Re: [CAD_CAM_EDM_DRO] spinning ball nuts

plastiguy 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?
>
>

The Bridgeport BOSS machines do this on the X axis. I have one of these
screw/nut assemblies. You really can't tell much from the outside, but
they have a barrel that is supended between tapered roller bearings.
The nut mounts inside the barrel, and a toothed pulley mounts on the
end, outside the bearings. The nut mount has to be done so the screw
doesn't wobble around in a circle as the barrel and nut turn.

Jon