The framework of expanded metals is actually a solid piece of construction that exhibits an open grid like pattern.
While a number of other metals are common in expansion, the properties and characteristics of aluminum make it ideal for industrial, commercial and residential use. Aluminum is a silvery-white non-ferrous metal that is both durable and aesthetically pleasing. With lighter weight and better corrosion resistance than expanded steel, aluminum is used in construction, automotive, water and air filtration, cooking, packaging, aquarium, aerospace, power generation, marine, medical and electronics industries.
Unlike many metals that become brittle in cold temperatures, aluminum actually strengthens at low temperatures making expanded aluminum enclosures essential for refrigeration applications as well. Pure aluminum, however, is very ductile and malleable, which limits its use. To improve strength to weight ratio, expanded aluminum is often alloyed. Alloyed aluminum is used for support, security and protection in the form of grilles, guards, floors and walkways.
Because metal expansion results in a pattern of uniform openings, air, sound, liquid and light can pass through these barriers for improved ventilation, visibility and acoustics. Compared to punched or perforated metal, expanded aluminum is cost effective as it slits the metal leaving no waste. As the third most abundant element in the Earth’s crust, the cost of aluminum is already much lower than many competing metals, such as titanium.
Metal expansion is a fairly simple, but effective process that has changed little throughout the years. Sheets or plates of aluminum are fed into an automated expansion machine. In the machine, several dies are used to slit the metal hundreds or even thousands of times depending on the size and desired outcome. This creates an offset alternating pattern of small cuts. While the dies are in motion, the metal is simultaneously drawn through a press or roller.
The combination of heat and pressure stretches the metal and causes the diamond, round or irregularly shaped holes to swell. The solid aluminum is transformed into a mesh-like screen. Despite the gaps, the sheet is still a solid piece of construction and therefore has no seams, welds or joints that might work loose over time in other metallurgical processes.
The use of a single sheet is important as the interconnected network of strands and bonds distribute weight evenly so no one portion is overloaded. The size and density of the apertures or percentage of open space plays a significant role in the weight capacity of expanded aluminum and should be taken into account with regards to intended use. Gauge, length, width and height of the metal frame should also be considered.