How to Diagnose your Sick Plasma Cutter

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Plasma cutters work by sending a pressurized “gas” (in our case compressed air), through a small channel. In the center of this channel, you’ll find a negatively charged electrode. When you apply power to the negative electrode, and you touch the tip of the nozzle to the grounded metal (or a pilot arc touches), the connection creates a circuit. A powerful spark is generated between the electrode and the metal. As the inert gas passes through the channel, the spark heats the gas until it reaches the fourth state of matter. This reaction creates a stream of directed plasma, approximately 30,000 F and moving at 20,000 feet per second that reduces metal to molten slag. The plasma itself conducts electrical current. The cycle of creating the arc is continuous as long as power is supplied to the electrode and the plasma stays in contact with the metal that is being cut. The cutter nozzle has a second set of channels. These channels release a constant flow of shielding gas around the cutting area. The pressure of this gas flow effectively controls the radius of the plasma beam.

What does this mean to you? That small, intense plasma beam is extremely powerful and can cut through metal with ease. This also means it can wear out consumables. We get calls from time to time about customers that have had issues with their plasma cutters. The symptoms are often that the plasma cutter won’t initiate an arc on the metal, or the arc will start and stop erratically while you’re cutting. I decided to put together a few causes for those sort of issues. Hopefully one of them can save you time when diagnosing an issue with your plasma cutter.

1.Initiating an arc with no or too little air pressure- Without the air to cool the consumables the arc alone can super-heat the electrode and burn up the tungsten found in the center of the electrode almost instantly. It can happen easily and in an instant. Say you forgot to flip the pressure valve to feed your airline and hit the trigger once or twice before realizing what the issue is, you probably damaged your electrode.

2. Too slow of travel speed when cutting- Moving excessively slow when cutting (especially at higher amps) overheats the torch consumables and can cause the parts to wear out prematurely. It can also cause the arc to terminate.

3. Dragging the Torch Nozzle on work piece- This is a common mistake beginners make. It can overheat the nozzle and it also exposes the nozzle to an abundance of slag which can wear it out extremely quick.

4. Inadequate Water separator or air dryer on compressor or internal separator full. Water in the air stream will “put the fire out” in the torch. It can cause the arc to be erratic and unstable and may seem like the plasma cutter isn’t working correctly. Make sure at the least you are running a small disposable in-line water separator or upgrade to a desiccant system on your compressor. The internal plasma cutter’s separator should be checked or drained periodically.

5. Too long or small of an extension cord being used on the machine- If you have a low quality, thin gauge extension cord or too long of a cord the machine could have trouble initiating an arc or it won’t cut metal as thick as rated or the settings on machine don’t match what it can cut.

Below are some samples of bad consumables. If your nozzle has an elnlarged, oblong, or otherwise gouged out center it will cause the plasma beam to wander and will lose it’s punch. If you allow it to get too worn like seen below, it will burn a divot into the center of the electrode, thus burning out the conductive tungsten that’s creates the arc in the electrode. Lastly if you get the torch too hot or you light up the torch with no air pressure it can overheat and melt the swirl cup/diffusor and it may look something like below. This will cause the air to fail to mix in the torch and will make an unstable arc. The moral of the story is to be sure to inspect your torch parts regularly and make sure that none are worn out.

Photo Aug 21, 2 46 48 PM

Photo Aug 21, 2 46 53 PM

47 Comments

  1. Very informative and helpful. I have a used plasma and have had limited success from it eating my tips like candy. I now know a little better what I should be doing. Thanks and keep the info coming. I’m a long time Eastwood customer and fan, Trevor in Alsip is THE man.

  2. You say “dragging the nozzle on the work piece” is incorrect; I thought that is how it is used. What am I missing?

  3. Generally holding the torch tip just above the workpiece is more ideal and will double to triple your tips lifespan. Our plasma cutters have a high-frequency start and do not require “scratch starting” or dragging the nozzle like some others on the market. Hope that helps!

  4. I have an eastwood Plasma cutter it came with a small water separator but it did not tell me were to put it , Can you help me with this . Thanks Tom

  5. 3. Dragging the Torch Nozzle on work piece- This is a common mistake beginners make. It can overheat the nozzle and it also exposes the nozzle to an abundance of slag which can wear it out extremely quick.

    This statement is not TRUE as the tips sold by Eastwood are made to DRAG on the metal being cut.

  6. IN the answer to bill, you mention that your plasma cutters have a ‘high frequency start’. What is this? What is the best way to start a cut from the middle of a piece of 1/8 hot roll steel?
    Thank you

  7. Good point, the tips we include can withstand dragging, but the point I’m making is that dragging them for long cuts, especially on dirty metal, or on thick materials where the plasma stream may not cut all the way through instantly can cause premature wear of the nozzles, electrodes, and diffusors. There are times when dragging is necessary but doing it 100% of the time can cause the parts to wear out faster. Good point, I’m glad we could clarify better for other readers!

  8. Hi Tom, which plasma cutter do you have, we can happily send you a set of instructions if you’d like more info on where the internal separator is.

  9. Hi Mark,

    This means that the plasma cutter can “jump” the arc and does not require you to drag the tip to initiate an arc. This high frequency start also allows you to start an arc on metal that isn’t perfectly bare, clean metal (for instance cutting out an old rusty floor). I generally like to make an “entrance path” cut if it’s something that you want to cut a shape out of the middle of a panel. Starting directly on your pattern can cause that first cut to be a little larger than needed. I start just to the side of the piece and once I have the cut started and controlled I work over to my shape and cut it out, always worked well for me!

  10. Great tips on plasma cutting….I have just learned a lot about consumable damage!!
    I have both your 40 & 60 amp plasmas.
    They work great as do your mig175 and 250amp!! Spool guns are a dream to use also.
    Thanks for all the great info on your products.
    Ed
    BC Canada

  11. Good tips, perhaps you can answer my question. Why is it on all the car shows when they are using a plasma to skin a quarter etc. the cut always comes out clean, tight and no bleeding edges and requires minimal grinding..I have an Eastwood 40 and no matter what the setup is my edges are jagged, slaggy and the cut is wide..requiring either cleaning up with a cutoff wheel or excessive grinding ?

  12. Matt — How do I prevent slag/molten metal from back-filling the cut? What am I doing wrong?

  13. Could you shine a little insight on extended tips and nozzles? Theres not alot of info on this. Thanks!

  14. In the second picture, what is wrong with the first and third consumables? They appear fine. In fact the third one (nozzle tip) looks brand new.

  15. The problem I had to work through was initially getting the air pressure correct. My air system pressure into the regulator on the plasma cutter was too high for the cutter regulator to drop fast enough. result was it would blow out the torch before it could drop pressure fast enough. Fix was a second air regulator on the air line to feed cutter at lower pressure so torch regulator would work correctly. 🙂

  16. My plasma cutter recently started to cut on an angle. I’ve replaced all the consumables in the handle, which helps for a very short time. It wears the hole in the tip to one side & the cut leaves an angled edge on the material. Should I replace my whole handle next?

  17. Hi Jaison,

    The handle itself wouldn’t cause that. If you always hold the torch and cut at the same angle it will always wear the nozzle the same. Similar to how your heel of your shoes may wear out quicker than the front if you drag your heel. That side of the nozzle is seeing most of the heat and sparks while cutting so it will wear that edge away the same. Hope that helps!

  18. Hi John, you may need to check your air pressure while the machine is cutting or an arc is initiated. Often times too low of an air pressure will not push the molten metal or slag away from the cut completely and can backfill the cut or stick to the edges causing excessive cleanup.

  19. The cleanliness of the metal you’re cutting makes a big difference. The more paint, grease, rust, etc that your torch has to cut through, the more slag or spatter it can cause. Also make sure that your air pressure and amperage are high enough that it can EASILY blow through the piece your cutting. For the cleanest cut I always start with new consumables. Especially when cutting sheet metal where I need to be ultra accurate. I’ve also used a straight edge and set my torch up so the edge of the cup can ride against the straight edge as I cut to make sure that my hand doesn’t wander during cutting.

  20. There are 3 tips for a plasma cutter one is a dragging tip where it can touch the metal,gouging for cutting welds and a cutting tip where you hold it above the metal and do not let it touch or it will ground out and ruin the tip

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