Roll Forming is a system of Sheet Metal Forming. A flat sheet of metal is power fed through a successive series of Rollers, which shape the metal station to station as it passes through them.
The rolls (left) are known as roller dies and are precision made for each job. The above system has 14 roll stations. Each station might have a unique roller die, which progressively bends the sheet metal as it is drawn between the rollers. This allows for very clean forming of the metal into profiles. Of course the shapes are basically straight profiles. Sometime symmetrical, but not necessarily.
The part on left is a good example of a symmetrical roll formed part. The successive rolling through the roller dies allows for profiles that are closed or open. These profiles have enormous application in manufacturing, commercial building, aerospace and other applications. Parts can be fabricated from aluminum through 6 gauge steel (1/2" thick). They are rigid, with very high strength.
Additional operations can "pre-punch" holes in precise locations for mounting holes or to reduce weight of the final shape. "Notching" is another operation that can either punch through or punch part of the metal out from the surface.
Shapes can be cut to precise length after they are done with the "roll forming" part of the system with a "Flying Cut-Off". This style of "Cut-Off" allows for cutting, while the system is still moving the sheet metal through the roller dies, increasing throughput.
A Complete Rollforming system with shape being formed for a greenhouse support in Form Process Engineering's roll forming operations center.