Bending thick sheet metal

The bending of thick sheet metal is one of the many material-machining processes that require the application of a high-intensity force to deform the material.

The importance of sheet metal in metalworking

Sheet metal comes as sheets of different gauges or thicknesses, which are widely used in metalworking. With a sheet, for example, machines or car bodies can be built, to give just a few examples. This type of part is made from different materials; so we can find sheets of stainless steel, carbon steel, iron, wood, etc. However, the most widely used in metalworking is stainless steel, because of its versatility.

Indeed, a steel plate can be cut many times to obtain, at the same time, smaller plates of different sizes. Sheets come in widely varying thicknesses; for example, there are stainless steel sheets with a thickness of 1 mm up to sheets with a thickness of 50 mm, which are more difficult to work.

Sheet metal is generally machined using pressing and blanking processes. Cuts can also be made using various machine tools, such as laser cutting and engraving, but one of the most common processes is undoubtedly the bending and folding of these sheets.

Sheet metal is used in all industrial sectors, but curved or folded sheets have a strong presence in industries such as boilermaking.

The process of bending thick sheet metal

The aim of sheet bending is to make a flat part acquire curved edges. To achieve these results, a specific force and intensity is applied to the sheet so that it deforms permanently; the pressure exerted on the sheet varies according to the degree of curvature to be achieved.

For a sheet to bend effectively, certain factors must be met. We start with the elasticity of the material, which may mean that the sheet does not deform or bend permanently but instead returns to its original position. To avoid this, it is important to accentuate the angles where the bend is made and to do so using high intensity and force. In addition, the bending radius is also a decisive factor in these processes, as it bears directly on the thickness of the sheet, because cracks may appear or the part may break after bending.

The last characteristic of sheet metal to which special attention must be paid is the direction in which the grain of the sheet runs; if the bend is made against that direction, the results will not be of good quality.

When the sheet is bent, it can be seen how the metal plate, in this case, expands and compresses to the maximum. This is because the process compresses the inside and expands the outside. Curiously, when this work is done, the particles that make up the sheet change position.

It is important that the process of bending thick sheet metal is carried out by an expert who masters this technique and who is also able to find the neutral axis of the sheet in order to achieve a quality bend.

The press: the machine tool for bending

The machine tool most commonly used for this type of machining is the press, but it is also possible to use special rolls and plates for bending, as well as press brakes for sheet metal.

The press is an ideal machine for hot and cold operations, consisting of a frame on which a bed and a ram are supported; in addition, this machine has a power source and a mechanism through which the ram is moved linearly and at right angles to the bed.

This type of machine is the most suitable for bending thick sheet metal because of the large amounts of energy that these machines are able to produce, which, for this particular work, is of vital importance. For bending or forming functions, for example, presses must be fitted with special tooling such as dies and punches. In the case of bending, some machining workshops opt to use presses with dies, since this increases production speed and saves costs.

There are many types of presses capable of performing different tasks, but the best known are mechanical and hydraulic presses. The former work using an electric motor that produces energy, which is transferred through a clutch or coupling. Hydraulic presses, for their part, are based on Pascal's principle of physics and use a piston, driven by a fluid at high pressure, through which considerable force can be exerted.

It is also possible to find combination presses, in which, for example, the sheet is cut and then bent. These presses always work in two stages, carrying out two processes on the same part.