The difference between twin-screw extruder and single-screw extruder

Extruders can be divided into single screw, twin screw and multi-screw extruders according to the number of screw. At present, single screw extruder is the most widely used and suitable for extrusion processing of general materials. The twin screw extruder has the advantages of uniform shear of heat generated by friction, large screw conveying capacity, stable extrusion volume, long residence time of materials in the barrel and even mixing.

Single screw machine and twin screw machine: one is a screw, one is two screw. They are driven by a motor, and the power varies with the screw. The power of 50 cones is about 20 kW and that of 65 is about 37 kW. The yield of 50 cones and 65 cones is about 100-150 kg/h and 200-280 kg/h respectively. The output of single screw is only half.

Single screw extruder plays an important role in both plasticizing and granulating machine and forming and processing machine. In recent years, single screw extruder has made great progress. The single screw extruder produced in Germany has a diameter of 700 mm and a output of 36 t/h. The main sign of the development of single screw extruder lies in the development of its key parts - screw. In recent years, a large number of theoretical and experimental studies have been carried out on screw. Up to now, there are nearly 100 kinds of screw, such as separation type, shear type, wavy type and so on. From the point of view of single screw development, although single screw extruder has been relatively perfect, with the continuous development of polymer materials and plastic products, there will emerge more characteristic new screw and special single screw extruder. Generally speaking, single screw is developing in the direction of high efficiency and specialization.

Twin-screw extruder has the characteristics of forced extrusion, high quality, wide adaptability, long life, low shear rate, difficult decomposition of materials, good mixing and plasticizing performance, powder direct forming, temperature self-control, vacuum exhaust and so on. Suitable for pipe production.

Twin-screw extruder has good feeding characteristics and is suitable for powder processing. It has better mixing, exhaust, reaction and self-cleaning functions than single-screw extruder. It is characterized by its superiority in processing plastics and blends with poor thermal stability. In recent years, extruders have been greatly developed. Twin-screw extruders of various forms have been serialized and commercialized, and there are many manufacturers, which can be roughly classified as follows:

(1) According to the relative position of two axes, there are parallel and conical.

(2) According to the meshing procedure of two screw, there are meshing type and non-meshing type.

(3) According to the rotation direction of the two screw, there are homo-directional and hetero-directional, and in hetero-directional, there are inward and outward.

(4) According to the rotating speed of the screw, it can be divided into high speed and low speed.

(5) According to the structure of screw and barrel, there are integral and combined parts.

On the basis of twin-screw extruder, in order to process blends with poor thermal stability more easily, some manufacturers have developed multi-screw extruders and so on.