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Perforated metal versus expanded metal

Perforated metal versus expanded metal

Take a close look at industrial filtration operations, and you’ll often find both perforated metal and expanded metal filters in use. Both products feature apertures that allow certain substances or materials to pass through while retaining others. Similarly, you’ll find both perforated and expanded metal used for applications as diverse as speaker grilles, walkways, balustrades, beehive trays, grain dryers, and machine guards.

And you’ll often see interior design features such as screens and building facades created with perforated metal or expanded metal.

Both materials have advantages for filtration, ventilation, acoustic attenuation and light control, and can be used to create eye-catching features.  

So what’s the difference?

Let’s start with a little bit of history…

Perforated metal

The perforation of metal sheets has its industrial origins in the 19th-century coal mining industry. Perforated metal sheets were used to separate coal, with the holes being manually punched through.

Manual perforation was eventually replaced by more efficient methods. These include ‘cold perforation’, where a roller full of pins is run over a metal sheet to punch the holes and ‘hot perforation’ – a similar technique, but instead using heated pins which create welts around the holes.

In addition, there is the die and punch process, in which a sheet with protruding needles is pressed on to a metal sheet as it rolls through a punch press, and laser perforation, where holes are burned into the metal.

Expanded metal

The expanded metal manufacturing process was invented by John French Golding – and the first British patent was issued to him in 1884. John was the founder of The Expanded Metal Company and with Mathew Gray, Christopher Furness, Robert Irving Jr. and W.B Close, brought the manufacture of expanded metal to Hartlepool (and to the site where we are still located).

The expanding process entails slitting and stretching the material to create holes – which are often diamond-shaped – rather than punching them out.

When a sheet of expanded metal first emerges from a press, it is always of a ‘raised’ appearance and is characteristic of the ‘slit and stretch’ technique. This presents angular strands which are inclined from the plane of the sheet. 

Flattened mesh is created via a secondary process, which utilises heavy rolls to flatten the angular strands. The end result is a mesh sheet that is completely two dimensional with its strands in the same plane as the sheet.

Expanded metal – the advantages…

While both expanded metal and perforated metal can allow water and airflow, and can be used to create lighting effects or design features, there is a key difference…

In the metal perforation process, the process of punching out the holes creates a substantial amount of raw material waste. The slit and stretch technique, however, results in minimal waste of raw material. This has significant advantages when applied to a material such as stainless steel or galvanised steel – especially where high volumes are concerned – and even more advantages when high-value raw materials are used. Up to 50 percent of raw material costs could be saved by swapping a perforated metal sheet with an expanded metal equivalent, such as Experf.

We developed Experf in order to offer a product with a very similar aesthetic and open area percentage to perforated metal, which would still retain all the benefits of expanded metal. Experf is available in materials including stainless steel and pre-galvanised steel. 

In addition, where high value raw materials such as platinum, nickel or titanium are used – for instance in specialist components – a fine expanded metal product such as Micromesh can offer a much more cost-effective solution than perforated metal.

Another advantage of raised expanded metal is its ability to offer a very strong grip, due to the knuckles formed by the slit and stretch process: combined with its ability to allow water to drain, and snow and ice to break off underfoot, this makes it a highly effective material for use in walkways, gantries and staircases.

Raised mesh’s angular appearance which not only gives it strong aesthetic appeal but also gives it the ability to direct air, liquid and light.

For more information on the benefits of expanded metal for applications such as filtration, architecture and acoustic attenuation, contact our team today on +44 (0)1429 867 388 or email sales@exmesh.co.uk.