1. Feeding Section: Material enters the feeding section of the extruder from the hopper and is evenly fed into the thread grooves of the twin screws by an agitator or screw conveyor in the hopper.
2. Screw Rotation: The twin-screw extruder consists of two meshing screws that rotate in opposite directions at different speeds (usually the same or slightly different). The rotation of the screws propels the material forward through the thread propulsion.
3. Plasticizing Section: Under the propulsion of the screws, the material gradually enters the plasticizing section. In this section, the material is subjected to the shearing and frictional forces of the screws, as well as heating by the external heating system, gradually melting and plasticizing. The thread shape and pitch design of the screws facilitate material mixing and plasticizing.
4. Mixing and Conveying: The meshing area of the two screws in the twin-screw extruder forms a self-cleaning zone, which effectively prevents material accumulation on the screws and promotes axial and radial mixing of the material. The material is continuously mixed, plasticized, and conveyed within the screw's threaded grooves.
5. Venting Section: Following the plasticizing section, there is typically a venting section to remove gases and volatile components from the material, improving product quality.
6. Forming Section: The plasticized and mixed material finally reaches the forming section, where it is further plasticized and prepared for molding. In the forming section, the material is extruded through a die under specific pressure and temperature to form a continuous product of the desired shape.
7. Discharge and Cooling: The extruded product is cooled and shaped using a cooling device (such as a water tank or air cooler), and then cut or wound by a traction device.
The advantages of a twin-screw extruder lie in its high production capacity, excellent material mixing performance, stable operating performance, and wide range of applications. It is suitable for the extrusion production of various plastics, such as pipes, sheets, profiles, and granules.
