How Does the Hydraulic System of Press Brake Work?
As important equipment for sheet metal processing, press brakes play an essential role in production. Usually, the press brake is the upper piston type press machine, which is composed of the sliding block, frame, hydraulic system, mold, back gauge and electrical system, etc. (as shown in figure 1)
Two hydraulic cylinders form vertical downward pressure to make the die on the bending beam complete bending process.
The brain of the press brake—the hydraulic control system mainly controls the positioning of the hydraulic cylinder and the synchronous operation of the bending process when the press brake machine is fully loaded.
The typical bending process of the upper bending beam can be divided into 6 parts:
(1) Oil pump
The oil is discharged into the valve plate through the pipeline. Then, the oil returns to the tank through the electromagnetic overflow valve. When the No.19 valve is closed, the oil in the lower cavity of the No.20 cylinder is kept in a fixed position.
(2) Downward movement
For most of press brakes, the bending beam, self-weight of the accessories and the pressure of the oil produce fast descending motion of the press brake. In this process, there is no rod cavity through the filling valve in the hydraulic cylinder. The rod cavity will produce back pressure and the oil will return quickly. The fast forward movement starts from the top dead center.
When the No.9 YV1, No.24 YV6, No.13 YV4 and No.17 YV5 electromagnets are working, the sliding block drops rapidly. The No.18 valve adjusts the descending speed. The oil in the lower chamber of the No.20 cylinder enters the tank through the No.19, No.18 and No.17.
(3) Bending
The bending speed is limited by the quantity of oil. On the other hand, it can be adjusted by the direction valve. At the same time, the direction valve also controls the synchronous operation of the bending beam and the positioning of the lower dead center. The bending force is limited by the proportional relief valve. The speed of the slide drop is adjusted by valve 16. The slide is controlled by No.11 YV3 and No.24 YV6.
(4) Pressure relief
The pressure relief begins when the slide reaches the bottom of the dead center. During the process, the machine will bend plates according to the requirements from the CNC system. Besides, the optimization of the whole process is realized by the proportional directional valve.
(5) Cylinders return
The return also requires the synchronous operation, starting with the pressure reduction of the bar cavity. The No.11 YV3, No.24 YV6 electromagnet start work. Then, the slide returns whose return speed remains constant.
(6) Pressure adjustment
The No.6 high-pressure overflow valve and the No.11 electromagnetic overflow valve are mainly for maintaining the rated power of the press brake. The No.14 overflow valve regulates the return force of the machines in order to prevent the machine from overloading. The working pressure in the hydraulic system can be read from the No.7 pressure gauge. The nitrogen pressure of the No.10 accumulator mainly controls the pressure to operate the valve No.19/ 21.
This passage briefly introduces the hydraulic system of the press brake. If you want to know more knowledge about CNC press brakes and other sheet metal machines, you can follow our facebook and linkedin. We will share you more interesting things about CNC machinery.
