Re: [CAD_CAM_EDM_DRO] Re: ECM, The poor man's EDM??

one time as an experiment i drew out a superfine glass
tube from an eyedropper. then i put an electrode in it
and a little salt in a glass and a 9v and overnight it
ate a very tiny hole (about .003 or so) half way thru
the penny and made the water all blue.
so you can use a glass tube. mine ws so tiny the
electrolyte wouldn't even drip out.
if you are doing more than drilling holes, such as is
the great glory of EDM, sinking a die rather than
removing a broken bit- then you may find your best
result with a tool made of bisque fired clay or any
other non-conductive sintered material.

to automate it, there is nothing simpler.
it's a screw with a very wide platter for a head. the
bare shaft of a tiny motor drives the giant wheel with
direct contact or a pulley.
the feedback loop is:
if the lm317K isn't on shutdown, rotate the screw to
move down. if the v reg has done its thermal overload
protection shutdown, then back the motor up.
i've seen EDM machines made on this mechanism.

--- Graham Stabler <eexgs@...> wrote:

>
> > Op's I had assumed a unitary electrod on the end,
> not one that
> would
> > be intermitant.
>
> You have to have some insulator with the gravity
> feed method or it
> will short.
>
> > If it were unitary, then the time of etching would
> be constant,
> > whereas a small say, 10% section on the side,
> would etch at a much
> > slower rate.
>
> You have lost me to be honest.
>
> > Another not about rotating, if you use an tube
> type electrode and
> have a wire across the end, there will be no stub
> left as the unit
> will cut it out. This will take longer of course,
> but the wire
> would allow flushing.
>
> They do that with EDM, they have a twisted divider
> in the tube, as
> the electrode disapears the bar effectively rotates
> removing the
> part of the workpiece that had been left. For ECM a
> wire od
> something might be good however unlike EDM, ECM does
> not have the
> spark gap problem, the plug that forms will be
> removed as it
> progresses. However it will slow the cutting rate
> as it will take
> current away from the small gap area at the tip.
>
> Idealy I would be able to take a normal copper tube
> or an EDM
> electrode with some internal walls and dip the end
> in some magic
> goop. The goop would dry as a tough but porous
> insulator. Then the
> walls of the tube would be insulated with varnish or
> even heat
> shrink. This would allow side ways machining at a
> rate fast enough
> for fast downwards machining. The insulation
> properities would
> prevent shorting while the porousness would allow
> current flow in
> the electrolyte and machining.
>
> Graham
>
>
>
>
>
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