RE: [CAD_CAM_EDM_DRO] Re: 4th Axis Concept (long)

It would seem to me that you could us an indexed optical encoder, then you
could just turn off the optical encoder, free run the servo motor for normal
turning, then when you needed precise positioning of the spindle, switch on
the optical encoder, and because it is indexed you could easily find the
home position and work from there. I would mount the encoder disk on the
spindle and not the motor, especially if you are using belt drive. This
would eliminate any slippage between the encoder disk and the spindle. I
also assume one would need to come to a full stop before changing modes from
free-run to servo.

John Guenther

> -----Original Message-----
> From: Alan Marconett KM6VV [mailto:KM6VV@...]
> Sent: Monday, August 06, 2001 2:42 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Re: 4th Axis Concept (long)
>
>
> Hi Chris, Roger,
>
> If you use the servo, and also free-run it as a spindle motor, I'd
> suggest using an "optical interrupter switch" (or hall effect sw) to
> "find home". You should be able to switch control back to servo, and
> "drive" it back to this "home".
>
> Alan KM6VV
>
>
> vrsculptor@... wrote:
> >
> > --- In CAD_CAM_EDM_DRO@y..., datac@l... wrote:
> > > In the following explanation, picture in your minds 2 motors
> > driving a Sherline or similar Lathe spindle, First motor: a dis-
> > engagable stepper, The Other: A traditional spindle drive motor....
> >
> > Chris,
> > Interesting idea. If I where to do this I would use a servo motor
> > instead of a stepper. A servo motor with encoder can be controlled
> > with a Gecko 340 using step and direction input just like a stepper.
> > When in lathe mode just switch out the controller and apply DC
> > directly to the servo. You could get the RPM you need without having
> > to clutch a motor in an out.
> >
> > There is still the problem reseting the piece to zero. I think this
> > could be handled by turning off the power and rotating the shaft by
> > hand to a known position. A fixed position could be established by
> > resting an arm, attached at a right angle to the 4th axis shaft, on
> > the top of a 1-2-3 block or some such.
> >
> > Roger
> >
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