Difference Between Twin-Screw Extruder And Single Screw Extruder

The difference between twin-screw extruder and single screw extruder
Transportation method of materials
In a single screw extruder, there is frictional drag in the solid conveying section and viscous drag in the melt conveying section. The friction performance of solid materials and the viscosity of molten materials determine the conveying behavior. If the friction performance of some materials is poor and the feeding problem is not solved, it will be difficult to feed the materials into the single screw extruder. In twin-screw extruders, especially meshing twin-screw extruders, material transportation is to some extent forward displacement transportation, and the degree of forward displacement depends on the proximity of the screw edge of one screw to the relative groove of the other screw. The screw geometry of a tightly meshed counter rotating extruder can achieve highly positive displacement conveying characteristics.
Flow velocity field of materials
At present, the flow velocity distribution of materials in a single screw extruder has been described quite clearly, while the flow velocity distribution of materials in a twin-screw extruder is quite complex and difficult to describe. Many researchers only analyze the flow velocity field of materials without considering the material flow situation in the meshing zone, but these analysis results differ greatly from the actual situation. Because the mixing characteristics and overall behavior of twin-screw extruders mainly depend on the leakage flow that occurs in the meshing zone, however, the flow situation in the meshing zone is quite complex. The complex flow spectrum of materials in twin-screw extruders exhibits macroscopic advantages that single screw extruders cannot match, such as sufficient mixing, good heat transfer, high melting capacity, strong exhaust capacity, and good temperature control of materials.