In which orientation is a profile bent?

A profile's resistance to bending depends on the section modulus in the plane in which it is bent. Bending a beam or profile about its strong axis —the one of greater inertia— demands far more force than about its weak axis, even for the same part. It is the variable that does not exist in plate rolling, where the surface is flat and has no preferred axes, and the one that most confuses machine requests.

In profiles with legs —angles, channels, T-sections— orientation has a second effect: bending with the leg out of the radius is not the same as with the leg in. Each orientation changes how the section is compressed or stretched, and therefore the profile's tendency to distort, wrinkle the compressed leg or twist. The right orientation depends on the final part and the available tooling, and is best defined before choosing the equipment.

Because the required force changes so much with orientation, a machine can be more than enough for a profile on its weak axis and fall short for the same profile on its strong axis. That is why, when specifying a profile bending machine, saying which profile will be bent is not enough: you must say in which orientation. The rest of the variables —material, minimum radius and tooling— are developed in the article on how to specify a profile bending machine.

Orientation is the variable unique to profile bending, the one that does not appear with plate. Defining which axis each profile will be bent about is what avoids requesting a machine that is oversized in one case and falls short in the other. With orientation clear, the rest of the specification —material, radius and tooling— falls into place on its own.