Re: Rotary table DRO

If you had a 5,000 count encoder in a wheel that contacts the outside
diameter, much like a trav-a-dial, you would then be able to slice up
your circumference into pieces.
http://www.southwesternindustries.com/swi/prod_measurement1.shtml

the contact wheel would need to be the the dia to slice up your od.

a single rotation would need a wheel the same size as your table.
2 rotations, 1/2 circumference 5,000 count = 10,000 bits
200 rotations = 1,000,000 bit count

that would make your contact wheel OD around 100 mm.
they make the contact wheel with a radius, then tilt the unit to get
the proper ratio.

I would think that adding an optical band on the OD would offer
additional reference points.

Dave

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "babinda01" <a_k@a...> wrote:
>
> Hello,
>
> I was wondering if someone may be able to help me with a problem
I
> have at the moment.
> I am trying to add a DRO to my 'little' rotary table. It is 6
meter
> diameter. I am looking to get .05mm accuracy if at all possible.
I
> was thinking of puting a rotary encoder onto the main spindle which
> is coupled directly to the table, but to get the resolution I am
> looking for I need approx 400 000 pulses per rev (0.00095 deg).
All
> the encoders I have looked at seem to be about 8000 pulses per rev
in
> quad. Is it possible to gear an encoder up? If so how (so as to
get
> minimal backlash)?
>
> Thanks for your help
> Andrew