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# Box Bending

Box, Shelf, Panel, Enclosure whichever way you call them, if you're a fabricator you know what I'm talking about.

Those parts with full closure and side legs that hit the ram on the last bend, making us guess:

### How tall of a punch do I need?

The solution for this quest comes from ancient Greece... or from high school geometry if you remember it!!

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If our box has 90° angles (like 99.9% of boxes do) then the side legs intersecting our punch bending line create a right isosceles triangle (green), and the same bending line creates another right isosceles triangle with the upper beam of our PB (brown).

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Either we know how tall our punch is or how tall our side legs need to be. In our example we know:

• H=height of our punch

• h=height of our side leg

• &=45° angle (half of the 90° we're bending our box to)

• W=distance from the bending line to the edge of the ram or clamp hitting the box

Remember Trig rules... SOHCAHTOA.... well, let's just remember the last 3 letters TOA:

Being a right isosceles triangle we know

Tan(&)=1 because a=h (that's why we call them isosceles)

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We also know there's a couple direct relations between b and h

b h x 1.4144....

h(or a) = b x 0.707

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The same trig rules apply to the brown triangle. which means that

W= C (which is the missing height of our punch once we have b

If we know the height of our enclosure side leg (h) and we want to know the height of the upper tool we need, we run the following operation:

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H = (h x 1.4144)+W (h and W are variables we can easily measure)

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If we know the height of the punch and want to know the max height of our box side legs:

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h = (H - W) x 0.707

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