Flattened Expanded Metal
Although the difference between the standard and flattened metal expansion may seem slight, it makes a significant impact. The major difference is in the bond, the interconnected metal pieces that frame the openings. Standard expanded metal has a raised, textured and rough bond whereas flattened bonds are smooth and flat. Heavy duty flattened
expanded metal sheets are more popular in the construction of walkways, ramps, catwalks, bridges and gangways where the texture of standard metal would create unnecessary friction or impede the movement of shelving or rolling equipment. The benefits are, however, much the same as standard expanded metal.
Expanded metal is stronger, lighter and more rigid than the original material. Additionally, flattened expanded metal allows for varying degrees of light, water and air to pass through them for improved circulation, visibility and fire safety. Compared to solid sheet metal, materials having undergone the expansion processes are also more easily formed, making customized components readily available. Compared to alternative processes such as perforating metal, flattened metal expansion is far more economic; the sheet metal is slit rather than punched meaning no material is wasted. Additionally, fewer raw materials, such as
copper,
steel,
titanium and
aluminum, are needed. This is because the initial process can expand the sheet to as much as ten times its original size.
Before secondary operations such as bending and forming can occur, however, the metal expansion process itself must be completed. Flattened metal expansion begins in the same way as standard methods. Sheet metal of varying thickness is fed into the expansion machine. It is important to consider that the thickness will be significantly reduced and the length increased in order to select the most appropriate sheet metal for a given application. Once in the machine, a special die cuts several hundred to several thousand of uniform slits into the metal in an offset alternating pattern. At the same time the metal is drawn through a hot rolling press that expands the metal and slits alike. The result is an open mesh like metal surface. To flatten expanded metal, the newly formed screen is fed through an additional reducing mill. This cold-rolling process further reduces the thickness, by about 5%. The end product is a smooth, flat sheet of expanded metal. The size and quantity of holes depends upon the specific die used to cut and draw the metal. A diamond shaped pattern, made with a pyramid shaped knife, is the most common.
