The invention relates to an expanded metal, comprising: a sheet of expanded sheet metal including openings configured as loops that are essentially introduced without a material loss and which are defined by a loop width, a loop length and a loop shape; and bars that envelop the loops and that are defined by a bar width and a bar thickness, wherein plural loops are arranged in columns behind one another and in rows adjacent to each other. It is an object of the invention to find new applications for expanded metal in the production of automobiles by providing an expanded metal with new properties. The object is achieved by an expanded metal with the features of claim 1, in particular its characterizing features, wherein columns of first loops differ from columns of second loops in a loop width and/or in a loop length so that the sheet of the expanded metal is provided with openings with different loop shapes.

A first roll (20) and a second roll (40) of a roll forming device are provided with a plurality of stacked cutting blades (22, 122) and retainers (21, 121). The retainers (21, 121) pass through the stacked cutting blades (22, 122) and receive a first rotating shaft (16) and a second rotating shaft (18). Projections (21a, 121a) are formed on end portions of the retainers (21, 121). When the cutting blades (22, 122) are stacked, the projections (21a, 121a) control positioning operation of the cutting blades (22, 122). With this constitution, when the cutting blades (22, 122) are joined in a stacked state to the retainers (21, 121), the cutting blades (22, 122) in the stacking direction is controlled with the retainers (21, 121).