How Is a Corrugated Sheet Made?
Corrugated sheets combine the low cost of coiled metal with the support of a ridge-and-furrow cross section. Most commonly used as roofing material, corrugated sheets are fabricated through a process known as cold roll forming.
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Loading the Sheet Metal Coils
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The manufacturer purchases 100-meter rolls of aluminum alloy sheet metal with a width anywhere one and two meters. At the factory, a ceiling-mounted crane slides the roll onto a machine called an uncoiler or pay-off reel. The sheet feeds from the uncoiler into a pair of rollers that squeeze the curve out of the metal, flattening it in preparation for the next step: cold roll forming.
Cold Roll Forming
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The sheet goes from the straightening rollers into a long passage lined with dozens of specially shaped roller pairs called passes. Rather than bend the entire sheet in one pass, roll formers gradually create and deepen ridges onto the sheet through a series of evolving pass shapes. This gradual bending prevents corrugated sheet from developing bows or twists in its final form.
The first pass consists of two rollers: the top roller a smooth cylinder with a 2-centimeter-wide, 1-centimeter-high collar in the center. The bottom roller is a smooth cylinder with a 2-centimeter-wide, 1-centimeter-deep trough in the center. When the sheet rolls through this pass, the interlocking collar and trench of the cylinders form a 2-centimeter-wide, 1-centimeter deep ridge on the sheet.
The second pass will have a center collar/trough slightly larger than the first's as well as two new 2cm-by-1cm collar/trench spaces on either side. This will deepen the sheet's original ridge while forming two new, small ridges.
With each subsequent pass, the collars and troughs increase in number and dimensions until the last pass, at which point the sheet will have reached its final cross-sectional shape.
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Cutting
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After the last pass, the corrugated metal passes through a narrow opening shaped just like the sheet's cross section. Once a pre-set length of sheet has crossed through, a powerful hydraulic press right above the opening severs the metal. Because of the opening's similar shape, the press doesn't flatten the ridges on either side of the cut. The result is a final, individual sheet of corrugated metal.
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