Re: spinning ball nuts

Scott,

Spinning the nuts is a good idea, but htere are issues there as well.
(Means you CAN'T go "as fast as you want then") Things like
lubrication being hindered by the flinging effect of the nut...

Notice that the reply posted earlier mentions 2TPI ballscrews. To
keep the nut rotating speed down.

It is much harder to build an accurately spinning nut assembly, and
yo may find that cyclical errors are increased (So far, EMC is the
only controller in the "hobby" arena that could map these away.)

You also still have column loading issues to contend with, either by
using a larger diameter screw ANYWAY, or increasing the structural
support significantly.

I've long argued FOR spinning nuts, and it's a great way to go. Just
don't consider it anything other than a DIFFERENT engineering
question; subject to its own limitations and strengths.

Hope this helps,

Ballendo

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "plastiguy" <plastiguy@a...>
wrote:

> OK, new idea for my fast running long axis CNC router. The overall
> travel the long way will be about 100". From all of the mechanical
> calculations to attain the rapid traverse speed I wanted, out

popped

> an unrealistically large diameter lead screw solution (financially
> unrealistic, that is). So, instead of putting in a 1.5" diameter
> screw and spinning the screw, I'm considering a smaller dia.
> stationary screw and then spinning the nut (can go as fast as I

want

> then). Besides the added design challenge of having the servo

motor

> move with the gantry that it drives, what snafus might I encounter
> with this approach? Anyone have any experience using spinning ball
> screw nuts instead of spinning the screw?
> Scott