Roll forming, often called open-section forming, uses successive sets of roller dies to bend a strip of steel progressively until the desired shape is achieved. This process is very similar to traditional tube - and pipe making, but differs in that it can form more complicated sections.
Roll formed sections have an advantage over extrusions of a similar shapes. Roll formed parts are generally much lighter and stronger, having been work hardened in a cold state. Another advantage is that the part can be made having a finish or already painted. Labor is greatly reduced since volume is a major consideration for choosing the roll forming process.
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| Roll Forming Machine |
Roll forming lines can be set up with multiple configurations to punch and cut off parts in a continuous operation. For cutting a part to length, the lines can be set up to use a pre-cut die where a single blank runs through the roll mill, or a post-cut die where the profile is cutoff after the roll forming process. Features may be added in a hole, notch, embossment, or shear form by punching in a roll forming line.
Both roll forming and tube and pipe forming involve bending steel with roller dies, with each pair of rolls working the strip progressively until the desired shape is achieved. How roll forming differs is that it lends itself well to prepunching, midpiercing, and postpunching all inline, as well as sweeping before cutoff.
Although the processes are similar and some of the equipment may be the same, there are differences in the design of a roll formed section and the tooling needed and in the layout and setup of the machine.
Process:
The process of roll forming is one of the simpler manufacturing processes. It begins with a large spool of metal strips, usually between 1 in. and 20in. in width, and 0.004 in. and 0.125 in. thick. This is held by a device called a dispenser. The metalstrip is then unrolled and fed into a machine starting with the stock feeder which is connected to the cutoff attachment. After the cutoff attachment, the metal strip is fed into the forming rolls. These mating die-set rolls are constructed to form the desired shape in stages sequentially by means of various shaped rolls. The layout of these rolls can be flower shaped as mentioned previously, progressive upper/lower rolls, side rolls, or as overhung spindle rolls.
