On Thursday 25 March 2010, Mark Wendt (Contractor) wrote: >Mornin' Gents, > > Had a little time to play yesterday evening to play around with my >machine, so I decided to stick a dial indicator on both my X and Z >axes (I only have those two, it's a gantry machine that cuts tapered >triangular bamboo strips for making bamboo fly rods). The Z axis was >dead nuts on, but I was get varied responses to jogs on the X >axis. I tried it at .001, .05, .01 and .1 on the jog movement. At >.001, sometimes I'd get no movement (I'd here stepper motor noise but >no movement on the dial indicator), other times I'd get a half-thou, >and other times it would jump .002" - .004". At .01, the first >couple of jogs would show about .001" - .002" short of the full .01" >movement, then occasionally move the full .01", and then sometimes >slightly more than .01". About the same for the .05" movement. At >.1", the movement for the first few times was .003" - .004" short, >but then would move almost dead nuts on to .1" each jog. I don't >think backlash would come into play since all the moves were in the >same direction.
At 165 pounds, it may be that the gantry is actually taking up some backlash as its stopping from the longer moves which would be faster. Can you, as its hooked up & the motors enabled, induce a motion visible on the indicator by manually pushing or pulling it? And, equally important, does this 'slack' remain constant as you move it with the motors? If constant, then perhaps adding some backlash comp might help (but that's only effective for motion reversals of course), or if its position related, it might be possible to map the screws error. Wear patterns can be elusive, and mapping a cyclic error can be 'fun' for some definitions of fun. If you have many hours on the machine doing the same cuts over and over it might even be advisable to replace the screws. Or if the cutting dust can get to them, a really good cleaning might help. > I disconnected the pinion gears from the racks, moved the gantry >back and forth the length of the X axis a few times by hand, and >didn't really notice any binding. It seemed pretty smooth, and >relatively easy to move a 165 lb gantry on the rails. Pinion gears, same thoughts about cleaning apply. I assume they are preloaded? > I thought maybe it was a software setting, so I futzed around with >the MAX_VELOCITY, MAX_ACCELERATION, and the STEPGEN_MAXACCEL. It is >pretty cool to see a heavy gantry zipping back and forth on the >machine at 180 inches a minute... ;-) > > Anything else I should look at? Or should I keep concentrating on >tuning with the three variables above? > >Thanks, >Mark > > > > >--------------------------------------------------------------------------- >--- Download Intel® Parallel Studio Eval >Try the new software tools for yourself. Speed compiling, find bugs >proactively, and fine-tune applications for parallel performance. >See why Intel Parallel Studio got high marks during beta. >http://p.sf.net/sfu/intel-sw-dev >_______________________________________________ >Emc-users mailing list >[email protected] >https://lists.sourceforge.net/lists/listinfo/emc-users > -- 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) All that glitters has a high refractive index. ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
