PURPOSE: To provide a wide sheet which is provided with a folded part on one part and whose shape precision is excellent.
CONSTITUTION: In a manufacturing method of a wide sheet where the strip is folded in the width direction by a multistage roll forming machine along the single or a plurality of folding lines extending in the longitudinal direction, and the wide sheet with a flat part which is not bent over the wide area, the line length in the longitudinal direction of the strip 20 corresponding to the folded part is larger than that of the strip 20 corresponding to the flat part using a preliminary forming device 10. The preliminary forming device 10 where multistage non-drive type rolls are arranged is used. For example, upper rolls 11-13 of cone-cave shape are arranged opposite to flat lower rolls 15-18, and the penetration is adjusted by the relative movement of the upper rolls 11-13 to the lower rolls 15-18. The difference in the line length in the longitudinal direction cancels the shrinkage in the longitudinal direction of the folded part in the roll forming, and prevents the generation of the wave attributed to the compressive stress in the flat part.
AZUMA TSUTOMU
NOBUTOKI TOMOKAZU
