Re: [CAD_CAM_EDM_DRO] Re: EDM PSU info

ballendo@... wrote:

> Jon,
> Re:
> >I made a mini-EDM system for burning out taps, etc. I did a couple
> >broken taps using about 30 VDC, a 30 Ohm resistor and about 3 uF of
> >capacitor right across the EDm electrodes.
>
> What wattage resistor? What did you use for fluid? Connection to the
> part and the stick electrode? (like arc welding?)

You should look at my web page on this :
http://ascc.artsci.wustl.edu/~jmelson/edm.html
It describes it fairly well, but I'll answer your specific questions.

The 30 Ohm resistor is 50 Watts. If you find a 100 W resistor, or 2 15
Ohm, 50 W
resistors, that might be even better. The 50 W resistor gets REAL hot
when the
electrode shorts out.

I used just a few drops of alum-tap, a flammable tapping fluid. It
worked very well,
but I wouldn't recommend it for real EDM jobs. Distilled water is
recommended
by many, but you have to keep it real clean.

I used a piece of stranded wire wrapped around the electrode, so as to
make a
rotary 'joint', which would keep a good connection while the electrode
was
rotated. It worked better than I would have thought.

The workpiece connection was with a clip lead. Relatively small wires,
like
around 14-18 gauge are fine. The currents are not very high, maybe 100
A
for a very short peak. The average current is 1/4 to 1/2 Amp.

Jon