Horn-type punches for press brakes are special tools with a milling cavity. They are mainly designed to bend boxes and lids with enclosed shapes. Find out more about horn punches down in this article.
Horns – where does this name come from?
The name derives from the special tool shapes usually located at the extremes of hornpunches for press brakes. There are situations where they are turned to the inside, especially when making more complicated workpieces, where already bent parts of the workpiece could snag on the punch surface. Milling cavities are special modification to the tool that allows the bent flange to be shifted into the area where the punch body would normally be when bending with standard punches.
In which cases do we use these punches?
A practical application of this type of tools is bending products such as boxes or lids so what is it like with bending boxes? To begin with, a “box” is a product that requires segmented tooling (i.e. a punch and sometimes a die segmented into sections). At Otinus, we meet such requirements as our presses are equipped with segmented tooling.
Why is it the only solution? It is because of bending four sides of a workpiece. It means that one cannot use tools of any length as when bending open-shape parts or sections.
When performing subsequent bending steps, the bent flange resulting from previous operations would hit the standard punch. In this scenario, we need a punch with the exact length as the actual bending length. The safest option is application of punches 5mm shorter than bending lengths because of potential deformation in omitted areas.
In most cases, when making enclosed boxes, segmented tools alone are not enough. Due to the folding or hemming, it is still necessary to use tools with cavities such as horn-type punches.
Application of horn punches
Horn-type punches are used for bending in situations when the upper flange of the box would cause a collision with the punch. An example of such bending is below. Horns are the only solution for bending in such cases which grants the possibility of getting the bent piece out of the working area. Punches of this type can be found, for example, at the Polish tool manufacturer Plasmet.
Boxes with larger flanges (dimensions after bending) require special shaping of the corners. Especially, if the bending boxes or panels will be at angles other than 90 degrees.
As a result, before we start planning to bend the boxes, we need to answer two questions. Firstly, what is the bending sequence (using segmented tools + horns for the last internal bends), and secondly, how to pull the workpiece out of the work area once it has been finished.
By pulling-out-problems, I mean that after making the last planned bend, you cannot always just pull out the workpiece. Removing a part in the similar manner you placed it in a press brake will not work. Oftentimes, you have to turn the workpiece diagonally.
Naturally, even this method is sometimes not enough. Nevertheless, it allows us to remove the horn-type punches so that we are able to pull the bent workpiece out of the working area.
Horn punches with specially milled cavities should be applied where previously made flanges would hit the surface of the standard punch. They allow the workpiece to be produced correctly, without damage, and in addition, they allow the part to be removed freely from the working area of our press brake. Manufacturers are coming up with new solutions step-by-step to make things easier for operators every day. In upcoming articles, I will describe more “special” types of tools.