During the extrusion process of the hydraulic system of the aluminum profile extrusion press machine plant line, the master cylinder advances rapidly, the electromagnet is energized, the pressure oil of the pump converges with the pressure oil of the pump and the pump through the lower position of the valve in front of the change-over valve, enters the small cavity of the master cylinder through the left position of the change-over valve, and drives the extrusion rod to move forward quickly (right). At the same time, the pressure oil of the pump enters the cavity of the master cylinder through the outlet check valve and the right position of the change-over valve, so as to move the piston up and open the liquid filling port, The auxiliary oil tank fills the cavity of the master cylinder with liquid.

When the extrusion rod of the aluminum profile extrusion press machine plant line sends the aluminum material into the extrusion barrel, the system pressure increases. When the pressure increases to the set value of the sequence valve and opens, the pressure oil of the pump enters the cavity of the master cylinder through the valve. At the same time, the pressure relay sends a signal to cut off the electromagnet and return the valve to the left position. The liquid filling piston moves down under the action of the spring to close the liquid filling port. At the same time, the electromagnet cuts off the power to unload the pump through the valve, and the electromagnet cuts off the power to separate the left and right circuits. At this time, only the pump supplies oil to the master cylinder, and the action area of the high-pressure oil input into the master cylinder becomes the sum of the cavity area and the cavity area. The master cylinder pushes the extrusion rod forward slowly with a large thrust, and the extrusion speed is set by the opening of the bypass speed regulating valve.

After the extrusion of the aluminum profile extrusion press machine plant line, the electromagnet is powered off, and the directional valve returns to the middle position. The four oil ports of the valve are not connected with each other. The residual high-pressure oil in the master cylinder cannot stop the master cylinder immediately. At this time, the electromagnet is powered off, and the residual high-pressure oil in the master cylinder is unloaded and relieved through the electromagnetic overflow valve (through the oil tank). However, the master cylinder should also maintain a certain pressure in order to make the extrusion barrel retreat smoothly, so the unloading time should not be too long. Generally, the unloading time is set to 2S through the time relay. The pressure relay is used for safety protection during extrusion, that is, once the master cylinder pressure exceeds the set value of the relay, it will send a signal to automatically stop extrusion.

When the extrusion cylinder retreats to the middle position, the solenoid iron is energized, and the pressure oil of the pump enters the master cylinder cavity through the right position of the reversing valve. The master cylinder returns quickly, and the oil in the master cylinder cavity is discharged back to the oil tank through the check valve in the one-way sequence valve and the oil in the cavity through the right position of the reversing valve. If the master cylinder is required to have a higher fast retreat speed, it can also make the second position

The two-way electro-hydraulic directional valve is switched to the lower position to allow the pump to supply oil to the master cylinder together with the pump