The working principle and characteristics of twin-screw extruder

1. Twin-Screw Extruder structure
The matching material is sent to the conditioner through the conveying device, and the material is quenched and tempered by the high temperature steam in the tempering device, and the septic tank enters the expanding mechanism, and is pumped by a pair of parallel meshing screws, from a certain shape of the die hole Instantly cut and cut into pellets.

2. The principle of a twin-screw extruder Expanded
The expansion mechanism of a typical twin-screw extruder is to push the material forward by a pair of screws that mesh with each other in parallel, and the screw is divided into three sections: a conveying section, a compression melting section, and a uniform section. In the conveying section, the material enters the barrel from the hopper, and as the screw rotates, it is conveyed forward along the direction of the groove and is gradually compacted. After entering the compression melting section, the pressure rises due to the change in the spiral structure, and the material is heated by the external heat from the barrel and the material is stirred, mixed and sheared between the two screws and the screw and the barrel. The temperature rises and begins to melt until it is completely melted. As the space of the groove is further reduced, the material is further heated and pressurized, and the cooking is carried out to fully gelatinize the raw starch, a series of complex biochemical reactions such as fat and protein denaturation, and the structure is further homogenized to reach a uniform section, and the splitter plate will be The material from the expansion chamber is evenly distributed to the template. The pressure is usually 3-6 MPa (depending on the expansion requirements) and the temperature can reach 150-200 °C. Because of the high pressure in the closed sleeve, the pressure is higher than that. The saturated vapor pressure at the pressing temperature, so the moisture does not evaporate quickly. When the material is instantaneously extruded from a certain shape of the die hole, the pressure is quickly released, the free water evaporates rapidly, the material expands, and the moisture is quickly lost from the material. The product is quickly cooled to about 80 ° C to be solidified and retained in its expanded shape.

3. Features of twin-screw extruder
The development of twin-screw extruder is relatively late in China. Due to the wide range of properties of the expanded raw material, the screw speed needs to be adjusted within a large range. The working principle is much more complicated than that of the single-screw extruder. Large differences, especially the arrangement of the barrel, screw and thrust bearing gear box are more complicated, resulting in an increase in equipment cost, such as single-screw belt-type transmission, and twin-screw extruder using gear box transmission, both in manufacturing and There are big differences in transmission efficiency.