Let's talk briefly about twin-screw puffing machines

The twin-screw extruder is a type of multi screw extruder developed on the basis of the single screw extruder. Two screws are placed side by side in the barrel of the twin-screw extruder, hence the name twin-screw extruder.
According to the relative position of the screw, it can be divided into meshing type and non meshing type, and meshing type can be further divided into partially meshing type and fully meshing type;
According to the rotation direction of the screw, it can be divided into two types: co rotation and reverse rotation, and reverse rotation can be further divided into inward and outward rotation. The properties of the pressure zone of co rotating twin-screw are different, and the material is subjected to the rotation of the screw in the sleeve cavity, resulting in a high-pressure zone and a low-pressure zone.
The twin-screw extruder has the advantages of strong adaptability, slip conveying, and self-cleaning, but its structure is complex, the investment cost is high, and the corresponding maintenance and operation costs are also high. Therefore, twin-screw extrusion puffing machines are generally used in the production of high-value aquatic and pet feed, such as eel, turtle, and juvenile fish feed, because the prices of these products sold in the market are sufficient to repay the cost of manufacturing products using twin-screw technology; In addition, some special aquatic feed such as micro particle aquatic feed (with a diameter of 0.8-1.5mm), high-fat aquatic feed, and feed with small production volume but constantly changing formula also need to be produced using twin-screw extrusion puffing machines.
The development of twin-screw extrusion puffing machines in China is relatively late. For medium-sized and above twin-screw extrusion puffing machines, due to the large range of changes in their raw material characteristics, the screw speed needs to be adjusted within a large range. As their working principle is different from that of single screw extrusion puffing machines, there are significant differences in their specific structures, especially in the complex arrangement of the barrel, screw, thrust bearing, and gearbox, resulting in an increase in equipment costs. Two C-shaped material flows are formed along the inner wall of the sleeve, which is the main flow of the material; The other is to form a reverse flow through the gap between the screw engagement parts. The reason for the backflow is that the left screw pulls the material into the gap of the engagement, while the right screw pulls the material out of the gap, resulting in the material advancing in an "∞" shape and changing the direction of the material flow. This not only helps with the mixing and homogenization of materials, but also generates grinding (i.e. shearing) and rolling effects between the teeth of the screw, resulting in rolling effect, which is much smaller than the reverse screw rolling effect.