Re: repeatable vs accurate switch

I've been considering this myself, and have been thinking of dual
sensors on each axis, one on the table itself for coarse position,
and another on the back of the motor for fine position.

In a stepper driven environment, this should give repeatability
limited only by the backlash in the table.

In a servo driven setup, I think you'd need a full encoder.

> -----Original Message-----
> From: Torsten [mailto:torsten@g...]
> Sent: Wednesday, November 05, 2003 1:32 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: repeatable vs accurate switch
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Don Rogers <Don@C...> wrote:
> > I am working on a machine design that needs a signal that is
> repeatable to
> > a very tight tolerance. I don't care if it trips at 0.250" or at
> > 0.000250", as long as it is the same each time. My thoughts now
> are
> > focusing on optical sensors. First is just a plane flag through

an

> optical
> > coupler, and the second is a mechanical amplified version, IE a

10X

> gear
> > driven optical aperture.
> >
> > Any pitfalls or ideas that come to mind??
> >
> > Thanks Don
>
> Every switch should be repeatable unless the switch is broke.
> Accurate is largely defined as very fast switching in motion
> control.
> A table moving at a fast velocity is recieving a move pulse
> in microsecond intervals. The switch will have to send the
> signal also at a very fast speed to let the controller know
> that it has triggered.
> Keep in mind that if the object of the switch is to stop motion
> that a mass moving can not be stopped instantly but has to allow
> for some distance to decelerate.
> Find a suitable switch with a fast responds time.
> Good Luck
>
>
>
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