Re: EDM home brew units ?

> Langolis offers a couple circuts that use a FET to open the circuit
> beteen the power supply and the cap.
>
> This he says, improves the finish, but he doesn't say it imporves the
> speed.
>

When I say a pulsed circuit I refer to one without a capacitor, DC is
simply applied to the gap via a current limiting resister for the on
time. The limiting resister and the gap resistance form a potential
divider, the servo tries to control the gap resistance to create the
wanted gap voltage.

> In my tests, a smaller cap delivered faster cutting speeds.

Smaller than what? If you go to pF does it get even faster? ;) With
an RC circuit (and all others) there is probably a sweet spot, a
balance between the charging time and the power delivered per
discharge and the flushing of course. Poor flushing and you spend
more time going backwards than forwards.

> In the above formula, the energy delivered would increase greatly by
> the isolation circuit. Take a 15 ohm resistor out of the loop and
>you get 15 times more energy per spark.

Well no, because the above formula is not for a capacitor based
system, besides the current limit is not in the discharge path.

to clarify I have nothing against isolation circuits, you see plenty
in patents but you must always use the correct formula.

Graham