Re: EDM capacitors and voltage

Hi James,

In my research, I found that the spark gap can be increased with
voltage. once a spark gap is initiated, needs something like 10
volts to jump the first 0.001", but then the voltage needs to rise
sharply as the distance increases.

I have also found contradictory information on voltages. one source
says that most commercial units are 100 volts or less. Another says
300 volts.

Seems the higher the amps, the faster the cutting. 150 amps seems
like a very high unit, and 15amp at the low end. I am hoping some
EDM guru's will shed some light on this.

I have read that some cuts in metal take days.

Seems the high speed charging needed limits the type of capacitors
that can be used. aluminum electrolytic being the easiest to find
and cheapest, but not up to the task. Motor run capacitors seem like
the best alternative, but with the high voltages they offer at very
low prices, is seems that using higher voltages offers a lower value
cap bank, and lower prices, with the same current available for
zaping the metal.

I've seen some references to using inductors in lieu of caps, but no
technical discussions. I'm not sure that they are not just used for
creating a high voltage arc to allow greater distances for the spark
gap, or for a voltage detection circuit to indicate close proximity
of the cutter to the part.

Dave









--- In CAD_CAM_EDM_DRO@yahoogroups.com, "James Stevens"
<jstevens@c...> wrote:

> Dave,
>
> I believe that Langlois is using 82 VDC. I've seen a professional

setup

> using 100 V with no problem (using EDM cutting fluid - not water).
>
> How high a voltage are you talking? You should be fine with

anything less

> than 100VDC. My experience has been that the real benefit is the

increased

> spark gap - important if you are doing the work by hand. Too

little a

> voltage causes the gap to shrink and the arcing to increase as it's

more

> difficult to control by hand. An automated system is likely a

different

> story.
>
> James
> ----- Original Message -----
> From: <davemucha@j...>
>
> Have I got this right ? am I on the right track ? does higher
> voltage create any problems ? I'm hoping to avoid some shocking
> discoveries.