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

Something simular to this is done with floppy disk drive steppers.

Home out until you trip the home switch then step to a certain phase of the
drive is energized on out.

Hugh
Very glad that floppy drives are so cheap you don't have to field align
them.

----- Original Message -----
From: Carey L. Culpepper <mr.c@...>
To: <CAD_CAM_EDM_DRO@egroups.com>
Sent: Sunday, August 27, 2000 7:01 PM
Subject: 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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