General Introduction of the Roll Forming Machine

Cluster roll set

Process

Roll forming is, among the manufacturing processes, one of the simplest. 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.

Geometric possibilities

The geometric possibilities can be very broad and even include enclosed shapes as long as the cross-section is uniform. Typical sheet thicknesses range from 0.004 inches (0.10 mm) to 0.125 inches (3.2 mm), but they can exceed that. Length is almost unaffected by the rolling process. The part widths typically are not smaller than 1 inch (2.5 cm) however they can exceed 20 inches (51 cm). The primary limitation is profile depth, which is generally limited to less than 4 inches (10 cm) and rarely larger than 6 inches (15 cm) due to roll-imparted stresses and surface speed differentials that increase with depth.

Tolerances can typically be held within ±0.015 inches (0.38 mm) for the width of the cross-sectional form, and ±0.060 inches (1.5 mm) for its depth.[3]

Production Rates

The production rate depends greatly on the material thickness and the bend radius; it is however also affected by the number of required stations or steps. For bend radii of 50 times the material thickness of a low carbon steel 0.7 inches (18 mm) 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.

The time for one product to take shape can be represented by a simple function: t = (L + n⋅d) / V, where L is the length of the piece being formed, n is the number of forming stands, d is the distance between stands, and V is the velocity of the strip through the rolls. 

In general roll forming lines can run from 5 to 500 feet per minute (1.5 to 152.4 m/min) or higher, depending on the application. In some cases the limiting factor is the punching or cutoff applications.

Other considerations

While dealing with manufacturing, Things to consider are, for example, lubrication, the effect of the process on material properties, cost, and of course safety.

Lubrication provides an essential barrier between the roll dies and the work-piece surface. It helps reducing the tool wear and allows things to move along faster. This table shows the different kinds of lubricants, their application, and the ideal metals to use them on.

The effects of the process on the material's properties are minimal.[clarification needed] The physical and chemical properties virtually don't change, but the process may cause work-hardening, micro-cracks, or thinning at bends when discussing the mechanical properties of the material.

The cost of roll forming is relatively low. When calculating the cost of the process things such as setup time, equipment and tool costs, load/unload time, direct labor rate, overhead rate, and the amortization of equipment and tooling must be considered.

Safety is also a bit of an issue with this process. The main hazards that need to be taken into consideration are dealing with moving work-pieces (up to 800 feet per minute (240 m/min)), high pressure rolls, or sharp, sheared metal edges