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Contact：Liu sheng
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Address：Jinlan business building in Changan town of Dongguan City
Common problems
Working principle and structure characteristic of new type screw design
Author：admin Addtion Date：2018-04-16 View：645
Before 70s, the screw extrusion was designed according to the hydrodynamic equation of metering section. At this time, extrusion is influenced by head pressure and is related to viscosity. Several functions of screw -- transportation, compression, melting and homogenization -- are overlapped on the three segments of screw. They affect each other for a variety of reasons. For example, because of the unloosening of the plastic material added, the existence of bridge phenomenon in the hopper and the geometry of the entrance are not reasonable... These factors often lead to the instability of the feeding section and the instability of the plastic compression state, the position of the compression point to a certain pressure is ahead for a while and later later. In addition, the position of the melting point of the plastic on the screw is not only determined by the heat conduction of the cylinder, the condition of the shear heat and the thermal performance of the plastic, but also directly depends on the compression of the plastics, that is, the position of the compression point and the pressure rise. Therefore, if the compression point is swinging on the screw, it is bound to cause the melting point to swing on the screw, and the pressure, temperature and output will fluctuate, and the phenomenon is more serious when the speed is raised. If some measures are taken to improve the above deficiencies, such as the stability of the good feeding through forced metering, the use of mixed original and lengthening measurement sections will reduce the fluctuation of the melt. But some other problems are still not well solved, such as: plastics are not compacted on the screw, and the pressure is slow. In addition to the axial movement of the plastic in the screw, there is a very serious radial sliding, so the transport efficiency is very low, only 0.3-0.5; the extrusion quantity is influenced by the pressure of the machine head and so on. Since 70s, some research workers in the plastic processing Institute of Rheinisch Westfaelische Technische Hochschule Aachen University (IKV) and the BASF of the Ba based aniline soda plant (BASF) have been studied, designed and produced a superior performance extruder. The main feature of this machine is to improve the transmission efficiency of the screw by forced feeding in the screw feeding section. At the same time, the extruding quality is ensured by the mixing original set on the melting section and the measurement section. The three functions of the screw - transport, plasticization and homogenization - are independently completed on the three segment of the screw (Figure 10-40), which overcame the instability and fluctuation of several functions of the common screw.
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