Build A Baby Plasma Cutter–Right Now!

What hacker doesn’t want a plasma cutter? Even if you aren’t MacGyver, you can probably build this one in a few minutes using things you have on hand. The catch? You probably can’t cut anything more than tin foil with it, and it is probably more a carbon-air arc gouger (which uses plasma) than a true plasma cutter. Still, as [Little Shop of Physics] shows on the video, it does a fine job of slicing right through foil.

If you are like us, you are back now after getting four 9V batteries, some tin foil, a pencil lead, and some clip leads and trying it. If you have more self-restraint than we do, you might want to think about what you are going to put the tin foil over. In the video, they used a laundry basket and a rubber band, but anything that keeps the foil suspended would do the trick.

Although it isn’t really a practical plasma cutter, we were thinking about strapping something like this to a 3D printer and cutting foil stencils. The jagged edges on the video are, hopefully, more from being operated by hand and less from the jagged mini-lightning bolt vaporizing the foil.

The video repeatedly talks about lead, but a pencil lead is confusingly not made of lead. It is actually graphite (a form of carbon) which makes it a good (and inexpensive) electrode for this application, even though it is mixed with a clay binder.

If you want something more practical, prepare to spend at least a few hundred dollars or more. You’ll need a source of gas (or maybe a few gasses), a high voltage supply in the MHz range, and a hefty constant current DC power supply. You might also want to throw in LinuxCNC.

43 thoughts on “Build A Baby Plasma Cutter–Right Now!

  1. If that’s true and those jaggies are from being hand held and not from the arc, this would be awesome for cutting foils.

    A while back, I had a printing company create some foil based stickers. They were very nice but came in whole sheets because the foil destroyed their cutting blade. I had to use an X-acto blade to cut the tedious shape a computer would have more patience for.

    If I could do the entire process at home using a 3D printer to cut the stickers, I would absolutely do it.

    1. This. A plasma cutter relies on a jet of — Plasma. It’s obviously not a plasma cutter. One might argue whether there’s a tiny amount of plasma involved, but as long as that plasma is not accelerated towards the machined part, it’s **not** plasma cutting.

      Arc Gouging also requires the molten material to be blasted away.

      No, this is simple electrical discharge machining, where the higher-resistance arc heats up the metal, and in the case of thin aluminium foil oxidates it or evaporates it, or melts it to droplets on the new cut edges.

      Hence, I really don’t think the irregularities are caused by the hand motion alone — hot aluminium doesn’t nicely get soft and melt, but it has what I call a “mushy” phase, where it’s not quite liquid yet, but aluminum foil will crumble up in this condition. The crumbling behaviour depends on movement relative to stretch direction, and hence the cut quality will depend on the direction you cut.

      Frankly, this is a badly done spark weld. The fact alone that they need to use 36V inidicates that contact is irregular and bad, and that current and thus, power, can’t be properly delivered.

      1. Yeah, aluminum does not get red like steel before it goes. It goes from solid to in your lap in a fraction of a second. It does become mushy like you say. Kind of like a metal slushy.

        Aluminum cuts pretty terrible with a plasma cutter, you really need a big machine to do it semi-clean. Even with the big 4400w laser at the place I used to work at aluminum cuts pretty rough. When you cut steel with a plasma or laser you have an assist gas (air on cheap plasmas) that burns away the steel but that just does not work with aluminum. You are pretty much melting the aluminum and blowing it away. I thing Ar/H2 mix is supposed to be good for cutting aluminum. I dont know, I have never tried it. My plasma cutter does have a provision for separate shield and plasma gasses.

    1. Hi I tried it with lab power supply. 36V 2.5 – 3 A. It goes well and it cut like wild. if i give it 5 A it cut a 5mm wide incision in foil. I got 0.5 mm diameter of carbon pencil.

    1. The answer to this is yes if you use it more than a few times. Even looking at a video recording of someone welding is bad for your eyes although you probably wont go blind immediately. (Someone will correct me if i’m wrong, or possibly if I’m right :p)

      1. Your screen must be way better than mine, mine only has red green and blue. I will have to get a screen like yours, then record myself welding, then use that to expose my pcb’s. Maybe I can etch them too! Anyone have picture of ferric chloride?

        1. So that’s why i got sunburned from watching a Baywatch marathon! To save power consumption lets record our microwave ovens and play it back to heat popcorn! 1500w vs 50w of the led tv.

  2. The usage of the word lead comes from the old times, when lead was actually used in pencils. They’re still called lead pens / pencils in my language. I used to try to make small arc lamps using 0.9 mm automatic pencil leads when I was a kid. All I could get was little sparks due to using only a single AA battery, and not having anything to hold them at a stable distance with.

    1. When I was a kid we took the carbon rods out of D cells to make arc furnaces with rectified 120V going in and a flower pot as the crucible or whatever you call it. I’m sure today you can’t let kids take D cell batteries apart, though…

  3. I used to love doing this as a kid. I was using two 12V really bad quality power adapters(about 25V unloaded each) and as many capacitors in parallel as I could find. I remember that the cheapest quality leads were the best for this.

    But still, not a plasma cutter.

    1. A pc ATX style power supply works well.
      5V tends to trip the protection less often than the 12V they supply plenty of current.
      Although rather than a pencil I’d suggest the centre of a dry old fashioned zinc carbon D cell or perhaps a carpenters pencil.

  4. Just did this with a stick of pencil lead, bench power supply set to 30V and 3A and some aluminium tape. White spot in the centre of my vision now. Think I will bring my welding goggles in to work tomorrow. Might attach a big capacitor and see if I can get it to spot weld wire…

    1. Uh, be a bit more careful, please. White spot in centre == dangerous! See a doctor; I know it gets better by itself, but if you’ve got what later might become permanent damage, an ophthalmologist might be able to diagnose and help the healing process. Don’t take this lightly, please.

      Also, with 90W and a bit of bad luck, the aluminium foil might start to develop a self-sustaining flame, which will burn through the whole foil and incite the rest of your surroundings. Metal fires are extremely hot. Be warned.

  5. I went to Colorado State University for my electrical engineering degree. If you are ever around when The Little Shop of Physics is doing an open house, DEFINITELY GO. They have endless rooms of amazing physics demos that make you giggle with happiness.

    1. I fully agree. Compared to the American Hacker ( https://www.youtube.com/watch?v=CZaclt2MsmI ) this presentation is much better, smooth aluminum foil instead of some wrinkled leftover obviously retrieved from the bin, a finer rod of graphiteclay but more importantly normal pronounciation and a cool T-shirt to look at. The good parts are kept of course: the smiley face happy ending :-) The video may be uploaded a bit later, but a month is only a small price to pay. People have been trying to swim more upstream, so the first presentation may be hard to find, but I once saw a very old B/W depiction of a hand holding a sharpened pencil cracked open along its length with a wire atached. I think it was a 100yrs old. But the presentation was not so good as here.

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