Plastic extruder can be divided into single screw extruder, twin screw extruder 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 twin-screw extruder has less heat generated by friction, more uniform shearing of the material, larger screw conveying capacity, more stable extrusion capacity, longer material stay in the barrel, and uniform mixing.
Conical twin-screw extruder has the characteristics of forced extrusion, high quality, wide adaptability, long life, small shear rate, difficult to decompose materials, good mixing and plasticizing performance, direct molding of powder, etc., temperature self-control, vacuum exhaust Gas and other devices. Applicable to the production of pipes, plates, shaped materials and other products.
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. At present, the single-screw extruder for large-scale pelletization produced in Germany has a screw diameter of 700mm and an output of 36t / h.
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 single screw development, although the single screw extruder has been relatively perfect in recent years, with the continuous development of polymer materials and plastic products, new types of screws and special single screw extruders with more characteristics will emerge. On the whole, the single screw extruder is developing towards high speed, high efficiency and specialization.
The twin screw extruder has good feeding characteristics, is suitable for powder processing, and has better mixing, venting, reaction and self-cleaning functions than the single screw extruder. It is characterized by processing plastics and blends with poor thermal stability. Shows its superiority when the material. In recent years, foreign twin-screw extruders have been greatly developed. Various forms of twin-screw extruders have been serialized and commercialized, and there are many manufacturers, which are roughly classified as follows:
(1) According to the relative positions of the two axes, there are parallel and tapered points;
(2) According to the meshing procedure of the two screws, there are two types of meshing and non-meshing;
(3) According to the direction of rotation of the two screws, there are points of the same direction and different directions, and there are points of inward and outward in the different directions;
(4) There are high speed and low speed according to the rotation speed of the screw;
(5) According to the structure of the screw and barrel, there are integral and combined points.