On Sunday 03 April 2016 09:38:59 Mark wrote: > On 04/03/2016 09:28 AM, Dave Caroline wrote: > > A number is a number regardless of trailing 0's, no affect on > > accuracy or resolution. > > Where users do get it wrong though, is not understanding how path > > following has a tolerance. This is separate from the number and its > > 0's but the speed of how you can change direction. > > see http://wiki.linuxcnc.org/cgi-bin/wiki.pl?TrajectoryControl > > and > > http://linuxcnc.org/docs/2.6/html/gcode/gcode.html#sec:G64 > > > > Dave Caroline > > Okay, assuming you have the theoretical perfect machine, what actually > determines the accuracy and/or resolution? To keep it simple, lets > just assume straight line moves. > > Mark
All the springiness in the motor coupling or belt drive, the errors in the screws (which can be cumulative or canceling as thats usually rated at .001" per foot) and the nuts backlash, and the springing of the frame error caused by stiction at low speeds. Overall thats difficult to measure but put a dial on the axis, and remove the backlash from the ini for that axis, then command a slow move, .01" a minute, and watch the dial, when it has moved to a convienient mark on the dial, write down the DRO readings, then move some more in the same direction to check for jerking moves which would be stiction, running it to the dials limit. Then do an mdi move in the other direction back to the co-ordinate you wrote down. The dial won't come back to that mark, but the amount it lacks is pretty close to the backlash setting you should then put into the ini file for that axis. Reset the dial to watch Y, wash rinse & repeat, ditto for Z. As for mapping screws to compensate for their error, that would take an external DRO of known accuracy, something I do not have. That level of accuracy is more lab standard stuff, and will need a childs wagonload of SBAnthony dollars to obtain. And I don't even have the childs wagon. :( 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> ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
