How Much Air Does a Plasma Cutter Need? (A Complete Guide)

Plasma cutters are great tools to have in the shop. You could hardly find a faster tool for cutting out all kinds of shapes from metal plates and sheets. Before you get one, though, you should ensure your shop can support it. One of the things that plasma cutters need is compressed air.

So, how much air does a plasma cutter need? Air requirements for a plasma cutter will require about 4-8 SCFM delivered at 90-120 PSI. This will cover units that are intended for up to 3/8″ thick steel to large units that can handle 7/8″ this steel.

Of course, there are caveats to this. Also, there are some things to keep in mind when matching a plasma cutter to an air compressor. Let’s go over some of these things that are worth knowing.

How Much Air Does A Plasma Cutter Need

Plasma cutters require a high volume of clean, dry compressed air to blow away the molten metal. 

A good rule of thumb is the air compressor should be able to supply 2.5 liters/second at 90 psi or 625 kPa. This equals about 4.5-5.5 CFM (cubic feet per minute) of free air delivery.

Examples of Plasma Cutters Along with Air Requirements

To give one blanket statement about air requirements for all types of plasma cutters offers no guarantees of success. Let’s go over some examples of common plasma cutters and what their requirements are. Then you can match this to what you have or are interested in.

Smaller units (3/8″ steel cutting) commonly have air requirements at about 4-5 SCFM at 90-120 PSI. Examples of this are the Hypertherm Powermax45 Plasma Cutter and the Miller Spectrum 375.

Medium-sized units (5/8″-3/4″ steel cutting) like the Miller Spectrum 625 and the Hypertherm Powermax 65 take about 6 SCFM at 90-120 PSI.

Heavy-duty units (3/4″-1″ steel cutting)like the the Miller Spectrum 875 will need about 7-8 SCFM at 90-120 PSI.

Really heavy-duty units (1-3/4″ steel cutting) like the Hypertherm Powermax 125 take about 9 SCFM at 85 PSI.

What Else Does A Plasma Cutter Need?

Aside from the main unit itself, a plasma cutter needs 2 extra pieces of gear: an air compressor and an air drying/filtering system.

The compressor is pretty self-explanatory: It provides the necessary air for the plasma cutter to work properly. If you don’t have this, you won’t be able to get very far.

The Compressor that I currently recommend is the California Air Tools 2-HP compressor (available on Amazon).

As the name implies, this is a 2-hp compressor, which is more than enough for working in a garage or a small workshop.

To learn more, check out this in-depth guide on the best air compressor for plasma cutters.

The second piece of equipment you need, the air filter/drying system, will ensure your plasma cutter stays as dry as possible.

As you probably know already, moisture is one of the main reasons why tools stop working prematurely, so this is very important to ensure your tools stay working as long as possible. The air drying system that I recommend is this Pneumatic Plus Three Stage Air Drying System, and it’s one of the best ways to protect your plasma cutter. Highly recommended!

How Is The Air Regulated In Plasma Cutters

Plasma cutters require compressed air at high pressure in order to generate sufficient plasma flow for cutting. The air inlet fitting on the cutter will specify a required pressure range, typically 80-100 PSI.

This incoming air must be supplied at the specified pressure from the compressor and filtration system. However, too much pressure can damage internal components over time.

So most plasma cutters have an internal regulator that takes this high inlet pressure and reduces it to a precise lower level for optimal cutting performance.

The regulator steps the pressure down to the ideal psi at the torch based on the cutter’s design and capacity rating. This is usually in the range of 60-80 psi.

What Is CFM And SCFM

While we are talking about air pressure, one thing you might have noticed is CFM and SCFM ratings. So what are they exactly and how do they differ?

CFM stands for cubic feet per minute and refers to the volume of air flow. 

SCFM stands for standard cubic feet per minute. It is a measurement used to compensate for differences in atmospheric pressure and temperature. While CFM is an absolute measurement, SCFM standardizes the volume of gas to a base set of conditions (typically 14.7 psi and 68°F).

This allows for an apples-to-apples comparison when sizing air compressors and other air delivery equipment. The conversion between CFM and SCFM depends on the actual atmospheric pressure and temperature.

At sea level and 68°F, CFM and SCFM are equal. But with change in altitude and temperature, the values will differ.

How to Match an Air Compressor to a Plasma Cutter

Don’t pair a plasma cutter that requires 4 CFM to a compressor that produces 4 SCFM. It’s unlikely that the compressor will be able to keep up. There are a few reasons for this.

One is that this is the max rating for the compressor. It’s like saying your car has a max speed of 160 MPH and then expecting it to maintain that speed on a long road trip across the country. It’s just not a good idea; you’ll burn out your compressor for sure. Good compressors ain’t cheap, either.

Another problem is that the output rating is calibrated to a particular altitude, temperature and humidity level. You’ll notice that there’s an S in front of the CFM rating. This means Standard Cubic Feet per Minute. This is calibrated to 68ºF, 0% humidity and at sea level. If any of these numbers rise, your compressor output will drop.

Here’s an example: If you live in Denver, Colorado, you’ll likely have a 20% efficiency drop because of the altitude. For those that live in Miami, Florida, you’ll probably have a 7% drop because of the humidity. If your compressor is sucking hot air in from a small enclosed boiler room, you might lose 10-20% efficiency.

If you don’t want to figure out compressor specs based on environmental conditions, just add a 50% fudge factor. For example, if your plasma cutter needs 4 CFM at 100 PSI, you should at least have a compressor that’s rated for 6 CFM.

The Importance Of Properly Sized Compressors For Plasma Cutters

Plasma cutters require a constant supply of compressed air while operating. Small compressors often cannot maintain the required airflow for more than brief periods, resulting in the cutter repeatedly shutting off to allow the compressor to catch up.

Compressors with very small 2-10 liter tanks simply cannot provide sustained airflow for adequate plasma cutting. Even for thin sheet metal, the plasma cutter may cut out after only 10-30 seconds before the tiny tank re-pressurizes.

For example, a 20 liter tank may supply 10 seconds of continuous cutting before the compressor starts up again. This makes completing longer cuts very difficult and frustrating.

Larger external compressors in the 20+ gallon size range with 3-5 HP motors are far better suited for plasma cutting needs. The larger tank volume allows much longer run times before needing to kick on and refill the tank. This provides smooth, uninterrupted airflow to maintain the plasma arc.

The larger motor also enables faster recovery time to recharge the tank volume.

Now there’s another option too – getting a plasma cutter with built-in air compressor. But remember that the built-in compressors on compact plasma cutters are very limited in duty cycle and cutting capacity.

Although they help make the unit portable, the small air pump and reservoir overheats quickly. This restricts its ability to make longer cuts or cut thicker material.

Speaking of plasma cutters, are you interested in purchasing a new plasma cutter on a budget? Then don’t forget to check out our guide on the best cheap plasma cutters.

Does Air Quality Affect Plasma Cutting?

The air quality is actually really important for plasma cutting. If there is oil or water in the compressed air, the cut quality will go down, and you’ll be burning through your consumables very quickly. Here’s a list of the consumables for a plasma cutter, all of which will be negatively affected by poor-quality air:

• Nozzle
• Shield
• Retaining Cap
• Electrode
• Swirl Ring

Another factor to keep in mind for air quality is dust control. Excessive dust that gets into the system can damage your equipment, mess up your electrodes, and make your cuts ugly.

The solution for all of this is to buy an inline compressed air filter. It will take care of dust, oils, and moisture. These things are pretty hard to justify not getting.

While you could drop a few hundred on an industrial version, you can get one that will work perfectly for your garage at a budget-friendly price like this one here available on Amazon. This will keep all of your tools in great condition.

The bottom line is that if your air isn’t filtered and dry, your cut quality will go down, and your equipment won’t last.

Alternative Plasma Table Gases

While compressed air is the most common and cheapest for plasma cutting, it’s not the only option. You can also use other gases. Here are some other options, along with why you might want to use them:

Oxygen

This is an industry standard for cutting mild steel. It allows for really efficient cutting, and the cut quality is excellent. This is because the oxygen reacts with the plasma in a way that keeps the spray fast and narrow, so the cutting is highly concentrated.

However, cutting aluminum or stainless with plasma isn’t recommended. Oxygen in the plasma will also put a lot of extra wear and tear on the consumables, especially during piercing. To counteract this, some advanced systems use two different gases: nitrogen for piercing and then oxygen for cutting.

Ultimately, though, oxygen is expensive. You’ll need a really efficient, streamlined system to take advantage of the faster cutting speeds in a way that makes cents. Awful pun intended.

Nitrogen

This is the best gas to use if you cut a lot of aluminum or stainless. Cut quality and consumables life is good (1000 starts is pretty average). For thick materials over 1/2″, though, it doesn’t perform as well as other gases.

Ultimately, though, nitrogen systems often don’t make much sense. Cut speed and quality are only slightly better than compressed air, and nitrogen is significantly more expensive.

Argon-Hydrogen

This is awesome for thick aluminum and stainless. It’s the hottest burning gas in the typical lineup, so it really boosts the heavy-duty applications. The only problem is that this stuff is really pricey, so you’re best off only using it when you need to.

The main challenge with these alternate gases is that your machine needs to be compatible. This is why lots of job shops and garages just go with a regular compressed air unit. It’s the simplest and cheapest to maintain.

Usually, the only time that using other gases makes sense is when you’re doing a lot of well-paid production cutting.

Setting Plasma Cutter Air Pressure

A common oversight when using a plasma cutter is that operators incorrectly set the air pressure. Many machines say they work with a range of 90-120 PSI, so some people just set them to 90 and forget about it.

The recommended air pressure actually varies by material type, material thickness, and type of operation. For example, gouging usually takes higher air pressure than cutting.

Your best bet is just thoroughly to read your machine manual. Every machine is a little different, but your manual will likely give you a chart or two of the recommended settings based on what you’re doing. You may decide to fine-tune these later, but they generally work really well.

At the end of the day, you need to ensure that your air supply meets the needs of your plasma cutter. With a compressor that is too small, you could starve the plasma or burn out your compressor.

If the air quality is poor, containing moisture, oil, or dust, you could damage your equipment, and you’ll have lower-quality cuts. If your air pressure isn’t set right, you’ll lose efficiency, and your cuts won’t be as pretty as they could be.

Now that you know about how much air is needed for plasma cutter, it time to start working on the actual projects? Check out this guide on the best plasma cutter project ideas.

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