Has anyone made an EDM/Spark Eroder?

[PeteF]

Has anyone built a simple spark eroder type of device suitable for eroding broken taps? I wondered if a simple version could be made that wouldn't take forever to erode a tap yet would be small enough to tuck away somewhere in the workshop just waiting for one of these "Oh #$%^" moments?

Pete

[studentjim]

Has anyone built a simple spark eroder type of device suitable for eroding broken taps? I wondered if a simple version could be made that wouldn't take forever to erode a tap yet would be small enough to tuck away somewhere in the workshop just waiting for one of these "Oh #$%^" moments?

Pete

I have most of the parts gathered up to make the one designed by Ben Fleming, but haven't had the time to put it together yet. You can get a lot of info from the yahooedmgroups page if you're interested. ...Jim

[Weston Bye]

I built the HSM's Build an EDM. It works as advertised, but I don't use it much. Most significant thing I did with it was a hole in the end of an arbor to engage a special shaped shaft. (imagine a circle or pie with one quarter removed) I duplicated the shaft in brass and plunged the brass electrode into the end of the arbor.

[Circlip]

I think this ones been on here before.

http://modelengineeringwebsite.com/EDM_1.html

Regards Ian.

[drmico60]

Hi Pete,
I have made a simple spark eroder as shown here:

http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html

Mike

[Dawai]

http://smg.photobucket.com/albums/v8...rganmethod.mp4

http://smg.photobucket.com/albums/v8...ingedmtest.mp4

Yes... the di-electric fluid is as important as the capacitors.. some people use kerosene, I never could bring myself to try it.. some used tap magic.. some..

Next version which I have not got back onto, a unit ran by old car alternator w external regulator driven by electric motor, a pot controlling field generation and the generated dc bussed into the capacitor circuits..

When I do, I'll try to post results.. the vibrating "pen" is a great addition to keep the spark going.. it stimulates the spark by altering the gap allowing a current to build, then bringing close to spark..

[Circlip]

Kerosene, or parraffin as we know it, was used as the standard fluid in our toolroom?

Regards Ian

[PeteF]

What sort of erosion rates are you guys getting from a simple solenoid type eroder? I think it would take an awful long time to punch down through a tap with something like that.

Pete

[drmico60]

What sort of erosion rates are you guys getting from a simple solenoid type eroder? I think it would take an awful long time to punch down through a tap with something like that.

Pete

I can achieve erosion rates of about 9mm/hour with a 3 mm tool with my set up.
Mike

[lazlo]

Rich Carlstadt built a really nice Ben Flemming EDM, but I haven't seen Rich on here in awhile.

[MaxHeadRoom]

The commercial Tap Disintegrators such as ElectroArc use a much simpler principle than EDM, for one there is no large DC supply, but low voltage, high current AC, much the same as a welder supply but around 9~12vac IIRC,
The electrode is advanced, often manually and with a simple 60hz vibrator moving the electrode on and off the part for erosion.
The electrode is hollow tube for coolant flush, made from hard copper or the like.
Max.

[Circlip]

I think it would take an awful long time to punch down through a tap with something like that.

Beauty about a simple system like this PeteF is that it's cheap to make for HSM use and you can leave it to its own devices rather than standing watching it.

If you're in a rush, a commercial operator is usually available, - - - at a cost.

Regards Ian.

[DougC_582]

An EDM would be fun to play with--but if all you wanted to do was remove busted taps, I'd suggest that making single-edge drills from tungsten carbide blanks would be a lot easier and faster.

A diamond wheel on a Dremel tool will grind them; when shaped properly it only takes light pressure at 200 RPM and they'll just sink right through a HSS tap.

[Jaakko Fagerlund]

I have the Ben Fleming book and Robert Langlois book, just out of interest. Both use RC type circuitry, meaning resistors and capacitors. They do work and are easy to build, but I like to have more control of the process than that.

That is the reason I'm at the moment designing a pulsed type EDM electronics, I have the circuits already sketched on a paper but have to get time to prototype them and to build the actual machine to test them out. The thing has all the bells and whistles - ON/OFF times, current selector, pulsed flushing, manual and automatic modes, edge finder and what else there is in a "basic" commercial machine

Though, I'm not publishing the work as such in a long time as I'm intending to have it published in HSM magazine and to get it as a book, but as said, it is a long way up to that.

[PeteF]

The electrode is hollow tube for coolant flush, made from hard copper or the like.
Max.

Thanks Max, that's a good idea and should speed up erosion too.

Ian, it's not so much about being in a rush, I don't think the word can even go in a sentence with EDM I've seen some very simple RC type devices operating with a solenoid to pulse and I thought it could be something that would be easy enough to build. However I'd also read they were getting erosion rates of only around 3 mm per hour.

I've never had any luck in trying to remove a tap with commercial extractors, but then again I've never had a tap that I simply HAD to get out either, so maybe my efforts were a bit too token? What I tend to find however is broken end of the tap is typically as an angle, and on the small taps I use, the drill won't start properly. I'll certainly look more in to this however, because sooner or later there will be one that I absolutely need to get out.

Pete