Karl Speed control is normally a direct function of a current setpoint in the PWM controller. EDM power supplies look at every single pulse to determine if the current and voltage is within a specified range. The quality of the cut is partly a function of the speed and the energy in every pulse. So the control of the speed is integrated with the power management or power supply controller.
------ Original Message ------ From: "Nicklas Karlsson" <[email protected]> To: "EMC developers" <[email protected]> Sent: 2016-02-26 15:10:04 Subject: Re: [Emc-developers] EDM gap control (Control parameters) >I understand flushing is important but nothing about how ot adapt >speed. > > >> On Friday 26 February 2016 05:07:20 Nicklas Karlsson wrote: >> >> > > >Anybody familiar with EDM who could tell me how to adjust the >>feed >> > > > rate for EDM operations? >> > > >> > > Not a very trivial task but it can be done. There is a youtube >>video >> > > showing and EDM running on linuxcnc. Do a search. The problem >>comes >> > > in when you have to backup as some EDM machines do. >> > >> > Programming I could solve. Then controlling speed and backup what >>do >> > they try to achieve: A certain average gap voltage? Ignition >>voltage? >> > Power in each pulse? >> > >> I have only used edm 3 times, in each case in blind holes. The first >>time >> I drove it by hand from the arrow keys, but found the blind holes >>lack >> of the electrolite fluid circulation to be a major problem as the >>juice >> in the hole would gradually get conductive & short it out. I did get >>the >> first broken tap removed but it was an all day job. I found also >>that >> if the electrode was rotating at 50 to 100 revs, that induced >> circulation seems to help. So I wrote a loop that drove it to a >>fixed >> very small increment farther each time, doing g0 moves so the >> electrolite was somewhat pumped in and out of the hole, and the >>second >> busted tap was cut out in about 1/3rd of the time. But I felt the >>power >> supply was a bit puny, so the next time I traded the 2uf capacitor >>out >> for a 10 uf (both oil filled paper caps) and doubled the voltage to >> around 75 volts while reducing the resistor from 50 ohms to 25, lots >> more power per pulse. >> >> Later, needing mounting holes in a 10" carbide tipped saw blade so I >> could mount it on a rotary table to sharpen it, I used hollow brass >> tubing as the electrode, rotating in the mills chuck to help >>circulate >> the juice. With more power it was faster, but even with 29db >>shooting >> earmuffs on, the noise was still in the 130 db area and a bit >>painfull. >> That saw blade made a great sounding board and I expect it could be >> easily heard 3 to 6 blocks away. It also drilled the cleanest holes >>I >> have ever seen in that hard chrome plated steel. >> >> So the importance of being able to circulate the juice to keep the >> metalic debris flushed from the working area is at last as important >>as >> the height control. As for active height control, one might be able >>to >> use one of the thc modules for that but I've not tried it. >> >> With very short, heavy leads between the capacitor and the workface, >>a >> diode to rectify the peak voltage reached at the capcitor would seem >>to >> be the measurement method of choice, but that, even with very short >> leads, might need some r/c filtering because the discharge IS going >>to >> induce some resonant ringing, likely sufficient to cause micro-arcing >>in >> a common bulk carbon resistor, which will manifest itself as an >>initial >> lowering of the filtering resistors measured resistance, and a drift >>in >> the desired operating voltage until the resistor is destroyed. For >>the >> same reason, the diode needs to be a very fast recovery diode and >>rated >> at least to 1 kilovolt. >> >> Not hugely helpfull Nicklas, but that is what I learned based on 65+ >> years of making electrons do useful work. >> >> > Nicklas Karlsson >> > >> > >>---------------------------------------------------------------------- >> >-------- Site24x7 APM Insight: Get Deep Visibility into Application >> > Performance APM + Mobile APM + RUM: Monitor 3 App instances at just >> > $35/Month Monitor end-to-end web transactions and take corrective >> > actions now Troubleshoot faster and improve end-user experience. >> > Signup Now! >> > http://pubads.g.doubleclick.net/gampad/clk?id=272487151&iu=/4140 >> > _______________________________________________ >> > Emc-developers mailing list >> > [email protected] >> > https://lists.sourceforge.net/lists/listinfo/emc-developers >> >> >> Cheers, Gene Heskett >> -- >> "There are four boxes to be used in defense of liberty: >> soap, ballot, jury, and ammo. Please use in that order." >> -Ed Howdershelt (Author) >> Genes Web page <http://geneslinuxbox.net:6309/gene> >> >> >>------------------------------------------------------------------------------ >> Site24x7 APM Insight: Get Deep Visibility into Application >>Performance >> APM + Mobile APM + RUM: Monitor 3 App instances at just $35/Month >> Monitor end-to-end web transactions and take corrective actions now >> Troubleshoot faster and improve end-user experience. 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