Originally Posted by
MARV
I must be missing something here; by your calculation 360 degree rotation equals 12,000 steps (a whole number, micro steps included). That breaks down to 1 degree equals 33.3333333 micro steps (which has no practical value as it isn't a whole number and steppers are expected to move only in whole micro steps), again by your calculation. Your initial indexed moves were -90, 90, -90, 90 and then back to zero. Do the math and each of these moves yields something other than a whole number of steps, but by calculation tends to cancel errors out. Other angular series of moves may not yield expected accuracy. The question that arises is, how are rounding errors handled in the software and can they yield cumulative errors? That may be where all the angst is coming from.
Not meaning to throw a wrench into the works here, but; its my understanding there is also a tolerance issue here as well. Do servos or steppers always land on the exact designated step? Some of the info I've stumbled across suggests there is an acceptable range often set by the mfg. or end user. A bit like the tolerance set in any given tool path (loose for roughing and tight for finish cuts). I would be interested in hearing from others on this subject.