Gene Heskett wrote: > Greetings everybody; > > I was working on the frame for my new z axis drive for that micro-mill, and > have managed now to break off not one, but 2, 6-nc32 taps in the holes > drilled into the edge of a piece of 1/4"x1.5" steel bar. > > I now have the work insulated, a copper wire in the chuck bent to wobble > about > enough to cover the ends of the taps, and tried a 50 volt AC supply for about > 20 minutes, but the transformers were way too puny and have already smoked. > I have an air jet blowing on the work, and the wire running about 200 rpm. > While it worked, I'd guess I got rid of 5 thou total, from the work and the > electrode wire end, so its not gonna be exactly a 5 minute job unless I can > get some more effective firepower into it. > > Figuring that DC, with a current limiter of sorts and a storage capacitor to > hold more bang will probably work better, I've resigned myself to building > it. > > The question then is, for an air quenched lashup, what is a suitable voltage, > and a suitable current limit in terms of average milliamps, that I should try > and build? Googleing doesn't seem to spit that sort of info out readily. >
Look at my info at http://jelinux.pico-systems.com/edm.html You need a current-limited supply of DC to a film-type capacitor to deliver the current pulses that do the EDM work. Also, I think a dielectric fluid is really important to make the difference between welding and EDM. I run 30 V at about 1 A, mostly due to the parts in my EDM power supply. I found alum-tap (an aluminum tapping fluid) works great, although it is flammable. I only keep a couple drops of it in the hole at a time to reduce the risk of a big fire. (I did get it to flash once, but it did not sustain a fire, so it must have some fire retardant or vapor suppression in it.) Water won't work unless it is really pure. Some people have reported plain distilled water works well. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
