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Do you understand the characteristics of the co-rotating twin-screw extruder? How does it work?

by:TENGDA     2022-12-12

Twin-screw extruder has always been a kind of processing equipment welcomed by material processing manufacturers, because compared with single-screw extruder, its advantages are more obvious. The co-rotating twin-screw extruder is one of the classifications. This extruder has higher conveying efficiency and good self-cleaning ability. It is relatively excellent among twin-screw extruders, so it is also used in processing plants. more. So do you know other features of the co-rotating twin-screw extruder besides the features just introduced? In addition, do you know its working principle? Let’s learn about it together with TENGDA Plastic Extruder Machine Manufacturers.

Features of co-rotating twin-screw extruder:

1. Screw with building block design

The most notable feature of the co-rotating twin-screw extruder is that both the screw and the barrel are made of“Building blocks”design. The screw is composed of several components set on the mandrel, such as threaded elements, kneading blocks, toothed mixing discs, retaining rings, etc.; the barrel is also composed of different barrel sections (fully enclosed, with exhaust port, with feeding port) .

According to the requirements of specific materials, formulations and properties of the mixture to be prepared, through scientific combination, different types and numbers of screw elements and barrel elements are combined in a certain order, so as to efficiently complete the set mixing task. And by changing the combination sequence of the screw and the barrel, the best use effect on different materials and formulas can be achieved, and the purpose of one machine with multiple functions and one machine with multiple functions can be achieved.

In addition, another advantage of the building block design is that worn out thread elements and barrel elements can be replaced locally, avoiding the scrapping of the entire screw or barrel, and greatly reducing maintenance costs.

2. Combined barrel

The modular design barrel can be connected by flange or tie rod, and usually the small machine is connected by tie rod. The barrel is usually embedded with bimetallic bushings to improve the wear resistance of the inner surface of the barrel. For precise temperature history, individual heating/cooling is designed on each barrel to achieve an optimal combination of cooling and heating functions.

3. Extrusion process

By combining various screw elements, all co-rotating twin-screw extruders have the functions of feeding, melting, mixing, venting, pressure building and conveying, and realize material conveying, plasticizing, shearing, venting, pressure building and extrusion. Out of various processes.

Working principle of co-rotating twin-screw extruder:

The structure and function of the co-rotating twin-screw extruder are very similar to the single-screw extruder, but there are great differences in the working principle. Mainly manifested in the following aspects:

1. Forced delivery

The twin-screws rotate in the same direction, and the two screws move in opposite directions at the meshing point. One screw pulls the material into the meshing gap, while the other screw pushes the material out of the gap, so that the material flows out of the groove of one screw. Go to another screw groove, the material is along the screw“∞”The shape is forced to be conveyed in the direction of the nose.

2. Homogenization and mixing

The co-rotating twin-screws have a small gap at the meshing point, and the speed direction of the screw edge and the screw groove is opposite, and the relative speed is large, so the meshing zone has a high shear speed and a large shear force, and the mixing effect is much better than that of a single screw. Screw extruders and counter-rotating twin-screw extruders.

3. Self-cleaning

Co-rotating twin-screw extruder, because the speed direction of the screw edge and the screw groove in the meshing area is opposite, and the relative speed is large, so it has a relatively high shear speed, which can scrape off any accumulated material adhering to the screw, and is very effective. Good self-cleaning effect, so that the residence time of the material is very short, and it is not easy to produce local degradation and deterioration.

4. Plasticization of materials

The size of the screw gap has a great influence on the plasticizing quality of the material. The smaller the gap, the greater the shear force, but the amount of material passing decreases; the larger the gap, the greater the amount of material passing, but the shear force decreases.

5. Compression of materials

The co-rotating twin-screw extruder has many ways to compress materials, and the comprehensive effect is good.

6. Feeding method

The co-rotating twin-screw extruder requires uniform and quantitative feeding, and adopts metered starvation feeding method.

7. Exhaust

Since it is starvation feeding, a large-lead threaded conveying element can be used to make the screw groove not full and in a zero-pressure state, so that an exhaust section can be set.

The above is the introduction of the characteristics and working principle of the co-rotating twin-screw extruder. Compared with the single-screw extruder, its advantages are quite obvious. You can consider the co-rotating twin-screw extruder when choosing in the future. .

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