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Structure Principle For Plastic Extruder
Aug 22, 2017

The basic mechanism of extrusion is simple - a screw rotates in the barrel and pushes the plastic materials forward. The screw is actually a ramp or slope that is wound around the center layer. The aim is to increase the pressure to overcome the greater resistance. Is an extruder, there are 3 kinds of resistance to overcome: solid particles (feed) on the cylinder wall friction and screw rotation before laps (feed) the mutual friction between them; melt in the cylinder wall adhesion; melt pushed forward when the resistance of the internal logistics.

Newton once explained that if an object does not move in a given direction, then the force on this object is balanced in this direction. The screw does not move in an axial direction, although it may rotate laterally in the vicinity of the circle. Thus, the axial force on the screw is balanced, and if it exerts a large forward thrust on the plastic melt, it also exerts an equal back thrust on an object. Here, it exerts thrust on the thrust bearing, which acts on the rear of the feed port.

Most single screws are right-handed threads, such as screws and bolts used in woodworking and machinery. If viewed from the rear, they rotate in reverse direction, as they try to spin the cylinder backwards. In some twin screw extruders, the two screws rotate in opposite directions and intersect each other in the two cylinders, so one must be right and the other must be left. In other twin screws, two screws rotate in the same direction and must have the same orientation. However, in either case there are thrust bearings that absorb backward forces, and Newton's principle still hold in this area.

The above reported structure principle of plastic extruder has to be paid attention to in the plastic extrusion technology.