The basic working principle of the injection machine can be understood as that after plastic raw materials are uniformly plasticized in the barrel, the injection products are formed after injection, flow filling, pressure maintaining, and cooling.

An automatic injection molding machine is a process test instrument used in the fields of material science and mechanical engineering.

Full-automatic, semi-automatic, manual, and inching four production modes; Plasticizing, injection, automatic heating of barrel, protection of low-pressure mold, automatic cleaning of the barrel, selection of ejection mode, and alarm of injection shortage.

Under the action of the screw, the granular plastic stored in the hopper keeps moving along the screw groove. 

Due to the combined action of the external heat of the barrel and the shear of the screw, the plastic is continuously heated and softened and finally becomes a molten viscous flow state. 

At the same time, the force of molten material at the screw head pushes the screw back. By changing the screw back pressure (working oil back flow resistance), the screw retreat speed can be adjusted, and the plastic flow in the screw groove can be changed, so as to finally achieve the purpose of controlling the plasticizing performance of plastics. 

For example, increasing the back pressure can improve the homogenization of the melt and raise the melt temperature, which will inevitably affect the conveying capacity of the screw. When the screw retreats, its actual working length changes, resulting in a decrease in plasticizing capacity. At the same time, the temperature of melted plastic has a large deviation in the axial direction of the screw and increases with the increase of injection stroke and screw speed. 

Therefore, by using the linear relationship between back pressure and melt temperature, the back pressure can be dynamically adjusted according to the actual melt temperature to compensate for the axial temperature difference caused by the shortening of the effective length of the screw during pre-molding.

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