Re: EDM home brew units ?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler" <eexgs@n...>
wrote:

>
>
> > I have not seen a working non-capacitor EDM circuit. Since the
> readily
> > available circuits use capacitors, I am still thinking capacitors.
> >
> > That would mean your formula is not relavant to the R/C type
> machines,
> > but is really for a non-capacitor circuit.
> >
> > do you have a schematic for such a circuit ?
>
>
> I didn't say it was for an RC circuit!

I figured that out, but since we started the discussion by talking
Langolis, And the gentleman who wanted a power formula was using a
Langoiks type circuit, I assumed you were also talking an R/C circuit.

> > I agree that there is a sweet spot, but that has not been offered
> as a > known formula that I am aware of.
>
> That is why each EDM machine comes with a book of "technology"
> settings for the machine for differing materials and finishes etc.

Pogo graphite offers the formulas for thier products in so many amps
per square inch. I assume that different machines use different
technology and each has it's own formulas.

> > OK, now I'm confused. if there is no capacitor and the resistor is
> > not in the discharge path, but it has an effect on the energy,
> then it > must be in the active circuit.
>
> You thought that the equation related to RC circuits and thought
> changing R would increase the energy, I am saying that R in an RC
> circuit will not change the energy as it is not in the discharge
> circuit.
>
> In a switched circuit the current limiting resister is in the
> discharge path and offers a way to affect the current at the working
> voltage controlled by the servo system.

I understand now that there is or may be a filter cap in the power
supply but there is not a sparking cap.

But, since there is no public schematic that discusses that type of
circuit the two worlds do not directly relate.

But, in the Sodick/Hurco circuit, without sparking caps, the closed
circuit would seem to be at some voltage that was a function of
dielectric resistance and electrode distance. the closer to the part,
the lower the voltage, the higher the current. The poorer the
dielectric the same low voltage, high current reaction.

But that would also mean that either the unit is continuous sparking
and not in a pulse type circuit or that the spark voltage goes from a
working voltage to zero when the cuircuit is open.

Can you elaborate a little more on the type of circuit you are talking
about ?

Dave