[Ben Krasnow] Drills Really Small Holes With Electricity

Drilling holes is easy; humans have been doing it in one form or another for almost 40,000 years. Drilling really tiny holes in hard materials is more challenging, but still doable. Drilling deep, straight holes in hard materials is another thing altogether.

Luckily, these days we have electric discharge machining (EDM), a technique that opens up all kinds of possibilities. And just as luckily, [Ben Krasnow] got his hands on some EDM gear to try out, with fascinating results. As [Ben] explains, at its heart EDM is just the use of a small arc to ablate metal from a surface. The arc is precisely controlled, both its frequency via an arc controller, and its location using CNC motion control. The arc controller has always been the sticking point for home EDM, but the one [Ben] tried out, a BaxEDM BX17, is squarely aimed at the small shop market. The whole test platform that [Ben] built has a decidedly home-brew look to it, with a CNC gantry rigged up to a water tank, an EDM drill head spinning the drill rods slowly, and an airless paint gun providing high-pressure process fluid. The video below shows that it works remarkably well nonetheless.

While we’re certainly keen to see [Ben]’s promised videos on EDM milling and cutting, we doubt we’ll line up to shell out €2,950 for the arc controller he used. If you have more courage than money, this mains-powered EDM might be a better fit.

Thanks to [Måns Almered] for the tip.

21 thoughts on “[Ben Krasnow] Drills Really Small Holes With Electricity

  1. I run 2 Aggie Charmilles ram EDMs everyday for my day job, working with H13 tool steel in a die making shop. They are running right now while I’m on lunch.

    Because they are very thick dies up to 10 in thick, they need ejector pin holes often 6 to 7″ deep, and straight to sub 0.001″.

    We do this using graphite electrodes with a special system for EDM called 3R. I can’t explain fully how it works because that’s proprietary, but I can tell you since I am literally doing this right now the key to getting straight holes is straight electrodes. Indicate your electrode in the machine you cut it on true with however it goes into your spindle, cutting them between centers helps, hint hint. Make sure you indicate them again in place in the spindle of the EDM before you run it.

    The other thing that is critical to getting a straight hole is using multiple electrodes all perfectly straight. Electrode wear accounts for a lot of the error in making straight holes. They will always be tapered smaller at the bottom of the hole unless you use multiple electrodes, at least 2. I use 3 when I need it near perfect, but I use graphite. Other materials, such as cuprotungsten, wear far less.

    Last bit of advice I can give is flushing is critical. You need fresh oil across the electrode if possible through the piece you are burning, and there are various ways of doing this, depending on the setup of your EDM and how it uses Flushing for the dielectric oil. a hollow electrode with cleverly ported holes might help, if its a blind hole. The pressure of the oil flow is also critical to keeping straightness. Too much is bad, too little is bad.

    Thats as much as I can say, hope it helps someone. 3R is something you might be able to look up. Its a system for setting up professional machines, but it might give you some ideas. I myself would really like an EDM for home use so I will be checking this model out now. Cool stuff!

      1. Go deep or go home, haha.

        As long as you can indicate to 0.0001″ with a good tenths reading indicator, it doesn’t take too long to learn. The neat thing I have found out is that graphite does and can bend when your electrode is 13″ long and sonetimes only 0.370 or so in diameter. Not much, but maybe 0.01″. You can actually get it to keep that bend if you’re careful and want to burn a carefully tapered hole for various ressons.

        Didn’t mention this earlier- but my machines both use 50 RPM spindle rotation when I’m doing these long holes. Helps average out electrode wear and any minor out of concentrity errors in the spindle, kind of like an electrical boring head

    1. Thanks for the tips,
      I read a few EDM papers that guided our group to use lower regulated drive-currents of around 3A to 5A (for small electrodes), 65v to 110v DC potentials, and an optimal removal frequency (1MHz-3MHz 32% duty cycle PWM). This setup will actually drill a proper hole with better surface properties and precision. Tip: we just use Tapping Fluid and a few fuel filters on a electric diesel fuel-pump… as we don’t require ridiculous fluid flushing rates.

      If Ben has the patience to reduce his output current by 500% and sets the voltage to around 50v-65v than he will probably get better results. The severe EMI problems also indicate the EDM supply designer did not include proper snubber circuitry for the output (or a grounding issue). Have a look around, as some hobbyists have built some great alternatives.

      We are using far more primitive equipment for our own internal setup (a complete commercial EDM drill is $2500 if you look around), and I think we may follow Ben’s pressure-head sourcing strategy. The delrin insert we currently use is not that great, but I’ve never seen that severity of chowder around the holes like Ben is getting on that rig.

      Nice project though, and it is great to see other groups working on making the process more accessible.
      To mill 3D printed stainless-bronze metal parts from Shapeways, you pretty much have to use this kind of process (or hide the box of broken carbide bits). ;-)

      Cheers,
      J

  2. System 3R is proprietary??? There’s absolutely nothing you could say about the tooling that hasn’t been said a million times before and that’s not readily available on the internet. It’s the standard for repeatable tooling in the tool and die and mold making industry. I have been running wire EDM and sinker/hole poppers for going on 24 years now. (Currently we have 8 Fanuc wires and 2 Current EDM hole poppers)And I’ve been using 3R and Hirschmann System 2000 and Hermann Schmidt tooling and fixtures since I started in tool and die. We specialize in Automotive, Aerospace and medical tooling. Though you are correct in stating the importance of flushing and using straight electrodes. There are other important variables to consider. Electrode feed rate, power settings and electrode rotation. But my point to this reply is the “Magical” proprietary 3R system that you mention has no bearing on making straight holes. It only assists in your ability to fixture and to have repeatability in multiple setup operations. Also.. You’re tolerance for ejector pin holes is .001 over 10 inches??? With a hole popper???? First off… What parts are your dies making and what planet is the rocket they’ll be used in heading to?? That’s a ridiculous claim and no offense…I smell B.S. If the holes were being used in a critical mold where flashing was a issue.. I could see that tolerance requirement… But a hole to guide a ejector pin that’s whole purpose is to push the material off the punch face.. Theres absolutely no reason to hold that tolerance. Just my 2 cents…

    1. Ok.. I think my wording in one place led to confusion, and you missed a couple details of mine.

      3R itself is not proprietary- hence why I suggested people look it up. I figured someone doing a homebrew EDM might not have known of it, and wouldnt have thought of adapting it directly. I was a little sparse on details due to the fact that my shop doesn’t use 3R as it comes fully standard- we have made custom fixturing and toolholders that 3R doesn’t offer to do some of what we do, and I’m under an NDA here, so I didn’t want to give more info than I thought would be helpful lest I violate that.

      That said, my shop is only medical and aerospace, and we specialize in titanium forged parts. My dies are up to 10″ thick, several feet in size, but the ejector pins are never 10″ tall. usually around 4″, but sometimes upwards of 6 or 7″, which is why I didn’t state I’m burning 10″ deep ejectors.

      Flashing is critical to us, for various reasons I can’t discuss, and hole straightness is spec’ed that way because of ejector pins bending and getting stuck, though whether or not that is the only reason, I am not privy. That’s just what my boss expects generally. I can get away with a little bit more than that, but there’s no need to. Part of that is too our spindles are not fully concentric, and need to be retrammed, but I don’t get time to fix that, so holding the hole as staight ss possible helps me hold runout down.

      You’ve been running EDMs longer than I have, and I’ve only run these 2 Agie Charmille ram EDMs, never a wire EDM. Would love to, they are really amazing machines. Would love to experience perfectly cut mating parts with no air gap that you can make on those.

      Hope that helps some, just wanted to give a bit of detail where I can offer some, where I think itll help, which is why I post on Hackaday. I have a really weird background with watchmaking, machining, and blacksmithing, and noticed how many people in my local Makerspace kept asking me questions about it all, so I started posting some of what I know here because I figured there had to be a lot more people that were interested in some of the stuff I knew. Didn’t mean to mislead anyone, hope I didn’t.

      Really cool to run into people here who arent just serious hobbiests, but also do these things for a living too. Too many people with specialized knowledge in manufacturing keep it to themselves I’m just trying to break the trend.

      1. Forgot to adda couple things- these aren’t hole popper EDMs. Those are pretty simple compared to these from what I’ve been told. Agie Charmilles SP300 if that helps any. And they use 50 RPM spindle rotation when I do ejector pin holes. See above for details.

      1. Dude, I literally just told him he’s been running these longer than I have.

        He most certainly knows a lot more than I do!

        You? I fail to see what constructive thing you add here, other than proving there are, indeed, some tools that actually make themselves, without my help

  3. I remember being 15 at the technician school, were my teacher left me responsible for an EDM machine that used a flammable fluid as dieletric.
    It was a very useful class, I learned how to operate the machine, how to use a fire extiguinsher, and how I looked without eyebrows.

    1. At 15, I was trying to learn how to run a lathe in shop class, but shop class was a glorified study hall in my school filled with delinquents, and s teacher who didn’t encourage using snything beyond a hammer.

      I ended up going to college, got a degree and worked in teaching a foreign language, long story short, changed careers and worked my way up to what you got to run at 15. I never heard of a middle school with an EDM, you were a lucky guy, except for eyebrows. At least those grow back!

  4. the problem with this whole thing is why get a crappy edm machine that hooks up kinda of to a mill when you can go out and purchase a nice used wire for that price or less and sinker edm machines around here are even less. nice idea but look into used machines first if you need this you will get better results at a lower price with more support.

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