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The extruder can be divided into single screw, twin screw and multi-screw extruder according to the number of screws. At present, single screw extruder is the most widely used and suitable for extrusion processing of general materials. The single-screw extruder occupies an important position whether it is a plasticizing granulation machine or a molding processing machine. In recent years, the single-screw extruder has developed greatly. The main sign of the development of a single screw extruder is the development of its key component, the screw. In recent years, people have conducted a lot of theoretical and experimental researches on screws. So far, there are nearly a hundred types of screws. Common types are separation type, shear type, barrier type, shunt type and wave type. From the perspective of the development of single screw, although the single screw extruder is relatively complete, with the continuous development of polymer materials and plastic products, more new types of features will emerge.