axis clamps/brakes was Re: Measuring backlash more accurately?

Juha,

My reply on this was thinking steppers, even though you mentioned
servos... I believe the rutex drives close the loop within the drive,
like geckos? In this case, I think you can treat the system like
steppers...

Jon, Won't the "violent jump" be limited to the "hunting" error/size
in these type servo drives? I would think that clamping an axis
driven by these would be nearly the same as clamping a stepper axis?

Mariss, how about an "experiment"<G>?

Thank you in advance,

Ballendo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> justjuha wrote:
>
> >One thing more for the backlash discussion.
> >I'm rebuilding the Cincinnati 10VC-1000 milling machine. There is
a
> >possibility to brake the movement of an axis when it is not moving
> >(original arrangement). I'm going to fit the machine with the
Rutex's
> >drives and control it with Mach1.
> >Is there any chance to implement such feature into the drive such
> >Rutex R90 or R997, that it would be possible to enable the brake
when
> >the servo drive does not drive the servo motor. What I would need
is
> >just one change-over contact. Any ideas??
> >I've asked this from the Rutex without responce.
> >As you can see, I am also trying to get rid of the backlash
broblems.
> >
> >
> You are trying to get rid of backlash with a brake? Do you mean an
axis
> clamp?
> You really can't do this. A servo system needs to be in a closed-
loop
> condition.
> Activating the brake changes it to open-loop (beacuse torque from
the
> motor will
> not cause any movement) and when you release the brake, it will
jump
> violently.
>
> A brake isn't a fix for backlash, because the backlash will be
there
> whenever the axis is
> unclamped and moving. If you have ballscrews that are worn, send
them
> out for a
> rebuild. That is MUCH less expensive than new screws and nuts.
>
> Jon