i would suggest finding a Charmilles/Andrew ef-330 for a beginners edm, it is brain dead simple to run and program.
i have several customers that manufacture $20,000 dollar shotguns and rifles using an edm for making some of the components....
these guns are made for professional target shooting and very rich people.....
i never had a complaint about an edm process messing up the material being eroded....
the majority of my customers manufacture aircraft parts... and been doing it for years......jet turbine blades....engine seals and other things i cannot discuss here....due to propietary information.....
Argonne National Labs uses one of my machines to do "destructive inspection" of Zircalloy tubes used for fuel rods in nuclear reactors, the reason why they edm the part before electron microscope inspection, is that it does not alter the material very much, if at all.....
another one of my customers, Halliburton, uses a wire edm to also do destructive inspection of broken drilling heads.....they use the edm process as it does not alter the material thery are attempting to inspect....
when a drill head fails in the well core they bring them back to the lab to find out what caused the failure.....and the edm process is the start point of choice in this process.....
the US Army, and the DoD, use edm to do similar inspection.......
unless all these people are wrong, i would say that wire edm is THE choice for minimum material damage.
just my 2 cents.....
Registered Linux User #348337
EMC2 Rocks!!!!