Re: SeriesII Quill Zaxis CNC addon ideas: Like JonE's?

Dan,
No disagreement with what you said but there are significant
differences between the Tree's knee and a Bridgeport knee. The box
ways on the Tree's knee are huge and the bearing surface (turcite) is
several times larger than a Bridgeport. It was designed from the get
go to be active. I haven't powered mine yet but plan to soon.

How big a motor did you end up with?

Roger

--- In CAD_CAM_EDM_DRO@y..., "Dan Mauch" <dmauch@s...> wrote:
> I have to jump in here.
> I recently helped a customer put a 4 axis servo system onto a Ebay
> purchased 3500# Tree Mill which is probablty equivalent to a series
2
> mill. The machine as purchased had beautiful ballscrews with zero
> backlash on the XY axis. The knee was driven by a AC servo motor
mounted
> onto a 5:1 gearhead driving an acme leadscrew. It was obvious that
the
> machine had seen a lot of use but was in near perfect mechanical
> condition. The A/C servo controls were dead. During the retrofit we
> simply replaced the existing servo motors with ones compatible
with the
> G320. It was really simple . Unbolt the existing motors and replace
it
> with a standard servo motor with a 5/8" shaft. It used a 2/1 ratio
> timing belt/pulley. After it was changed over the only problem we
ran
> into was that for some reasons the calculated size of the motor for
the
> knee proved inadequate so we replaced the Z motor with a larger
motor.
> It ran beautifully with a low (50)cpr encoder on the knee servo
motor.
> From what I could see that machine must have had many thousands
hours or
> use and yet the acme leadscrew on the massive knee, with no other
> assistance, seemed to be in good condition as we never did see any
> backlash or slop in the knee. The guy is currently using it to make
> parts. I can see no reason why driving the knee will cause him any
wear
> concerns.
> Dan
>
> -----Original Message-----
> From: Marv Frankel [mailto:dcdziner@p...]
> Sent: Friday, November 22, 2002 12:46 AM
> To: CAD_CAM_EDM_DRO@y...
> Subject: Re: [CAD_CAM_EDM_DRO] SeriesII Quill Zaxis CNC addon ideas:
> Like JonE's?
>
>
> Tim,
> Thanks for pointing out the screw wear problem to me. I
hadn't
> even considered it, but it makes sense if you think about the
constant
> up-and-down in almost the same area on the screw. I was pointed to
some
> pictures the other day, at http://www.motovidia.com/MILL%20pics/,
which
> showed a Z axis knee, with a ballscrew, and to keep the knee from
> falling through gravity, he had to mount a 150 lb. gas spring from
the
> knee to the base, to balance it. I wonder if the tendency of the
knee to
> fall, can be overcome by using a ball screw with a greater number of
> TPI?
>
> Marv Frankel
> Los Angeles
>
> ----- Original Message -----
> From: "Tim Goldstein" <timg@k...>
> To: <CAD_CAM_EDM_DRO@y...>
> Sent: Thursday, November 21, 2002 4:43 PM
> Subject: Re: [CAD_CAM_EDM_DRO] SeriesII Quill Zaxis CNC addon ideas:
> Like Jon E's?
>
>
> > Marv,
> >
> > The only downside of doing it with an acme screw is the wear.
Carrying
> that
> > much weight and moving it all the time will likely yield an
> > inconsistent pitch in a relatively short time. Besides, on my
machine
> > it was already equipped with the ground screws from the factory.
> >
> > Tim
> > [Denver, CO]
> > Sherline products at Deep Discount (now Mach1 CNC controller too)
> > www.KTMarketing.com/Sherline
> >
> > ----- Original Message -----
> > > Tim
> > > If you size your motor properly, with the right gearing,
is it
> > really
> > > necessary to convert the knee to ballscrew? It seems to me,
with
> > > that
> much
> > > weight on the screw, the original acme screw would have
virtually no
>
> > > backlash. Gravity would take care of it. If we could figure out
how
> > > to
> put
> > > the same amount of tension on the x and y axes, we would
probably
> > > never
> > have
> > > to concern ourselves with their backlash. Aren't we doing
almost the
> same
> > > thing with pre-loaded nuts?
> > >
> > > Marv Frankel
> > > Los Angeles
> >
> >
> >
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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
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>
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