Roll-forming is a process by which strip is passed through a number of pairs of mated profile rolls. The strip is either unwound from a coil or sheet fed into the machine. Each roll pair is designed to progressively develop a profile by predetermined increments.

Roll-forming is a high productivity process capable of achieving close tolerance control, provide economy in labour and materials and has the ability to produce long continuous lengths and profiles of a complexity beyond the capacity of the press bending process.

In roll-forming, rolls gradually and progressively change the shape of a section, but the thickness of the metal generally remains constant and equal to that of the flat strip being fed into the machine.

Thus it is a bending not a stretching process, nor a rolling process in the usual sense in which a material is squeezed between rolls to reduce thickness. The gap between forming roll surfaces is ideally equal to (in practice always lightly greater than) the overall thickness of the material so that no reduction can take place. In fact, any presence of cold reduction in a roll-forming process is highly undesirable. It is often caused by some malfunctioning such as material pick-up by rolls, incorrect roll setting with regard to height or alignment, bad design or bad manufacture.

Roll-forming machines can produce sections of almost any shape and dimension, consistently and within close tolerances.

Roll-forming equipment, tooling and power usage are relatively expensive. In assessing the viability of roll-forming a profile which could be produced by alternative methods, the following points must be considered: 1. Relative costs of equipment, tooling andlabour, 2. Relative production rates of satisfactory product. 3. Volume requirement.

The variety of products roll-formed from steel strip and their fields of applications in all types of industry are almost infinite. Some idea of the variety of section profiles which can be roll-formed.

When purchasing or setting up a roll forming line, it is very important to have set up charts. These charts should tell the operator: 1. Where the critical alignment points are for string lining 2. Roll gaps for each stage and where to measure these gaps. 3. Alignment procedure for idler rolls. 4. Alignment and setting procedure for shears and other equipment used on the line.