Re: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????

on 2003-08-11 12:10:58 UTC

If both ends ride in bearings then your ballscrews are constantly going
to be pushing your rod straight. Depending upon your servo motor, you
might or might not have the power to do that.

Kim

On Mon, 2003-08-11 at 10:36, Bill Kichman wrote:
> I had the same problem, Kim and I conversed recently on this. My 48" length
> Nook 3/4" x 0.2 screw is over a quarter inch out of straighness. When you
> roll it across a table it makes a nice "wallop wallop" sound as it hits
> highs and lows. I contacted McMaster and they indicate the tolerances per
> the manufacturer, I cannot remember them all, but I believe they stated a
> 0.01 inch per foot number for straighness. That makes mine over 10x out of
> tolerance. Ditto on the overnighted replacement, it's exactly the same. The
> problem will be more a hassle on my situation, since both ends will ride in
> bearings. Will have to find a way to bend it back more straight I guess.
>
> R. William Kichman, P.E.
> Kichman Engineering Associates
> 103 Old Furnace Road
> Cornwall, PA 17016-0643
> tel/fax 717/270-0714
> ----- Original Message -----
> From: "Carlos Guillermo" <carlos@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Monday, August 11, 2003 12:18 PM
> Subject: RE: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????
>
>
> > Hi Kim -
> >
> > Can you measure the bend? What kinds of numbers are you seeing?
> > Or, are you assuming they're bent because the ballnuts are
> > jamming? I ask this because I've heard that the pitch variation on
> > rolled ballscrews can be enough to cause jamming if there is no
> > compliance element between the two nuts.
> >
> > Regards,
> >
> > Carlos Guillermo
> > VERVE Engineering & Design
> >
> > -----Original Message-----
> > From: Kim Lux [mailto:lux@...]
> > Sent: Monday, August 11, 2003 8:48 AM
> > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > Subject: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????
> >
> > Hi people.
> >
> > We've purchased a couple Nook ballscrews, one directly from Nook
> > and the
> > rest from McMasterCarr. All the ballscrews were slightly bent.
> > An
> > email friend of mine purchased one from McMaster Carr and had the
> > same
> > thing.
> >
> > On Friday I increased the tension on our Z axis zero backlash ball
> > nut
> > mounts. It worked OK for the machining we were doing then.
> > However
> > today we are machining a different, longer part and we found that
> > the
> > ballnuts are jamming on the screw, probably due to the bend.
> > (There is
> > no foreign matter on the screw, etc.) Backing the tension off the
> > preload cured the problem.
> >
> > I'm not sure that there was a backlash problem when I tightened
> > the
> > preload on Friday. The parts coming off the lathe were spot on
> > for
> > tolerance.
> >
> > This bent ballscrew issue bothers me.
> >
> > Does anyone else have this problem ?
> >
> >
> > --
> > Kim Lux <lux@...>
> >
> >
> >
> >
> > Addresses:
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>
> Addresses:
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> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
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>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
--
Kim Lux <lux@...>

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