Re: [CAD_CAM_EDM_DRO] move error in MACH3

Thanks for the comment. And with the exception of going a long
distance, we did do axis calibration. We only have a 1" dial indicator,
but using MACH axis calibration in settings at 0.500" move, we get a
0.500" move on dial indicator. BUT THEN when we go to the MDI page and
do a G0 X0.5 we get a 0.455" move. That's nearly a 10% error. Motors
sound good in both cases (don't hear any missed steps, as we often do
when we run up against mechanical limit. And again there is 0.000 to
0.001" backlash on this X axis.

This is very befuddling.

C

On 12/1/2012 10:14 PM, Ron Thompson wrote:
>
> On 12/1/2012 7:03 PM, ebiz_59 wrote:
> > We have a Grizzly mini mill with 276 ozin steppers, Gecko 540 (24v)
> > supply, and MACH3. We are making egg shaped circles and want them to
> > be round.
> >
> > We have calibrated the axis's and they are both right on (and very
> > similar steps per inch numbers of 15984.xxx and 16000.xxxx. And we
> > have redone the backlash, (home made plastic nuts on ACME threads) X
> > was 0.001 and Y was 0.009. And we have restarted MACH several times to
> > and confirmed that the settings have changed.
> >
> > HOWEVER, when we go to MDI in MACH and tell the X axis to move 0.5",
> > it actually moves 0.455" - and is pretty repeatable (+/- a thou or
> > sometimes 2).
> >
> > Interestingly (and frustratingly) when we do an 8 hole bolt pattern,
> > and measure the major and minor axis's and subtract the smaller from
> > the larger, we get a difference of 0.046"... note that 0.5-0.455 =
> > 0.046. We must have some setting messed up, but just can't find it.
> >
> > Any help would be great!
> > Thanks,
> > Chuck
> Sounds like your steps per inch isn't right.
> On the settings tab, use the axis calibration just above the reset
> button. Try to use the longest move you can, as it will be more accurate
> than a short move.
>
> --
>
> Ron Thompson
> On the Beautiful Florida Space Coast, right beside the Kennedy Space
> Center, USA
>
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