Re: [CAD_CAM_EDM_DRO] Re: Home-built EDM

Hi All:
You don't want much conductivity in the dielectric.
What you do want is just enough conductivity and close enough proximity
between the workpiece and the electrode that a controlled amount of current
at a predetermined voltage will jump the gap and knock a bit of the
workpiece away as it does the jump.
The dielectric is ionized locally in the process, both by the energy of the
discharge and by the contaminants that are produced by the erosion of the
workpiece and electrode.
Commercial wire EDM's go to great lengths to get the ions back out of the
dielectric (they mostly use water as a dielectric) so it won't be too
conductive.
The conductivity should be such that several amperes at 30 odd volts is
needed to traverse a gap of roughly 0.001", and should stay that way as much
as possible throughout the burn.
Dumping salts into the water will make it far too conductive to work.
Cheers

Marcus

> > First I have no experience with EDM. Though I do have
> > excellent experience in getting water to conduct
> > electricity. Simply adding table salt will
> > dramatically increase conductivity, say 10% by weight.
> > Pure water will not conduct electricity, simply test
> > with a multimeter. Commercially sodium potash or Lye
> > is used to increase electrical conductivity. In a
> > ratio of 30 to 50% by volume though these are caustic
> > solutions.
> >
> > Ken
> > Kenneth A. Emmert