Roll forming, also spelled rollforming, is a continuous bending operation in which a long strip of sheet metal (typically coiled steel) is passed through sets of rolls mounted on consecutive stands, each set performing only an incremental part of the bend, until the desired cross-section profile is obtained. Roll forming is ideal for producing constant-profile parts with long lengths and in large quantities.
The process of roll forming is one of the simpler manufacturing processes. It typically begins with a large coil of sheet metal, between 1 inch (2.5 cm) and 20 inches (51 cm). in width, and 0.004 inches (0.10 mm) and 0.125 inches (3.2 mm) thick, supported on an uncoiler. The strip is fed through an entry guide to properly align the material as it passes through the rolls of the mill, each set of rolls forming a bend until the material reaches its desired shape. Roll sets are typically mounted one over the other on a pair of horizontal parallel shafts supported by a stand(s). Side rolls and cluster rolls may also be used to provide greater precision and flexibility and to limit stresses on the material. The shaped strips can be cut to length ahead of a roll forming mill, between mills, or at the end of the roll forming line.
The production rate depends greatly on the material thickness and the bend radius, it is also affected by the number of stations or steps required. For bend radii of 50 times the material thickness of a low carbon steel 0.7 inches (1.8 cm) thick can range from 85 feet per minute (26 m/min) through eight stations to 55 feet per minute (17 m/min) through 12 stations or 50 feet per minute (15 m/min) through 22 stations.
In general roll forming lines can run from 5 feet per minute (1.5 m/min) to 500 + depending on the application. In some cases the limiting factor is the punching or cutoff applications.