Calculation formula of extruder output and screw speedThe theoretical output of single screw:
Theoretical output Q=0.06 * (screw pitch-screw width) * screw groove depth at the discharge end * (screw diameter-screw groove depth at the discharge end) * pi * melt density * speed.
Among them, the screw pitch, screw rib width, screw groove depth at the discharge end, screw diameter are in centimeters; the speed unit is how many revolutions per minute; the density unit is grams/cubic centimeter; the theoretical output unit is kilograms/hour.
The actual output also needs to consider the material transport efficiency, because there is a gap between the screw and the barrel, there will be backflow, and the amount of backflow depends on the pressure of the machine head and the viscosity of the material, as well as the speed and the size of the gap and many other factors related.
Plastic extruder is divided into twin screw extruder and single screw extruder
The difference between the two extruders:
Single screw machine and twin screw machine: one is one screw and the other is two screws. Both are driven by a motor. The power varies with different screws. The power of 50 cone pair is about 20kW, 65 is about 37kW. The output is related to the material and screw. The output of 50 cone pair is about 100-150kg/h, and the 65 cone pair is about 200-280kg/h. The output of a single screw is only half.
The extruder can be divided into single screw, twin screw and multi screw extruder according to the number of screws. Today, single-screw extruders are the most widely used and suitable for general materials extrusion processing. The twin-screw extruder has less heat generated by friction, more uniform shear on the material, larger screw conveying capacity, more stable extrusion volume, longer material stay in the barrel, and uniform mixing.
The main symbol of the development of single-screw extruder lies in the development of its key part-screw. In recent years, people have conducted a large number of theoretical and experimental studies on the screw. There are now nearly one hundred kinds of screws. Common types are separation type, shear type, barrier type, split type and wave type.
From the perspective of the development of single screw, although the single screw extruder has been relatively perfect, with the continuous development of polymer materials and plastic products, more new types of special screw and special single screw extruder will emerge. Overall, single screw extruders are developing towards high speed, high efficiency and specialization.
The twin-screw extruder has good feeding characteristics, suitable for powder processing, and has better mixing, venting, reaction and self-cleaning functions than the single-screw extruder. It is characterized by processing plastics and blends with poor thermal stability. It also shows its superiority.