- a Stepper ( 1.8 DEG ) REQUIRES 200 STEPS or pulses to turn one rev

( .9 DEG ) " 400 "

- So if you have no gearing, or like you describe, attached directly to the the spindle and are micro stepping

then 200 steps/rev x 4 us = 800 steps / rev for indexing. No more and no less........

- lets say you want to rotate 90 deg, then 800 steps / rev x 90/360 = 200 steps and you would see the dro indicate 45.00 deg

" 30 " 800 x 30/360 = 66.6666 steps so you will see the dro display 29.*********xx deg and not a

even number for the degrees. That's becuase you can't move a fraction of a step like .66 steps.In fact it may be something different than the

calculated depending on the stepper used.

- The best you will do in movement accuracy, if all was ideal would be 1/800=.00125 of a rev = 0.45 degrees, thus your something less or more

than a degree. Now if you increase the resolution via gearing then the resolution will improve such that you will get a display which would show 30 deg

for a commanded G0 A 30. So if you use gearing with a ratio of 10.8 then you will get even steps and the dro will show even deg.

-Now if you use gearing, then the stepper will need to run faster for a given feedrate, and as you increase rpm of the stepper motor, the stepper

will loose torque and thus you start to limit the max speed you can index at. Because the spindle has drag and that drag increases with velocity then

the velocity will not linear. Just like a typical stepper curve shows.

So as Gerry (oops...Ian) said, you need gearing to get an true increase in resolution. ie: more pulses to the stepper to move the same axis travel,

RICH