On Sunday, April 15, 2012 03:01:56 PM Scott Hasse did opine: > Definitely an interesting idea. To answer Thomas' question from > earlier, I was able to read a 500-1000 Hz range reliably enough to > successfully control EDM plunge/retreat for successful EDM on our first > try using the simple conditional gcode I referenced on the wiki page > describing this. > > A lot more refinement is necessary, and I still have questions/further > investigations about why the frequency limit is so low, and additional > encountered some of the same sort of instability that Gene is > encountering in his encoder readings (even at a stable frequency > input), but have not filtered it as of yet using the component > referenced in that thread. I'm not sure an EDM system would really > benefit from it anyway, as fast response is more important than a > stable reading, and there is no mechanical momentum as their is on a > lathe spindle. > > Scott > You can slice it pretty thin, but there will _always_ be the mass of the moving electrode and its mechanism to move it, so that 'blanket' statement cannot be as true as you say. However, I think asking LinuxCNC to manage that in real time, with millisecond responses, may be asking a bit much, and I'd expect to see a need for some amount of filtering via the lowpass module might be required.
I have yet to play with that as I am currently awaiting the arrival of a new spindle controller after having played Dumbass and hooked my scope probes ground to the - rail of the interface cards power supply AFTER hooking it to the lathes controller board. Contact was of course instant fireworks that among other things, cleared the controllers main fuse, and one trace on the interface card plus I have no idea what else. So I just bought another interface card, the DSO Nano V1 from fleabay, and enough caps to shotgun the nearly open ones on the lathes 10 year old controller. Hopefully I will not have another similar attack of Dumbass when I get it all back in 1 box the next time. :( I am however, making some mods to this interface that should give it about 2 decades faster response, as it exists, it is way too slow, optimized for a 50-200/second pwm rate. At thread cutting rpms, 200 hz, filtered down to about .25 hz at the interfaces output doesn't strike me as being at all desirable. Hence the mods to increase its control bandwidth. Once I get the spindle running again, then I'll see what is the minimum multiplier for lowpass to give me a quasi-stable value. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> It is the business of little minds to shrink. -- Carl Sandburg ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
