Re: Ballscrew Installation issues

I'm shopping for a few good used ballscrew/linear motion assemblies
(preferably already assembled) for a router I've got in mind, and I was
wondering: do these have to match in screw pitch and inches traveled per
revolution? While I'd prefer to have everything the same, it seems
difficult to procure matching slider assemblies. Is it okay to get these as
they come up, and trust that I'll be able to reconcile their differences in
the software setup? Or should I hold out for matching parts? Does this vary
between control systems?

What about motors? Is it possible to combine different stepper motors in
the same machine, and expect them to operate in tandem? Is it any easier
with brushless DC servo/encoder combinations?

Andrew Werby
http://www.computersculpture.com

Roger Brower <rbrower@...> wrote:
Subject: Ballscrew installation issues

stratton@... Wrote:

Subject: Ballscrew installation issues

>With a .200 lead screw and a 200 step/r

motor I need 2:1 reduction
just to get steps of .001, but am
planning on going for .0005 or
.00033 if I use a 10 tooth driving a 60
tooth.

You may well end up using a half step
driver for increased torque and reduced
resonance reasons.
A 200 step per rev motor is 400 discrete
half steps per rev.
Also note the McMaster 5/8 screws are
31/64" pitch; with 1:1 drive, I
calculate: 1.8 deg per step motors, 200
steps per rev, 400 steps per rev half
step mode;
13/64" screw lead =(.203125 inch per
rev, or 4.9230769 rev per inch)
So: .203125 / 400 = ~1969(.2792) steps
per inch for ~.0005 resolution.

Am I in some kind of trouble with this
odd number (vs 2000)?
I know CNCPro can't use the decimal
remainder (.2792) on steps per rev
setting.
I didn't want to gear it down and lose
the travel speed potential or, God
forbid, lose steps by trying to spin the
motors too fast...



Andrew Werby - United Artworks
Sculpture, Jewelry, and Other Art Stuff
http://unitedartworks.com