Bend sheet metal using less force, and with less risk of damaging your press brake
You may have seen “Avatar: The Last Airbender” on the box back home, but we won’t talk about that kind of air bending here.
Air bending – in the world of press brakes – is a special bending technique, which uses less energy than the traditional bottoming would, to perform the same operation.
Basically it is a matter of using a punch with a steeper angle than desired in the bend, and a die with a shallower angle than desired in the bend. Imagine having a thin strip of aluminum. Now support that strip with your index and thumb on your left hand, while pressing down on the middle of the strip with your right hand index finger. You don’t need to press the strip all the way down into the palm of your hand to bend it, right? That is air bending working right there.

If we continue with our analogy – suppose you wanted to use the bottoming technique instead of air bending:
You would now have to press the strip all the way down into your palm, and upon releasing your index finger, you might find that the strip won’t quite hold it’s desired angle – it would come back a few degrees. This phenomenon is called springback, and will happen both with air bending and bottom bending. An inexperienced operator could easily damage his press brake trying to compensate for springback when bottom bending, while the setup for air bending poses less risk to the equipment, and is often simpler to set up. That said, there are times when bottom bending is the right way to do the job, so this technique should be part of the repertoire of any press brake operator.

A few rules of thumb for air bending tooling
To produce a 90 degree bend, you need a punch with a steeper angle – around 85 degrees or so.
You also need a v-shaped die, with an opening width of about 8 times the thickness of the material to be bent,
but at the same time, you want to make sure the tip-radius of the punch is equal to the material thickness.
Please be advised that these are only general rules – to do proper bending with a press brake, you should recruit the help
of an experienced operator.

See the page on press brakes for more general info about this great piece of metalworking equipment.

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