Re: Question fro Jon Elson

> Will you give us details of your RC EDM circuit? I would like to

> how it works.
>
> Thanks
> Scott

>
> --- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> > thscarince@h... wrote:
> >
> > > Ah Ha!
> > >
> > > Out of curiosity I searched McMaster-Carr to see if they might
> have
> > > copper hex stock (electrode by the foot!). They don't, but

> do
> > > carry *beryllium* copper hex wrenches for non-sparking
> applications.
> > >
> > > No idea if the beryllium would be a problem...
> >
> > I wouldn't use it! The EDM fluid would be serious HAZ-MAT after
> > use, and you wouldn't want to touch it. The polarity of the EDM
> > circuit puts most of the erosion into the workpiece, but the
> electrode
> > does wear away, too. And, so, you would have finely atomized
> beryllium
> > floating around in the fluid.
> >
> > >
> > > BTW, I was captivated by Jon's junkbox EDM setup! Is that

> all
> > > there is to it?
> >
> > Well, it works! but, it isn't fast.
> >
> > > Does EDM require short pulses or a continuous arc
> > > like a welder?
> >
> > It is short pulses. If a continuous arc develops, it will burn a
> big hole
> > in both
> > the work and electrode at that spot. What you want is lots of
> little sparks
> >
> > all over the tiny space between work and electrode.
> >
> > > Does polarity matter?
> >
> > Yes, it is the only thing that determines which is electrode and
> which
> > is workpiece!
> >
> > > How about AC?
> >
> > No, then the electrode and workpiece would be eroded equally.
> >
> > > What properties
> > > are make a good electrode material?
> >
> > Something that resists burning away. Copper-loaded materials
> (brazing rod,
> > brass, copper, bronze, etc.) and graphite are favorites.
> >
> > Anyway, my (and many others') RC EDM circuits are slow and a bit
> > temperamental.
> > For the best results, an electronic switch that cuts off current
> some time
> > interval after the discharge starts, and then restores the power
> after a
> > set 'deionizing' time will give much faster cutting. You can
> probably get
> > 10,000 discharges a second with a pulser, and rarely more than

> with
> > the RC. But, it is simple, and it does work.
> >
> > Jon