Plasma cutting is a term you have probably heard before, but what does it mean? Well, this is the process used to cut electrically conductive metals. These are metals such as aluminum, copper, silver, and gold.
Basically, these are metals that allow electric currents to pass through them with little to no resistance. As such, cutting them requires the use of specialized tools and techniques. And this is where plasma cutting comes in.
A Short Note About Plasma Cutting
So what is plasma cutting, and how does this process work? But before we get into plasma cutting we need to first understand what plasma is. Plasma can be described as a state of matter different from the common states of solid, liquid, and gas.
Plasma is generated when you superheat steam at temperatures above 11,000 degrees celsius. Heating steam at these temperatures causes it to break down into gases which become electrically conductive or ionized. This ionized gas is called plasma.
That being said, plasma cutting is the process of cutting metal using a jet of ionized gas or plasma. In the process, an electrode is used to strike an arc with the material being cut. The electrode usually has water or gas-cooled nozzle.
This constricts the arc leading to the formation of the high-temperature plasma jet. This plasma jet melts the metal and eventually cuts it.
Can aluminum be cut with a plasma cutter?
As we have already seen, aluminum is an electrically conductive metal. As such, it is one of the metals that can be cut using the best plasma cutter.
Aluminum plasma cutting techniques
Now that we know that we can cut aluminum using plasma cutting, what techniques and tips can we employ in the process? Here are a few basic tips on how to cut aluminum using a plasma cutter.
1. Ensure a solid connection between the cutter and air source
When plasma cutting you need an air source that you connect the cutter too. The purpose of the air source is to ensure the plasma jet remains under high pressure. When working with aluminum there is always the danger of the aluminum becoming warm.
When this happens the aluminum sheet will become sticky. To avoid this ensure you have a secure connection between the cutter and the air source. This will allow for cross ventilation that keeps the aluminum metal at an average temperature.
2. Wait for the cutter to respond
After connecting the cutter to the air source it is time to turn it on. Give the machine a few minutes before using it. This allows it to generate enough heat to cut through aluminum.
3. Thickness of the metal
When cutting a thick sheet of aluminum ensure you use a cutter with a wide gap and arc. Thin sheets of aluminum metal will not require a wider gap and arc.
4. Watch your speed
The travel speed of the torch and the amperage are crucial to the success of your cut. Move the torch fast but the arc slowly. This way you prevent the arc from penetrating the metal.
5. Use a pattern
Having a pattern laid out first is important especially if you are working with a large sheet of aluminum. Following the sketch laid out on the sheet of metal, will make your work easier.
Aluminum plasma cutting misconceptions
When it comes to the aluminum there are some misconceptions. And because of these misconceptions, some people think that plasma cutting aluminum is a bad idea. But is it really? Let’s take a look at some of the common misconceptions on plasma cutting aluminum.
- Aluminum cannot withstand the plasma flame: One common misconception is that aluminum cannot withstand the plasma flame. The evidence given to support this is often the porosity on the edges of the cut side. However, this issue boils down to gas selection and with the right gas selection, you can make nice clean cuts on aluminum.
- Technology used in aluminum plates cannot meet tight tolerance: This misconception stems from the flaws of older plasma cutters of the 90s and 80s. But as plasma cutting technology has evolved, today we have cutters that can hold tolerance almost as well as laser cutters.
- Plasma cutting aluminum leaves a hard to clean mess: This is another misconception that has a lot to do with the gas selection. Cutting with air leaves a rough layer of aluminum oxide. This does not happen with the right selection of inert gases though.
- Laser cutting aluminum is cheaper: While plasma cutting equipment isn’t cheap, to say that laser cutting is cheaper is wrong. The reason being that laser cutting requires an exothermic reaction, which relies heavily on oxygen. However, oxygen cannot be used to cut aluminum so in its stead nitrogen is used. A tremendous amount of nitrogen is required, which greatly increases the cost of laser cutting aluminum.
- An experienced operator is required: While skill and experience are an added advantage, you don’t really need an experienced operator to supervise aluminum cutting. Most plasma cutters have controls that allow the cutter to maintain the proper standoff height.
Benefits of plasma cutting aluminum
- The process is significantly quicker than using oxy fuel especially for thin sheets of aluminum metal
- When an inert gas is used instead of oxygen as is the case with oxyfuel there is no after cut clean up required as there is on aluminum oxide created
- The speed of plasma cutting means you are able to cut thin sheets of metal without worrying about warping
- Plasma cutters are capable of making precise and accurate cuts meaning you can achieve many different cut patterns
- As we have already seen plasma cutting will prove to be considerably cheaper than laser cutting aluminum.
Gases and gas combinations used for aluminum cutting
When mixed with oxygen aluminum forms a thin layer of aluminum oxide, which is hard to get rid of. For this reason, oxygen is not the best gas to use when cutting aluminum. So which gas combinations are best for aluminum cutting.
A combination of nitrogen and CO2 gas produce an excellent cut on aluminum. Also, a combination of nitrogen and air produces good quality cuts on aluminum.
Another gas combination you can use to cut aluminum is that of nitrogen and water. This combination results in a good quality cut.
For cutting metals that are ½ inch thick you can use a combination of hydrogen, argon, and nitrogen.
Recommended amperage for cutting aluminum sheets of different thickness
Amperage is affected by metal thickness. When cutting a thicker sheet of metal you need a higher amperage. On the flip side, you need lower amperage when cutting thinner sheets of metal.
For example, a ¼ inch thick sheet of metal can be cut with an amperage of about 25 amps. To cut a ½ inch thick sheet of metal you will need about 50 to 80 amps. Trying to cut a thick sheet of metal with a low amperage will result in a poor cut.
How to know if you did a good cut
Looking at your finished work is the best way to know if you did a good job. A good plasma cut will be clean and smooth.
Plasma Cutting Aluminum with a water table, can it be done?
Dry cutting aluminum with a plasma cutter may require expensive dust removal. Additionally, it is a process that tends to be loud. It is for this reason that most companies prefer plasma cutting aluminum on a water table.
Aluminum and most aluminum alloys can be cut on a water table, with one exception aluminum-lithium alloys. The latter should never be cut on a water table.
The risks of plasma cutting aluminum
While plasma cutting aluminum on a water bed seems like the better option to dry cutting, it can be dangerous. When submerged in water aluminum metal forms hydrogen gas. It is a phenomenon similar to the bubbles that you see forming on a coca-cola bottle.
The hydrogen gas bubbles form on the surface and eventually escape to the surface. The amount of hydrogen gas will depend on two main things. The surface is exposed to water and the length of time it is exposed to the water.
These bubbles of hydrogen gas when they accumulate can lead to an explosion when cutting aluminum. This is an ever-present danger when plasma cutting aluminum on a water table.
That being said, it can be dangerous cutting aluminum with a plasma cutter using a water table. This danger is not present if the water is not being used.
How to overcome the risk?
So what can you do to avoid this explosion? There are three things you can do to prevent this danger.
- The first is to install an aerator. This is made up of a few tubes with holes drilled into them and is hooked up to the air source. When it’s at the bottom of the tank it will push up underneath the workpiece and push the hydrogen bubbles out of the way.
- Second, you can use a bubble muffler, which is installed on the plasma torch, and uses compressed air to shield the inner nozzle. The muffler pumps water at high pressure that removes anything away from the arc.
- Finally, you can opt for a filtration system. This is usually in the form of a pump and a centrifuge. Water is spun around inside the unit separating the hydrogen molecules before they can form bubbles.
Are There Dangerous Fumes When Plasma Cutting Aluminum?
Plasma cutting is a process that does generate fumes that can be dangerous to your health. This is especially so when cutting aluminum. Therefore, it is important to take safety precautions when cutting aluminum.
This entails using a breathing mask that is designed for keeping out dangerous fumes.
Aluminum is a metal used in the making and fabrication of a wide variety of things. From airplane parts to smartphones. While it is widely used, it is a somewhat unique metal and this is one of the main reasons it is used.
Thus, while you can cut it using a plasma cutter, it is important to know how to go about it. The same technique you use for plasma cutting copper may not work for aluminum.