The characteristic of a co rotating twin-screw extruder is that both the screw and barrel adopt a "building block" design. The screw is composed of several components mounted on the core shaft, such as threaded components, 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).

Based on specific materials, formulas, and performance requirements for the mixture to be prepared, different types and numbers of screw elements and barrel elements are scientifically combined in order to complete the set mixing task. And by changing the combination order of screws and barrels, the optimal use effect of different materials and formulas can be achieved, achieving the goal of one machine for multiple purposes and multiple functions.

In addition, another advantage of modular design is that worn threaded and barrel components can be replaced locally, avoiding the scrapping of the entire screw or barrel and greatly reducing maintenance costs.

The modular design of the machine barrel can be connected by flanges or pull rods, and usually small-sized machines use pull rod connections. The barrel is usually embedded with a bimetallic liner to improve the wear resistance of the inner surface of the barrel. To achieve a temperature history, each barrel has a separate heating/cooling design, thus achieving a combination of cooling and heating functions.

Analysis of Extrusion Process

By combining various threaded components, all co rotating twin-screw extruders have functions such as feeding, melting, mixing, venting, pressure building, and conveying, achieving various processes such as material conveying, plasticization, shearing, venting, pressure building, and extrusion.

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

1) Forced delivery. The twin-screw rotates in the opposite direction during meshing. At the meshing point, the two screws move in opposite directions. One screw pulls the material into the meshing gap, while the other screw pushes the material out of the gap. As a result, the material is transferred from one screw slot to the other screw slot, and the material is forcibly conveyed along the screw in an "∞" shape towards the machine head.

2) Homogenization and mixing. The clearance at the meshing point of co rotating twin-screw is very small, and the speed direction of the screw edge and groove is opposite, with a relatively high relative speed. Therefore, the meshing area has a high shear speed and a large shear force, and the mixing effect is much better than that of single screw extruder and counter rotating twin-screw extruder.

3) Self cleanliness. The co rotating twin-screw extruder has a relatively high shear speed due to the opposite speed direction of the screw edge and groove in the meshing area, which can scrape off the accumulated material adhered to the screw and has a very good self-cleaning effect. This results in a short residence time of the material and is not prone to local degradation and deterioration.

4) Plasticization of materials. The size of screw clearance has a significant impact on the plasticization quality of materials. The smaller the gap, the greater the shear force, but the amount of material passing through decreases; The larger the gap, the more material passes through, but the shear force decreases.

5) Compression of materials. There are many more methods for compressing materials with co rotating twin-screw extruders, and the overall effect is good.

6) Feeding method. The co rotating twin-screw extruder requires uniform and quantitative feeding, using a metering starvation feeding method.

7) Exhaust. Due to hunger feeding, a large lead threaded conveying element can be used to keep the screw groove in an unfilled state and at zero pressure, thus allowing for the installation of an exhaust section.

Scope of use of twin-screw extruder

Filling modification, such as filling CaCO3, Talc, TiO2, etc. with PE, PP, ABS, VA, etc;

process flow

Twin screw plastic granulator process; Raw material weighing ratio high mixing machine spiral automatic feeding machine twin-screw granulator cooling water tank blow dryer pellet cutting machine