RE: [CAD_CAM_EDM_DRO] SeriesII Quill Zaxis CNC addon ideas: Like JonE's?

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@...]
Sent: Friday, November 22, 2002 12:46 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
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@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
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
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