Gene Heskett wrote: > 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.
I meant decrease the BASE_PERIOD. Sorry if what I wrote was confusing. My steppers have a max torque of 305 oz-in at 3A and I am running them at 2A (36VDC input I believe). Do you know of a formula or graph that allows me to work out the optimal cutting speed for the most torque? My machine is quite small - 18" x 12" x 3" cutting area. I assumed the motors I have are overkill for this size of machine (when cutting wood), but maybe that is wrong? 30 IPM is an arbitrary value that I picked that I didn't feel comfortable going above. If I knew I could run it faster I would, but I'm just starting out. >> 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? pre-2.2 CVS HEAD. The backlash settings are: X: 0.005375" Y: 0.0025" Z: 0.0003" The backlash was measured with a dial indicator. As I mentioned before, I've cut lots of g-code files without a problem using the same settings. But I think this g-code file has more small rapid movements than the others. thanks, Andy -- Andy PGP Key ID: 0xDC1B5864 ------------------------------------------------------------------------- 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
