Re: [CAD_CAM_EDM_DRO] Another EDM Approach

Ian Wright wrote:

> ----- Original Message -----
> From: "Jon Elson" <elson@...>
> >
> > > When the circuit was working, it did a
> > > fairly good job of tap removal etc. but just wasn't refined enough to do
> any
> > > really useful work.
> >
> > This mUst be EXTREMELY slow. The pulsed EDM systems run 10,000 sparks
> > a second and more! backing up the electrode after every spark must take
> > hours to make even a thousandth of an inch progress.
>
> Hi Jon,
>
> It was, in fact, fairly quick and would go through 1/8" steel sheet in about
> 10 minutes. I suppose that what you actually get is a stream of sparks not
> just one as the electrode is slowly lifted by the motor. i.e. there will be
> a significant time interval where the electrode/work distance will support a
> spark current flow. The big trouble is, of course, that it is uncontrolled
> and each spark will start off very strong and progressively weaken before it
> dies. Also such a system is slow because each time the motor lifts and
> lowers the electrode, backlash will have to be overcome. A system which
> monitors current and just maintains a fixed gap must be far more efficient.

I did this manually, with a CNC system with low backlash and extremely fine
encoder interval (.000025"). I monitored the EDM current and adjusted the
feedrate to keep the burning going. It worked fine for burning out taps, and
was going close to .001" per second when things were working well. i used
a .060" brazing rod as an electrode, and rotated it at about 60 RPM in the
spindle. I didn't have a method to flush the EDM fluid, so I had to stop every

.010 to .025" to clear out the black metal dust and refill with clear fluid.

Jon