# Thread: Air bending force calculation

1. ## Air bending force calculation

Hi to all,

First post here, seems like a great forum

I need a formula to calculate the capacity to air bend steel plates with a Pirahna.

I already have a formula to calculate the force required but it has been developped (approximated) for a mild steel application only and I would like one with the possibility to change the material.

Here's the one I found:

P = (575*t^2*L)/D

P : Tons produced by press
t : Thickness of plate (inches)
D : Space between contact point on die (inches)
L : Length of the bend

Reference: Presse brake forming by W. Earl Peters

Thanks

airbending1.jpg

2. Ummm, hate to state the obvious, but why not ask Piranha?

3. I know the capacity of the machine in tons.

now I have a custom die that I have to rate the capacity for this specific operation and for differents materials (44W, CHT100 etc)

I have to produce a chart to state what is the max lentgh of plate that the worker can bend in each thickness.

ex:

44W

Thickness / Max lenght of bend
1/4 / 12''
3/8 / 10''

4. Yes, I got that, but -- wouldn't have Piranha already have gone through those things designing their iron workers around and rate them for different tonnages?

If I worked for Piranha and was asked to design an iron worker, I would map out all that stuff to form a guide of what might be required of, say, a 20-ton machine. It can 90-degree bend 3/8" 5051 aluminum, 3/16" A36 steel... I'd be very surprised if it hasn't all been done before.

Soooooo, asking Piranha tech support could save you a lot of work.

Other than that, I am of no help.

5. For future reference, I found this online calculator. And I emailed Piranha and an engineer sent me the link to the very same calculator.

6. Ummm, kinda what I kept saying? No?

7. Originally Posted by Goingforsound
For future reference, I found this online calculator. And I emailed Piranha and an engineer sent me the link to the very same calculator.
No equations with the related calculator.... Wish they published the math, or did I miss it?

8. No you didnt miss it. Nothing is published :(

9. Here is an expression for the maximum press force F needed to air bend a sheet of length L and thickness t using a V die with an opening width W:

F=1.33*T*L*(t^2)/W

T is the tensile strength of the material. The factor 1.33 accounts for various factors, including friction, and should only be used when tool radius and sheet thickness are small compared to W. Otherwise just consider it a ballpark estimate.

This is from the book, Manufacturing Processes for Engineering Materials, 4th ed, Kalpakjian et al.

10. A lot of calculators presented online and in general any press brake manufacturer normally provide bending table in the manual or attached to the machine

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