Double screw extruder detailed introduction

Twin screw extruder is developed on the basis of single screw extruder. Two screws are placed side by side in the barrel of the twin screw extruder. According to the meshing degree of the two screws can be divided into mutual meshing type and non-meshing type. According to the rotation direction of the two screw shafts, it can be divided into reverse rotation type and co-rotation type.
(1) meshing twin screw: Because the meshing gap of the meshing screw is very small, the material has the ability of forced conveying, not easy to produce backflow, leakage phenomenon. It can build up high pressure in a short time, push the material through the various parts of the screw. This kind of matching method, the material flow is stable, the conveying effect is better.
(2) non-meshing twin screw: because the non-meshing twin screw is not fully meshing, the gap between them is large, the conveying capacity of the screw is worse than that of the meshing type, which is easy to produce leakage flow, backflow and material flow instability phenomenon, difficult to achieve the forced conveying effect.
(3) Reverse rotation type twin screw: in the reverse rotation type twin screw, the material into the extrusion screw, the first in
The pressure between the two screws is easy to cause the separation and eccentricity of the two screws, so the friction between the sleeve and the screw is easy to produce, resulting in equipment wear.
Therefore, the speed of the reverse rotating twin screw extruder should not be too high, generally controlled below 50r/min. There is a speed difference between the screw thread and the screw groove at the meshing of the counter-rotating screw, which can produce a certain shear speed. In the process of rotation, the material sticking to the screw will be stripped from each other, so that the screw can be self-cleaning.
(4) twin screw in the same direction of rotation: Because of the opposite direction of rotation of the screw in the meshing, the role of the two screws on the material is not the same. A screw to pull the material into the meshing gap, and the other screw is to push the material out of the gap, so that the material is transferred from one screw to another screw, the change of material flow direction, more conducive to the uniform mixing of materials.
The twin screw rotating in the same direction at the meshing place, the rotation direction of thread and screw groove is opposite, the relative speed is large, the shear force is also large, and it is more conducive to the stripping of adhesive materials, and the self-cleaning effect is better. The twin screw extruder rotating in the same direction is less sensitive to wear because it does not produce the pressure that makes the screws separate from each other. It can work at a higher speed of 300r/min.
In food processing, the most commonly used parallel twin-screw extrusion in the same direction is completely meshing
Machine.