Perforated Material Selection

 

There are many types of material that can be used for a perforated sheet. Some common materials used are mild or carbon steel (either hot roll or cold roll), coated steel (i.e. zintec, galvanized), aluminum, copper, brass, plastic and stainless steel for various grades (e.g. T304 and T316). The selection of raw material for a perforated sheet project will be usually justified according to its price. Among all the common materials for perforated sheets, aluminum and stainless steel are the most expensive. However they offer many advantages for a perforated sheet metal project. The two major benefits of aluminum sheet are that they are very lightweight and very corrosion-resistant. A benefit of stainless steel is that it is also very corrosion-resistant but also stronger and tougher than aluminum. Moreover, stainless steel also resists bacterial growth. Therefore, they are often used in the food industry and pharmaceutical factories, especially for T316 grade. Both aluminum and stainless steel have an appealing surface and they are the favorite materials for use in architectural building.

On the other hand, mild steel and coated steel do not resist corrosion, but they are cheaper than aluminum and stainless steel. Besides being cost-effective, carbon steel  material types are always favoured when the perforated panel gets a paint or coating of powder. They are also softer than stainless steel and as a consequence, are easier to manufacture. One thing that needs to be considered is that, if coated steel such as zintec or galvanized steel is used as the material for perforated metal, the sheared surface after being punched will be exposed to rusting and corrosion. Though this will only affect a small area on the perforated sheet, it would be wise to have a further treatment of a powder coating to prevent rust in the future.

Other than the raw material cost, we also need to look at other factors such as how the perforated panels are attached to other components. For example, if we want to use perforated metal for a car park fascia we need to evaluate how it is joined to the main structure. Are they welded or are there bolt-and-nut fittings. Are the perforated sheets folded so they are attached as “slip-in” and “clamp-on” components? Is there any need for other treatment to the perforated metal such as flattening the sheets, sand blasting, powder coating or painting?

The material characteristic and thickness also affects the material cost in the manufacturing process. The thicker material make stronger perforated metal but it also increases the cost and tends to be more difficult to manufacture, as distortion and sheet deformation will also be more apparent. On the other hand, the thinner material seems to make the perforating process easier, but this is not really so. This is especially true if the material is too thin. Thinner material tends to have punched marks after punching and the punch and die needs to be always in sharp condition to avoid any trouble in the perforating process.

The strength of the raw material for perforated sheet gives a designer the ability to reduce the thickness by selecting stronger material. However, stronger the material will make the punching process even harder because of deformation, so there will be a trade-off in selecting material in terms of material characteristic and thickness and manufacturing process to find the least cost for perforated sheet metal project. A good rule from the IPA handbook (www.iperf.org)  is to keep the material hardness below 80rb (Rockwell Hardness) to make the perforating process run smoothly.

 


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