Re: [CAD_CAM_EDM_DRO] Re: Home-built EDM

Rich,

I use liquid parafin mixed with kerosine in the ratio of 3:1 on my
commercial EDM. With this ratio the dielectric doesn't catch fire even when
I do rough cutting upto 8 amperes on the electrode. For higher currents of
course I fill the work envelop with the dielectric to extinguish any sparks
before they reach the surface. And always remember to keep a couple of fire
extinguishers handy near an EDM.

Zafar

----- Original Message -----
From: "Rich" <rmancini@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, July 21, 2003 2:29 AM
Subject: [CAD_CAM_EDM_DRO] Re: Home-built EDM


--- 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



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