Re: [CAD_CAM_EDM_DRO] DRO questions

"Carey L. Culpepper" wrote:

> I have a few DRO questions. I have a Teledyne Gurney PathfinderII on
> my
>
> piece. First question is: will the Kaluga/Mauch setup accept input
> from
> these scales? In the event that I cannot repair the problem in my
> Pathfinder. The linear scales are .0005 resolution optical.
> Question #2 : I would like to go with the closed loop stepper system.
> My
> motors are equipped with encoders( BEI probably 500 pulse). But has
> anyone considered using linear scales in the closed loop system to
> deal
> with back-lash? Or is that an impossible situation of playing
> catch-up?

Ooh - imperial scales are old. But, if they output standard TTL level
quardature
signals, then it should be no problem. Some of the oldest scales had no
electronics
other than photodiodes in the heads. If so, you will need to make some
simple
comparator circuits to convert analog to TTL levels. If the scales
output TTL
already, then any of the computer-DRO setups should work.

Yes, linear encoders, if they have sufficient resolution, are fine for
CNC. The problem is that
.0005" resolution is marginal. If you don't plan to do fancy arc
milling and such, then
it should work fine. Also, if there is much backlash, as with Acme
screws, it is hard
for either servo or stepper motors to instantly get on the other side of
the backlash,
so there are ripples in the milled surface whenever an axis has to
change direction.

Jon