafter referred to as the "PM" program). If necessary, check and measure the screw and cylinder, pull out the screw, reinstall or replace. Because very little wear can also affect the quality of the product.
The best way to protect equipment from aggressive and corrosive resins is to choose the right materials for the screw and cylinder. In order to cope with corrosive, abrasive and high-temperature melts, the manufacturing cost of wear-resistant cylinders and screws is about 3 to 4 times higher than that of standard polyolefin screws. This is because the price of wear-resistant alloys is relatively high and difficult to process. However, they can provide longer life and extended maintenance intervals.
When the flat double barrel material is not plasticized or mixed with metal foreign matter: the torque force of the screw increases sharply, the torque exceeds the screw strength limit of the screw extruder, and the screw moves, which is not a conventional damage.
The plasticizing range of each plastic is different: each plastic has an ideal plasticizing processing temperature range. The granular plastic enters the barrel from the hopper and first reaches the feeding section. The feeding section will inevitably produce dry friction. If these plastics are melted due to insufficient heat If it is not uniform, the plastic will melt unevenly. Similarly, in the compression section and the homogenization section, the molten state of the plastic is not uniform, and the wear increases.