Re: EDM troubles

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:

>
>
> turbulatordude wrote:
>
> >Hi all,
> >
> >simple RC EDM unit. after test drilling some holes in steel with

a

> >copper electrode, I pulled the electrode out mid spark to inspect

the

> >progress and now it does not start to spark easily.
> >
> >It went from full voltage to sparking voltage without a spark,

then

> >quickly went to a short.
> >
> >do the electrodes get dirty with carbon ?
> >
> >
> If your dielectric is hydrocarbon, then definitely yes. Otherwise,

metal

> oxides can form that will degrade the operation. But, the

polarizing

> voltage
> is supposed to be enough to burn through it.

I'm using water, well water, so I have no idea what is in the stuff
other than calcium and a little iron. Once it goes past the house
filter the salt is supposed to replace the calcuium so I figured on a
greater conductivity with the house water.

> How are you advancing
> the electrode? It is VERY sensitive to MICROSCOPIC movements.
> I use my CNC system, which has encoder resolution of .000025"

I'm using a Xylotex on a 400spr stepper on a 10tpi leadscrew. with
the Xylotex set at 8x microsetpping, that come out to 0.00003125 so
ware are in the same neighborhood.

my step logic is not tuned as yet, but a 1/2 step worked pretty well
and that would be 0.000125, but you are correct. most people don't
understand that you can move the head of a mill by putting weight on
it.

as an aside, if you wanna see and indicator really swing, chuck it up
in your drill press and rest your hand on top of the belt guard !


Bottom line, water = hydrocarbons = insulation on electrode = need
for cleaning.

I wonder how dab of a little Tarn-X might work......

Dave