Press brakes are used to make bends in thick heavy sheets and to make complex bends in thin materials. There are two types of press brakes: mechanical and hydraulic. Since a large amount of power is required to bend the sheets or plates, the hydraulic presses are usually more appropriate for each job. Hydraulic presses are available in capacities exceeding 50,000 metric tones. They are highly preferable in operations requiring steady pressure throughout the substantial stroke length, wide variations in the stroke length, and high or variable forces.
In order to fully understand the operation of a hydraulic press brake, you need to know how it works. Since hydraulic press brakes are made up of a number of components, keeping track of them all can be difficult. So, here is a basic list of some of the most prominent components.
1. Hydraulic fluid - Hydraulic fluid is transmitted through various parts of the machine. High pressure is exerted on hydraulic fluid by the hydraulic pump, thus creating highly energized fluid. This fluid then travels to the cylinders (actuators) where it delivers its stock of large amounts of energy to the piston, which operates the bending tools. After delivering the energy, the de-energized hydraulic fluid travels back to the pump to regain its energy and continue the operation of the machine. The hydraulic fluid is usually petroleum oil with various additives.
Apart from transferring the energy, the hydraulic fluid also lubricates the various components of the hydraulic press brake and removes the contaminants and metal fittings. The hydraulic fluid should be capable of operating at high temperatures, including a few hundred degrees Celsius, as it gets heated when it receives the energy in the hydraulic pump.
2. Hydraulic pump - The hydraulic pump actually produces the power that energizes the hydraulic fluid and transmits it through the machine to carry out the pressing operations. If a pump has the rating of say 5,000 psi, it can maintain the flow of liquid against the loads of 5,000 psi or it can apply that much pressure. The power density of hydraulic motors is ten times that of electric motors by volume. The hydraulic pump is operated by an electric motor or an engine connected by gears, belts, or flexible couplings. It can be a gear pump, vane pump, axial piston pump, or radial piston pump. The hydraulic pump is the "generator" side of the whole hydraulic press brake system.
3. Actuator - The power contained in the hydraulic fluid is delivered to the actuator, which carries out the pressing operation. There are various types of actuators, but the one used in hydraulic press brake is the hydraulic cylinder. The hydraulic cylinder is comprised of a cylinder barrel and a reciprocating piston. The large amount of energy contained in the hydraulic fluid is transmitted to the piston to carry out the linear work of pressing the metal sheets. The stroke length of the piston can be programmed to vary depending upon the thickness of the metal sheet and angle of the bend. The total stroke length of the piston depends on the length of the cylinder. The forces and pressure of the piston can be accurately controlled, and full pressure is available throughout the entire stroke. During the operation of the presses, the speed can be programmed to vary or remain constant. The hydraulic cylinder is the "motor" side of the whole hydraulic press brake system.
4. Control valves - The control valves direct the hydraulic fluid to the desired actuators. They control the amount of fluid and energy that is transmitted to the actuator. If there are multiple actuators, control valves distribute the fluid evenly among them as per the requirements of the operation.
And there you have it: the four main components in a hydraulic press brake. Now, you should be able to understand more fully the complete inner workings of a press brake system.