Jack Ensor wrote: >>When you say homing is OK, but axis is bad, is that all due to >>speed? >> >> > > Slowing things down by a factor of ten makes no difference in position > error. It still jumps all over the place. > Hmmm, strange. Usually resonance issues are greatly affected by speed. Is backlash compensation off (backlash value in ini file set to zero)? By "jumps all over the place" you mean it is totally unpredictable how far off it will be? If you make several 1" moves in the same direction with incremental jog, what is the error? Does it accumulate or all appear at one point in the series of moves? What happens if you jog back and forth one inch? What is your acceleration set to?
> Could you explain why the following speed calculation is in error? > I have a unipolar motor, driven in quadrature phase A, phase A not, > Phase B, and phase B not., where phase B lags phase A by 90 degrees. > Motor plate specifies 200 steps/rev > step down from motor to screw: 2.5 to 1 > Screw pitch: .2 in/rev > .2 in/rev x 1/2.5 rev/rev x1/200 rev/step = .0004 in/step. This is > correct because this is what I see the system do. > > For speed: > The max jog speed is set in emc to 90 ipm (1.5 in/sec). When jogging at > the max rate I measured a step frequency of 813 Hz on phase A. > Calculating the table speed: > 800 pulses/sec x 60 sec/min x .0004 in/step = 19.2 ipm > However just by looking at the table move, it is moving much faster than > that. > Is this because due to the nature of quadrature drive, the table > actually moves 4 times faster than the step rate? Yes, precisely. Every change of either A or B is a "full step" of the motor. 813 Hz should give 3252 steps/second, or 78 IPM. I'm not sure why you aren't getting the full 90 IPM you are requesting. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
