Re: EDM home brew units ?

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

>
> > There is a formual that relates surface area to amps. more amps
> > allows a larger surface area. more amps in a smaller area does not
> > offer any benifits.
>
> There are usually guidance values on max current densities for the
> various electrode materials but they are still quite high values.
>
> For a pulser unit then the power delivered per spark is proportional
> to the current. Energy delivered per spark assuming there is a zero
> ionization delay is:
>
> E = Vo.Ton(Vs-Vo)/Rl
>
> where
> Vo = operating voltage (average gap voltage maintained by servo system
> Ton = on time
> Vs = supply voltage
> Rl = limiting resister.
>

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.

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

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.

I thought I had a formula that listed amps per square inch of
electrode. I'll search more to see if I can find it.

Dave