Re: [CAD_CAM_EDM_DRO] Home-built EDM

Rich wrote:

>I just completed construction of a home-built EDM from an article by
>Arnold Gregrich in Home Shop Machinist (October/November 2002).
>The initial test results were disappointing to say the least. Using
>plain tap water, I could hardly get any sparking at all. When it did
>spark, there didn't seem to be enough power to start a hole, much
>less burn clean through a piece of 1/16" thick steel. I changed over
>to deionized water with no real improvement. The sparks seem to
>wander and not concentrate in one area.
>These are the specs: Used two 3600 uf caps, a 400V rectifier and 200
>watt light bulbs in both sockets. The electrodes I tried were .062"
>mild steel welding rod, ¼" copper tubing and a piece of a telescoping
>car antenna (chrome plated brass which didn't work at all).
>If anyone is familiar with this machine, I sure could use some tips
>on increasing performance. I need more aggressive sparking, but how
>to achieve it is the question.
>
>

This doesn't sound like it will work at all. The voltage is too high
for water (especially impure water). I have had some success with
a somewhat similar device. See my web page
http://jelinux.pico-systems.com/edm.html
<http://jelinux.pico-systems.com/edm.html> for details.
The major difference here is the lower voltage and the small
capacitor directly across the output terminals. This delivers a
strong spark of very short duration. I generally run this in my
Bridgeport mill, and rotate the electrode at a very slow rate, around
60 RPM. This helps do the same sort of clearing action as a
flow of fluid through the electrode (although not as well).
I have used alum-tap, an aluminum tapping fluid, as an EDM
fluid, and find it works a lot better than water.

After some discussions on this list about 2 months ago, I am
going to design a more sophisticated electronic pulser sometime,
and see how that works.

Jon

Jon