Re: EDM troubles

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Richard" <phrh@w...> wrote:

> Dave, I would bet you have serious positioning problems.

not postioning as much as clamping.

I put my part in an old taki-outtie plastic tub, sitting on a couple
piecs of scarp 1/4 aluminum. then C'clamped a piece of channel to
the table, then c-clamped an aluminum bar so it hung over tub.

then I put a threaded rod from that to the work and snugged it so the
part didn't move easily and the ovrhanging bar didn't move too much.

a slight bang on the tub let the works slide around pretty well.

the very first unit was just a 1/2" brass pipe fitting held in place
gravity and the wire. any little movement let it slide.

that is how I learned about a little arc can lift a small piece that
weighs ounces. I would not doubt that the bubble from the sparking
were able to move the small brass piece.

Bottom line, clamping is required.

so far, I have insulated the clamp from the part, but once I use a
higher quality tank, I will put a means of clamping inside.

Dave





I have used

> my EDM with the dielectric being air, kerosene, or tap water,
> successfully and never lost sparking action until the hole was
> completed and the electrode comes out the bottom end.
> Kerosene stinks, air is wild (sparks all over the place) and water
> just hums along. Maybe I am lucky<G>. My power supply voltage max

is

> about 74 volts. You need 75 to jump 1 mil in air at sea level if I
> remember my physics. I am normally running at around : 40 volts
> across the gap and the electrode is driven toward the work, and at
> about 20 volts the electrode moves away from the work. These values
> are set via comparators which control the down/up direction of the
> stepper drive. So I am working in a gap which averages about 0.5

mil.

> That is small and touchy. Richard
>
> Ps Hang in there!
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <davemucha@j...> 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 ?
> >
> > any suggestions ?
> >
> > Sparkless in New Jersey. (Dave)