Three stages of plastic extrusion

The most important basis for plastic extrusion is the plasticity of the plastic. The plastic forming process in the extruder is a complex physical process, which includes mixing, crushing, melting, plasticizing, venting, compacting and finally shaping. It is worth noting that this process is implemented continuously. However, it is customary that people often divide the continuous process of extrusion process artificially into different stages according to different reactions of plastics, namely: plasticization stage (mixing, melting and homogenization of plastics); molding stage (plastic extrusion Forming); setting stage (cooling and solidification of the plastic layer).

The first stage is the plasticization stage. Also called the compression phase. It is completed in the barrel of the extruder. Through the rotation of the screw, the plastic is changed from a granular solid to a plastic viscous fluid. There are two sources of heat for plastics in the plasticization stage: one is the electric heating outside the barrel; the other is the friction heat generated when the screw rotates. Initially, the heat is generated by the electric heating outside the barrel. After normal driving, the heat is obtained by the friction between the screw and the inner wall of the barrel during the compression, shearing, and mixing process, and the inner wall of the material. Caused by friction.

The second stage is the forming stage. It is carried out in the machine head. Due to the rotation of the screw and the pressure, the viscous fluid is pushed to the machine head, and the viscous fluid is formed into the required extruded materials of various sizes and shapes through the mold in the head. Cover the core or conductor.

The third stage is the finalization stage. It is carried out in a cooling water tank or a cooling pipe. After the plastic extruded layer is cooled, it changes from an amorphous plastic state to a fixed solid state.



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Post time: Apr-10-2021