On Saturday 22 November 2008, Andrew Ayre wrote: >Jon Elson wrote: >> Andrew Ayre wrote: >>> Hi, I've been happily generating g-code files and cutting them with >>> AXIS. I'm using EMC2 pre-2.2 CVS HEAD. Yes, I know it's old but I have >>> everything working and I am reluctant to change it right now as I am >>> trying to get Christmas gifts made as quickly as possible. >>> >>> With a new g-code file I get "Joint 0 Following Error" at the same point >>> every time in the file. Line 161 I believe. The g-code file is here: >>> >>> http://files.britishideas.com/public/emc2/jointerror1.ngc >>> >>> On April 17th, 2007 Chris Radek said this about the error message: >>> >>> "It means the difference between the commanded position and feedback >>> position differ by more than the allowed following error." >>> >>> I am using a simple, HobbyCNC card with steppers, three axis, no >>> feedback. I have backlash compensation set in the emc2 ini file. I have >>> cut lots of g-code files without a problem until now. Can anyone give me >>> some hints on how to solve this? Is it a problem with the g-code? >> >> A following error in this case means that the commanded velocity >> required more steps/second than the step generator could produce, with >> the settings of your system. It may be possible to make the step >> generator run faster by decreasing the value of BASE_PERIOD in the >> [EMCMOT] section of your .ini file. Warning! If you make this value >> too small, your system will freeze up when you start EMC. A quick check >> would be to set your feed override to 50% and see if the program gets >> past this spot. I didn't see anything near line 161 that looked like a >> sudden fast and long move. I do notice some G00 moves at other spots, >> which would command the fastest motion permitted by the .ini file >> parameters. That would be where I'd expect to see a following error. A >> 50% feed override ALSO affects G00 moves, so all motion should slow to >> 50%, and it should get past the bad spot. If it is really tripping on a >> G00 move, then you need to lower the MAX velocity in your .ini file >> (unless speeding up the BASE_PERIOD is possible.) > >Thanks for the detailed reply. I set the feed override to 44% and it >works (slowly), but I would like to better understand this so I can >avoid this in the future. > >I've set the BASE_PERIOD based on the latency test, and it is the >maximum my machine can run at. It gives me a max speed of 71.6 IPM. I >can't decrease this value, unfortunately.
And why not? All it takes is an editor to change that value in the .ini file, it is in (I think) nanoseconds, and a 25% upward increment should still work just fine if your limit is 30 ipm. For steppers though, 30 ipm is pushing them, and torque at that speed, unless you have lots higher voltages available than I, is going to be well below the motors rated value. >The g-code file is supposed to limit the speed to 30 IPM, and you can >see this when running the file in AXIS. > >However I now notice that when the file is running in AXIS the velocity >occasionally and only for a split second displays a value of 71.6 IPM. >This raises two questions for me: > > - why would a movement cause the velocity to go beyond the maximum of >30 IPM that I set? Is that a problem with AXIS/EMC2 or the g-code? What version of emc, and what backlash settings please? > - is this a symptom of the problem or is it normal? > >thanks, Andy -- 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) You are in a maze of UUCP connections, all alike. ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
