Re: ECM, The poor man's EDM??

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Graham Stabler" <eexgs@n...>
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

That's what I was getting at. if one uses an insulated eelctrode, it
can only cut in one direction, and might not be able to cut the hole
diameter large enough to allow the passage of the insulated electrode.
but your porous method, or my single point and rotate method, the hole
OD could be controlled.

I'm putting together another EDM, this one based on the Flemming book.
once done, I will have all the bits needed to try your ECM unit.

Dave