In this article you will learn how to correctly choose tooling for press brakes we either operate or intend to purchase.
Selecting the proper tooling is essential for press brakes. Thanks to the tool application we obtain the desired shape of processed parts. It completes the process of bending using well designed and correctly matched press brake. Today, the market allows for achieving an accuracy that was unimaginable in the past. The press brake equipment should not exceed the dimension tolerance in the range of 0.01 mm which allows to maintain the repetitiveness and precision.
We need to consider the choice of tools based on the needs of our production. Here, we can help out ourselves by applying the rule of 8 x 2, (which we will describe later) that allows us to determine accurately what dies we need. This solution will do especially when our budget is tight.
By using this rule we first need to define what material thickness we want to bend. The size of the smallest die can be estimated by multiplying the thickness of the thinnest material we use in our company. Analogically, to estimate the largest die size, we need to multiply the thickness of the thickest material by 8.
The sizes of other grooves are estimated by multiplying the smallest groove width by 2.
Hence this method allows us to quickly and effectively determine the tool sizes that can help us out to do our upcoming tasks with little effort.
To meet our Clients’ expectations the Otinus company equips their press brakes with a universal multi V-die toolset.
The thinnest sheet metal we intend to bend is 1mm thick. Therefore we need to apply a V=8mm wide lower die.
The thickest sheet we intend to bend is 10mm thick. As a result, the maximum width of the lower die we need should be V=80mm.
From above data it is easy to calculate that the minimum size of lower dies would include 5 dimensions. The set would consist of the following grooves V=8/16/32/64/80.
If we want to choose tooling more accurately we should use the calculator of bending force for press brakes.
To be precise, everything is based on the bending angles and radii. Using the V32 lower die you cannot bend an 8mm thick sheet at an angle of 90 degrees. Moreover such an attempt would be noncompliant with the principle of air bending technology.
Here, we must consider the durability of tools as well as the structural strength of materials as bending with improper tooling may result in fracture and inferior structure strength at the bending length of a part. Especially, when we apply upper dies with radii smaller than acceptable by technology and structure principles, it appears that considering the strength of tools is not the end of the design process. We must also have regard to the mentioned above width of grooves matched in accordance with the sheet thickness.
If we intend to bend thin sheets, for example 1mm thick, and at the same time want to obtain high radii (e.g. R20) using lower dies with wide grooves (e.g. V50), the result of such processes will be perfect angle values. On the contrary, when applying punches with radii relevant to the sheet thickness (in this case, R1 for sheet metal 1mm thick), we cannot complete the part according to our expectations; the sheet would be pushed against the too wide die resulting in damage/tearing and exceeding the tolerance.
We have talked about how to correctly match tools for press brakes step-by-step.
The right choice of tooling for press brakes is a frequent part of the operational process. Even the most skilled theoretician may struggle determining the choice of right tools.
Everything is based on one’s experience with the bending process which includes:
-examination of a bent part;
-selecting tooling to minimize needed material for workpieces and eliminate tool failures;
-applying corrections (for values and operational sequences.
For example some tooling do not allow performing a correction of the second bend if you do not make correction of the third and forth bend in the operational sequence.
This is it, if it comes to the theory of tool matching for bending. In practice, a testing operation is always performed beforehand (either on a remnant or the correct material added by the technologist or designer to the series of parts being made) to check the compatibility of all planned steps, e.g. the selection of tooling for the material or vice versa.
