Sheet roll forming method, and running cutter and round bender applied thereto

A sheet roll forming method comprising:

• an uncoiling step for uncoiling a coil by an uncoiler provided at a start of a process line;
• a straightening step for straightening the coil from the uncoiler to be a flat panel;
• a piercing step for forming holes for various purposes in the panel fed from the straightening step by a piercing press;
• a sheet roll forming step for cutting the panel to be a sheet with a predetermined dimension by a running cutter and for successively bending the cut sheet to be a shaped beam by a multi-stage roll forming unit;
• and
• a bending step for curvature forming the shaped beam to be a shaped product by a round bender,
• wherein the round bender comprises a plurality of upper and lower bending rollers equipped to a frame disposed on a base in the process line along a curve with a predetermined curvature radius,
• wherein the lower bending rollers disposed at an outside of the curve from a curvature radius center have a smaller diameter than the upper bending rollers and two of the lower bending rollers are disposed corresponding to one of the upper bending rollers,
• wherein the round bender further comprises a correction means which is disposed at a rear of last ones of the upper and lower bending rollers and corrects curvature variation of the shaped beam,
• wherein the correction means comprises:
• an upper correction roller and a lower correction roller rotatably disposed at a rear of the last upper and lower bending rollers through a slider;
• and
• a servo motor disposed on the frame corresponding to the slider and moving the slider to inside or outside of the curvature radius,
• wherein a diameter of the upper correction roller is always larger than a diameter of the lower correction roller at any portion.