What is the working principle of plastic extruder?

Screw extruder is one of the most important equipment for plastic molding. It transports, compacts, melts, shears, mixes and extrudes plastic solids through external power transmission and heat transfer of external heating elements. Since its birth, screw extruder has developed from ordinary screw extruder to new screw extruder after nearly a hundred years of development. Although there are many kinds of new screw extruders, the extrusion mechanism is basically the same. The extrusion process of traditional screw extruder is realized by external heating, solid material and barrel heating, screw friction and melt shear force. Friction coefficient, friction force, viscosity and shear stress are the main factors affecting the working performance of traditional screw extruder. Because the factors affecting friction and viscosity are very complicated, the extrusion process of traditional screw extruder is unstable and difficult to control, especially for some heat-sensitive plastics with poor thermal stability and high viscosity. Since the 1960s, scholars all over the world have done a lot of research on the mechanism of screw extrusion and achieved remarkable results. However, because their research is mostly limited to the traditional plastic extrusion mechanism, mechanical structure and energy conversion mode, they have not made a major breakthrough. A series of shortcomings of traditional screw extruder, such as huge volume, high energy consumption, loud noise and difficulty in improving product quality, have not been fundamentally solved.