vjaqua wrote:

Actually you can make your own EDM machine for demo purposes
with about 20 bucks worth of parts from Radio Shack
A 60 w light bulb, a diode rectifier, and an eltrolytic capacitor
clip one lead on a pc of aluminum in isulated container of
a dielectric liquid (kerosine works quite well)
on your drill press or mill and use a brass tube as an elctrode
(square tube is even mor impressive) - Vance
--

You got plans Vance ?

vjaqua wrote:

Paul and others. I will recreate this sketch from (imperfect) memory.
It has been a long time since I last lashed on together, and I think
that the polarity is right - and they do work. What you have created
ia a simple relaxation oscillator with the break down voltage across
the gap cyclicly discharging the capacitor, and the dielectric

(insulating)

fluid recondensing and carrying away the vaporized material from the

gap.

Ideally the frequency of this oscillator would closely match the 60

cycle

source, but it does not appear to be critical. It is probably a good

idea

to wrap the electrode in insulating tape or similar, to reduce shock
hazard (nothing here is OSHA approved). One of those black trays
you throw away after you Nuke your burrito is ideal for the pan.
The fluid is almost any high flash point. insulating oil or solvent i ie
kerosine is very common, hydraulic or brake fluid would probably
work or even deionized water has been used but is easily contaminated.
Brass electrode, and aluminum work piece is the easiest for demo
purposes, as I said, square tubing gives a dramatic result, or the

little

brass pinion gear off a toy motor is quite fun.
It is a bit like arc welding - you touch the electrode to the work piece
and draw back to a frying bacon sound. A light touch will quickly
establish a semi steady state result, Both electrode and work will be
eroded, but if I gave you the right polarity, the work part will be
removed more rapidly (as you will find out, rapidly is a relative thing)
This sort of thing has been shown in scores of hobby and home
work shop sources, and I am sure one of the guys will find a better.
more up to date description. I will lash one together to verify
that this still works, and get back with mre info.
Obiously the mega bucks machines have complex pulse shaping
circuits for better surface finish and more exotic materials, but you
can have a lot of fun, and possibly some utility at this level. Vance

Robert Barnard wrote:

Ya know, using a copper tube for the electrode and pumping an eltrolytic
through (recalculating) it could make a dandy tap/bolt remover on something
big, like a block.  Setup a slow plunge rate (and preset depth), walk away
and come back in a few hours to check on it.

I like this sketch!

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