The process for creating expanded metal was first developed and patented in the 1880’s in Hartlepool, UK. Despite technological advancements, the modern process for expanding metal remains similar to the original technique.
Expanded metal is plate or sheet that has been cut and stretched into a mesh. Stretching the metal results in a mesh with diamond-shaped spaces – although many other patterns can be created. Many types of metal can be expanded, including: stainless steel, hot rolled steel, cold rolled steel, aluminum and more.
The pattern of the mesh can either be staggered (providing the most open area) or in a straight pattern with all rows and columns aligned. The proportion of open area determines the amount of space for the passage of air, water and light, and will vary according to the intended application of the expanded metal.
There are several benefits to using expanded metal:
Expanded metal is produced by an expanding machine, which turns solid metal sheets and coils into an expanded metal mesh. The expanding machine is fitted with a knife which determines pattern for the mesh. As the metal is fed through the expanding machine, it is cut and stretched simultaneously using a pressured slitting and stretching process. The slits created by the knife allow the metal to be stretched, which produces uniform holes. To ensure a consistent pattern, the expanding machine is programmed or operated manually as the metal is fed through. The finished expanded metal is then wound into coils or cut into sheets.
Depending on the intended application, different thicknesses of metal can be used and different mesh patterns can be chosen. L.W.D (Long Way Diamond) and S.W.D. (Short Way Diamond) are commonly used to indicate the desired length and width of the diamond shaped mesh holes.
The most common types of expanded metal are:
Standard Expanded Metal
Standard expanded metal is extremely versatile and economical. It comes in a variety of gauge and opening sizes. It’s often used to provide a rigid, raised, slip-resistant surface. In standard expanded metal the strands and bonds are set at a uniform angle. This provides extra strength and rigidity whilst allowing maximum air circulation.
Flattened expanded metal is produced by cold rolling expanded metal to flatten it. It is chosen when a smooth surface is required. The flattening process generally elongates the length of the sheet by 5%.
Hexagonal Expanded Metal
Hexagonal expanded metal has hexagonal openings instead of the usual diamond ones. The hexagonal shape gives the metal extra strength while allowing the passage of air, light, heat, sound and liquid. Hexagonal openings are preferred over diamond openings when the metal is heavily expanded.
Architectural Expanded Metal
Architectural expanded metal features the diamond pattern with added architectural features. The result is a design which combines good aesthetics, increased security and privacy, and improved ventilation. It’s suitable for functional and decorative purposes, or a combination of the two.
Micro Expanded Metal
Micro expanded metal features small openings in light gauge metal. The openings can be standard, flattened, hexagonal and square. This type of expanded metal is often used in filters.