Working principle of twin screw extruder


Although the structure of the twin-screw extruder is very similar to that of the single-screw extruder, there are great differences between them in the working principle. In the single screw extruder, the power of the material moving forward mainly depends on the difference of the friction coefficient between the material and the barrel and the screw. If the friction coefficient between the material and the inner wall of the barrel is too small, when the screw rotates, the material will hold the screw and rotate together, so that the thread cannot play its role in advancing, and the material cannot be transported forward. This is different in twin-screw extruders, where the two screws mesh with each other. At the engagement, the thread of one screw is inserted into the groove of the other screw, so that the continuous groove is divided into C- shaped cells separated from each other. When the screw rotates, with the axial movement of the meshing part, the C- shaped chamber also moves along the axial direction. For each revolution of the screw, the C- shaped chamber moves forward by a lead distance. Due to the thrust of the meshing thread, the tendency of the material to hold the screw and rotate is hindered and pushed forward by the thread. There is no backflow or stagnation during the transportation process, so it has the greatest forced transportation.

Because the twin screw extruder has the material in the twin screw in the residence time is short and uniform, not easy to produce local degradation and deterioration of the characteristics of the processing material residence time will be heated decomposition, curing or condensation of heat sensitive plastics, such as PVC material coloring, mixing, product production has a unique advantage.

Due to the excellent mixing and plasticizing characteristics of the twin-screw extruder, it is mainly used for polymer modification, such as blending, filler, enhanced extrusion and other operations, and can also directly extrude plates, pipes, profiles and other products.

Twin-screw extruder has a wide range of applications, can be applied to a variety of materials processing, can achieve high yield, high quality, high efficiency and other characteristics, although its structure is more complex, but it still has been widespread attention and rapid development.

In recent years, with the development of synthetic materials, fine chemicals and other new fields, new products and new technologies, the number of special or special state polymers to be treated is increasing, so that the application of twin screw extruder is more and more extensive. At present, the trend of twin screw extruder in the world is to develop in the direction of high torque, high speed and low energy consumption.