If your plasma cutter suddenly feels like it's lost half its power, don't be too quick to blame the machine. Most of the time it hasn't lost power at all. It's just not getting something it needs to do its job properly.
I learnt that one the hard way. I was cutting something up on the back of a trailer one day, so I grabbed the nearest extension lead out of the garage like everyone does. I plugged the plasma cutter in and after about five minutes I was wondering why the bloody thing had turned gutless. It could still cut, but it was struggling way more than it should have been.
Then I noticed a little wisp of smoke coming off the extension lead. I'd never bothered unrolling it properly, so most of it was still coiled up. It was that hot it was basically acting like a bloody heater element. The extension lead was robbing the plasma cutter of the power it needed, and the poor thing never had a chance.
That was a lesson I only needed once. These days, if a plasma cutter suddenly feels weak, I don't automatically blame the machine. I start looking at everything around it first.
These days I've got a dedicated 15 amp outlet in my workshop just for the plasma cutter. I don't muck around with fifty metres of extension lead anymore. The only lead I use is about two and a half metres long, and it's made from heavy-duty cable that was made up specifically for the job.
Have a look at the plug on your plasma cutter. A lot of the 45 and 50 amp machines in New Zealand come with a proper 15 amp plug. The earth pin is bigger than a standard 10 amp plug, and that's there for a reason. It's meant to be plugged into a matching 15 amp socket that's designed to supply the current the machine needs.
I've even seen blokes file the bigger earth pin down so they can jam it into a normal 10 amp socket. Yeah, it'll plug in, and if you're cutting a bit of thin steel you might get away with it. But once you start asking the machine to do some real work, don't be surprised if it feels gutless or keeps tripping breakers. You're making the machine work with one hand tied behind its back.
If there's one thing I'd tell anyone buying a plasma cutter, it's this. Keep the plasma cutter as close as you can to what you're cutting and as close as you can to the power supply. Short, heavy-duty leads are your friend.
Your compressor's a different story. If it's noisy, stick it outside or around the corner if you want. Just run a longer air hose. That won't hurt a thing if it's the right size. It's a lot better to run another ten or twenty metres of air hose than another twenty metres of electrical extension lead.
I always try to keep the plasma cutter, the earth clamp, the job I'm cutting and the power outlet all within a few metres of each other. That way the machine gets the best electrical supply possible, the earth lead stays nice and short, and you're giving the plasma cutter every chance to do what it was designed to do.
If your plasma cutter has only started feeling weak recently, have a look at my article on why a plasma cutter suddenly starts cutting like shit. Sometimes the problem isn't the machine at all—it's something that's changed around it.
One thing that caught me out more than once was loose consumables. I honestly wouldn't have believed they could make that much difference until it happened to me several times. Every time you pull the trigger there's a bit of vibration through the torch, and if the electrode isn't done up properly it can slowly work itself loose.
When that happens, it's a bit like having a bad electrical connection. The machine still works, but it just doesn't seem to have the power it used to. The cut quality turns to rubbish, the arc becomes inconsistent and you start wondering if the plasma cutter is dying.
While you're checking the consumables, have a good look at the ceramic cup as well. If it's cracked, replace it. They're cheap enough, and a cracked cup can cause all sorts of strange cutting problems that are easy to blame on the plasma cutter.
If you're not even sure you've got the right consumables fitted, have a look through my Plasma Torch Identification Guide. It's a lot easier to identify the torch first than waste money ordering the wrong parts.
The next thing I'd check is the earth lead. I'd move the earth clamp right up beside where I was cutting. I'm talking five or six centimetres away if I can get it there. Then I'd try another cut on a clean bit of steel.
If the plasma cutter suddenly comes back to life, you've just learnt something. The problem probably isn't inside the plasma cutter at all. It's far more likely to be an electrical problem somewhere between the machine, the earth lead and the job you're cutting.
Another thing people miss is the earth clamp itself. I've seen cables burnt back until they're hanging on by a handful of copper strands, and I've seen the copper braid inside the clamp snap clean off. The clamp still grabs the steel, so everyone assumes it's fine, but electrically it's struggling.
Even if you've got a pilot arc plasma cutter, don't get lazy with the earth clamp. The pilot arc helps start the cut, but the machine still needs a good clean earth to carry the current back. Clip the earth onto rusty or painted steel and you're only making life harder for yourself.
The next thing I'd check is the air supply. Not just whether you've got air, but whether you've actually got enough of it. I've seen plenty of blokes trying to run a plasma cutter on a little compressor that's flat out trying to keep up.
The regulator might look fine while you're standing there doing nothing, but as soon as you start cutting the pressure drops away. Suddenly the plasma cutter feels like it's lost half its power, when really it's just starving for air.
Wet air is another one that catches people out. I don't know how many compressors I've seen with half a litre of water sloshing around in the bottom because nobody ever drains them. Every time the compressor starts up it's sucking moisture straight through the airline and into the torch.
It doesn't take much moisture before the cut quality starts going downhill. Drain your compressor regularly and keep the air as clean and dry as you can. It's one of the easiest maintenance jobs you'll ever do.
If you've been through everything else and the plasma cutter still feels gutless, then I'd start looking at the torch lead. This isn't a common fault—I think I've only seen it once in about fifteen years—but it does happen.
Most people think the torch lead is just an air hose with a couple of trigger wires running through it. It isn't. Inside that lead is a heavy power cable carrying all the current to the torch, while the air flowing through the lead helps keep that cable cool before it reaches the torch head.
If that lead has been run over, crushed or had a really hard life, the cable inside can start to break down. You might still have enough connection for the plasma cutter to work, but not enough to carry full current. The machine suddenly feels weak and the cut quality drops away.
If you've worked through everything else in this article, that's one of the last things I'd be checking.
One mistake I see all the time is people changing five things at once. They tighten the consumables, move the earth clamp, wind the air pressure up, swap extension leads and start turning knobs on the plasma cutter. Then they pull the trigger and it starts working. Great... but what actually fixed it?
I always change one thing at a time and then make another cut. It might take an extra five minutes, but at least you know what the fault was. Otherwise you're just guessing, and the next time it happens you're back to square one.
Diagnosing a plasma cutter is no different to diagnosing a car. Start with the simple stuff first, change one thing at a time and don't assume the most expensive part is the one that's failed. Nine times out of ten it'll be something simple that's been overlooked.
If you've worked through everything in this guide and your plasma cutter still isn't right, don't just start replacing parts. The next step depends on the symptoms you're seeing.
