| Quantity: | |
|---|---|
shengsai
The difference between twin screw extruder and single screw extruder is mainly reflected in the following two aspects.
How materials are transported:
In a single screw extruder, friction drag is used in the solid conveying section and viscous drag is used in the melt conveying section. The frictional properties of solid materials and the viscosity of molten materials determine the conveying behavior. If some materials have poor friction performance, if the feeding problem is not solved, it is more difficult to feed the material into the single screw extruder. In twin-screw extruders, especially meshing twin-screw extruders, the transfer of materials is to some extent a positive displacement transfer, and the degree of positive displacement depends on the proximity of the screw edge of one screw to the relative screw groove of another screw. The geometry of the screw of the tightly engaged cross-rotating extruder can obtain high forward displacement transport characteristics.
Flow velocity field of material:
At present, the flow velocity distribution of the material in a single screw extruder has been described quite clearly, but the flow velocity distribution of the material in a twin screw extruder is quite complicated and difficult to describe. Many researchers just do not consider the material flow in the meshing zone to analyze the material flow velocity field, but these analysis results are very different from the actual situation. Because the mixing characteristics and the overall behavior of the twin-screw extruder mainly depend on the leakage flow in the meshing zone, the flow situation in the meshing zone is quite complex. The complex flow spectrum of the material in the twin screw extruder shows the advantages that the single screw extruder can not compete in the macro, such as sufficient mixing, good heat transfer, large melting capacity, strong exhaust capacity and good temperature control of the material.
1.screw material selection:
The material of the screw is one of the important factors affecting its performance. In general, the material of the screw should be compatible with the processed plastic material, and have good corrosion resistance, wear resistance and high temperature performance. Commonly used screw materials are carbon steel, alloy steel, stainless steel and so on. The specific selection should be determined according to the type of plastic material processed, processing temperature and yield.
2.the length of the screw selection:
The length of the screw is also one of the important factors affecting the performance of the extruder. In general, the longer the length of the screw, the higher the output of the extruder, but at the same time, it will increase the friction resistance of the screw, resulting in increased energy consumption. Therefore, when choosing the length of the screw, it is necessary to make comprehensive consideration according to the actual production needs and equipment specifications.
3.screw diameter selection:
The diameter of the screw determines the output and plasticizing capacity of the extruder. Larger diameter screws have higher plasticizing capacity and yield, but at the same time, they also require greater drive power and higher processing temperatures. Therefore, when choosing the screw diameter, it is necessary to comprehensively consider according to the actual production needs and equipment specifications.
4.screw speed selection:
The speed of screw is one of the important factors affecting the production efficiency of extruder. The higher the speed, the greater the output of the extruder, but at the same time, it will increase the wear and energy consumption of the screw. Therefore, when choosing the screw speed, it is necessary to comprehensively consider according to the actual production needs and equipment specifications.
5. screw design parameters selection:
The design parameters of screw are also one of the important factors affecting its performance. It mainly includes screw lift Angle, lead, compression ratio and so on. The selection of these parameters needs to be comprehensively considered according to the actual production needs and equipment specifications to ensure the normal operation and production efficiency of the extruder.
