Extrusion screw is an important part in plastic machine […]
Extrusion screw is an important part in plastic machine equipment, it is directly related to the plasticizing effect and output of plastic machine.
The material of the extruder screw must have high mechanical strength, be able to withstand huge torsional moments, and have properties that do not deform under high temperature and high pressure conditions.
The rotation of the extruder screw in the barrel is performed under high temperature, high pressure and high torque. Because it strongly pushes the material forward during rotation, it also needs to withstand strong friction and the corrosion of plastic decomposition corrosion gas. Therefore, the extruder screw must have these advantages.
Common problems of extruder screws:
During the rotation of the extruder screw, the plastic is mainly sheared and plasticized by screw edges, and the plastic is pushed forward, so the screw edges will bear huge shear stress and friction.
Due to long-term work under severe conditions, screw ribs wear, screw ribs become smaller, and the gap between the same barrel increases, so the amount of plastic extrusion will be reduced, and in severe cases, plastic backflow will occur, and the plasticizing effect will be reduced, and grains will appear And severe decline in production capacity.
Briefly introduce the process of melt extrusion
The process of melt extrusion is to feed the pre-mixed material from the feeding port into the extruder barrel. The first section of the barrel is the feeding section. The material does not melt at this stage, but is driven by the extruder screw. The material is brought into the second section, which is the compression section. This stage is the heating stage. The material starts to melt and the material The friction between them increases to form a highly viscous body; the third stage that continues to be driven into the high shear with the extruder screw is the homogenization stage. This stage will make it very effective in separating pigment aggregates and achieve sufficient dispersion.
The quality of the extruder directly determines the degree of dispersion of the material
At present, the extruder equipment used in powder coatings is twin extruder screw extruder, single extruder screw extruder and star extruder screw extruder. Although the type of extruder, The internal structure is different, but the design purpose is the same, that is, the material is evenly dispersed to the greatest extent