The injection device is a device that causes the resin material to be melted by heat and then injected into the mold. The resin is extruded from the head into the barrel as shown, and the melt is conveyed to the front end of the barrel by the rotation of the screw. In that process, the resin material in the barrel is heated by the action of the heater, and the resin is melted under the shear stress of the screw, and the molten resin corresponding to the molded product and the main flow path and the runner is retained. At the front end of the barrel (referred to as metering), the screw continuously feeds the material into the mold cavity. When the molten resin flows in the mold, the moving speed (ejection speed) of the screw must be controlled, and the pressure (pressure maintaining) is controlled after the resin is filled in the cavity. When the screw position and the injection pressure reach a certain value, we can switch the speed control to pressure control.