Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

This was posted on another Yahoo group. I tried to find the
schematic that he planed to post but it wasn't there. Keep in mind
this is more of a manual machine than a CNC, however, the power
supply description seemed interesting to me - simple.






I have built three small home shop type sinker EDM systems and
thought I would share my experiences. The one that worked out the
best for me was added on to a small bench top drill press. The quill
down feed was modified with a worm gear and a stepper motor driving
it. The quill normally feeds at about 10 thou. per minute and is
adjustable over a wider range. Nothing fancy, mind you, just a
simple, adjustable, stepper driver not controlled by a computer.
I use distilled water to flush the pocket every few seconds rather
than a constant flow as the spark will not discharge when the water
is flowing.
For electrodes, I usually use brass tubing, and it has worked well
for me. Occasionally, though, I will use a specially shaped graphite
electrode for odd shaped holes.
The power supply is very simple as well 120VAC right out of the
wall that is fused with a bridge rectifier a couple of light bulbs
and a few capacitors that can be switched in or out of the circuit.
This simple grass-roots EDM is not very fast but I have yet to find
any conductive material that it won't cut. Just for grins, I punched
a 3/16" hole in a 3/4" ball out of a ball bearing and gave it to my
boss the next day. He still hasn't figured out how I did it to this
day. (The hole was square)
This little machine is great for burning out the occasional broken
tap, drill bit, or ease out and has the potential for much more.
Thanks for letting me toss in my 2 cents worth.