Re: [CAD_CAM_EDM_DRO] Best source for inexpensive ballscrews?

Wow, so you use (2) nuts per axis, and torque one against the other?
Sounds like a good plan...


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

----- Original Message -----
From: "Kim Lux" <lux@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Friday, August 01, 2003 9:29 PM
Subject: Re: [CAD_CAM_EDM_DRO] Best source for inexpensive ballscrews?


> We just retrofitted a couple of machines for commercial use. We
> purchased Nook ballscrews and nuts directly from Nook and from McMaster
> Carr.
>
> McMaster Carr sells Nook ballscrews and nuts for less than what Nook
> sells them for.
>
> There are two grades of ballscrews: rolled and ground. Rolled
> ballscrews have an accuracy of 4 thou/foot. Ground ballscrews have an
> accuracy of 1 thou per foot.
>
> We too were turned off by the price and the size/mounting of the Nook
> preloaded ballsnuts. We made our own preloaded ballnuts by mounting one
> ballnut solid to table or slide and then mounting the other one to the
> solid one via 2 fine threaded studs with aircraft nuts on them. This
> allows one to tension one nut against the other nut. This setup has
> worked very well although space is at premium because this setup is
> physically large. Nevertheless we were able to implement this design on
> 5 of 5 axes between two machines.
>
> This system has been in operation and testing for several days now.
> We've checked backlash and positioning accuracy on our lathe for example
> and found no backlash and virtually perfect positioning (0.0001") after
> several hours of heavy duty machining.
>
> Some preloaded nut designs rely on using a spring to hold the nuts
> apart. I highly recommend avoiding these sorts of designs as the forces
> generated by a decent servo motor on a ball screw are tremendous, ie a
> thousand pounds or more.
>
> In case anyone is interested, we used a pair of SKF 7203 bearings on the
> motor end of the ballscrews to eliminate the endplay on the shaft
> itself.
>
> I also highly recommend direct driving the ballscrews. 3 of 5 axes we
> did are direct drive; the other two are 1:1 belt drive. All axes have
> more than enough force to machine at the power limit of the spindle all
> day long. We only used the belt drives where space limitations required
> us to do so. During quick rapid machining moves one can see the belt
> vibrate and dance. We also dislike the size of the belt pulleys (ie
> their thickness) and their cost.
>
> Our machines have axis speeds of 150 inches per minute, limited by the
> step generation rate of the software we use.
>
> Ballscrews may seem expensive at the time of purchase but they
> dramatically improve the performance of the machine. In a long run they
> are a bargain. I highly, highly recommend them.
>
> Kim Lux
>
>
> On Fri, 2003-08-01 at 19:00, Bill Kichman wrote:
> > Just curious what others have done in the way of obtaining cost
effective
> > ballscrews for their conversions. I am doing a full sized mill
conversion,
> > and simply cannot see spending $1k to $3k for a set of preload style
> > ballscrews for a hobby venture. What is the least costly solution?
> > Thanks
> >
> > 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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> Kim Lux <lux@...>
>
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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/
>
>
>