Steel section bending, whether it is curving angles, bars, beams, channels, tees, or other sections, most always requires extra material at the ends of the rolled material. This extra material goes by several names: “trim,” “waste,” “pick-up,” “tangent,” “grip,” “run-off,” and “lead in” and “lead out.”
If the steel section is being curved on a three-roll bender (also called a “profile bender,” a “pyramid roll,” or simply an “angle roll”), extra material equal to the distance between the two back or bottom rolls would be required.
There are circumstances, however, where this calculation would not apply. For example, when doing extremely tight bending of, say, an angle, more pick-up might be required because there may be deformation as the member begins to be formed. Alternately, when curving, say, a large tube over a very large radius, if there is no deformation at all, the result could be more usable arc length. Also, no grip is required when cambering a steel section.
The amount of pick-up can also be reduced by grouping multiple pieces within longer lengths of material. Lengths beyond 100 feet can be curved and then shorter sections cut out with the only waste occurring at each end of the long member. And if straight tangents are required at the ends of the curved sections, then only minimal, if any, trim is required.
Because of the variation in equipment, operator skill, shop capacity, and methodology, different companies have different capabilities for reducing the waste that is generated by trimming. It is best to contact the companies who specialize in this service to determine how much material will be required.
