Re: EDM Plans

jdelgado@... wrote:

> From: jdelgado@...
>
> I have been on the list for about a month and really enjoy the info!
> The CAD_CAM_EDM_DRO email has become a favorite, and readily gets opened before
> other emails! :)
>
> Jon, I checked out your main page with links and definitions, and its good.
> The ECM link is not working at this time. Any info?

Right. I know what the acronym means, and a little bit more than that, but I
really know very little about the process in detail. Especially with regard to
how deep the grooves can be, and whether you get undercutting (like with
etching) or tapering of the grooves.

>
> I did check out the EDM link and am particlulary interested in building a small
> edm. Do you think the power supply you have shown will work for larger electrodes?

No, you would probably want to scale the power source up a bit, depending on the
area of the cutting face (but probably not a linear scaling up). I think for small machines
and small parts, 4-5 Amps is often the current mentioned.

> Will distilled water make a good dilectric solution?

I doubt it. You just can't keep it clean enough. Even if it IS clean, the electric field
in the gap is strong enough to disassociate the water, producing H and O gas. Enough
of this can get dangerous, and at 4-5 Amps, you definitely would have a hazard.

> Is something else better?

Very light oils with low vapor pressure seem to be the ideal. 'Odorless' solvent
or paint thinner is the sort of thing to use.
I only needed drops of the stuff for tap burning, so I used what was close at hand,
Alum-Tap, a fluid for tapping in aluminum. It has almost no odor, and worked GREAT!
(If I had a fire, it would have been quite small, and easily contained, so I wasn't
worried. I did keep the rags away from the work area. In your case, you might
need quite a lot of fluid, so you should have a bucket of sand and a fire extinguisher
handy.)

> Does anyone have any other info? I have several injection molding machines, and build my own tooling. I currently have about 100 hours of run time on my latest cnc retrofit using steppers. I am currently working on a complex mold which is begging for some edm work. Now I am ready for another Goldberg machine..and that edm keeps coming up! I love homebrew machinery! Boy it gets in your blood. I will also be posting some photos of my CNC retrofit on my website soon. Also Steve, I will be posting photos of a 40 ton injection molding machine, which I will be offering in both kit and plans form. It will have a 1 1/2 oz. capacity! Something really useful around the shop.

Well, for mold work, EDM is real nice. And, an existing CNC machine could be quite useful.
You could use a small electrode, maybe square, with sharp corners, and move it with the
X and Y axes to carve out the cavity.