good going nicklaus! many experienced operator never see the relation of setpoint and 'smooth' but beware, too smooth is sluggish, so jab a screwdriver in the gap during tests to make sure the system immediately retracts.
the setpoint for graphite to steel for positive polarity is 29 to 32 volts ( 29 for large average currents, 32 for tiny ) its different for copper to steel copper to wolfram steel to steel the german reseach call this 'paarung' the anode & cathode pairing determines the setpoint please look at the ISEM and JSEM journals for info it is handy to use 2 scope traces 1 on the process variable 1 on the velocity command to the single axis ( your case) they should track each other tightly tomp On 02/26/2016 10:59 PM, Nicklas Karlsson wrote: > Thanks. > > I start with Z-motion only and try to control distance to keep discharge > voltage at 29 volt. Then this work it is time for optimal paramers and other > directions. > > Regards Nicklas Karlsson > > > > On Fri, 26 Feb 2016 14:06:19 +0000 (UTC) > Pete_Gruendeman <gruende...@att.net> wrote: > >> Hi:Pete Gruendeman, long time EDM operator here. I have also written EDM >> software which went forward, backward and escaped sideways off the program >> path. >> EDM motion is based on either:Positioning, at whatever rate you program >> though it's typically rather slow;or >> Erosion, with no feedrate what so ever. Sparks radiate from the wire or >> carbon/copper electrode in all directions, eroding the workpiece where those >> sparks make contact. Motion forward in the programmed path is all about >> maintaining erosion gap voltage, and possibly current, within limits which >> is controlled entirely by movement of the electrode. Don't call it a >> feedrate because It's not a feedrate. >> Read the gap voltage;If/ gap voltage > 3/4 Voc, move ahead;If/ gap voltage > >> 3/4 Voc && < 2/3 Voc, stay put;If/ gap voltage < 2/3 Voc, backup;repeat >> All of this start, stop, backup motion will result in an average rate of >> travel that is on the order of inches per hour. It's not fast. Though the >> positioning rate for forward and reverse motion can be inches per minute. >> What's really needed for useful EDM control is all of the above plus backing >> up on or escaping off the programmed path at timed intervals or based on >> erosion conditions. It's not that hard to write as I have already done it >> in four axis moves, linear interpolation only, no wire diameter >> compensation. Code or ideas sent upon request. >> Pete Gruendeman >> >> On Friday, February 26, 2016 7:10 AM, Nicklas Karlsson >> <nicklas.karlsso...@gmail.com> wrote: >> >> >> 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 >>>> Emc-developers@lists.sourceforge.net >>>> 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. 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