Plasma Cutting Aluminum
Have you ever wondered why people in the welding industry don’t use oxy-acetylene in cutting up non-ferrous metals and instead use plasma cutter on aluminum?
Well, the fact is, oxy-acetylene can get through any type of metal. But when it comes to coming up for a clean-cut for softer metals, the result can be ugly. The reason for this is because of oxidation.
Aluminum is a non-ferrous metal and does not contain iron so it does not undergo an oxidation process that fast. Much like with other soft metals like brass, copper, and zinc.
Ferrous metals like steel, high carbon steel, mild steel and cast iron have lots of iron and so they undergo oxidation which simply is the process of disintegration of their iron molecules. Rusting and corrosion are good examples of natural oxidation of ferrous metals.
When heat from oxyfuel is blasted on to the ferrous metal, the heat disintegrates the carbon atoms quickly and the flame cuts through the metal cleanly.
However, with non-ferrous metals, what happens is a different story.
Because non-ferrous metals do not contain iron and do not oxidize, instead of cutting them up clean, you tend to melt its soft metal so that what you produce is ragged out cut metal when using oxy fuel.
So how does plasma cut aluminium with a more precise cut?
Plasma Cutting Aluminum easiest way
Cutting aluminium with a plasma cutter can be an easy process. Unlike with oxy fuel that delivers heated oxy-acetylene gas, plasma cutters utilize a high-velocity stream of ionized gas that is blasted from a constricting cavity and loaded with electricity.
This gas is the plasma that is composed of natural gas or sometimes a mixture of gases but underwent an ionization process that gets heated by electricity. So with plasma cutting, you may only need a compressor, some forms of gas (when needed) and a plasma cutter to produce the most reliable cutting gas on earth.
However, it is not always good news with aluminium plasma cutting because the thicker the aluminum gets, the more unreliable using only compressed air. So you need to use other forms of gases to produce more intense flame or otherwise you won’t be producing clean cuts as aluminum oxide will form on the surface and even more under the metal if you will use only compressed air for cutting.
For example, you can easily cut aluminium with plasma cutter that is 3mm or ¼-inch thick using a cheap 50-amp plasma machine and compressed air. But if you cut a ½-inch thick aluminium with it, you may be surprised that the cut won’t be clean even though the aluminium metal is softer and easier to cut than steel.
On the contrary, with the same 50-amp plasma machine, cutting up steel that is ½-inch thick won’t pose any problem and the result is a very clean cut. So what happened why the thick aluminium was not cut cleanly while the steel was good?
The thing is when aluminium is even exposed to plasma arc but the arc lacks the heat to prevent the formation of iron oxide, what can be produced are jagged edges on the cut. So the secret lies in the use of intense heat to cut aluminum with plasma cutter and you can only get that heat with the right combination of gases.
In the old days when new high-precision plasma cutters were not present, welders use a mixture of argon and helium in cutting up aluminum and they can produce good results. They also use high-pressure nitrogen to produce laser-cut results.
Will High-Amperage Plasma System Enough to Cut Thick Aluminum?
There is a myth that says if you can use a high-amperage plasma system this can be able to cut up to 1-inch thick aluminum cleanly regardless if you only use compressed air. But this is not reliable information.
Amperages only provide power to the machine and this is very effective when cutting ferrous thick metal. But with aluminum, the aluminum oxide will still form on the cut even though you will use high-amperage plasma cutter on thick aluminum that is more than 1/2 of an inch and relying only on compressed gas.
A machine that is packed with 45 to 260 amps can cleanly cut aluminum up to 1/4 inch nicely even with compressed air but beyond this thickness, don’t expect a clean edge finish. So the secret still lies in the mixture of gases and pairing it with high amperage plasma cutters.
For example, fabricators would prefer to use 130-amps plasma cutters and use a combination of argon and helium when cutting aluminum with a plasma cutter. But if they want to cut faster without the need to refine their cut, they can go as high as using 260 amps plasma cutters.
Gases That Can Work Well With Aluminum Cutting
When using a good combination of gases such as it can emit about 50,000 amps per square inch to cut aluminum up to 1/2 inch thick or even thicker, it was recently found out that argon+hydrogen makes out the perfect combination while the secondary gas would be nitrogen.
But if you want to plasma cut on aluminum plate that is thinner, a combination of nitrogen and air or nitrogen and carbon dioxide will also produce nice edges without leaving any rough particles on both the surface and down edges of the aluminum.
Well, the good news is that if you can use a 50-amp plasma cutter on aluminum with about 3 mm thin, using compressed air would be good enough considering that you are applying the best cutting technique. But you would notice that with 1/2 thick aluminum, the arc would be weak to produce the clean nice cut.
Hydrogen is also an excellent thermal conductor with properties that can be able to cool hot surfaces without melting the metal on the sides when cutting aluminum. However, it must also be combined with a secondary gas such as pure air or carbon dioxide or even water to produce a very high intense plasma arc.
Nitrogen can also work well with aluminum and stainless steel. This gas is very economical to use. The bad news is it won’t work well in cutting 1/2-inch thick aluminum and so it must also be paired with secondary gases such as carbon dioxide, pure air or water to produce intense arc flame.
Tips When Cutting Aluminum With Plasma Cutter
The lesson we can learn from this article is that when plasma cutting aluminum you should consider few tips to produce the excellent cut finish.
First, you have to consider the thickness of the aluminum you want to cut. The thicker the metal, the more intense heat you need which you can derive with the good combination of gases and the use of a high-amperage plasma cutter for more cutting power.
Second, the wider the aluminum sheet, the more you need a plasma cutter with a wide gap that can produce big arcs. This is most useful when you want to plasma cut aluminium plate.
Third, you have to set your speed along with the amperage you use based on the thickness and cut of the aluminum sheet. Moving the torch fast while maintaining the arc at a slow pace according to some experts is a good method.
Fourth, when buying your plasma cutter, buy one that has print indicating the cutting speed requirements for the thickness of metal measured in inches per minute (IPM) and this should include soft metals such as aluminum.
Don’t forget also to consider the duty cycle. This is the time you can cut continuously before the machine reaches its overheating point.
And lastly, watch for more videos about how to use plasma cutter on aluminium where you should see techniques, selection of plasma cutters with right amperage and the use of the right combination of gases.
So the question of how will plasma cutter cut aluminium to produce precise results, the answer solely depends on the power (amperage) of the machine and the right combination of gases plus using the right technique.
Many of us think that because aluminium is lighter, cutting aluminium with plasma cutter can be done easily using only compressed air for plasma.
So to show you the result of cutting up a 3 mm aluminum piece versus a 3 mm steel and 1/2-inch thick aluminum versus 1/2 steel block using my 50-amp plasma cutter, I’ve made a video (below) for your actual observation and learning.
You’ll be surprised by the result and you’ll be able to realize the significance of our message here.