Abstract: A press forming process is composed of a step of removing wrinkles of the surface of a curved elongate flat sheet metal workpiece which has been prepared by a so-called edge bending process. The wrinkle removing step is carried out prior to a U-shape bending step in which the workpiece is bent to have a U-shaped cross-section in order to obtain an curved elongate channel-shaped article, thereby improving the quality of the resulting article while preventing press dies from being damaged.

Abstract: A flat metal strip is placed horizontally on a base plate which is vertically movable between a ram and a bolster of a press. A bending die for bending the metal strip by applying pressure in the widthwise direction is fixed to a slide cam slidable horizontally on the base plate. The slide cam has a slide cam face abutting on a front cam face formed in a drive cam mounted on the bolster. When the ram is moved downwards, a cover plate fixed to the ram covers the metal strip, pushes the base plate and the slide cam downwards, and compels the slide cam to slide horizontally toward the metal strip with the aid of the front and slide cam faces to bend the metal strip with the bending die. On the other hand, the drive cam has a rear cam face abutting on a press cam face formed in a press cam fixed to the ram.