The Structure Principle of Twin Screw Extruder


Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.


The basic mechanism of the extrusion process is simply a screw that rotates in the barrel and pushes the plastic forward. The screw structure is a slope or slope wound on the center layer, the purpose of which is to increase the pressure in order to overcome the greater resistance. As far as the extruder is concerned, there are three kinds of resistance that need to be overcome when working: one is friction, which includes the friction between solid particles (feeding) against the barrel wall and the first few revolutions of the screw (feeding zone) between them. There are two kinds of mutual friction; the second is the adhesion of the melt on the cylinder wall; the third is the internal logistics resistance of the melt when it is pushed forward.


According to Newton's theorem, if an object is at rest in a certain direction, then the object is in a balanced state of force in this direction. For a screw that moves in the circumferential direction, it has no axial movement, which means that the axial force on the screw is in a balanced state. So if the screw applies a large forward thrust to the plastic melt, it also applies a backward thrust of the same magnitude but the same direction to another object at the same time. Obviously, the thrust it exerts is acting on the thrust bearing behind the inlet. Most single screws are right-handed threads. If viewed from the back, they rotate in the opposite direction, and they rotate back out of the barrel by rotating motion. In some twin-screw extruders, the two screws rotate in opposite directions in the two barrels and cross each other, so they must be one right-handed and one left-handed. For bite twin screws, the two screws are the same. The direction of rotation must be the same orientation. However, in either case, there are thrust bearings that can withstand the backward force, which still conforms to Newton's theorem.


If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.

  • QR