Twin-screw granulator_Jiade_Twin-screw plastic granulator When conducting research on twin-screw extrusion theory, we should also pay attention to the diversity of material movement in order to determine the specific movement form of the material under specific conditions, and target various forms to model separately. 1. 4 Positive displacement in co-rotating twin-screw extrusion It is generally believed that single-screw extrusion is based on the friction drag mechanism, while twin-screw extrusion is based on positive displacement. Positive displacement refers to the distance of one lead that the material in the screw conveyor is forcibly pushed forward in the axial direction during one revolution of the screw. It is only related to geometric factors (such as thread lead) and screw speed, but has nothing to do with the friction between the material and the screw and barrel.
Twin-screw granulator_Jiade_Twin-screw plastic granulator In fact positive displacement requires strict geometric conditions. Twin-screw granulator_Jiade_Twin-screw plastic granulator For example, in twin-screw extrusion, positive displacement is only possible when the screw channel is closed both transversely and longitudinally. But for co-rotating twin-screw extruders, this is impossible. The leakage generated in several gaps and the existence of reverse elements and neutral elements further weaken the positive displacement; on the other hand, in the non-meshing area of the twin-screw, the movement phenomenon and mechanism of the material are exactly the same as those of single-screw extrusion. There are similarities. Therefore, the co-rotating twin-screw extrusion process has both friction drag and positive displacement. Melting in co-rotating twin-screw extrusion is mentioned above. The mechanism of single-screw extrusion is friction drag. At this time, normal extrusion can only occur when the screw
