Re: [CAD_CAM_EDM_DRO] Re: How to establish repeatable home position w/steppers?

How about homing to the same exact step every time? To do this you need
two switching devices. One would be the index on an encoder ,if so
equipped. The other would be a switching device to indicate which
revolution of the encoder to look for. When that switch is triggered it
will look for the next index pulse to shut down.The first switch could
be an optical switch, proximity sensor, microswitch, etc.. Of course
things need to get slowed down before it gets there so it does not
overshoot.

dougrasmussen@... wrote:

> Dave,
>
> .0002" is getting into the ballpark. .000125" is my theoretical
> resolution so that's what I'm shooting for.
>
> Maybe some sort of encoder device on the motor shaft would be the way
> to go?
>
> thanks,
>
> Doug
>
>
>
>
> --- In CAD_CAM_EDM_DRO@egroups.com, dave engvall <dengvall@n...>
> wrote:
> >
> >
> > There has been some discussion of limit switchs/home on the list in
> the last month or so. One person was getting a thou or so out
> > of micro-switches ( he did not state his limit of resolution) and I
> get 0.0002"repeatibiliity from hall effect devices. They might
> > be better than that but that is my resolution limit. :-)
> >
> >
> > Dave
> >
> > dougrasmussen@c... wrote:
> >
> >
> > > Group,
> > >
> > > On an open loop stepper system how do you establish a repeatable
> home
> > > position? I'm thinking of a home position that will repeat to
> within
> > > the resolution of the machine.
> > >
> > > I can't see that normal, every day limit switches will do the job.
>
> > > Dial indicators would be a pain, but would work provided they
> didn't
> > > get bumped or readjusted. Some very old machines used a vernier
> dial
> > > which was manually stepped to position.
> > >
> > > So, what method are most of you using?
> > >
> > > thanks,
> > >
> > > Doug
> > >
> > >
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