Thread: Press brake punch depth and angle formulas

1. Press brake punch depth and angle formulas

I am building my own controller for a press brake. I want to enter all the tooling dimensions & part thickness & have the controller calculate the die depth penetration needed for a certain angle.

Can a formula be used for this? I would be glad for any pointers!

2. Well, let me try to fill something...
- you can't put inside all tool dimensions because tools are different which means or you need to deal with one manufacturer or to put inside several most common tools. But normally CNC allows just possibility to import .DXF of tool geometry.
- tooling doesn't connected with part thickness, only according to max. tonnage allowance.

3. The equation provided by "local" in a similar post can theoretically provide the tonnage required based upon the material properties and die dimensions except for the fact that the tensile strengths published for materials are "minimum" or "average" and will vary from one sheet of material to another of the same alloy; and, the final bend angle is also controlled by the brake stroke depth setting which must compensate for the "spring back" of the material, which is dependent upon the yield strength of the material and those published values are always "min yield" which insures that your received material will generally always exceed that published value by anywhere up to 15% of of that.

For those reasons, even if you were able to develop a calculation that would predict the results for a given "representative material" it would rarely be accurate for any received piece of material. In a few years of operating a precision metal fabrication shop with a couple of the regions top rated sheet metal mechanics, every bending run started with a sample of the received sheet and an angle gauge to set the the plunge depth required to obtain the required bend angle.

4. Thanks for the replies

I am not interested in knowing the tonnage requirements. Had been hoping there would be a not to complicated way to figure out how far the punch needs to penetrate into the die to bend to a specific angle if I know the die width, sheet thickness etc.. I do realize this can vary from one sheet to the next, but I would be happy with a formula that can get me close.

5. Even ignoring the tonnage the principle issue in getting any usable solution is still accurately calculating the the amount of spring back after load release and this is still dependent upon the combined effects of the tensile and yield strength of the given material. To see a study addressing the complexity of the issue see: http://www.sciencedirect.com/science...07904X08000826

6. We are strictly forming A36 HRPO, with a fairly loose tolerance.

7. If I understood well the request the correct answer will be - position of punch into die to have the desired bend angle, for example 90 degree + additional for springback / material compensation (it is value you should get from material properties, angle of bending, tests etc), so theoretically for example 90 + 1,7 degrees, 1,7 for compensation.
Mainly all fabric manufactured dies are made for 90 deg bending not as 90 deg V but 88/86/85/78 etc. It helps to have air bending even with compensation. Maybe you want some DXF examples? I can spare...

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