Re: [CAD_CAM_EDM_DRO] EDM troubles

turbulatordude wrote:

>Hi all,
>
>simple RC EDM unit. after test drilling some holes in steel with a
>copper electrode, I pulled the electrode out mid spark to inspect the
>progress and now it does not start to spark easily.
>
>It went from full voltage to sparking voltage without a spark, then
>quickly went to a short.
>
>do the electrodes get dirty with carbon ?
>
>

If your dielectric is hydrocarbon, then definitely yes. Otherwise, metal
oxides can form that will degrade the operation. But, the polarizing
voltage
is supposed to be enough to burn through it.

What voltage are you running? What dielectric? How are you advancing
the electrode? It is VERY sensitive to MICROSCOPIC movements.
I use my CNC system, which has encoder resolution of .000025" (no
typo, that's 25 micro-inches) in the Z axis. I leaned on the head of the
machine (Bridgeport) to modulate the gap and break shorts! When I
was working with this, I didn't have a dielectric flushing system, and so
I rotated the electrode at about 60 RPM with the mill spindle. This
helped keep the burn even and flush the dirt somewhat.

If your dielectric is black, you may need a flushing system, which feeds
dielectric through a hollow electrode.

Jon