Re: [CAD_CAM_EDM_DRO] Digest Number 2937 - Steps per inch

P. J. Hicks wrote:

>In following the discussion on calculation vs. trial and error setting of
>the spi I would like to relate my experience and ask if it makes sense or is
>way out of line.
>
>I initially set the spi by calculation; sherline supplied standard lead
>screws 20 tpi X 200 steps per motor revolution X 4x stepping equals 16000
>steps per inch, Correct?
>
>However when I measured the travel (at several places along the axis) using
>MDI commands my dial indicator repeatedly indicated that 16070 steps were
>necessary to get 1 inch of travel. Similar experience (slightly different
>numbers) on the other axis. Does this sound reasonable or do I have
>something to track down? And what might it be?
>
>

Try it at a lower speed. If you get different results, then it may be
losing some steps.
If you get the same result, then the pitch of the leadscrew is not what
you think.
This difference is only .4 %, so it may well be within the tolerance of
the screws.
If you don't take both measurements moving the same direction, you will
be adding
backlash to the measurement, which could easily account for this much.

Jon