Do you have a second-hand machine for forming sheet metal? You will need dies for a used press brake. Press brakes are known for their complex tooling, which allows precision work without deforming the workpiece. Do you know what the dies of a used press brake look like?
What is a press brake?
Press brakes are machine tools for working sheet metal. These machines carry out processes without metal cutting, as they only deform and bend the material into sheet-metal parts. For good-quality results you need suitable dies for the used press brake in question, as well as punches and other tooling compatible with the machine. It is also important that the machine is operated by an experienced and qualified operator to avoid marks on the surface of the part once it has been formed.
The parts of a press brake
Sheet metal press brakes, whether new or used, are large machines with electronic and mechanical components, depending on the type of machine. They include a bed that must be rigid and stable, because bending forces are high and the machine must not wobble, which would affect the result. They also have a kind of table, where the workpiece is placed.
Two of the most important elements of a press brake are its tooling: the punch and the die. The punch is fitted to the upper, moving part of the machine tool; the die, on the other hand, is fixed to the base of the structure, in line with the punch. The dies on a used press brake are what give the sheet its shape.
How does the sheet metal bending process work?
The sheet is placed between the die, forming an angle, and the punch of the press brake. The punch applies the necessary force to the die to bend the sheet. As you can see, the procedure is very simple, but it also varies depending on the type of bending being done. Cold working does not pose major difficulties; when the sheet is hot, the elastic properties of the material can be lost. That is why it is preferable to have an expert carry out the work.
Types of bending
There are three different types of sheet metal forming. The work depends on the force the punches exert on the dies of the used press brake.
- Bottoming. This type of work does not need much pressure. It is also known as V-bending, because the pressure is applied at three points: the punch radius and the radius of the edges of the V in the die. For this type of bending, dies for used press brakes known as single-V dies are used.
- Partial (air bending). Partial bending occurs when the sheet touches up to three points, similar to bottoming, but the aim is to create different angles. In these cases the pressure between the punch and the die angle is lower.
- Coining. In coining there is no air gap between the die and the punch. Perfect angles with sharp edges are created. A machine tool capable of generating high pressure is required.
Choosing dies for a used press brake
Punches and dies are part of what is known as the tooling of machine tools. The most important thing is to have a good height between the die and the punch, as this avoids many problems during bending. Tall tools make it possible to produce parts with larger flanges. That is why it is so important to know what type of bending will be done on the machine, as well as the characteristics and conditions of the parts.
Machine shops generally choose versatile options, with dies and punches at a 30º angle. Why? Because it allows parts with many different features to be bent, such as angled flanges. However, the operator must be experienced, as a 30º die could completely deform a hole; an 88º die keeps deformation to a minimum.
It is also possible to choose dies for a used press brake with an anti-marking feature. These are fitted with rollers that follow the die throughout the bending process. Their advantage is that they avoid leaving marks on the surface of the part. Choosing this type of tooling for press brakes depends not only on how the machine is used, but also on the tolerances the parts require.
Finally, when choosing dies and punches for a used press brake, check the hardness of the material. This is vitally important, because a high-quality die or punch does not deform over time.