Common uses for expanded metal screens include decorative panels, window guards, railings, floors, grills, security partitions, anti-dazzle or glare reducing screens, protective coverings and more. In any of these contexts, expanded metal screens offer protection and support while still allowing for the passage of air, water and light. The strength of a particular screen is largely dependent upon the metal chosen for its construction.
Popular options include aluminum, steel, stainless steel, copper, iron, brass, titanium and nickel. While the material has an impact on permeability as well, this property is chiefly determined by the percentage of open area in each individual expanded metal screen. In other words, the size and shape of the gaps or voids between the interlocking metal frameworks determines what can go through a screen and at what rate.
Measured both the long and short way across the aperture, micro-mesh openings can sometimes be as small as 0.6mm by 0.5mm. The density is also important to consider as a screen with thousands of small openings could allow the same passage as one with hundreds of larger.
Expanded metal screens are made in much the same way as other expanded metal products, but with a smaller die and less stretching of the already smaller gauged metal. A metal sheet or plate is first fed into the expanding machine just below the knife-like die cutter. Hundreds or thousands of uniform slits are cut into the stock metal in an offset alternating pattern.
The pyramid die, which produces a diamond pattern between the frameworks, is most often used, though custom dies can make virtually any pattern. No matter the shape, the metal is simultaneously drawn through a hot press as it is cut. The pressured slitting and stretching process causes the holes to swell, transforming the solid sheet into a mesh-like screen.
As the metal is cut instead of punched, there is no material waste. Instead, the metal is pulled into thin strands and bonds that create an interconnecting structural network that distributes weight evenly along the entirety of the screen. Often expanded metals are more rigid and have better weight to strength ratios than the solid metals they come from.
The strength and weight capacity should nevertheless be carefully considered. In addition to this and the material and percentage of open space mentioned above, the overall dimensions should be taken into account with an understanding that the size and thickness of the finish product may be very different from the original material.