How to Properly Select Tools for a Press Brake
In this article, you will learn how to properly select tools for the press brake you operate or plan to purchase.
Properly Selected Tools Are Truly a Recipe for Success!
Selecting the right tools for press brakes is extremely important. It is thanks to them that we achieve the desired shape of the workpiece. They complete the bending process on a properly selected and well-designed press brake. Modern press brakes available on the market allow accuracy that was unimaginable in the past. Tooling for press brakes should not exceed a dimensional tolerance of 0.01 mm, which allows maintaining repeatability and precision.
Bending a C-channel on an Otinus press brake
How to Approach the Topic? – Our Technician Will Clear Up Any Doubts
The selection of appropriate tools should be considered based on production needs. The 8 × 2 rule is helpful here, as it allows you to calculate exactly which dies are required. This solution works especially well if your budget is limited.
Using this rule, you should determine the range of material thicknesses you intend to bend.
The size of the smallest die is determined by multiplying the thickness of the thinnest part you bend in your company by 8.
The largest die is calculated in the same way, multiplying the thickest part by 8.
The sizes of the remaining dies required for production are calculated by doubling the size of the smallest one.
This method allows you to quickly and efficiently determine which tools are the minimum required to perform most upcoming tasks without any issues.
Multi-V die from the Otinus PBO2563 press brake
Meeting customer needs, Otinus equips its press brakes with a universal, multi-V tooling set.
Example of Using the 8 × 2 Rule
The thinnest sheet metal you plan to bend is 1 mm. Therefore, the minimum required V-die width is V = 8 mm.
The thickest sheet metal you will bend on your machine is 10 mm. As a result, the minimum required V-die width is V = 80 mm.
Based on the above data, it is easy to calculate that the minimum set of dies required for your production will include five items.
The set includes the following dies: V = 8 / 16 / 32 / 64 / 80.
If you want to select the tools even more precisely, you should use a press brake tonnage calculator.
A Bit of Practical Knowledge on Selecting Press Brake Tools
To be precise, everything comes down to the bending angle and the bending radius.
It is not possible to bend 8 mm sheet metal to a 90-degree angle using a V32 die, so such an attempt will not comply with air bending technology.
You must consider both the strength of the tools themselves and the structural strength of the material after bending. Defects such as cracking at the bend line or low strength at the bend may occur—especially when bending with a punch radius smaller than what is technologically and structurally permissible.
It turns out that tool strength is not the end of the bending process design. You must also consider the previously mentioned die opening width, selected appropriately for the given sheet thickness.
Bending Thin Sheets? – The Choice Still Matters!
If you want to bend thin sheet metal (e.g. 1 mm) on a large die (e.g. V50) with a large radius (e.g. R20), the part will bend perfectly to the desired angle.
Using a radius selected only according to material thickness (in this case R1 for 1 mm sheet metal) will not produce the expected result. The sheet will be pressed into a wide die opening, which may cause damage or wear and result in dimensions exceeding the assumed tolerances.
Close-up of punch radius R 0.5 mm
Summary – Now You Know How to Properly Select Tools
Step by step, we have explained how to properly select tools for a press brake.
Tool selection for bending is a purely practical part of the process. Even the most theoretically trained specialist may have difficulty selecting the right tool. Everything is based on experience with the bending process itself:
– observing the bent material
– selecting tools to minimize or eliminate damage to both the material and the tools
– bending direction
– proper bending sequence
– introducing corrections (their values and order of execution – sometimes tool design will not allow correction of bend 2 if correction of bend 3 or 4 has not been performed earlier)
That is all when it comes to the theory of selecting bending tools. In practice, a test is almost always performed (either on scrap material or on the actual material included by the technologist or designer in the production batch) to verify the correctness of all planned steps, such as tool selection relative to the material or vice versa.
