Re: [CAD_CAM_EDM_DRO] How do you get 6/10 of a step?

Rounding is done to the nearest step (.4 rounds down, .5 rounds up). If you
are programming in incremental (G91) you have the possibility of
accumulating the rounding and creating a position error. If you program in
absolute (G90), you will never be more than a half step off.
Darrell
http://www.machinemaster.com

----- Original Message -----
From: "John D. Guenther" <jguenther@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Wednesday, August 30, 2000 1:49 PM
Subject: [CAD_CAM_EDM_DRO] How do you get 6/10 of a step?


>
> Ok, here is my dumb question for those that know how all this stuff
> works.
>
> If you have a stepper motor running is 1/2 step mode so that there are
> 400 steps per revolution attached to a 20 tpi lead screw you get 8000
> steps per inch. Now supposing I want to move that axis exactly 1.0197
> inches, that would appear to me to take 8157.6 steps. The question is
> how do you get the 6/10 of a step? I know, that is only .000075 of an
> inch, maybe I am being paranoid about precision but it seems to me
> that all this can accumulate to quite a bit over many moves along the
> same axis. Is it the common practice to round up or down when
> calculating the number of steps to move?
>
> Thanks
>
> John Guenther
>
>
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