Plasma Cutting With and Without Air: Which Should You Choose?

Can you use a plasma cutter without an air compressor?

Plasma cutters typically come with an air compressor, but some units come without this component. Air compressors can help you cut more precisely. They can also make your plasma cutter portable for off-the-grid jobs. However, they do come with some downsides. While you can plasma cut with or without air, your intended application will determine which is the better of the two.  

We’ve put together the following guide to help you understand the difference between plasma cutters with and without air compressors.

What is a plasma cutter?

Before we even delve into what plasma cutting is, let’s first establish what plasma is.

The word plasma describes the “fourth state of matter.” Materials move through the states of matter from a solid, to a liquid, to a gas, and then to a plasma once that gas is heated up enough. The difference between gas and plasma is that the latter is electrically conductive. In other words, plasma is ionized gas.

Plasma cutters, then, use this electrically conductive property to cut through many materials. In fact, believe it or not, people have used plasma cutters since World War II. To put it simply, plasma cutters work so well because the same electrons that ionize the gas “collide with other electrons and ions,” which releases vast amounts of energy. Enough energy to cut through thick pieces of metal, for example.

Though plasma cutters are often used in daily machine work, you’ve likely seen “cool plasma” more often than you’d think. “Neon signs, fluorescent lighting and plasma displays, just to name a few, all rely on it to get the job done.” This cool plasma, like the “hot” plasma used in cutting torches, still requires careful use.

How does a plasma cutter work?

So, it’s easy to understand what a plasma cutter does, but how exactly does ionized gas cut tangible metal pieces?

In a nutshell, plasma cutters create “a high-temperature, electrical channel of ionized gas.” This gas is then used to cut ferrous and non-ferrous materials such as “steel, copper, brass,” and aluminum, to name a few. Most plasma cutters available to the public are handheld and include a torch that allows the user to freehand cuts as needed. However, CNC plasma cutters are also becoming more popular. We’ll get more into that later, so stay tuned.

Lincoln Electric explains the process of plasma cutting as follows: “The plasma arc formation begins when a gas such as oxygen, nitrogen, argon, or even shop air is forced through a small nozzle orifice inside the torch.  An electric arc generated from the external power supply is then introduced to this high pressured gas flow, resulting in what is commonly referred to as a “plasma jet”.  The plasma jet immediately reaches temperatures up to 40,000° F, quickly piercing through the work piece and blowing away the molten material.” Basically, the plasma torch directs gas in a focused area, where electricity then turns that gas into plasma. Because temperatures achieve such high levels, the energy released cuts through thick pieces of metal. It’s a bit like welding, in the way that using a chainsaw is similar to wood burning.

How is plasma cutting used in everyday life?

WeldingTipsandTricks.com offers an instructional video on how plasma cutters work. If you understand how a welder works, the plasma cutter isn’t that much different. And since the components of a plasma cutter are more widely available nowadays, they’re more common than you might think.

For example, plasma is used “largely in custom auto shops as well as by car manufacturers to customize and create chassis and frames.” Construction workers and locksmiths use plasma cutting as well. It’s much easier to cut using plasma than investing in water-jet or laser cutting. “Hobbyists and artists use them to cut out different shapes and designs of metal that are then combined to create artwork.” Whether or not you make any profit off of the metal you cut with a plasma torch, you’ll probably find any excuse to fire it up and go to town.

And as the technology grows, “engineers are working continuously to make the unit more powerful but smaller in size while improving cut quality, increasing cut speed and extending consumable life.” And of course, improved models will soon become available to the hobbyist. Those plasma cutters already on the market should begin to offer more features as well.

What are the components of a plasma cutter?

Without seeing a plasma cutter in person, it can be a bit difficult to conceptualize how they’re set up. But there are a few components necessary to a functioning plasma cutter. Let’s go a bit further in-depth so you can see what each part is and what it’s responsible for doing.

Power Source

This one is a no-brainer. For every power tool, you need a power source. Lincoln Electric states, “The plasma power supply converts single or three phase AC line voltage into a smooth, constant DC voltage ranging from 200 to 400VDC. This DC voltage is responsible for maintaining the plasma arc throughout the cut.  It also regulates the current output required based on the material type and thickness being processed.” Whereas you might want to modulate the power output when welding, plasma cutting generally requires a pretty consistent flow of power.

Work Clamp

Similar to the welding process, you want to ground out the piece you’re working with so all that high voltage doesn’t journey through your body and wreak havoc. Most plasma cutting units will come with this standard, just as welders do.

Arc-Starting Console

The arc-starting console, or ASC, “produces an AC voltage of approximately 5,000 VAC at 2 MHz which produces the spark inside of the plasma torch to create the plasma arc.” Tremendous heat turns the gas into a plasma. In order for that to happen, the arc-starting console ignites a large flame. The gas flowing through the torch sustains the flame as you cut.

Handheld/CNC Torch

Otherwise known as the plasma torch, this is the component you hold onto as you cut. Shaped like the tip of a ballpoint pen, the torch provides “proper alignment and cooling of the consumables.” These consumables include “the electrode, swirl ring, and nozzle.” Depending on how much plasma cutting you plan on doing, you might be changing these components more often than normal.

CNC machines use fixed plasma torches to cut through large pieces of metal. You’ll find plenty of videos of CNC plasma cutting machines on the internet. The basic principle of a handheld plasma torch is the same, though CNC machines of course can cut faster, with more precision, and with arguably less variance in execution. Either way you slice it, the plasma torch directs the flow of plasma to where you want it to cut through metal.

Air Compressor

Though not a required component, air compressors can do a lot for plasma cutting. There are also some caveats to using an air compressor. Since this is the focus of our discussion today, let’s first talk about what an air compressor actually does for a plasma cutter.

What is the function of an air compressor in plasma cutting?

We know that plasma cutters use a combination of heated gas and electricity to cut through various metals. In short, it’s a hot knife and the metal is the butter. But where does compressed air come into play in plasma cutting?

Basic science lessons tell us that matter change state via high temperatures. A solid moves to a liquid, a liquid to a gas, and a gas to a plasma. The beauty of plasma cutters is that they harness this high intensity heat in order to cut metal. But that flame needs a direction, and it’s a combination of multiple gases and compressed air that push it towards the exit of the nozzle—and also removes the melted metal left behind.

Many shops use their air compressor supply to power the plasma cutter. Since they’ve already invested in the compressor, they can easily hook it up to the plasma cutter and let the gas burn. But even if you’re a hobbyist at home and you don’t have a compressor, it’s easy to drive over to your local hardware store and pick one up.

Therefore, compressed air comprises the very plasma that you can cut metal with. Since you’re already using other gases when plasma cutting, you don’t always need compressed air. In short, plasma cutters with a built-in air compressor simply add another component to the mix that brings with it both good and bad qualities.

What are the benefits of an air compressor?

Plasma cutters with built-in air compressors bring a lot of potential to the table. For example, using an air compressor allows for higher precision when it comes to cutting. The purer the plasma flame can be, the cleaner your cuts will come out. And in some cases, if you’re able to adjust the pressure coming out of the air compressor, you’ll be able to replicate settings in order to reproduce the same results over and over again.

Another upside to using compressed air—or at least owning plasma cutting units with an air compressor built-in—finds value in portability. Instead of having to power both your plasma cutter and an air compressor, you only have one power cord. And when it comes to cutting results, it’s hard to find differences between plasma cutters that have built-in air compressors and those that don’t.

What are the drawbacks of an air compressor?  

One of the biggest factors keeping plasma cutting fanatics away from units with built-in air compressors is price. There is a noticeable difference in cost between those that do and don’t have this feature. Most of the time, a standard air compressor will suffice. You can find these affordable, standalone at your local hardware store. So many people consider saving a few dollars to spend on other tools and/or accessories.

Output power can be another concern. Plasma cutters designed without a compressor on-board do not have to boot up the unit or feed it constant power either. While this may or may not have a huge effect on your power bill, it does affect the potency of the plasma cutter.

Plasma cutters with built-in air compressors rely on a fixed air pressure. And since that pressure is such a key component, any leaks in the system can have a huge effect on your cutting results. For example, your plasma cutter may develop “internal air valve leaks after extensive use,” which wastes potential cutting power. Maintaining a closed system is critical to optimal performance.

Finally, air quality plays an incredible role in the effectiveness of your plasma cutting torch. After so long, humidity may cause moisture to form. Adding water—a liquid—to the hot gas state that is plasma is detrimental to the entire cutting process. There are some machines that have accounted for moisture build-up. These units “have a release valve that can be activated to purge water buildup, but additional filtration is required to completely remove all remaining moisture in the transport lines.” Build-up of the lubricating oil is another challenge you might face. Filtration, again, ensures the cleanest plasma flame.

Summary

Pop quiz! What role does compressed air play in the plasma cutting process?

We hope you’re able to answer this question now. There are, of course, intricacies and details we couldn’t get into at the moment, but the basic idea is there. Plasma cutting allows for optimal machining and fabricating processes in a variety of fields. And within those applications, compressed air may or may not be ideal for the circumstances. Whether or not you should purchase a plasma cutter with compressed air is a decision you’ll have to make.

Thanks for tuning in for another discussion. Don’t forget to check out more of our awesome articles, on all things welding and so much more!

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