Roll forming system for forming flanges in strip material

摘要

A V-shaped metal strip has a U-shaped bottom having U-shaped inside and outside surfaces. Only the U-shaped inside surface is formed with a plurality of fold lines extending in a longitudinal direction of the strip and reducing the influence of springback. The fold lines may be arranged in a manner of bilateral symmetry with respect to an imaginary median plane bisecting the V-shaped cross section of the metal strip.