The difference between single screw extruder and twin-screw extruder

The main differences between a single screw extruder and a twin-screw extruder lie in the material conveying method, material flow velocity field, feeding performance, mixing and plasticizing ability, exhaust performance, energy consumption, and application fields. ‌
Material conveying method: Single screw extruders mainly rely on friction drag for material conveying, while twin-screw extruders, especially meshing twin-screw extruders, have a certain degree of forward displacement conveying for material conveying. The tightly meshing screw geometry can achieve high forward displacement conveying characteristics.
Material flow velocity field: The material flow velocity distribution in a single screw extruder is relatively clear, while the material flow velocity distribution in a twin-screw extruder is complex and difficult to describe, because the mixing characteristics and overall behavior of the twin-screw extruder mainly depend on the leakage flow occurring in the meshing zone.
Feeding performance: The twin-screw extruder uses the principle of positive displacement to transport materials without pressure reflux, making it easy to feed and suitable for adding high or low viscosity materials, as well as materials with a wide range of friction coefficients with metal surfaces.
Mixing and plasticizing ability: The twin-screw extruder has excellent mixing and plasticizing effects. The two screws mesh with each other, allowing the material to undergo more complex movements during the extrusion process and withstand longitudinal and transverse shear mixing.
Exhaust performance: The twin-screw extruder has excellent exhaust performance. Due to the effective mixing of the meshing part and the self-cleaning function of the exhaust part, the material can achieve complete surface renewal in the exhaust section.
Energy consumption: The twin-screw extruder has a lower specific power consumption because its screw length and diameter are relatively short, and the energy of the material is mostly input from external heat; The length to diameter ratio of the screw in a single screw extruder is 20-30% larger, so the energy consumption of a twin-screw extruder with the same output is 50% lower than that of a single screw extruder.
Application areas: Single screw extruders are mainly used for the production of pipes, sheets, profiles, and other fields; Twin screw extruders are widely used for physical and chemical modification of matrix resins, such as filling, strengthening, toughening, reactive extrusion, etc.
In summary, twin-screw extruders are superior to single screw extruders in terms of feeding performance, mixing plasticization ability, and exhaust performance, and single screw extruders are more common in the production of simple plastic extrusion plates.