From the perspective of the motion principle, the co-directional and the anisotropic meshing and non-engaging type are different in the twin screw extruder.
1. Co-directional twin-screw extruder
There are two types of extruders, low speed and high speed. The former is mainly used for profile extrusion, while the latter is used for special polymer processing operations.
(1) A tight mesh extruder. The low speed extruder has a tight meshing screw geometry in which the helical profile of one screw closely matches the contour of the other screw, ie the conjugate screw profile.
(2) Self-cleaning extruder. The high speed co-rotating extruder has a closely matched spiral profile. The screw can be designed to have a relatively small screw clearance, so that the screw has a closed self-cleaning action. This twin-screw extruder is called a compact self-cleaning co-rotating twin-screw extruder.
2. Counter-engagement twin-screw extruder
The gap between the two screw channels of the tight meshing counter-rotating twin-screw extruder is small (much smaller than the gap in the co-rotating twin-screw extruder), so that the forward conveying characteristics can be achieved.
3. Non-intermeshing twin-screw extruder
The center-to-center distance between the two screws of the non-intermeshing twin-screw extruder is greater than the sum of the two screw radii.