Re: [CAD_CAM_EDM_DRO] Re: Home-built EDM

Rich
The commercial machines typically have a tub/tank that automatically fills
and submerges the work area to several inches with EDM fluid before any
motion starts. Jogging for set up is not submerged.
Any sparking produced fire is quenched long before reaching the surface.
RichD


Rich wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Rich" <rmancini@h...> 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.
> > Rich
>
> An update on the Home-Built EDM per Arnold Gregrich's article in
> Machinist's Workshop (Oct/Nov 2002):
> 1. As mentioned in the article, I tried replacing "Lamp B" with a
> fuse.
> This action worked well as I now have an aggressive enough spark to
> actually remove metal where before, none could be removed with a 200W
> lamp.
> 2. The use of deionized water also seemed to help although I'm not
> sure how much.I may also try Kerosene next.
> 3. The best electrode I've tried so far has been ¼" soft copper
> tubing. The biggest problem here has been to get it straight after
> uncoiling it. Mild steel and aluminum (Tig) welding rod didn't seem
> to remove much metal although the sparking action was most impressive.
>
> I find that you can tell by the sound (sizzling bacon) when cutting
> is most effective and by the production of a very fine "mud" that
> tends to obscure the work piece after a few minutes.
> I think I may be able to rig a pump/filter arrangement to keep the
> water from becoming so cloudy. I'm thinking of an aquarium pump and
> an in-line fuel filter. I've already tried a 12V windshield washer
> pump but it doesn't appear to be strong enough to move the water.
>
> I believe I'm on the right track, but I'd still welcome any
> suggestions.
> Rich
>