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What is the working principle of the twin-screw extruder?

Update:12 Oct 2018
Summary:

From the principle of motion, the co-directional and th […]

From the principle of motion, the co-directional and the anisotropic meshing and non-intermeshing 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) Tightly engaged extruder. The low speed extruder has a tight meshing screw geometry in which the helical rib shape of one screw closely matches the contour of the other screw, ie the conjugate screw profile.
(2) Self-cleaning extruder. High speed co-rotating extruders have a closely matched spiral profile. The screw can be designed to have a relatively small screw clearance to provide a closed self-cleaning action. This twin-screw extruder is referred to as 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.