motor/leadscrew/ps recomendations and calculations

I've built a prototype cnc router using 3/8-12 leadscrews, Dan's 2 amp
driver, and the following motors:
X - 210ozin from Dan Mauch
Y - 180ozin, high torque (read SLOW), from www.amsicorp.com
Z - ???ozin, salvaged from a printer

The power supply is an old AT supply.

For X I can get about 12 ipm before the motor stalls
For Y I can get about 8 ipm
for Z I can get about 10 ipm

I'm using half step mode, with 4800 steps per inch and CNCPro.

I'd like to increase the speed, but still have at least 50 lb of linear
force available.

I figure if I went to 3/8-4 screws, I would still have 1600 half steps per
inch, more than enough for me, and this would bring the machine motion
further down into the motors torque curve, but I'm not sure if this would
kill my linear force or not. What is the formula for calculating the linear
force available at different leadscrew pitches and motor ozin?

Another option I'm considering, at about the same cost, is to get another of
Dan's motors for Y, and increase the voltage of the power supply. Under load
right now, it puts out about 9v. Dan suggests I would get a 50% increase in
speed from the motors by going with an 18v supply. This would give me about
18ipm for X and Y. This route would keep the high linear force, at the cost
of higher screw rpm and a lower top speed than the new leadscrews.

What I like about the AT supply is the readily availble 5v for limit
switches, but I suppose I could pull 5v off Dan's board somewhere for the
same purpose...

Suggestions? Comments? Questions?



Richard Spelling, http://www.spellingbusiness.com/boats
From the muddy waters of Oklahoma