[mlg]

Hi there,

I am planning on getting a Taig and refitting it into an EDM mill (not an EDM wire or sinker machine, really a mill: the EDM tool will be rotating just like a regular cutter, and probably held in a normal collet). I have designed my own circuit for this (for the high-voltage part of it anyway) which works quite well in a breadboard version already.

The tricky part... the software driving this needs to be EDM-aware, so the speed at which it moves the tool will be "as fast as material is removed", not any specified speed To accomplish this the EDM circuitry would detect the rate of material removal and coordinate speed with whatever software is driving the XYZ axes. I will probably write a patched version of EMC first. Beyond that, if this takes off, maybe the Mach3 folks can put in some support for it in their software. Bottom line, you won't be able to use arbitrary CNC software with this, but the most popular options should be supported.

Also of course this will be quite slow... the volumetric material removal rate will be orders of magnitude slower than commercial sinker EDM machines for sure, and probably very slow compared to cutting metal with regular tools too. On the other hand of course you can machine almost anything conductive with it :devious:

So anyway, what I'm wondering is... would people be interested in this as a product? I see it as a kit that lets you convert more or less any small mill (or even a router/engraver/whatever) into an EDM mill, and back, not much more difficult than switching regular tools. As far as I know this is pretty unique, and I personally love the idea of it for my own use. I will probably do this regardless, but how much energy I put into it depends a lot on whether it seems to have a market. I'd really appreciate feedback on whether you are interested, and if yes what particular features/requirements you have for it.

Also maybe you can give some feedback on what you see as a realistic price range for this. I expect it will be sub-$1000, ie way below any other comparable commercial machine (even used). Beyond that, I'm not sure myself, I will start pricing the cost of the design after I have it working

Please vote in the poll too.

Thanks!
MLG

[mlg]

A few more data points about my design...

I'm aiming for about 50A peak current, a pulse repetition rate up to at least 20kHz, duty cycle 20-50%, tool-workpiece gap <0.003 inch. Doesn't mean I will hit those targets, but that is the design goal at the moment This will be powered from a standard 110V/15A outlet, but it will not be a super-efficient circuit (probably < 50% efficient).

You could use this as a ram/sinker (or even orbiting/vectoring ram) too, just lock the spindle and program it to move in the Z axis.

Automatic wear compensation, maybe... the software could periodically move the tool to a known surface until it just touches (and establishes electrical contact) and thus detect the current tool size. Doing this in 1D is relatively easy, in more dimensions quickly becomes really hard. If using a rod to machine mostly downwards (visualize it as drilling a series of possibly overlapping holes), the end wear (change in tool length) could be compensated pretty well. This would probably be the preferred method to remove bulk material, rather than machining sideways as with conventional milling. Compensating side wear seems prohibitively hard, because it won't be uniform along the length of the tool... ideas anyone?

What to use as a tool... I'm thinking a tungsten welding electrode, readily available in diameters up to 1/4 inch. Graphite may be too fragile.

[307startup]

Count me in, if you ever get this up and running. Sounds alot like an old product called the SparkDrill.

[mlg]

Count me in, if you ever get this up and running. Sounds alot like an old product called the SparkDrill.

Thanks!

Could you tell me a little about what features you're looking for and what your typical use would be?

I can't find any info about the SparkDrill, any pointers? From the name though, it sounds like they use uncontrolled discharges? (=fast tool erosion)

--MLG

[cheetahcnc]

I don,t know much about EDM's, except they have gone cheap at auctions. But your system sounds interesting, so I'm in for a subscription.

Jim

[lavrgs]

Sounds interesting. I recently bought a Hansvedt Benchman edm for next to nothing. There is also some great tooling deals on ebay if you're patient. You might look into the current (actually probably outdated) circuits that do the dithering to find the part. My machine has a servo controlled Z axis but the orbiting units probably allow for some x and y motion.
How do you plan to deal with the fluid? I have a 45 gallon reservoir of dielectric fluid that cost $800 to fill....almost what I paid for the machine Then it has to be filtered,pumped and all that stuff. If your machine is going to be slower than a plunger edm that's g o i n g t o b e r e a l sloooow?????

Keep us up to date it sounds interesting.

[mlg]

Sounds interesting. I recently bought a Hansvedt Benchman edm for next to nothing. There is also some great tooling deals on ebay if you're patient.

Hey lavrgs,

Modding a Hansvedt power supply to talk to EMC could be one way to do what I'm talking about, sure. I mainly want to reuse the XYZ motion and controls from an existing machine, and do the control in software, in order to have maximum versatility; building a power supply is incidental (but fun).

How do you plan to deal with the fluid? I have a 45 gallon reservoir of dielectric fluid that cost $800 to fill....almost what I paid for the machine Then it has to be filtered,pumped and all that stuff.

That is actually the easy part... I believe almost any cooking oil will do fine, just pick the one you think smells best corn or canola, or I think I might try peanut

The dielectric strength is a bit lower than of petroleum-based fluids, but on the plus side cooking oils have a very high flash point, and are relatively safer to be around chemically.

Filtration, how about a car oil filter? It is designed to remove metal bits out of oil What I was actually planning to try first, though, is to just machine my small parts in a tank full of a few gallons of oil (no filter/pump, maybe a stirrer), and replace the oil when it started looking gunked up.

If your machine is going to be slower than a plunger edm that's g o i n g t o b e r e a l sloooow?????

I mean slow in cubic inches per hour compared to a commercial machine with similar power supply specs. For a given pulse current/repetition rate/power etc, I think commercial machines will have a higher material removal rate because they control the gap more precisely, shape the pulse better, remove stuff out of the gap more effectively, etc etc. Which may all add up to a 2x-3x difference, maybe. Is that worth the price of a commercial CNC EDM? For some people, sure. I think for almost everyone doing one-offs it won't matter though.

Anyway, will definitely keep you posted.

--MLG

[307startup]

The site is locked by admin, but it is still online at www.sparkdrill.com

Another option that I find intriguing (at least for my limited EDM needs) is the Chevalier ALIC-1. I will try to attach a PDF if I am able to...the file is too big, so I am including the address where you can download the file. Select Portable EDM... http://www.chevalierusa.com/downloads4.htm

Something along these lines would let someone with a hobby/home CNC machine to get double duty.

Thanks!

Could you tell me a little about what features you're looking for and what your typical use would be?

I can't find any info about the SparkDrill, any pointers? From the name though, it sounds like they use uncontrolled discharges? (=fast tool erosion)

--MLG

[kulk_sd]

what is it like, any information ??

[mdynac]

The tricky part... the software driving this needs to be EDM-aware, so the speed at which it moves the tool will be "as fast as material is removed", not any specified speed To accomplish this the EDM circuitry would detect the rate of material removal and coordinate speed with whatever software is driving the XYZ axes. I will probably write a patched version of EMC first. Beyond that, if this takes off, maybe the Mach3 folks can put in some support for it in their software. Bottom line, you won't be able to use arbitrary CNC software with this, but the most popular options should be supported.

MLG

EMC2 already has this function, it is called "adaptive feed rate" i used it to successfully convert an Andrew EF330 edm from DEC pdp8\a control to a regular PC, using EMC2.
the code works fine, fed with an "a to d'ed" gap voltage signal.
we developed this several years ago at the CNCFEST in southern illinois. works like a charm.

so the "tricky" part has been done already.


mdynac

[KilrB]

How do you plan on compensating your tool offset to account for electrode wear?

[meatychips]

I personally wouldn't use cooking oil. It breaks down rather quickly and you'll get a nasty smell coming from it.

[meatychips]

Oh and bump. Any news on this? Just realized how old this thread is.