Mark Wendt (Contractor) wrote: > At 08:43 AM 3/25/2010, you wrote: > >> Mark Wendt (Contractor) pravi: >> >>> 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, >>> >>> >> This can be only mechanical then... Check backlash and endplay of nut... >> check coupler too.. If motor make step and gantry not then don't blew >> software :D >> >> Slavko. >> > This is on a rack and pinion system, pulley mounted directly on > stepper, pinion has pulley mounted directly to it, with cogged timing > belt driving the pinion. All these numbers were with the gantry > moving in one direction, jog and hold, jog and hold, while watching > the dial indicator for movement between jogs, which there was > none. Does backlash come into play when all moves are in the same direction? > Hmmm.
My first thought was also that it's a mechanical issue. I can imagine the rack geometry causing a problem like backlash. The thing I think of (and this is pure conjecture, I don't know that anyone would actually manufacture a rack with this "feature") is that there are "rest positions" as the pinion moves over the rack. You should try the moves with extremely slow acceleration and velocity. Take the numbers you're using and divide them by 5 or 10. If you still have position errors, then it's pretty much got to be mechanical. You can also test by repeatedly doing MDI moves like "G91 F10 G1 X0.001". The acceleration may be different for jogs vs. coordinated moves. One other thing, what's the axis scale? A small pinion (say 1.5 inches) moves ~4.7 inches per rev, which with a standard stepper, 10x microstepping, and 2:1 gearing is under 1000 steps/inch. You may not have the resolution to move 0.001 inches exactly. - Steve ------------------------------------------------------------------------------ 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
