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Choosing the Right Metal for Your Design: A look at the differences between perforated metal, expanded metal and wire cloth

IPA_NCCCCFrom function to aesthetics, perforated metal, expanded metal and wire cloth have many overlapping architectural applications. In recent years, suppliers have been working with architects to incorporate these materials into many new applications.

As the applications diversify, it's more important than ever for architects to distinguish the strengths and weaknesses of each material to achieve optimum performance and value.

This article will broadly compare the three materials against specific applications, providing tips on material selection.

Defining Your Options
Perforated metal is a sheet of metal (or plastic) with a series of holes punched into it. It comes in a virtually endless variety of sizes, gauges, hole shapes and material types. Hole diameters range from a few thousandths of an inch to more than 3 inches, punched in material as thin as foil or as thick as 1-inch steel plate.

Expanded metal is made from a sheet of metal that has been slit and stretched to form diamond-shaped openings in the sheet. The diamond-shaped trusses form a sharp angle to the original plane of the sheet adding strength and rigidity. Expanded metal is available in standard, raised, flattened and decorative diamond patterns, and comes in a range of gauges, opening sizes, materials and sheet sizes. Wire cloth, also known as wire mesh, is metal wire that is woven or welded to form a cloth.

Metal wire is made from various alloys including stainless steel, brass and copper. Wire cloth can be woven or welded to create a variety of opening sizes and wire diameters.

Price and Other Selection Issues
Because of raw materials costs, perforated metal typically carries the highest up-front price of the three options. However, many other attributes contribute to the overall value of a material in any given application, including:

  • Aesthetics
  • Strength
  • Durability
  • Sustainability
  • Resistance to environmental elements
  • Fabrication costs
  • Application-specific needs such as acoustical capabilities and radiation containment

Aesthetics
Expanded metal, perforated metal and wire cloth all offer a unique look that will enhance any design. Out of the three materials, however, perforated metal offers the greatest visual variety. Endless options in hole shapes, sizes, materials and geometric patterns are available to achieve a specific look. Perforated metal also is more easily painted than either expanded metal or wire cloth.

Wire cloth presents several options depending on the weave of the metal wire, while expanded metal is the most limited in design due to the stretching of the raw material. Both materials can only be cut to shape and framed.

Acoustics
All three of the materials can be used as a pass-through to support sound absorption in ceilings and walls. They can function as protective or decorative coverings for special acoustical materials.

Perforated metal, however, is the only material to offer more extensive sound-managing capabilities. It can play an active role in eliminating specific frequencies in sound-filtering systems, such as enclosures surrounding large air-conditioning or compressor units.

IPA_HeiferVentilation
In addition to sound filtering, all three materials can be used in other ventilation and filtration applications, as well. The openings in each permit passage of light, air, heat and gases.

In harsh environments, the estimated energy loss or pressure loss is often an important design consideration. If pressure control is important in your application, perforated metal provides the greatest ability to control or equalize pressure due to its high strength-to-weight ratio.

Structural Considerations
The structural strength of perforated metal is one of its key attributes. It can be used as a stand-alone component in several architectural designs such as sun screens and panels. The "open area" is the sheet of perforated metal, which has its own strength and physical properties.

With expanded metal or wire cloth, however, the "open area" can't stand alone. Wire cloth and expanded metal are lightweight, less rigid materials that need additional fabrication processes. They must be fastened and secured to a structure.

Fabrication Costs
In many cases, additional fabrication can significantly increase the total cost of expanded metal and wire cloth, despite their lower up-front price.

Wire cloth and expanded metal both require additional operations, including a punch press to open the material, bending to form the structure and three welding operations to fasten the open material to the structure.

Perforated metal typically requires less fabrication. Stainless-steel perforated parts often are finished in two operations: punching in a single pass and forming with a press brake.

The Right Material for Your Design
If any of the qualities discussed here is important in your circumstances, perforated metal's ability to outperform the other options may offset the higher initial price tag.

So, should you use perforated metal, expanded metal or wire cloth in your design? It's important to discuss the particulars of your application with engineers who have expert knowledge of the properties of each material option. Doing so will help you choose your best option, and ensure the material is specified for optimum performance in your application.

Bob Farber is the president of the Milwaukee-based Industrial Perforators Association. Discover more about the IPA and perforated materials at www.iperf.org.