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Next to Power Air is the life blood of your plasma cutter.   So many people think air is air and that all air is created equal well no that is not true for plasma.   Now lets make sure we are on the same page. We are talking about Air Plasma Systems here not High Definition systems that use oxygen, Argon and other gases.   Specifically we will be talking about the Hypertherm Powermax series plasma cutters which are air plasma cutting units.

Air quality can dramatically affect several things:  Cut quality, machine life,  and consumable life.

On the Hypertherm Plasma Cutters Page we talked about how much air you would need which is about 7 to 8 CFM (cubic feet a minute) at 90 psi.  This really is not a lot of air and most compressors can handle this.   There are a few factors that you need to consider though when selecting the compressor that is going to supply your air.  Your basic 3 to 5 HP 60 gallon compressor you would find at Home Depot or Lowes can usually output 11 CFM which will handle the demands of most plasma cutters, but wait you need to consider that if you are going to use any other air at the same time this needs to be factored in. With this size of compressor only being about 3 CFM above the needed and only having a 60 gallon tank your compressor will likely be running non stop. Which most of the cheap 60 gallon compressors are not designed for.  

My recommendation is if your using a 4x4 table get a 5HP 60 gallon at a minimum and if your have a 4x8 or larger you need to be at a minimum 5HP 80 gallon tank or larger.  Ideally your compressor should be able to output 1.5 to 2 times the CFM needs of your plasma cutter. Which is about 14 CFM at 90 psi.  


Delivering the CFM to your compressor -  Rarely do we place the compressor right next to the plasma machine for many reasons so we need to pipe the air to the Plasma Unit.  Distance and the size of your air line will hurt you more than you know. here are some examples.

Lets go back to the cheap 4hp compressor 60 gallon tank, 11 CFM at 90 psi 150 psi max.  We hook up your typical 3/8  100 ft air line which has an inside diameter close to .25 inches,  Your going to deliver 4.56 CFM to that plasma cutter.   Shorten that air line to 50 feet and you will deliver 6.45 CFM to the plasma cutter.    Now change the inside diameter of your air hose to .50 and a 100 foot hose will get 25.80 CFM to the plasma unit.  More than your compressor can deliver in this case.   

I see this all the time on the forums people are getting cut errors on there plasma cutter because the machine is not getting enough air.  They say the pressure gauge says 120 psi and I have a compressor that can deliver 11 CFM and I only need 7 so what is the problem and they blame the plasma unit.  With plasma cutting we need both volume and pressure.  The volume must meet the requirements at the required pressure.   Airline supply diameter has a huge influence on weather you can get the necessary CFM to the plasma cutter.    Its not uncommon to have longer runs than 100 feet.   

You can play with this air calculator on the Rapid Air Website.  

How do I know this is a real problem?  Because it happened to me.  I had a 5HP 80 gallon system delivering 14 CFM at 90 psi which was double the CFM I needed but I would run into problems in cut quality and machine errors until I found the Rapid Air site and plugged in my numbers on their website.   I ordered the ¾ Maxline Master Kit with ¾ Id tube.    The kit was super easy to install.  I ordered extra outlets and plumbed my entire shop.  One of the best investments I made for my shop.  No problems with air delivery since the install.   There is no soldering like with copper, easy connections unlike copper or black pipe.  Will not break like cheap PVC.  The system holds air and has no leaks I highly recommend it.   My delivery capability went from 5 CFM to 80 CFM after the install.   I can now run multiple air tools and the plasma without problems because of the Maxline system from Rapid Air.

Air Quality

So we talked about compressor and air lines and ensuring we can get enough air to the compressor but now we need to address the quality of the air that we deliver.   To get the best results on our cuts and to get our machine and consumable to last as long as possible we need to ensure that we deliver the cleanest, driest air possible.  No particles, no oil, no moisture. will your plasma cutter work if these things present sure, but just not as well as it could.  You can waste lots of money and time putting in a bunch of copper tubing or desiccant dryers that you will have to change continually or you can do the best thing for your system and install a refrigerated air dryer in your system.  

For my refrigerated dryer I went again with the EMAX Brand.  I selected the 58 CFM series unit.

based on my air delivery needs and the addition of the Maxline system this was plenty for my

system.  This unit cools the air below its dew point despite ambient temperature and extracts

the moisture from the air.   Sending perfectly dry air out to your shop and machines.

Here is some info on the unit:  The EMAX Premium Series of Refrigerated Electric Air Dryers are

the only energy efficient dryer system with aluminum refrigerated air inner cooler, non-corrosive

inner and after cooler. The air Filtered of all solid particles 0.01 micron and larger from the

coalescing filter and 0.05 micron from the pre-filter. Clean, Dry compressed air leaving the dryer

minimizes maintenance and repair and also reduces internal dryer contamination. We designed

them with non-corrosive inner and after cooler. Our dryers feature stainless steel heat exchanger

for maximum dryer life and less maintenance. EMAX dryers are UL-CSA approved scroll

compressor and electric system for high efficiency durability. They feature adjustable hot bypass

for complete dryer function in low and high CFM Flow preventing dryer freeze up. Our air dryers

also have built in automatic moisture drains and Built in Coalescing filters to deliver you the

driest air possible. We provide a 10 Year warranty on the Heat Exchanger and a 2 year parts

warranty.  LINK EMAX Dryer

It can be very expensive to do all of these things at the start.  You can use filters and and other

options In the beginning but they are not as good as going this route.  Just know that if moisture,

oil or contaminates are present in your air your cut quality will suffer.

My System

I have a 5HP 80 gallon tank with an additional 80 gallon receiver tank.  The air goes from these tanks through an oil water separator filter. This pulls oil and moisture off before it goes to the dryer not necessary but helps the dryer last longer. The air goes out the dryer and to a pressure regulator.  The pressure going to to my shop is regulated to 110 psi.   The air runs through the Maxline ¾ to a coalescing filter which removes any contaminates before going to the plasma unit via a .5 inch flexible hose.   Back at the compressor I have a bypass valve and extra filters just incase my dryer is out of service I can send air around the dryer and run it thorough two filers to remove as much moisture as possible in case the need arises.

Additional Air information resources -  Compressed Air Tech Tips

I really like the EMAX brand compressors.  They have many models but their silent air series are really nice.  The come in 5hp, 7.5HP, 10hp and 15HP and are available through Home Depot.   The one to the left is an example of their 5 HP model.  Nice and quiet, High CFM and a great warranty.    This model is about $2400.

Here is a link to check this model out on the Home Depot website:

EMAX 80 Gallon 5HP

There 7.5HP Silent compressor has an incredible output of 31 CFM @100 psi and operates at a super Quite 60 DBA.  This would be the compressor of choice for a 5x10 table or where you are cutting non stop.  Plenty of air to keep up and super quiet.   Here I a link:

EMAX 80 Gallon 7.5HP

The EMAX Brand compressors come with a lot of nice options included like the automatic tank drain and a great warranty.   

For Price, quality, options, noise levels and durability EMAX is my first choice.

Rotary Screw vs Piston - I touch briefly on this topic.  I was considering moving to a Rotary Screw machine from my Piston machine a few years back.  I went to the SEMA and FABTECH shows and talked with all of the major compressor manufactures.  Everyone told me for my application to stay in a piston compressor.  They said that unless I was using about 25 CFM or more constantly it was not worth it.  Rotary Screw compressors like to run nonstop not start and stop.  For just plasma my air demands were not great enough to justify the move to a rotary screw. They told me if I was running multiple operations all day like blasting and plasma and it was not stop and around 30 CFM demand the switch would be worth while.