| 主权项 |
1. A roll forming method comprising:
receiving a panel at a plurality of roll formers; sequentially forming, via the plurality of roll formers comprising forming portions, the panel into a shaped beam having at least one closed section by
forming a concave surface having a first depth, as formed without breakage, at a surface of a shaped beam;forming a slanted surface having a slanted angle connected to the concave surface;forming the concave surface to have a second depth shallower than the first depth; andrestoring the first depth of the concave surface and the slanted angle of the slanted surface in response to spring back by resistance of the closed section; and sequentially bending, via a round bender comprising a plurality of bending roll units, the shaped beam to have a curvature, wherein the concave surface is formed at a surface of a shaped beam having the closed section at the roll forming step, the concave surface is disposed so as to face toward an inward of a curvature of the shaped beam in the round bender, and the shaped beam is formed to have the curvature through multiple steps such that the concave portion has the first depth at the bending step. |
