A common question regarding the bending of beams is how many passes it takes when using a three-roll bender (also called a “section bender” or “angle roll.” The answer (like so many answers) is that it depends.
Modern benders of steel sections can be set to very precise positions with their sophisticated controls and digital readouts. Experience shows, however, that even if the machines are set precisely, beams come out curved differently even with identical settings on subsequent rollings. The variation from piece to piece is due to the varying dimensions of beams and the varying physical properties of beams.
As a result, multiple passes are usually required. After each pass, the machine operator checks not only the radius but also any twisting or other deformation and then adjusts the machine accordingly. So, a beam might be curved correctly in one pass or in three or four or more depending on the material.