Screw is the heart of the extruder, is the key component of the extruder, screw performance, determines the productivity of an extruder, plasticizing quality, filler dispersion, melt temperature, power consumption. It is the most important part of the extruder, which can directly affect the application range and production efficiency of the extruder.
Through the action of extreme pressure on the plastic caused by the rotation of the screw, the plastic can be moved, pressurized and obtain part of the heat from the friction in the cylinder, the plastic can be mixed and plasticized in the process of the movement of the cylinder, and the melt in the viscous flow state can obtain the desired shape and shape when it is squeezed and flows through the mouth mold. Like the barrel, the screw is made of a high strength, heat and corrosion resistant alloy.
As there are many kinds of plastics, their properties are also different. Therefore, in practical operation, in order to adapt to different plastic processing needs, the type of screw required is different, the structure is also different. In order to maximize the transport, extrusion, mixing and plasticizing of plastics with maximum efficiency.
The main functions of the screw include conveying solid materials, compressing and melting solid materials, homogenizing, metering and generating sufficient pressure to extrude molten materials.
The diameter of extruder screw increases, and the extruder productivity is proportional to the square of the screw diameter. It also depends on the size of the product being produced.
Screw length-diameter ratio (L/D) : the length-diameter ratio is the ratio of the effective length of the screw part to its diameter. Large L/D, can improve the material temperature distribution, conducive to the mixing and plasticizing of plastics, and can reduce leakage flow and counter-current, improve the productivity of the extruder.