John,
Right now I am looking at the machines specifics. Basically my machine
has a 6000 rpm spindle and a 12000 rpm motor with a reduction timing belt
drive. I could probably make something like you did and put it behind the
spindle body where the belt is not touching the timing pulley. That would
work and I dunno how many teeth it has but with two sensors it would be
decent tracking I am sure. I am also looking at what my pal Lee Osborn did
on his machine and that is to use an encoder in place of the resolver on
the motor and basically cheat the speed in the software to show actual
spindle RPM. That does not fix my spindle indexing issues for toolchange
tho. I would need another sensor for that on the spindle body somewhere.
The third option I could go with would be to buy two timing pulleys of
large diameter and machine one to fit over the approx 3" diameter spindle
body and another of the same diameter that would mount off to the side of
the spindle body and install an encoder wheel on it being a 1-1 belt ratio
that would allow me to track speed as well as use the index pulse on the
encoder to index for toolchange. Honestly this would be quite simple to do
and if you saw the layout of the millhead there is a rather large flat
steel plate that the power drawbar assembly mounts to that could easily
hold say a 2" boss with a bearing and the second timing pulley. I looked at
getting a large diameter encoder wheel but it seems like nobody makes one
cheap enough. I really don't like the motor encoder AND another encoder not
only for the complexity but also the 1-2 ratio causes some issues as well.
I really want the machine to be able to rigid tap like it did when new and
I NEED it to toolchange as well so this is quite important. I'd like to
hear other ideas about this.... Peace
Pete
On Sun, Feb 17, 2013 at 10:42 PM, Jon Elson <[email protected]> wrote:
> Pete Matos wrote:
> > s....
> >
> > Jon,
> > Those sensors are similar to the hall effect ones I have considered for
> > it. I am actually looking for input more about the idea of using the
> single
> > aperture shutter wheel on the spindle with linuxcnc as to whether it
> works
> > well or not more than I am looking for sensor suggestions although that
> is
> > welcome too....peace
> >
> These sensors have two Hall devices and a flip-flop, so they work very
> reliably
> at low speeds without flicker. I was worried about the position drifting
> at
> the reversal, and this family of sensors definitely fixes that problem.
>
> Jon
>
>
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