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Roll forming is a manufacturing process where strips of metal are bent into a new shape. The metal strip is placed in a series of rollers, each one slightly closer to the finished design. As the metal moves through the machine, each set of rollers bends the metal a very small amount. This prevents any additional deformation from sharp or unexpended bending. While roll forming is more expensive than many other forms of metal shaping, it has an extremely high success rate.
This form of manufacturing is nearly uniformly done with strips of steel. While some processes use other metals, these are a distinct minority. The steel used for these processes is often stored in large rolls shaped like a giant pinwheel. As the machine takes metal for roll forming, the wheel slowly unwinds until it needs replacement by another.
A roll-forming machine takes the strip of metal from the roll. As the metal feeds into the machine it is straightened out and measured for length. At certain preset intervals, the metal strips are cut to accommodate the size of the final product. The size of the roll and the cutting portion of the machine makes the starting side of a roll-forming machine much larger than the rest.
With the exception of the front area, most roll-forming machines are quite long and thin. This is to accommodate the slow and incremental way the machine shapes the metal. Since they take up so much space and have such a specialized design, these machines are only used for processes that will be ongoing. For limited batch processes, smaller and less expensive machines are typically used.
After the metal is in the machine, it encounters a series of rollers. These rollers move the metal forward and, at the same time, create a very small change in its shape. At the end of the process, the metal strip may be a very complex shape, entirely done in tiny steps.
The primary reason for this is to protect the metal. Since the strips used in the machine are so thin, other forming methods have a possibility of damaging the metal beyond recovery. This would result in a large amount of wasted metal, time and money. With roll forming, the changes are so small that the metal is never put under enough stress to actually damage it, even though the final shape contains many folds.
The only drawback to roll forming is its expense. The machines are very large and highly-specialized. This means they are very expensive. In addition, setting up the rollers is a complex process often done by computer, resulting in a long setup or change over time.
It is also important to note that the roll forming process is achieved at cold or room temperature so as not to change the properties of the metal.