Many years ago [ScorchWorks] built an electrical-discharge machining tool (EDM) and recently decided to write about it. And there’s a video embedded after the break.
The build is based on the designs described in the book “Build an EDM” by Robert Langolois. An EDM works by creating lots of little electrical discharges between an electrode in the desired shape and a material underneath a dielectric solvent bath. This dissolves the material exactly where the operator would like it dissolved. It is one of the most precise and gentle machining operations possible.
His EDM is built mostly out of found parts. The power supply is a microwave oven transformer rewired with 18 gauge wire to drop the voltage to sixty volts instead of the oven’s original boost to 1.5kV. The power resistor comes from a dryer element robbed from a unit sitting beside the road. The control board was etched using a hand traced schematic on the copper with a Sharpie.
The linear motion element are two square brass tubes, one sliding inside the other. A stepper motor slowly drives the electrode into the part. Coolant is pumped through the electrode which is held by a little 3D printed part.
The EDM works well, and he has a few example parts showing its ability to perform difficult cuts. Things such as a hole through a razor blade., a small hole through a very small piece of thick steel, and even a hole through a magnet.
this is very nice, EDM is a wonderful process for hard or very precise work, there were a couple of very large machines at an old workplace of mine, the capacitor banks were separate and huge. when we moved shop the owner decided to put them on the 1st as opposed to the ground floor, this led to a long and complicated struggle that entailed having to (temporarily) remove every single ventilation duct in the space and remove quite a few lamps before finally removing an entire wall leading in to the factory floor, that was fairly old machines even by the time i worked there.
“…microwave oven transformer rewired with 18 gauge wire to drop the voltage to sixty volts instead of the oven’s original boost to 1.5kV..”
Very disappointing that you would do such a terrible thing, [ScorchWorks]. (JK :P)
This is such an interesting build and I will try it out.
Could a homemade setup possibly work on non-conducive material?
Even if it can’t cut through maybe it could be an obscure way to etch glass. I know there is a way to do it with higher voltages and probably a different liquid bath.
It looks like same process I use to etch names into equipment – we use a special tape in a lable machine to create the name than hold that in position and apply a conductive sponge soaked in the fluid. About 4-8 Amps is passed through the sponge and the image is etched into the surface. It only works on electrically conductive materials – anodized aluminum doesn’t work so I suspect glass would also be a no go.
I believe the process you described is a form of anodizing certain metals. You can get great results doing it on titanium. :D
http://www.mrtitanium.com/anodizing.html
I wanted to link to a great candlepowerforum website, but it seems the server is absurdly slow lately. They have amazing examples of anodized flashlights on there.
EDM works through ablation of the surface usually using electric arcs.
They are very closely related and I suppose the processes overlap a bit.
EDM cuts conductive materials only normally, although there is considerable r&d happening in this space currently because of the engineering advantages of using ceramics and other non conducting fragile materials which need accurate machining still, so saying it as a absolute is no longer true.
There’s a technique named DESSEDG, where a non conductive material is simulatneously ground by a conductive grinding wheel and edm’d at the point of contact, or various ones that involve coating the workpiece to allow it to conduct at a surface layer, and a 3rd method using a second electrode to form the ground. As to if you can do that reliably in a home shop, don’t know.
DESSEDG was really interesting to look up. Thanks for the ideas! Some kind of electrified drill with an abrasive tip is under consideration for my experimentation.
…”Could a homemade setup possibly work on non-conducive material?”
Non conductive material (even glass) can be machined using ultrasonic method.
https://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=imgres&cd=&cad=rja&uact=8&ved=0ahUKEwi4ka2thLLOAhWIzIMKHWTYDmwQjRwIBw&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FUltrasonic_machining&psig=AFQjCNEHYqcqrWTEBFEdt29S4Ji6oqeKdA&ust=1470753089710142
That looks perfect for placing holes in glass, thanks! Pretty much what I’ve been looking for. :)
If I can make a homemade setup with adjustable X and Y I will make an IO page for it.
Nice link salad; I think we’ve all done that before. :P
https://en.wikipedia.org/wiki/Ultrasonic_machining
Why the hell would you make a link to Wikipedia go through freaking Google?? What’s wrong with you?
I browse HAD through an RSS feed. As such, untill I open the full contents of an article I only see the headline.
This had me wondering how Electronic Dance Music (EDM) was used to cut anything.
I, too, get HAD through RSS, but I see the entire article (usually before any typos are fixed). I have to come to the website if I want to see the pictures and videos, though. :)
EDM is usually used to cut some ridiculous dance moves. ;)
I’m impressed that it also cuts through thick steel.
Seriously? Never heard of cutting the rug?
Excellent! Ordered the $31 book.
https://www.scribd.com/document/244272841/Build-an-EDM-by-Robet-Langlois
A link to read the book.
Well, I guess I screwed that one up pretty badly.
You can read some of the book. :(
isnt this like what that other video showed a while back when someone tried to remove a broken off bit from a piece of metal?
Exactly. :)
The link to that article is in the sentence “It is one of the most precise and gentle machining operations possible.”
I almost missed the link as well.
http://hackaday.com/2016/07/02/removing-a-broken-tap-from-something-really-really-expensive/
Never heard of EDM before. Very interesting.
This kind is called a die sinker. Wire EDM is also very interesting. Very handy equipment if your shop is big enough.
Thanks for the info, I’ll check out the wire variant.
I have a sodick wire edm in my shed. Theyre expensive to run in general, you need to buy wire (obviously) and also DI resin to treat the water to make sure it stays non conductive. These are eaten away keeping the resistivity of the water high enough over time, and finally filters for the tank.
Having said that, you can pull some amazing things off with them, this is 316 stainless with a pen for comparison. Anyone that’s had the grief of machining 316 in a mill would not want to make this on one…
http://gallery.pipandphil.com/d/38569-1/wirecut_small_fluffy.jpg
It in action, its like having your own personal thunderstorm…
https://www.youtube.com/watch?v=Z1KA9JqOtAo
I’m trying to intergrate a 5th axis spindle on the bed, and that would give turn and burn which is a game changer in capability. At the moment like most wire’s its got xy and uv because it can move top and bottom dies independantly to cut tapers and mould draft etc. With a rotary axis you can wire out threads or odd shapes.
https://www.youtube.com/watch?v=Z1KA9JqOtAo
I bought it for scrap as it had blew up, but its been a big learning curve and I did it on the cheap, even the NEC pc9801 control computer I won on yahoo jp auctions and imported it to reduce costs. Now its apart trying to get a nic to work alongside the other stuff so I can dnc things to it without using the unreliable expensive floppies. It owes me under a thousand bucks though… Pretty good capability for the money if your a skiprat with some electronics gear.
Sideways camera action is sexy
Regarding Vertical Video Syndrome: https://www.youtube.com/watch?v=Bt9zSfinwFA
It’s a bit of a pain to google EDM(this one) without getting the musical variety!
That said, I’ve got experience at work. The machines I’ve used typically run 80vdc, however, they “rough” at 200V or a alternating 80/200(very effective!). Flushing oil(dielectric, they started using kerosene, however it is highly flammable)
Uses:
Tungsten carbide needs a square hole cut in it? EDM.
Do you need very intricate cavity with? EDM.
Broken tap!? … Try drilling it “like a boss” first. Then use EDM cuz it works! (size is difficult, however!)
…If it’s conductive, it can be burned EDM. See also wire edm (aka: WEDM)
Pro tapping tip: unless you’re using a high end CNC, you should stick with straight flute taps. I’ve burned out literally 100’s of them. Spiral flutes take about 20x longer. It’s not worth it!!!
If you’re a pro at tapping you will not break taps :)
The last holes I tapped were blind holes on my 12-speed V-belt hobby mill with a 1.5kW motor.
I put a cheap Chinese frequency inverter on it, run it on low frequencies /rpm / Torque and just let it run untill it bumps into the bottom of the hole with an M4 tap. Always straight, never breaks.
When I was young I just kept applying more torqe if the tap was in the hole under an angle or when it was blunt untill it usually broke. You do dat only a few times. People have to learn for themselves, just like me i guess…
Grinde or replace blunt taps.
Spirals work great in softer materials like aluminum even when done by hand with a cordless drill. The do a great job at removing chips and jamb up less. Straight flutes are generally better in harder materials steels. Buy the right tool for the job.
Caveat – if you can’t hold your tool straight then spirals will be harder to use.
Pro tapping tip: Don’t buy cheap taps or drill bits it isn’t worth the aggravation.
You just have to spell out the whole thing for the search engine “electrical-discharge machining”.
Google be like, “Did you mean vaginal discharge medication” …. artificial stupidity in action.
Then to add insult to injury after you’ve rapid fire modded the search terms and used what scant few operators they have left they go “Are you sure you’re not a bot?” and make you solve a capcha and you’re fuming “HEY I’m not the one exhibiting wayyyyy less than human level intelligence here!!!!”
There’s also the following link
http://www.homebuiltedmmachines.com/sand-box-rc-vs-pulse/
I don’t have this yet, but it suggests pulse based edm’s are better than RC ones