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

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47 thoughts on How to Diagnose your Sick Plasma Cutter

  • Thanks for the help. I see I wasn’t very clear, use it in a CNC machine, & also by hand. In both situations I’m having this issue. I’ll double check the CNC to be sure it’s squarely mounted.

  • Great questions & answers generated here Matt. I would like to say to all, as well, practice and experiment on like kind materials as your project and make your adjustments as needed before getting into your actual project material. Pay close attention to all variations as you go from one project to another and soon you’ll be able to set your machine right off the git go for any new job.

  • It all depends on what you’re cutting, how long the cuts are you’re making, cleanliness of the metal, etc. The key is to make sure you’re checking them regularly so your plasma cutter performs its best.

  • Ideally the torch should be as “straight” or perpendicular as possible but it’s often hard to see where you’re cutting. Torch angle should be as minimal as possible with it favoring the “straight” side of the cut (there’s a straight and angled side of a cut with a plasma cutter).

  • The Eastwood Versa-cut 40 is the workhorse of our shop. We almost always use new consumables for our projects. It seems expensive, but you have to consider how much you are saving by not having to buy near as many cutting and grinding wheels and drill bits.

  • Using the Plasma #40, without the “Cutting Guide”, what is the proper tip to work distance for 18 gage material?

  • My post air on my versa cut 60 stays on until I power down the machine. after I cycle the power it will be off until i cut again. What can I do to fix this? My air pressure is 60psi and the machine is running off of a dedicated 50 amp circuit with 6 gauge wiring so I don’t thing power is a problem. I am needing to use this for a couple weeks before I could send it back, i cant be with out it for 2 weeks at this point. If I send it back right now I might as well just return it and buy something else.

  • So nice post,very informative and helpful to me thanks for such a good post.plasma is best for cutting it works reliably for metal cutting.

  • My eastwood plasma cutter was working this morning and now won’t struck an arch. I changed the consumables and checked connections, what’s my next likely cause? Thanks

  • Hi wondering if anyone can help i am in AUS and have a boc cut 40 machine i have had it for about 5 years i do not use it much because eveytime i do the cut that i get is always on a angle. I changed my gun to a cheap ebay gun and this sort of corrected some of the problem. Any help would be great.
    Thanks.
    P.s this still happens with guide wheels.

  • Have you changed all of the nozzles and electrodes out? Usually a worn nozzle or electrode will cause that.

  • I have a Versa Cut 40. If it loses the arc or I stop a cut I have to wait until the air flow stops for the machine to again strike an arc. As long as I’m cutting it will keep the arc but once I stop I have to wait for the air flow to stop to begin again. Its frustrating when making short and numerous cuts. I have replaced the electrode and the nozzle but it still does it. The diffuser has some burnt spots on its edge. What could be my problem? Thanks…

  • Hi Dave,

    Our machine has a built in safety timer (for lack of a better term) that will require you to let the air flow stop before reigniting the torch. This is only when it senses the circuit is broken for too long and the torch isn’t cutting. It is meant to save the torch and machine from damage by leaving the high-frequency pilot arc on for too long. A poor ground, excessively dirty metal, or worn out electrode or nozzle could cause an issue with poor arc start.

  • I have a miller spectrum 375 plasma cutter and ice-27C torch. When I start cutting every 5 to 10 seconds it goes out then comes back on then goes out again. Why is that?and what do I have to do help please thanks

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