Roll forming, also known as roll forming or roll forming, is a rolling process that involves the continuous bending of a long strip of sheet metal (usually coiled steel) into a desired cross section. The strip is passed through multiple sets of rolls mounted on successive stands, with each set performing only incremental portions of the bend until the desired cross section (profile) is achieved. Roll forming is ideal for producing long parts with large lengths and large quantities of constant profile.

Overview

A variety of cross-sectional profiles can be produced, but each requires a carefully crafted set of roll tools. Roll design begins with a pattern, which is a sequence of profile cross sections, one for each set of rolls. Roll profiles are then derived from the pattern profiles. Because roll sets are expensive, computer simulations are often used to develop or validate roll designs and optimize the forming process to minimize the number of rolls and material stresses in the final product.

Roll-formed profiles may have advantages over similarly shaped extruded profiles. Roll-formed parts may be lighter, have thinner walls, and are stronger because they are work-hardened in the cold state than parts from the extrusion process. Parts can be finished or painted. In addition, the roll forming process is faster and uses less energy than extrusion.

Roll forming machines can produce shapes of varying sizes and material thicknesses using the same roll mill. Size changes are achieved by changing the distance between the rolls through manual adjustment or computer control, allowing for quick changeovers. These specialized mills are very common in the light framing industry, which uses metal posts and rails of standardized profiles and thicknesses. For example, a single mill may be able to produce metal posts with different web (e.g., 3-5/8 in. to 14 in.), flange (e.g., 1-3/8 in. to 2-1/2 in.), and lip (e.g., 3/8 in. to 5/8 in.) sizes from galvanized steel sheets of varying gauges (e.g., 20 to 12 GA).

Roll forming lines can be set up in a variety of configurations to punch and cut parts in a continuous operation. To cut parts to length, the line can be set up to use either a pre-cutting die, where individual blanks pass through the roll mill, or a post-cutting die, where the profile is cut off after the roll-forming process. Features in the form of holes, grooves, reliefs, or shears can be added by punching on the roll-forming line. These part features can be completed in a pre-punching application (before roll-forming begins), a mid-line punching application (in the middle of the roll-forming line/process), or a post-punching application (after roll-forming is complete). Some roll-forming lines incorporate only one of the above punching or cut-off applications, while others integrate some or all of the applications in one line.

The Process

Roll-forming is one of the simplest of the manufacturing processes. It typically starts with a large coil of sheet metal, ranging in width from 1 inch (2.5 cm) to 20 inches (51 cm) and thickness from 0.004 inches (0.10 mm) to 0.125 inches (3.2 mm), supported on an unwinder. The strip is fed through entry guides to align the material properly as it passes through the rolls of the mill, with each set of rolls forming a bend until the material reaches the desired shape. The sets of rolls are usually mounted one after the other on a pair of horizontal parallel shafts supported by a stand. Side rolls and multiple sets of rolls can also be used to provide greater precision and flexibility and to limit stress on the material. The formed strip can be cut to length before the roll former, between rolls, or at the end of the roll forming line.

The Process

Roll forming is one of the simplest of the manufacturing processes. It usually starts with a large coil of sheet metal, ranging in width from 1 inch (2.5 cm) to 20 inches (51 cm) and thickness from 0.004 inches (0.10 mm) to 0.125 inches (3.2 mm), supported on an unwinder. The strip is fed through entry guides to align the material properly as it passes through the rolls of the mill, with each set of rolls forming a bend until the material reaches the desired shape. The sets of rolls are usually mounted one after the other on a pair of horizontal parallel shafts supported by a stand. Side rolls and multiple sets of rolls can also be used to provide greater precision and flexibility and to limit stress on the material.The formed strip can be cut to length before the roll former, between rolls or at the end of the roll forming line.