Plastic extruders can be roughly divided into single screw extruder, twin-screw extruder and multi-screw extruder. Now single screw extruder is the most widely used, which is suitable for general data extrusion processing. The twin-screw extruder has the advantages of less heat caused by conflict, more uniform shearing of materials, larger screw conveying capacity, more stable extrusion capacity, longer material stay in the barrel and even mixing.
Conical twin screw extruder has the characteristics of forced extrusion, high quality, wide adaptability, long life, small shear rate, difficult material differentiation, good mixing and plasticizing performance, direct molding of powder, automatic temperature control, vacuum exhaust and other equipment. It is suitable for the production of pipes, plates, profiled materials and other products.
Single screw extruder plays an important role both as plasticizing and granulating machinery and as molding and processing machinery. In recent years, single screw extruder has a great development. The diameter of screw is 700mm and the output value is 36t / h.
The primary sign of single screw extruder is the development of its key parts - screw. In recent years, a lot of theoretical and experimental researches have been carried out on screw. Up to now, there are nearly 100 kinds of screw, including separation type, shear type, barrier type, split type and wavy type.

From the development of single screw, although the single screw extruder has been more perfect in recent years, with the continuous development of polymer materials and plastic products, there will be more distinctive new screw and special single screw extruder. As a whole, single screw extruder is developing towards high speed, high efficiency and specialization.
Compared with single screw extruder, twin-screw extruder has better mixing, exhausting, reaction and self-cleaning functions, especially in processing plastics and blends with poor thermal stability. In recent years, foreign twin-screw extruders have been greatly developed. Various types of twin-screw extruders have been serialized and commercialized, and there are many manufacturers. The classification is as follows:
(1) According to the relative orientation of the two axes, there are parallel and conical points;
(2) According to the meshing program of two screws, there are meshing type and non meshing type;
(3) According to the rotation direction of the two screws, there are the same direction and different direction, and in the different direction, there are inward and outward;
(4) According to the screw rotation speed, there are high speed and low speed;
(5) According to the structure of screw and barrel, there are all and combination.

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