RE: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????

On Mon, 2003-08-11 at 16:49, Carlos Guillermo wrote:

> Hi Kim -
>
> Are you designing your motors' pushing force to be equal to the
> max cutting loads you expect?

No. But that doesn't mean it won't happen. It is wasteful to have the
motors running at half the cutting force (for instance) just to tension
the ball nuts. See my next email.

> If so, your motors may be
> relatively small, with little reserve acceleration force, OR, you
> are expecting HUGE cutting forces, and you expect very small
> acceleration forces. I would think the max "pushing" force of a
> motor on a machine tool would be far greater than the expected
> cutting forces, partly in order to leave some force available for
> accelerating the machine around while following the toolpath.
> Does anyone know of a modern high-performance machine tool that
> uses spring elements in their preloaded ballnuts?

I looked closely at our neighbors CNC machine at the preload is set on
the nuts with a screw adjustment. No springs involved.

> Regards,
>
> Carlos Guillermo
> VERVE Engineering & Design
>
> -----Original Message-----
> From: Kim Lux [mailto:lux@...]
> Sent: Monday, August 11, 2003 12:17 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: RE: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????
>
>
> A substantial amount of force would have to be greater than the
> pushing
> capacity of the motor so that there was never a force that would
> displace the nuts against each other. If the spring is weaker
> than the
> pushing force of the motor, then it will displace the backlash
> under a
> heavy cut.
>
> As soon as the nuts are adjusted for the maximum force the motor
> is
> capable of moving, there isn't any force left to move the cutter.
>
> Kim
>
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--
Kim Lux <lux@...>