How to Choose aluminum expanded mesh?

06 May.,2024

 

How to measure and specify expanded metal - News

Our customers sometimes find themselves confused over what measurements they should provide in order to select the most suitable mesh pattern for their application. Ian Hutchinson, Product Manager at The Expanded Metal Company, provides a guide on how to measure and specify expanded metal…

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Raised or flattened mesh, what is the difference?

When measuring expanded metal mesh, the first thing to consider is whether the mesh is raised or flattened. Both have a unique set of terminologies with regard to their respective measurements.

The original form of expanded metal is always of a raised appearance and is characteristic of the unique ‘slit and stretch’ motion employed to manufacture the product. which presents angular strands which are inclined from the plane of the sheet.

Raised mesh is championed for its angular appearance which not only gives it strong aesthetic appeal but offers practical benefits: it offers grip underfoot, has the ability to direct air, liquid and light, and provides a key when used as a substrate.

Common applications for raised mesh include walkway ramps, security fencing, decorative building cladding for interiors and exteriors and laths for render and plaster.

A secondary process is often applied to expanded metal which utilises heavy rolls to flatten the angular strands. The end result is a sheet which is completely two dimensional with its strands in the same plane as the sheet. Flattened mesh is often championed when a flush finish is required.

Common applications for flattened meshes include security partition meshes, conical air filters and machine guards.

How do I measure a raised mesh?

The key measurements for a raised mesh are Longway Pitch (LWP), Shortway Pitch (SWP), Strand Width (SWDT) and Strand Thickness (STK).

LWP, measured horizontally from either knuckle to knuckle or centre to centre, is derived from the size of tooling used within the production process.

SWP, measured vertically from either knuckle to knuckle or centre to centre, is manifested through the overall expansion applied during manufacture.

SWDT is a measurement of the width of the resulting angular strand created during manufacture.

STK, is a measurement of starting raw material thickness. Contrary to belief, the expanding process does not directly alter material thickness. Strand Thickness should not be confused with the overall height or depth of expanded metal. Typically, mesh height can be as much as 1-2x the measurement of SWDT.

How do I measure a flattened mesh?

The key measurements for a flattened mesh are Longway Aperture (LWA), Shortway Aperture (SWA), Strand Width (SWDT) and Strand Thickness (STK).

LWA is measured horizontally from internal aperture point to point.

SWA is measured vertically from internal aperture point to point.

SWDT is a measurement of the width of the resulting angular strand created during manufacture.

STK is a measurement of starting raw material thickness.

Whilst the expanding process does not alter material thickness, the flattening process does. It is common to observe a 10-20% reduction in material thickness after the flattening process. As the mesh is completely two dimensional after flattening, the overall height measurement of the mesh is akin to starting material thickness with a further allowance of 10-20% reduction.

How do I specify sheet size and orientation?

Expanded metal mesh exhibits different mechanical and aesthetic properties when the sheet size is orientated at opposing angles.

When specifying sheet dimensions, one should also consider the orientation of the diamonds in relation to sheet size. The terminology employed to describe orientation is Longway Mesh (LWM) and Shortway Mesh (SWM).

For example, when raised mesh is used as a walkway ramp platform, the surface grip is strongest when the diamonds run left-to-right underfoot.

Alternatively, it is common within the security fencing industry to mount expanded mesh fencing panels with the diamonds longways pointing to the sky. This creates narrower openings and inhibits the ability to climb and scale the fence.

The below illustration provides a clear explanation on how 2440mm LW x 1220mm SW differs to 1220mm LW x 2440mm SW despite being dimensionally the same.

View an example of our 2076F flattened steel mesh at a horizontal orientation here and view the same mesh at a vertical orientation here.

You can also view our 2089 raised steel mesh at a horizontal orientation here and at a vertical orientation here.

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How to Choose the Right Expanded Metal Mesh Size for ...

Expanded metal baskets can be a great alternative to using sheet metal or custom wire baskets in many situations. Baskets made with expanded metal offer the better durability and tensile strength than steel wire while having better drainage and air flow than sheet metal baskets. This makes expanded metal baskets almost perfect for heavy-duty parts washing processes where thin custom wire baskets wouldn’t cut it, but sheet metal would interfere too much with parts finishing processes.

However, not all expanded metal baskets are the same. When building an expanded metal basket, it’s important to carefully consider the size of the mesh—i.e. how much open space there is between solid surfaces (also known as strands) in the expanded metal sheet and the size/thickness of those surfaces.

If the expanded metal mesh size is too tight, it might interfere with wash processes or allow water (or other chemicals and process runoff) to collect in the basket. Too open, and parts may fall through or the basket might be too weak.

So, how can you pick the right expanded metal mesh sizes for your custom parts washing baskets? Here is a quick guide:

The Factors Behind Your Mesh Size Choices

When creating a sheet of expanded metal mesh, the manufacturer will need to consider the:

  • Weight of Held Parts. Naturally, the weight the basket will be designed to hold plays a factor in how wide the space between strands can be, as well as how thick each strand needs to be. The heavier the expected load, the thicker the strands of the expanded metal mesh will need to be.
  • Type of Metal Used for the Mesh. The type of metal used in the expanded metal mesh also plays a role in determining how thick or thin the strands can be and how much open space there can be between strands. For example, 304 stainless steel is sturdier than aluminum at the same sizes, so 304 SS can be made thinner and wider for the same weight tolerances. High-carbon steels are even stronger, so carbon steel expanded metal mesh can take even more weight than 304 SS mesh of the same size.
  • Needs of the Wash Process. The wash process itself will heavily influence the design of a custom expanded metal mesh basket, right down to the spacing of the mesh. Many aqueous wash processes require a lot of open space to facilitate water/air flow and keep runoff from collecting in the basket (this is why custom wire baskets are usually the first option for these processes). So, for water- or chemical-based wash processes, thinner mesh with more open space is usually the go-to option. Additionally, the chemicals and temperatures used in the wash process may influence the material choice.

Some Examples of Different Mesh Size and Material Choices

Special thanks to Alro Steel for the following examples of metal mesh sizes for stainless steel, aluminum, and carbon steel:

Metal Type

Strand Width (inches)

Strand Thickness (inches)

% Open Area

Weight Capacity Per 100 Sq. Ft. (lbs.)

Carbon Steel

.072

.036

45

86

304 Stainless Steel

.080

.037

70

50

Aluminum

.094

.051

70

27

As you can see, the carbon steel example, though possessing the thinnest strands, had the highest weight capacity of all the expanded metals in the Alro Steel list. This may have been bolstered somewhat by the fact that it had the least open space, but the difference is still significant.

304 stainless steel serves as a great “all-round” option, with its ability to resist chemical attack/oxidation and moderately high tensile strength—being able to take nearly twice the weight of the aluminum expanded metal example. In most cases, the stainless steel would be the better option, unless the chemicals in the wash process were severe enough to corrode it but would not affect aluminum.

Some manufacturers may even choose to use a specialized polymer coating to protect their expanded metal baskets from corrosives so they can use stronger metals while prolonging the useful life of the basket.

Need help finding the perfect expanded metal basket for your heavy-duty parts washing and handling needs? Reach out to the experts at Marlin Steel for help and advice today!

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