Machining with Electricity Hack Chat

Machining isn't just making chips

Wednesday, January 18, 2023 12:00 pm PST Local time zone:
Hack Chat
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Daniel Herrington will host the Hack Chat on Wednesday, January 18 at noon Pacific.

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With few exceptions, metalworking has largely been about making chips, and finding something hard enough and tough enough to cut those chips has always been the challenge. Whether it's high-speed steel, tungsten carbide, or even little chunks of rocks like garnet or diamond, cutting metal has always used a mechanical interaction between tool and stock, often with spectacular results.

But then, some bright bulb somewhere realized that electricity could be used to remove metal from a workpiece in a controlled fashion. Whether it's using electric sparks to erode metal -- electric discharge machining (EDM) -- or using what amounts to electroplating in reverse -- electrochemical machining (ECM) -- electrical machining methods have made previously impossible operations commonplace.

While the technology behind ExM isn't really that popular in the hobby machine shop yet, a lot of the equipment needed and the methods to make it all work are conceivably DIY-able. But the first step toward that is understanding how it all works, and we're lucky enough to have Daniel Herrington stop by the Hack Chat to help us out with that. Daniel is CEO and founder of Voxel Innovations, a company that's on the cutting edge of electrochemical machining with its pulsed ECM technology. There's a lot to unpack, so make sure you stop by so we can all get up to speed on what's up with using electricity to do the machining.

  • Hack Chat Transcript, Part 2

    Dan Maloney01/18/2023 at 21:05 0 comments

    Thomas Shaddack12:41 PM
    Idea. A plastic bag, acting as an enclosure. Big enough and mobile enough to allow the tool moving around. Mild overpressure inside to keep it inflated to stay out of the way. Should contain the splatter.

    Cooper12:42 PM
    Thomas - not resin, but 3D printed plastic tooling I made:

    Daniel Herrington12:42 PM
    It leaks through things you thought were sealed, precision surfaces are destroyed, common of-the-shelf tooling is usually made of some carbon steel and it rapidly rusts.

    Cooper12:42 PM
    Yes. I've damaged expensive linear rails beyond repair with ECM

    anfractuosity12:43 PM
    What do you use for the electrolyte? I think I saw sodium chloride is used sometimes?

    Thomas Shaddack12:43 PM
    Oh, that's sweet! I thought about printing a negative shape, you just deposit metal on top of a printout.

    John12:43 PM
    @Thomas Shaddack I have played around with using rubber sheeting, way covers, plastic bags, and tubing to try and protect RepRap ECM machines from electrolyte corrosion. It is very difficult because the hydrogen/oxygen forms water droplets as it escapes, carrying the corrosive and poisonous vapor around the room/machine.

    Cooper12:43 PM
    Yep! That was a few years ago though. I've since switched to EDM because I'm not shooting for nanometer precision

    Daniel Herrington12:43 PM
    @anfractuosity - our standard electrolyte is sodium nitrate but we experiment with a wide range of electrolytes including concentrated acid or base

    Thomas Shaddack12:44 PM
    Hence the plastic bag. A sealing membrane over the water-air interface. What could also work is some sort of covers over the rails/screws and keeping that at mild overpressure so the air current blows away the corrosive aerosols.

    Thomas Shaddack12:44 PM
    Would a layer of oil on the surface prevent the aerosolization?

    Daniel Herrington12:45 PM
    And in case you were wondering, when you spring a leak and that electrolyte sprays on a VFD, it tends to catch on fire. The joys of using a very conductive electrolyte around electronics...

    John12:45 PM
    For DIY J-ECM I used table salt and detergent too good effect. Perfect for micromachining aluminum.

    Cooper12:46 PM
    I also used table salt when I experimented with JECM

    Thomas Shaddack12:46 PM
    Does it leak under pressure or just trickles out? The latter can be approached in the similar way the dykes and dams are around big oil tanks in refineries, to contain the spills and redirect them where they can be handled easier.

    RichardCollins12:46 PM
    Plasma electrochemistry is no different than wet electrochemistry, just dealing with water for cooling and ions. Gas mixtures just change the chemistry at the electrode. Electron and ion implantation and machining can be done in vacuum air or water. All these technologies are part of using electrons and ions and neutral particles for practical things.

    Thomas Shaddack12:46 PM
    ion implantation IN WATER?!?

    Daniel Herrington12:46 PM
    One of the biggest challenges we find is that there are all sorts of interested ideas in the litterature about organic electrolytes or electrolyte combinations but they often don't scale well so that you can recirculate it in a closed system and actively control the conductivity, temperature, ph, etc.

    Cooper12:47 PM
    Thomas - bc of the high currents involved it is necessary to have very high flow to prevent boiling. Most leaks would result in a large spray or misting of electrolyte

    Thomas Shaddack12:47 PM
    The nonscalable approaches can still have merits for one-off DIY-class component.

    Thomas Shaddack12:47 PM
    ARGH. The high flow is the fly in the ointment.

    Dan Maloney12:47 PM
    What kind of control systems are needed for the ECM process? I know EDM needs pretty tight control to keep the arc consistent, but it seems like ECM might be a "kinder, gentler" process

    RichardCollins12:48 PM
    If you can think of it, and search, you will find many people who have been at it for decades. I started with electrochemistry 55 years ago. The learned electrodynamics and try to...

    Read more »

  • Hack Chat Transcript, Part 1

    Dan Maloney01/18/2023 at 21:05 0 comments

    Dan Maloney12:00 PM
    OK folks, welcome to the first Hack Chat of 2023! I'm Dan, and as usual I'll be moderating today along with Dusan -- I think, anyway. Today we're welcoming Danel Herrington to the chat as we talked about machining with electricity.

    Cooper12:00 PM
    But it cuts well open loop

    Arthur Mercer joined  the room.12:00 PM

    Dan Maloney12:00 PM
    Daniel, are you online yet?

    Dusan Petrovic12:01 PM
    Hi Dan. welcome everyone!

    Daniel Herrington12:01 PM
    I am here!

    Cooper12:01 PM
    Welcome Daniel. Thank you for coming. I've been interested in your company for some time

    Dan Maloney12:01 PM
    Hi Dule, Happy belated New Year!

    John12:01 PM
    Welcome Daniel

    Dan Maloney12:02 PM
    Hi Daniel, welcome aboard. Can you tell us a little about what Voxel does, and about your involvement with ECM?

    Dusan Petrovic12:02 PM
    @Dan Maloney - Thanks, all the best to you too

    Daniel Herrington12:04 PM
    Sure, happy to. I started Voxel in 2015 and at the time it was just me in a garage building a piece of electrochemical machining equipment from scratch. We have been focused exclusively on electrochemical machining (ECM) and its variants including PECM, STEM, etc. Early on, we were mostly doing R&D funding by federal government research contracts but lately we have started making production parts for people in aerospace, medical, and energy industries.

    Daniel Herrington12:05 PM
    Although I am most familiar with the electrochemical varieties of metal machining, we use or compete with EDM (electrical discharge machining) all the time.

    Dan Maloney12:05 PM
    I love a good garage start-up story...

    Cooper12:05 PM
    Is there a reason you were drawn ECM versus EDM?

    Daniel Herrington12:06 PM
    ECM seemed like it had more untapped potential. It has the ability to be much faster and produce better surfaces than EDM but is not used as widely. I thought that if I could figure out why and improve the technology, maybe ECM could be used more frequently.

    Dan Maloney12:07 PM
    Seems like there's a huge established base of EDM technology already. I've only recently heard of ECM myself.

    Cooper12:07 PM
    Why do you think it is not as widely used if the surface finish is superior and the process can be faster?

    Dan Maloney12:08 PM
    Bit that I've exactly got my finger on the pulse of the industry, of course

    Dan Maloney12:08 PM
    *Not that

    Cooper12:08 PM
    I know the East has been developing ECM since the cold war, but I rarely hear of it

    Daniel Herrington12:08 PM
    Like many technologies, the core ideas are old. The first ECM companies started in the 60s. In the US that began with a company called Annocut but there were a number of Russian pioneers in this space as well.

    PatientLightning12:08 PM
    How did you find where the state of the art was, in order to get up to speed?

    I've been trying to learn about EDM but there isn't a lot of DIY

    epictaters joined  the room.12:09 PM

    Daniel Herrington12:09 PM
    But as CNC milling got better and the end mill materials improved, it started to replace some ECM applications. Also, some ECM companies mis-managed the waste stream (dumped into rivers in Ohio...bad idea), so that turned some people off.

    Thomas Shaddack12:10 PM
    How much does ECM differ from EDM?

    Cooper12:10 PM
    How does voxel deal with hazardous waste(e.g. Chromium 6)? This is one reason why I switched to EDM. Much more environmentally friendly on the maker-level

    Daniel Herrington12:11 PM
    So I think that has stymied some innovation in this space. But we are starting to see new interested in ECM processes because metal alloys are continuing to get harder to machine, surface finish requirements are pretty challenging, and ECM can be a cheaper way to make the parts so if you have high part volumes, it is worth exploring.

    Daniel Herrington12:12 PM
    When I started the business, I read countless research papers. I got access to the NC State University library and just read whatever I could find. You can find some academic papers that describe at least the principles of the technology....

    Read more »

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madmedix wrote 01/23/2023 at 11:33 point

*sigh* - I hope this post's author's next dump is square for posting crap like this.

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