Roll forming, also spelled rollforming or roll-forming, is a continuous bending operation in which a strip of metal (typically coiled steel or aluminum) is passed through consecutive sets of rolls, or stands,
each performing only an incremental part of the bend, until the desired cross-section profile is obtained. Roll forming is ideal for producing parts with long lengths or in large quantities with a minimum amount of handling as compared to other types of forming (i.e. press brake).
A variety of cross-section profiles can be produced, but each profile requires a carefully crafted set of roll tools. Design of the rolls starts with a flower pattern (see illustration below), which is the sequence of profile cross-sections, one for each stand of rolls. The roll contours are then derived from the profile contours. Because of the high cost of the roll sets, simulation is often used to validate the designed rolls and optimize the forming process to minimize the number of stands and material stresses in the final product.
Roll forming machines are now being produced so that for similar products with only a change in part width such as stud and track profiles, a new set of profile rolls is not required. This is achieved by the mill being split along its center line and the web, flange and return sizes are set using a control panel that moves the mill rafts centrally to increase or decrease the aforementioned features.
Roll forming lines can be set up with multiple configurations to punch and cut off parts in a continuous operation. For cutting a part to length, the lines can be set up to use a pre-cut die where a single blank runs through the roll mill, or a post-cut die where the profile is cutoff after the roll forming process. Features may be added in a hole, notch, embossment, or shear form by punching in a roll forming line. These part features can be done in a pre-punch application (before roll forming starts), in a mid-line punching application (in the middle of a roll forming line/process) or a post punching application (after roll forming is done).