What does the screw of twin-screw extruder do?

Of course, the role of screw in twin-screw extruder is very great. I believe everyone knows that the screw does not move in the axial direction, although it may rotate rapidly in the lateral direction near the circumference. Therefore, the axial force on the screw is balanced. If it exerts a great forward thrust on the plastic melt, it also exerts the same backward thrust on an object. Therefore, the screw is very important for twin-screw extruder, especially the pressure at the end is very important. So what are the specific aspects of this pressure of the screw? This pressure reflects the resistance of all objects downstream of the screw: filter screen and pollution crushing plate, adapter conveying pipe, fixed agitator (if any) and the mold itself. It depends not only on the geometry of these components, but also on the temperature in the system, which in turn affects the viscosity and passing speed of the resin. It does not depend on screw design unless it affects temperature, viscosity and yield. For safety reasons, measuring temperature is very important. If it is too high, the die head and die may explode and hurt people or machines nearby. Pressure is beneficial to mixing, especially in the last area (metering area) of single screw system. However, high pressure also means that the motor must output more energy and the melt temperature is higher, which can specify the pressure limit. In twin screw, the intermeshing of two screws is a more effective stirrer, so no pressure is needed for this purpose. When manufacturing hollow parts, such as pipes made of spider molds with brackets at the core, high pressure must be generated in the molds to help the separated streams recombine. Otherwise, the product along the welding line may be unstable and problems may occur in use.