Different uses of the hydraulic press in workpiece machining

The hydraulic press is a very versatile machine tool in the metalworking industry. It has various applications, but its use is not limited to metals: a hydraulic press can be used to work glass, in the pharmaceutical industry it is used to make tablets and in the cosmetics industry, to make make-up powders.

What is a hydraulic press?

A hydraulic press consists of a hydraulic cylinder that creates a compressive force. A hydraulic cylinder, in turn, is a mechanism made up of a cylinder through which a plunger or piston moves; when the plunger moves, the pressure of a liquid (usually oil) is converted into mechanical energy. The movement of this device is linear and serves to provide force.

Hydraulic presses are used in the metalworking industry to transform metals into sheets, plates, foils or slabs, since presses crush a body and leave it flat. They can compress large workpieces and are widely used because they take up much less space than mechanical presses. In addition, depending on the industry in which they are used, hydraulic presses can be manual or automatic.

The hydraulic press is also known as the Bramah press, because its inventor was Joseph Bramah in 1795 and, despite having been devised centuries ago, it is still frequently used in major industries such as metalworking, automotive and even cosmetics.

How does a hydraulic press work?

The hydraulic press has been part of industry for several centuries, thanks not only to the fact that it has managed to adapt and evolve, but also to the fact that it follows a very basic principle of physics. This is Pascal's principle. This principle, applied to the press, states that, in order to work, the pressure throughout a closed system must be constant.

The system will consist of a piston or plunger that acts as a pump and to which a moderate mechanical force is applied, in turn applied to a specific area of small dimensions. In addition, there must be another piston or plunger operating over a larger area and producing a mechanical force.

For this mechanism to work, a confined fluid is required, at constant pressure and acting with equal force in all areas or zones, at 90 degrees to the walls of the container holding it. The fluid in question is usually oil, which is displaced when the pistons move inwards. Since the fluid cannot be compressed, the small piston is able to displace the same volume as the large piston.

Uses of the hydraulic press in industry

The main function of the hydraulic press is the vertical compression of workpieces of different sizes that are difficult to work with at their original size. For that reason it would be necessary to transform them before machining them. Thanks to hydraulic presses, it is also possible to assemble parts: this is one of the main uses they are given in the automotive industry. Here, for example, presses of this type are used to join shock absorbers and brakes, and to fit other parts of the vehicle. This use also extends to the aerospace industry.

This type of machine tool also makes it possible to extract parts without difficulty, as well as to fit them, when the parts are very small or difficult to fit by hand.

The hydraulic press is very fast. This feature means that production line times are reduced, as is pressing time. Hence one of the main advantages of the hydraulic press is the reduction in production times and costs. For example, this machine is used for the rolling and machining of parts, such as making sheets of different metals.

This machine is fast because all that is needed for it to operate is to put the press in its original position and place the material to be worked in the specific part of the press, and then activate the pressing mechanism.

Machining processes

In the field of metalworking, a hydraulic press can carry out many operations, including:

• Punching: a procedure used for cutting sheets or plates of different metals such as stainless steel.
• Bending: this process causes the newly obtained sheet to be transformed or deformed into a completely different part from the one previously created in the hydraulic press itself, but without changing the thickness of the sheet.
• Curving: another procedure carried out in the hydraulic press, which consists of curving a sheet with straight edges by applying intense force to bring about the change.
• Deep drawing, by which the sheet is transformed into a body with a hollow cavity (cylinder).