Re: [CAD_CAM_EDM_DRO] Re: EDM capacitors and voltage

At 17:25 1/7/2003 +0000, you 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.

Most units with square wave freq. generators cut with graphite at around 30
volts, negative electrode, under normal conditions. Some generators will
allow you to up the voltage into a high range that can go as high as 200
volts for difficult to flush conditions and/or trying to achieve an
extremely high finish. Copper electrodes like higher voltages as well.
Copper is rarely used these days as it's slower burning and more difficult
to make electrodes with.

Roughing is usually done with a positive electrode and low frequency to get
very little electrode wear. Currents under 1 amp/sq. inch can result in
less than 2% electrode wear.

High frequency + low current + negative electrode = high finishes + high
electrode wear

Low frequency + High current + positive electrode= low finish + low
electrode wear

-Bob