Re: [CAD_CAM_EDM_DRO] Rolled vs. Ground ballscrews or other screws!

that's a new thought to me. i can see how rolling
could produce less wear over the long haul.
but i can't see how a brass nut is gonna wear down a
steel screw very fast. and a leadnut and backlash nut
are consumable parts, no?


--- R Rogers <rogersmach@...> wrote:

> A conventional thread is better than a ballscrew?
> Well the fit is easier to attain but, unfortunately
> doesn't last very long.
>
> Ron Rogers
> Closed loop monitoring for Mach CNC software:
> Encoder interfaces that send encoder data back to
> software
> and provide additional outputs and inputs.
> Parallel port cards
> Cables
> Special Combo pricing
> www.rogersmachine.net
>
> juan gelt <juangelt@...> wrote:
> hi. i had a rather long chat with cliff taig on just
> this topic.
> here is the sense i made of it all:
> 1 - there can be no tighter bearing than flat metal
> to
> metal
> 2- as soon as you introduce additional elements,
> like
> rollers, you are dealing with multiplied tolerances
> of
> all the parts (read as ERRORS of all the parts)
> 3- ball screws/nuts immediately reduce native
> resolution cuz they can not have as many tpi as a
> fine
> thread screw.
> 4- they are expensive, sound hella sexy in a
> specsmanship pissing contest.
>
> in other words, what has been conveyed to my mind is
> that they are not really worth having even if got
> for
> free!
>
> on principles, ballscrews can never be as good as a
> good screw.
>
> --- Dan Mauch wrote:
>
> > I installed some Thompson rolleed ball screws
> (.003
> > tolerance) on a mill
> > drill. I used two ballnuts and preloaded them so
> > there is about .0005
> > backlash on the X axis. I then proceeded to check
> > the accuracy by using a
> > long drift dial indicator and resetting it. The
> > .0005 backlash was taken out
> > before the X axis was moved in the + direction
> > The results were surpising
> > x =0 on manual dial dial indicator 0
> > x1.000 x.998
> > x2.000 x2.000
> > x3 x2.997
> > x4 x.3.999
> > x5.000 x.5.0
> > You decide it it meets your needs
> > Dan
> >
> > ----- Original Message -----
> > From: "Jim Colley"
> > To:
> > Sent: Sunday, September 18, 2005 3:25 PM
> > Subject: [CAD_CAM_EDM_DRO] Rolled vs. Ground
> > ballscrews
> >
> >
> > > Alright guys, maybe some of you are open to a
> > little debate.
> > >
> > > I am in the design phase (still) of a 5-axis
> mill
> > and have purchased
> > > nearly all of the pricy stuff except ballscrews.
> > Now, obviously
> > > ground ballscrews are more expensive due to
> their
> > higher accuracy,
> > > etc.
> > >
> > > My question is, exactly what are you getting for
> > your money and is it
> > > posssible to achieve the same end goal using
> > rolled screws and a
> > > little clever design?
> > >
> > > If the major difference is the accuracy of the
> > lead and backlash,
> > > then wouldn't it be possible to eliminate the
> > backlash in a rolled
> > > screw either by using a double nut design
> > (preferred) or repacking
> > > the ball nut with larger diameter balls? Then,
> > once the backlash is
> > > minimized, the only real concern is the accuracy
> > of the lead.
> > >
> > > Now, my thoughts here are that this is only a
> > concern if you are
> > > using the servo motor's encoder to close the
> > feedback loop by
> > > interpolating the axis position from the number
> of
> > rotations and the
> > > diameter of the screw. However, if you used
> linear
> > encoders on the
> > > axis (preferred) or used an arrangement with a
> > timing belt fixed to
> > > the slide, turning a pulley which drives a
> rotary
> > encoder, wouldn't
> > > that give a very precise readout of *actual*
> axis
> > location? Provided
> > > there is *no* backlash in the ballscrew
> > arrangement, there should be
> > > no problem with hunting on the servo mechanism,
> > etc.
> > >
> > > As I have said before, I base my statements on
> > absolutely zero
> > > experience and no intelligent thought
> whatsoever.
> > Just an idea
> > > I had.
> > >
> > > What do you guys think? Any problems? Better
> ways?
> > >
> > > Jim
> > >
> > >
> > >
> > >
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=== message truncated ===




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