Differences of Working Principle Between the Co-rotating Twin Screw Extruder and Single Screw Extruder

The structure and function of the co rotating twin screw extruder are similar to that of the single screw extruder, but the working principle is very different. It is mainly manifested in the following aspects:


1. Forced conveying


In terms of meshing co rotating twin screws, two screws in the meshing position move in the opposite direction, and one screw pulls the material into the mesh gap, while the other screw pushes the material out of the gap, causing the material to transfer from one screw slot to another screw slot, and the material is forcefully conveyed along the screw to the head.


2. Homogenization and mixing


There is a small gap in the meshing position of the co rotating twin screws extruder, and the speed of the screw reinforcement and the spiral groove are opposite, so the shear speed in the meshing area is high, the shear force is large, and its mixing effect is far better than that of the single screw extruder and the reverse rotating twin screw extruder.


3. Self cleaning


In the co rotating twin screw extruder, the relative speed is higher because the screw reinforcement and screw groove in the meshing zone have opposite velocity. As a result, it has a very high shear speed, which can scrape off any accumulated material attached to the screw, and has a very good self-cleaning effect, so the dwelling time of the material is very short and is not vulnerable to local degradation.


4. Plasticization of materials


The screw clearance has a great influence on the plasticizing quality of the material. The smaller the clearance, the greater the shear force, but the amount of material through it will be reduced; The larger the clearance, the greater the amount of material, but the shear force will decrease.


5. Material compression


There are many methods of compressing materials for the co rotating twin screw extruder, and the comprehensive effect is good.


6. Feeding method


The co rotating twin screw extruder requires uniform and quantitative feeding and adopts metering hungry feeding method.


7. Exhaust


Because the metering hungry feeding method is adopted, large lead spiral conveying element can be selected, making sure the spiral groove will be in the unfilled state and in the state of zero pressure, so that the exhaust section can be set.

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