Re: [CAD_CAM_EDM_DRO] Re: Preloading ball screws

Hey Torsten,,,,that's perfect!!!! No need for exposed studs that'll get in
the way on my installation. I can modify what I already built pretty
easily. Thanks to all you guys, this site is a wealth of valuable minds, it
just amazes me the amount of shared knowledge that is offered here.

Cheers, back to the shop....



R. William Kichman, P.E.
Kichman Engineering Associates
103 Old Furnace Road
Cornwall, PA 17016-0643
tel/fax 717/270-0714

----- Original Message -----
From: "Torsten" <torsten@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, September 27, 2003 2:45 PM
Subject: [CAD_CAM_EDM_DRO] Re: Preloading ball screws


> Bill, a good Antibacklash adjustment device for
> 2 Ballnuts on Ballscrews that have a posible
> pitch error features a ridgid takeup and a spring
> type preload.
>
> The ridgid takeup allows the Nuts to be ajusted
> apart from each other in a way that they are not
> allowed to ever get closer to each other then what
> they have been set at.
> They are however free to move further apart as this
> is nessesary to allow for the pitch error that may be
> fond at some point along the working range of the
> screw.
> This point is what is used to determine the final
> adjustment, the assembly should be able to move
> troughout the working range without binding up.
>
> The preload spring is ensuring the nuts are pushed
> apart durring the parts of travel where they are
> Not positioned at the tightest spot.
> The amount of pressure on the spring is a bit of a
> compromise, at a minimum the pressure should be adequate
> to push the weight of the machine table + any possible
> part mounted to it this will ensure backlash free positioning
> is possible, at a maximum it would have to be less then
> the load rating of the nut/screw getting too close to
> this value would likely course excessive wear and lots
> of drag because this will be the force between the components
> that is active at all times.
> You will not have to subtract this preload from the rating
> of the nut/screw because it is not acumulative.
> The spring force will likely be overcome by the force of the
> cutter durring machining but will restore after the force is
> dissipated.
>
> A example of a low profile device i have found is
> http://www.mmanrow.20m.com/anti_backlash_nuts.htm
>
> I have build a slightly modified version of this design
> that entails the basic principal of its functionality.
> Did not like the setscrews used and changed the outer
> dia. Works well now.
> Hope this helps good luck.
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bill Kichman"
> <billkichman@c...> wrote:
> > I am sure this has been covered ad nauseum, but here goes...I have 2
> > ballnuts threaded into a steel block which is attached to my table
> for my
> > ballscrew conversion...I had been depending on rigid backlash
> adjustment by
> > simply screwing one of the nuts tightly against the other, and
> tightening
> > both setscrews. As I understand it, a spring type arrangement is
> more
> > advantageous due to wear issues which act to change the fixed
> preload over
> > time.
> >
> > My question is this....as I have no room whatsoever on at least one
> of the
> > axes for adding anything to the periphery of the nut, and the
> threads
> > already are there, would it be reasonable to attach a strong spring
> such
> > that it would act to tighten the threaded ball nut's threads at all
> times?
> > That way, the spring wouldn't have to be nearly as strong as an
> installation
> > without the threads installed and a heavy spring arrrangement in-
> line with
> > the nut. Am I seeing this clearly? The spring could partially
> wrap around
> > the nut and keep a constant preload.
> > Has anybody done this?
> > R. William Kichman, P.E.
> > Kichman Engineering Associates
> > 103 Old Furnace Road
> > Cornwall, PA 17016-0643
> > tel/fax 717/270-0714
>
>
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