Re: [CAD_CAM_EDM_DRO] Affordable ball screws

Hello Jon,
As you say only a casted nut would work out this way for a short while.
As soon ther is some wear oil will spill all over the place and the
hidrostatic effect will be gone.
Sven Peter

Jon Elson wrote:

>
> Sven Peter wrote:
>
> > >
> > > Nic van der Walt wrote:
> > > .... If you can somehow drill a couple
> > > > of small
> > > > oil feeds around the centre line of the nut and then pump high pressure
> > > > oil through
> > > > it you form a pretty good imitation of a hydrostatic bearing.
> >
> > Dear Sirs.
> > My little experience from having changed some 5 or 8 ball screws on
> > different machines is following:
> > In a bearing factory I see the case that the screws get pitch damages.
> > The contact area of the balls to nut and screw are only spots. Each time
> > there is a G00 movement acceleration is incredibly high and the
> > carriages inertia gives a hit to the ball contact points. In batch
> > production that are always the same points. Pressure oil feed is good
>
> I'm pretty sure the original poster was thinking of a hydrostatic nut
> retrofit to an Acme screw machine. I think it is a pretty crazy idea, and
> would require hundreds of micro-sized holes drilled in the faces
> of the thread to work. Just squiring oil into an Acme nut will not turn it
> into a hydrostatic bearing. You have to establish a fluid film under high
> shear in the space between the two surfaces, and a nut's threads
> are a complicated geometry to do this in. If the whole nut was a very
> tight fit against the screw, both at minor and major diameter as well as
> at the flank of the thread, then it might be possible to just squirt oil in
> the middle. This might work with a cast (a la Moglice) nut. Oil collection
> would still be a complicated problem, as the screw would likely be
> dripping along its length.
>
> Jon
>
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