Like all metals, aluminium has its own unique characteristics that bring with them a set of dos and don’ts for effective plasma cutting.

In this article, we’ll explain exactly how and why plasma is the right solution for cutting aluminium. We will do this by answering eight frequently asked questions on the topic and hopefully, this will help you to achieve the best possible results.

Can you cut aluminium with a plasma cutter?

Yes, as with any electrically conductive metal, plasma cutting aluminium is not just possible, it is highly effective.

For the uninitiated, plasma cutting is a process that shoots a jet of ionized gas at high speed through an orifice. The gas, after being both superheated and electrically ionized, forms a completed circuit back to the cutter, via the earth lead.

We refer to this ionized gas as plasma, and the more electrical energy that is added, the hotter the plasma arc becomes. This arc is able to melt the metal and the gas blows away the molten material, creating a cut at the desired point. And this whole process works fantastically well with aluminium.

But… I heard plasma technology can’t meet tight tolerances for aluminium and it leaves a hard-to-clean mess on the surface of the material?

These are clear misconceptions from the past, referring to machines from the 1980s and early ’90s

Plasma cutting technology has evolved significantly.

Today, improved processes on both lower cost and state of the art systems have flipped the situation on its head.

Hypertherm’s higher-end XPR systems offer a range of processes and cutting combinations, which produce excellent results for aluminium, on a wide range of thicknesses. Being able to use dual gas systems such as these offer fabricators much finer control and a cleaner, quicker cut.

A dual gas system is one where a cutting gas is used with a shield gas. The role of the shield gas is to help focus and direct the plasma, and to improve the quality of the kerf and cut surface.

Using different combinations of cutting and shield gasses produce different results. For example, using air plasma with an air shield gas is an economical combination that with today’s technology results in a fairly clean and quick cut.

Using nitrogen plasma with a water shield (if your machine has a water table to enable this combination) provides a very high-quality cut and helps to prolong the life of consumables.

And using argon-hydrogen plasma with a nitrogen shield gas is an excellent solution for thicker aluminium.

But it’s not all about high-end machines like the XPR systems; lower-cost solutions such as Hypertherm’s Powermax plasma cutters, using air as the plasma gas, can produce satisfactory cutting for many applications on a range of aluminium thicknesses, from thin gauge upwards.

Which factor has the biggest impact on quality?

The single most important factor is whether your plasma cutter is capable of using the ideal gasses at the ideal pressure level and cutting speed or not!

With the proper selection of gases, you can get a dross-free surface and an excellent edge on aluminium with plasma.

A low-cost air plasma system can only work with compressed air and as a result, the edge quality will never be as good as industrial plasma cutting systems, which can use specialised gases like argon-hydrogen. 

Which cutting method is best for aluminium?

Laser has the edge when it comes to precision cutting, but whilst it’s certainly true that laser is capable of cutting finer detail, the more accurate tolerance delivered by laser cutting only really becomes relevant for those working in the aerospace industry, or with projects that require extremely fine detail. The quality of cut delivered by plasma is sufficient for most applications and industries.

✓ to indicate which cutting technology is better on a given aspect

Can you plasma cut thick aluminium plates?

Whatever your requirements, it’s reassuring to know that plasma cutting aluminium is effective over a wide range of thicknesses.

Earlier plasma cutting systems struggled to achieve results over this kind of range, modern systems face no such struggle and can cut aluminium with plasma from gauge thicknesses up to 38mm (pierce) and 50mm with an edge start.

The latest XPR systems from Hypertherm have a patented VWI (Vented Water Injection) process, which produces superb results on a wide range of aluminium thicknesses.

With thicker plates, mixed gas options (typically argon-hydrogen-nitrogen mixes) at higher amperages and with high cutting speeds result in a quick and simple process and a very smooth surface.

For extreme thickness applications, the Hypertherm HPR800XD can production-pierce up to 75mm aluminium plate and severance cut up to 160mm!

This is a really incredible leap forward in plasma cutting technology that finally consigns the poor results of the past – to history.

What is the Right gas for cutting aluminium?

When it comes to an air plasma system, the choice is easy – you will always cut with clean, dry air (which is, of course, still 78% nitrogen) as the plasma gas and produce very acceptable cutting results on a wide range of thicknesses. Air is the most cost-effective cutting gas, but it leaves a rougher edge coated with aluminium oxide.

Intermediate (e.g. MaxPro200) or industrial plasma systems (e.g. XPR300) are a popular choice for many fabricators as they obtain better results on aluminium. The best edge finish is often realised with the more exotic gas combinations.

These dual gas systems also more readily produce cuts that are weld-ready without further preparations to the metal needing to be made, because of cutting without oxygen.

Industrial systems (e.g. XPR300) specifically are capable of producing a high-quality dross free cut of aluminium over a broader range of thicknesses.

Here’s a brief rundown of the characteristics of different plasma gasses when cutting aluminium with a plasma cutter:

Cut quality plasma cutting aluminium with different plasma gasses

Recommendations:

You only need to think about the plasma gasses when you have a dual gas or multiple-gas system.

If you are cutting thick aluminium (> 12mm) argon hydrogen is the gas of choice.

In case you are cutting thinner aluminium (< 12mm) you best use nitrogen as plasma gas combined with CO₂ as the shield gas for the best cut quality. If you want to reduce costs, use air as secondary gas. It is less expensive and the cut quality is good.

If your system allows, water shield will provide the best edge quality and will extend your consumable life.

Cutting Range:

If As mentioned earlier, with plasma you can cut aluminium up to 160mm. In the table below you find an overview of the aluminium cutting ranges for every gas/amperage combination.

What are plasma cutting aluminium hazards?

Aluminium dust is of particular note here: it should not be mixed with mild steel cutting dust (for example in a filtration system) as spontaneous heating can occur.

It is rare but a thermite reaction can take place where the aluminium dust reacts with iron oxides from the mild steel in an exothermic chemical reaction. So careful management of filtration systems and work areas is key.

Next on the list is a risk that occurs with water table use. Where aluminium is plasma cut on a water table there is a risk of explosion due to the production of hydrogen. This risk only exists if the water table utilizes a submerged tank or chamber. 

Aluminium, when combined with water, can produce bubbles of hydrogen gas, which can collect under a submerged plate on the cutting table resulting in a dangerous build-up of hydrogen which can subsequently be ignited by plasma, resulting in damage to equipment or injury.

There is less risk with small parts that are only submerged for short periods of time, but be extremely cautious when you have a large surface area that is submerged for a long time. Using an aerator in your water table will help you to mitigate this risk.

Consult with the table manufacturer prior to cutting aluminium to check whether the water table, fume extraction, and other parts of the cutting system have been designed with aluminium cutting in mind.

When NOT to use plasma cutting for aluminium?

Most regular aluminium sheet and plate can be cut successfully with plasma, however, there are a couple of notable exceptions.

The first relates to anodised aluminium. When aluminium is anodised to increase the thickness of the natural oxide on the surface, that finish becomes vulnerable under the temperatures involved in plasma cutting and the heat of the plasma will damage the surface anodising close to the cut area.

The second exception is aluminium floor plate (also known as diamond plate, durbar plate and tread plate). The raised sections on the plate makes it difficult to cut as they can interfere with the arc-voltage height control on the plasma cutting machine, resulting in poor cut quality or occasional tip touches.

The third exception is aluminium-lithium alloys. Never cut aluminum-lithium alloys in the presence of water.

Anodised aluminium sheets

Can you use plasma to cut aluminum on a water table?

You might have heard about the dangers of a chemical reaction when cutting aluminium on a plasma water table.

This explosion hazard from dissociated hydrogen is real, as when cutting aluminium in a water environment hydrogen can be accumulated under a sheet of aluminium as it’s being cut.

Hot aluminium has a big affinity for oxygen, and it can grab some away from the H2O molecules, creating free hydrogen. But it must be said this production of hydrogen is most likely harmless, especially if you are not cutting multiple sheets in a short period of time.

On the other hand, if you are cutting aluminium daily, you might want to install a compressed air manifold “bubbler” system on your water. Such a system will create air bubbles in the bottom of the water table, so the hydrogen doesn’t pocket under the plate.

What is this bubbler system exactly? and can I make it myself?

You can already make an aeration manifold with 50mm PVC tubing combined with 25mm connection lines. Just make sure you drill small holes in the distribution lines. (3 mm) every 150mm. 

Cap the ends of the distribution lines so that oxygen is delivered to all parts of the cutting area.

Then simply connect the manifold to a shop airline and set the pressure regulator to obtain a steady stream of bubbles.

So is cutting aluminium on a water table safe?

Yes. In general, plasma cutting aluminium is safer than cutting stainless steel, which releases hexavalent chromium.

But always consult with the table manufacturer to implement a risk assessment and mitigation plan that eliminates the risk of detonation by preventing hydrogen accumulation.

Aeration Manifold or bubbler for Plasma cutting aluminium on a water table

What about aluminium alloys?

Do not cut aluminium alloys underwater or on a water table unless you can prevent the accumulation of hydrogen gas.

But with proper mitigation, most aluminium alloys can be plasma cut on a water table.

WARNING: Never cut aluminium-lithium alloys in the presence of water, which can burst into flames when they hit the water.

How to choose the right cutting machine?

When selecting the machinery and procedure that will work best for your requirements, the first thing to do is to prioritize needs.

For some operations, productivity may be the number one concern, while others may regard edge quality as the most important factor.

If you require extremely accurate tolerance levels, you should consider a fibre laser cutting machine. 

However, if you are looking for a cost-effective high volume work solution, or if you want to cut aluminium above 20mm, a high definition plasma cutting machine with an XPR plasma source might be just what you are looking for. 

In case the cut quality is not that important or you only occasionally cut aluminium you best opt for an air plasma system like the Hypertherm Powermax. 

These systems are a good balance of cut quality and affordability. Air plasma systems are by default handheld devices, but they can also be installed on a CNC plasma cutting table for a more intensive use.

Lastly, the choice of which solution to cut aluminium will work best for you also depend on which materials you cut on a daily basis. Therefore, we would always recommend getting in contact with a plasma or fibre laser machine manufacturer.

Whatever your requirements, the team of expert engineers at Esprit Automation can help you identify the right plasma cutting machine for your specific aluminium application and needs.

When done correctly, and with the right equipment and settings, plasma cutting aluminium is a straightforward process that produces excellent results.

Plasma cutting aluminium with a Hypertherm XPR300