Ultimate Guide: Working Principle of Press Brake Machine part Ⅱ

Hydraulic press brake machines are generally used for sheet bending in industry. It controls the strength according to the system parameters to achieve different bending effects. The structure of the hydraulic bending machine includes a bracket, a table, and a clamping plate. The workbench is placed on a bracket. The workbench consists of a base and a pressure plate. The base is connected to the clamping plate by a hinge. The base is composed of housing, a coil, and a cover plate.

Working principle of the hydraulic press brake machine

1.Start

 All electromagnets must not be electrified, and the output oil of the main pump is unloaded through valves 6, 21.

2. The master cylinder goes down quickly

 The electromagnets 1Y and 5Y are energized, and the valve 6 is in the right position, which controls the oil through valve 8 to open the hydraulic check valve 9.

Oil inlet route: pump 1- valve 6 right position -valve 13 - upper cavity of the master cylinder.

Oil return route: the lower cavity of the main cylinder - valve 9 - valve 6 right position - valve 21 middle position - fuel tank.

The slider of the master cylinder drops rapidly under its own weight. Although the pump 1 is at the maximum flow rate, it still cannot meet its needs. Therefore, the upper chamber of the master cylinder forms a negative pressure. The oil in the upper tank 15 enters the upper chamber of the master cylinder through the filling valve 14.

3. The master cylinder approaches the work-piece slowly and pressurizes

 When the slider of the master cylinder is lowered to a certain position and touching the stroke switch 2S, the 5Y loses power and the valve 9 is closed. The oil in the lower chamber of the master cylinder returns to the tank through the back-pressure valve 10, the right position of valve 6, and the middle position of valve 21. At this time, the pressure in the upper cavity of the master cylinder rises, the valve 14 is closed, and the master cylinder approaches the work-piece slowly under the action of the pressure oil supplied by the pump 1. After contacting the work-piece, the resistance increases sharply, the pressure further increases, and the output flow of the pump 1 automatically decreases.

4. Holding pressure

 When the pressure in the upper chamber of the main cylinder reaches a predetermined value, the pressure relay 7 sends a signal to make 1Y de-energized and the valve 6 returns to the neutral position. The upper and lower chambers of the main cylinder are closed. The tapered surfaces of the check valve 13 and the filling valve 14 ensure a good seal and keep the main cylinder pressure. The holding pressure time is adjusted by a time relay. During the holding pressure, the pump is unloaded via the middle position of valves 6,21.

5. Pressure relief

The holding pressure of the main cylinder's return is over, the time relay sends a signal, 2Y is energized, and the valve 6 is in the left position. Due to the high pressure in the upper chamber of the main cylinder, the hydraulic slide valve 12 is in the upper position, the pressure oil causes the external control sequence valve 11 to open, and the output oil of the pump 1 is returned to the oil tank through the valve 11.

Pump 1 works under low pressure. This pressure is not enough to open the main spool of the filling valve 14, but the unloading spool of the valve is opened first so that the oil in the upper cavity of the main cylinder is discharged back to the upper tank through the opening of the unloading spool. The pressure of main cylinder gradually decreases.

When the pressure in the upper chamber of the main cylinder reaches a certain value, the valve 12 returns to the lower position, the valve 11 is closed, the pressure of the pump 1 rises, and the valve 14 is completely opened.

At this time, the oil intake route: pump 1- valve 6 left position - valve 9 - main Under the cavity.

Oil return route: upper cavity of the main cylinder - valve 14 - upper oil tank 15.

All these can achieve a quick return of the master cylinder.

6. Master cylinder stops in place

When the slider of the master cylinder rises to touch the stroke switch 1S, then 2Y loses power, the valve 6 is in the neutral position, and the hydraulic control check valve 9 closes the lower cavity of the master cylinder, and the master cylinder stops in its original position. The output oil of pump 1 is unloaded through valves 6 and 21.

7. Lower cylinder ejection and return

 3Y is energized and valve 21 is in the left position. Oil inlet route: pump 1 - valve 6 center position - valve 21 left position - lower cylinder lower cavity. Oil return route: upper cavity of the lower cylinder - left position of valve 21 - fuel tank. The lower cylinder piston rises and ejects.

3Y loses power, 4Y gets electricity, valve 21 is in the right position, and the lower cylinder piston goes down and retracts.

8. Floating press edge

After the lower cylinder piston rises to a certain position, the valve 21 is in the neutral position. When the main cylinder slider is pressed down, the lower cylinder piston is forced to go down with it. The oil in the lower chamber of the lower cylinder is returned to the oil tank through the throttle 19 and the backpressure valve 20 so that the lower chamber of the lower cylinder maintains the required pressure of pressing edge. And the adjusting valve 20 can change the floating press edge pressure. The upper cavity of the lower cylinder is replenished oil from the fuel tank through the middle position of the valve 21. The relief valve 18 is a safety valve for the lower cavity of the lower cylinder.

BLMA Machinery is a professional press brake manufacturer and has 32 years of experience in the production of press brake machines. It provides high-quality NC press brake machines and CNC hydraulic press brake machines. If you have any needs, please contact us.