Re: [CAD_CAM_EDM_DRO] Re: EDM capacitors and voltage

turbulatordude wrote:

>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.
>
>

Sure, if you are plunging a whole mold cavity for a big bottle or
something, that WILL take a long
time, and several electrodes. Much better is to try to use wire EDM or
some other metal removal
technique to remove most of the metal, then switch to EDM to create the
final form.

>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.
>
>

Using inductors instead of the resistor in an RC EDM might allow quicker
charge times.
But, for real heavy work, an electronic pulser is going to be necessary.

Jon