The hydraulic control form of the CNC bending machine requires a high degree of automation and a standard rate of production. For this reason, the press brake should have a high integration rate of the hydraulic system into the machine. The frame thus becomes the basis for the installation of the hydraulics and through which the oil tank is integrated into the stamping frame. This integration rate is also different for various users with different requirements.
There are generally two styles as follows:
Three control valve block
This style has three control valve blocks. The two main control valve blocks with their associated intermediate plate filling valves are directly installed on the hydraulic cylinder to realize the pipeless connection between the main control block and the hydraulic cylinder.
The main control valve block
The main control valve block mainly consists of a proportional directional valve, a directional valve with position monitoring, and a back pressure cartridge assembly.
The proportional reversing valve plays a key role in the bending machine. Together with the CNC, it determines the moving direction, speed, synchronization accuracy, and positioning accuracy of the upper bending beam.
The current range of control blocks is equipped with proportional directional valves with integrated electronic amplifiers, which can be controlled directly by the CNC.
The back pressure component (generally composed of a reversing valve and two relief valves) is a non-leakage type corresponding to the customer’s requirements. The oil suction valve is responsible for the oil filling of the rodless cavity in the fast forward and the return of the large flow oil in the rodless cavity in the return stroke.
Pump control block
The above two control blocks plus the third control block, the pump control block, form a complete three-control valve block structure. The main installations here are the proportional relief valve and a maximum pressure shut-off valve, as well as a position-sensing directional valve that acts as a pilot valve for the charging valve. The proportional relief valve sets the maximum stamping pressure according to the given value of the numerical controller, and the manually adjustable relief valve connected in parallel is responsible for the pressure insurance of the whole system, especially for the excessively high given value from the numerical controller on the pump value.
The typical three-control block hydraulic system diagram is as follows:
Central control block
The central control block type is to combine three control valve blocks into one control block. It is mainly used in bending machines of some special structures (such as the case where the machine height is limited).
Due to control reasons, the connecting pipes between the control block and the two stamping hydraulic cylinders must be arranged symmetrically, and it must not exceed the maximum allowable distance between the two hydraulic cylinders (about 3m). Therefore, the central control block should be arranged as far as possible in the machine the center.
The control block is connected to the hydraulic cylinder through pipes. In this style, a flanged filling valve is used, which is directly installed on the hydraulic cylinder and has an oil suction pipe connected to the oil pipe. The compact structure of the filling valve is suitable for bending machines with a very low overall height.
A typical central control valve-type hydraulic system diagram is as follows:
