How to specify a profile bending machine

The same profile resists bending very differently depending on how it is oriented against the rolls. An angle with the leg out is not the same job as with the leg in, and a beam bent about its strong axis demands vastly more force than about its weak axis. What rules is the section modulus in the plane in which it is bent: that is why the first thing to define is not only which profile, but in which orientation it will be bent. It is the variable that does not exist in plate rolling, and the one that most confuses specification.

In profiles the radius to achieve is a central specification, not a consequence. The tighter the radius relative to the profile height, the more severe the work. Below a certain radius the profile no longer bends clean: the section distorts, the compressed leg wrinkles, or the machine simply cannot reach it. Defining the real minimum radius —for the working profile and orientation— is what separates a part that comes out round and even from one that has to be scrapped.

Unlike plate, a profile tends to deform its own section as it bends: a tube ovalizes, an angle twists, a channel's flanges open or buckle. In profiles the limit is often not the available force, but keeping the section undistorted, and that depends on the tooling —rolls matched to the profile— and on the guides that stop the part from twisting. A profile bending machine is judged not only by its power, but by its ability to deliver the curve without ruining the section.

As with plate, the material's yield strength and tensile strength define how much force is needed and how much the part springs back when released. In profiles the effect is amplified, because the section geometry concentrates the stresses: a high-strength profile may require several passes and over-bending to compensate for springback. That is why catalog capacities are stated for a reference material, and it is worth verifying them against the real working material.

A profile bending machine usually works with three rolls —one upper and two lower— on which the tooling matched to each profile is mounted. In profiles, the machine's versatility lies as much in its tooling as in its tonnage. Each type and size of profile, and each orientation, requires appropriate rolls and guides; one machine covers a wide range of work only if it has the right tooling set. When specifying, it is worth looking not only at the maximum capacity, but at which profiles and orientations the available tooling resolves. Models and their configurations are detailed on the product page.

Specifying a profile bending machine means describing well the most demanding profile you will bend: its type, its orientation against the rolls, the radius to achieve and the material. With that defined, the conversation stops being about tonnage in the abstract and becomes about the machine and tooling that deliver that radius on that profile without distorting the section. As the representative of AKYAPAK profile bending machines, CYM Materiales supports that definition so the equipment matches the real work.