Hydraulic system of the guillotine shear

Working principle of hydraulic system #

The hydraulic system of the machine (see Figure below) is mainly composed of motor 3, oil pump 2, pressure cylinder 4, main cylinder 5, auxiliary cylinder 6 and valve stack (Bosch-Rexboth).

Hydraulic schematic diagram

The whole system is reasonable.

The system pressure is controlled by the electromagnetic proportional overflow valve 30, and the pressing pressure of the pressing cylinder is controlled by the pressure reducing valve 50 (its change can be controlled by shifting the gears 0, I and II of the pressure adjustment switches installed on the electric cabinet).

The main action process of the machine is as follows:

Tool holder down:

After the oil pump is started, when the electromagnets Y1, Y2 and Y3 are powered on, the pressure oil of the oil pump is divided into two ways.

One way enters the pressing oil cylinder 4 through valves 40, 50 and 140 to drive the piston rod to move downward against the spring force;

The other way enters the upper chamber of main cylinder 5 through valve 60, the oil in the lower chamber of main cylinder 5 enters the upper chamber of auxiliary cylinder 6, and the oil in the lower chamber of auxiliary cylinder 6 flows back to the oil tank through valve 80 and valve 60, which drives the tool holder down.

Carriage return:

When the tool holder reaches the bottom dead center, the electromagnets Y2 and Y3 are powered off and Y4 is powered on.

The oil of the pressing cylinder flows back to the oil tank through valve 140 under the action of spring force.

The pressure oil of the oil pump enters the lower chamber of auxiliary oil cylinder 6 through valve 60 and valve 80, the oil in the upper chamber of auxiliary oil cylinder 6 enters the lower chamber of main oil cylinder 5, and the oil in the upper chamber of main oil cylinder 5 flows back to the oil tank through valve 60 to drive the tool holder return.

Shear angle reduction:

Changing the shear angle is to change the amount of oil in the lower chamber of main cylinder 5 and the upper chamber of auxiliary cylinder 6.

When the oil pump is rotating, when the electromagnets Y1 and y6 are powered on, the pressure oil of the oil pump enters the series cavity of the main cylinder 5 and the auxiliary cylinder 6 through valves 100, 70, 150 and 90.

Because the oil in the upper cavity of the main cylinder 5 is sealed, the pressure oil can only push the piston rod of the auxiliary cylinder 6 down, so as to reduce the shear angle.

The oil in the lower chamber of auxiliary cylinder 6 flows back to the oil tank through valves 80 and 60.

Increase in shear angle:

When the electromagnets Y1 and Y5 are energized, the pressure oil of the oil pump enters the lower chamber of the auxiliary oil cylinder 6 through valves 100, 70 and 110.

Similarly, because the oil in the upper chamber of the main oil cylinder 5 is sealed, the pressure oil can only push the piston rod of the auxiliary oil cylinder 6 upward, thereby increasing the shear angle.

The oil in the series chamber flows back to the tank through valves 90, 150 and 70.

Fault causes and troubleshooting of hydraulic system #

Noisy oil pump #

Causes

1. Pump parts damaged
2. Foreign matter at oil suction port
3. The oil pump is empty due to air leakage in the oil suction pipeline of the oil pump or low liquid level in the oil tank;
4. The oil temperature is too low and the oil viscosity is too high, resulting in excessive oil absorption resistance;

Solutions

1. Replace the pump
2. Check the oil suction port and remove foreign matters
3. Replace the seal of the air leakage part or add enough oil in the oil tank;
4. Replace with low viscosity oil;

The oil circuit cannot build up pressure, and the blade holder does not move #

Causes

The valve core of valve 10 or 60 is stuck or roughened by sundries and does not act.

Solutions

Inspection, disassembly and washing.

The shear angle cannot be adjusted #

Causes

The valve core of valve 10 or valve 70 is stuck or roughened by sundries and does not act

Solutions

Inspection, disassembly and washing.

The tool holder goes down and the pressing oil cylinder does not act #

Causes

The valve core of valve 140 is stuck or roughened by sundries and does not act

Solutions

Inspection, disassembly and washing.