Reverse rotation twin-screw extruders

2023-01-18

Reverse rotation twin-screw extruders generally use two screws of exactly the same size, but with opposite thread direction. The difference between inward rotation and outward rotation is the location of the pressure zone is different, twin screw inward rotation of the pressure generated by the upper high and lower low, the material through the twin-screw, the inlet will generate very high pressure, resulting in feeding difficulties, the current inward reverse rotation type is rarely used; twin-screw outward rotation of the pressure generated by the upper low and lower high, conducive to feeding. However, when compared to the counter-rotating twin-screw, the C-shaped material flow formed in the screw cannot be moved from one screw to the other, resulting in a significantly lower degree of material mixing and a less effective and stable self-cleaning capability than the counter-rotating twin-screw.

Reverse rotation twin screw due to the pressure difference between the upper and lower, resulting in the screw to the sides of the separation force F, the screw under the action of F pressed to the barrel, accelerating the barrel and screwwear, and the higher the speed, the greater the F, the more serious the wear, thus limiting the speed of the screw; and isotropic rotation twin screw does not exist to separate the two screw force, so less wear and tear, high-speed operation, and can reach a very high yield, so isotropic rotation The twin screw is widely used.

The source of heat required by the material, in addition to the same part as the single screw, comes mostly from the meshing gap; shearing, squeezing and mixing by the meshing threads, generating heat and homogenising it. The size of the gap has a great impact on the quality of the puffing, with a small gap and a large shear force, but the amount of material passing through is reduced; with a large gap, the amount of material passing through is increased, but the shear force is reduced. Twin-screw forced conveying and self-cleaning properties, so that the material in the barrel of the short residence time and uniform; twin-screw good mixing properties So that the material gets the heat in time to homogenize, accelerate the degree of maturation of the material, reduce the fluctuations in material temperature, improve the yield and quality of puffed products..