It is a molding method in which a plastic in a viscous […]
It is a molding method in which a plastic in a viscous state is passed through a die having a specific sectional shape at a high temperature and a certain pressure, and then shaped into a continuous profile of a desired sectional shape at a lower temperature. The production process of extrusion molding is to prepare molding materials, extrusion molding, cooling setting, drawing and cutting, and post-processing of extrusion products (tempering or heat treatment). In the extrusion molding process, it is necessary to adjust the process parameters such as the temperature of the heating section of the extruder barrel and the die of the machine head, the number of revolutions of the screw, the traction speed, etc. in order to obtain a qualified extruded profile. Particular attention should be paid to adjusting the rate at which the polymer melt is extruded from the die. Because when the rate of extrusion of the melt is low, the extrudate has a smooth surface and a uniform cross-sectional shape; however, when the extrusion rate of the molten material reaches a certain limit, the surface of the extrudate becomes rough and tarnished. , shark skin, orange peel, shape distortion and so on. As the extrusion rate is further increased, the surface of the extrudate is distorted, even fragmented and broken into melt fragments or cylinders. Therefore, the control of the extrusion rate is crucial.