Re: Max feedrate of ball screws?

--- In CAD_CAM_EDM_DRO@y..., "dgmachinist" <scsm@m...> wrote:

> --- In CAD_CAM_EDM_DRO@y..., "dgmachinist" <scsm@m...> wrote:
> > --- In CAD_CAM_EDM_DRO@y..., "Robert Campbell" <bob@c...> wrote:
> > > Seth,
> > >
> > > The current trend is to go to a rotating nut. The ball screw is
> > then fixed
> > > at both ends. Some machine go up to about 3,000 inches per
> minute.
> > >
> > > Bob Campbell
> >
> >
> > Bob,
> >
> > How in the good lord's name do I make a rotating nut? It's a
> > moving gantry..... Any ideas? Why is it different when the nut
> > rotates? Vibration?
> >
> > > Seth
>
> Guys,
>
> Other than a rotating nut, (which I may end up going with)
> what other method is there to acheive high travel speeds (300+ IPM)
> I really like the idea of a rotating nut, but unless someone has
> already built one and is willing to release the design...
> It looks like it will be a complex engineering progect, and rather
> expensive to machine...
>
>
> Seth

A rotating nut design will be more difficult in design and more
expensive in most cases!
It is nessesary in cases where the length to dia. ratio of the
screw would create a dynamic imbalance at higher speeds.
example a 0.25 pitch 1.25 dia. screw at 1000 ipm would
be rotating at 4000 ipr.
This would not be a problem for a screw of about 60 inches or less
of length.
Anything longer would incresingly be affected by the dynamic
imbalance, and a rotating nut with stationary screw becomes benefical.
My scope is if you dont' need it there is no benefit to have it.
Good luck..