Re: Question about steppers

I dont feel that the wear from moving the lift up and down would be
excessive, no worse than moving the quill around. They are polished
shafts and I would assume that they bushings were bored as there is
no deflection, it's quite sturdy. I think that with proper lubricant
they would be fine, the only hinderance would be speed. The only time
the z moves is to plunge in, hold, plunge out. I just dont see this
machine as a highspeed machine, more of an automated one.

My father said that he could make a circuit that would switch bewteen
two stepping motors, ie, I could write and m-code to switch between a
quill mounted motor for drilling and highspeed machining with a
vertical ballscrew and the stepper driving the lift. Rigidity is a
big concern, having the quill as retracted helps alot. You do not
tram the head in, you do it once and untill you need it better, you
tend to not mess with it. I'm pretty sure the screws are 1/2x10 acme,
but I've never measured them and current reside 600mi from the
machine. The twin leadscrews have a timing belt between them and one
screw, the motor only drives one screw. (The new bridgemills are
different, single leadscrew. They also have a fifth columm, and
ofcourse I built my own version, I plan to change the column lock to
a air operated cam - ala m-code.)

I figured the torque b/c I wanted a gear motor to run it around. The
firt time I measured it I had a "unique arrangement" of pulleys, a
rachet, some rope, and a bucket of water. Then I found out that my
grandpa had a torque wrench. I figure, if I cant make it click, 5lb-
ft aught to atleast give me a margin of safety. Then I got to
thinking, it would sure be nice to have a digital on the lift. But
for the price why not a stepper, that way you can move it exactly
where you want it, consistantly -- without having to use a rachet to
get it right were you want it, gearmotors dont stop on a dime. I've
read where guys cnc the z axis on bp's and report higher rigidity and
thought, I aught to be able to do the same lord knows that my machine
needs all the help it can get.

I do not know the etiquette on posting prices and the such, but the
motor was $125 from clickautomation.com, about the third of fouth
link when I googled "stepping motor nema 34" a couple weeks ago, so
it isnt exactly a secret. For that price I can at least try it, all I
need is a mounting plate, all the other hardware I can swipe from the
quill (belts and pulleys.)

If it doesnt work, oh well, I'll just put everything back. If it
fails, I want it to fail because the concept was flawed, not because
I picked a motor that couldn't do what I asked, that wouldn't prove
anything but my inability to pick out stepping motors.

William