Differences in working principle between co-rotating twin-screw extruder and single-screw extruder
Twin-screw extruder is the most common machinery in the modified plastics industry. It is widely used in the polymer processing industry and other production and processing fields. There are many types of twin-screw extruders, which can be divided into two types: meshing type and non-engaging type. The meshing type twin-screw extruder can be divided into two categories: the same direction rotation and the opposite direction rotation.
Differences in working principle between co-rotating twin-screw extruder and single-screw extruder
The structure and function of the co-rotating twin-screw extruder are similar to those of a single-screw extruder, but there are significant differences in the working principle. Mainly in the following aspects:
1) Forced delivery. Engaging the twin-screw in the same direction, the two screws move in opposite directions at the meshing position, one screw pulls the material into the meshing gap, and the other screw pushes the material out of the gap, so that the material is from a screw channel Going to another screw channel, the material is forced to convey along the screw in the direction of the head.
2) Homogenization and mixing. The co-rotating twin-screw has a small clearance at the meshing point, and the speed direction of the spiral rib and the groove is opposite, and the relative speed is large, so the meshing zone has a high shearing speed, the shearing force is large, and the mixing effect is much better than the single. Screw extruder and counter-rotating twin-screw extruder.
3) Self-cleaning. The co-rotating twin-screw extruder has a relatively high shear speed due to the opposite direction of the speed of the rib and the groove of the meshing zone, and can scrape off any accumulated material adhering to the screw. Good self-cleaning effect, so that the residence time of the material is very short, and it is not easy to cause local degradation and deterioration.
4) Plasticization of materials. The size of the screw gap has a great influence on the quality of material plasticization. The smaller the gap, the greater the shear force, but the amount of material passed is reduced; the larger the gap, the greater the amount of material passed, but the shear force is reduced.
5) Compression of materials. The method of compressing materials in the co-rotating twin-screw extruder is much more, and the comprehensive effect is good.
6) Feeding method. The co-rotating twin-screw extruder requires uniform and quantitative feeding, and adopts a metered hunger feeding method.
7) Exhaust. Due to the hunger feeding, a large lead threaded conveying element can be used, so that the groove is in an underfill state and is at a zero pressure state, so that the exhaust section can be set.
