I found three CMC servo motors, new old-stock, model 3515, winding type "C". Here's the datasheet, if anyone is interested:
http://www.torquesystems.com/downloads/platform3500.pdf
I talked to a tech at CMC, and he said that at 50VDC, this motor will run at approx 3500 RPM, and produce 4.0 in-lb of torque. I'm trying to figure out if this is good enough for my (approx) 33" x 48" x 7" wood router design.
So, here is what I figured:
Power supply: 50VDC, 20amp
unloaded RPM: 3500
80% of RPM: 2800
motor torque sensitivity Ke: .99 in-lb per amp (~ 16 in-oz/amp)
maximum continuous current: approx 4 amps
maximum continuous torque: 64 in-oz (4.0 in-lb)
example gearing: 4:1
example screw lead: 0.20" (5 TPI)
example screw efficiency: 0.907
geared torque at screw: 256 in-oz (16 in-lb)
screw rotational speed (loaded): 700 RPM
axis linear speed (loaded): 140 ipm
screw rotational speed (unloaded): 875 RPM
axis linear speed (unloaded): 175 ipm
axis thrust (pi/8 * TPI * in-oz * efficiency): 456 lbs
power delivered to load (RPM * in-oz / 1351): 133 watts
So, 456 lbs of thrust sounds like pleny, right? Next, I checked the Nook catalog and see that for a typical ballscrew, they say it takes 0.035 in-lbs of torque to raise a 1 lb load.
Okay, so that means after my 4:1 gearing, if I'm using this ballscrew, I should be able to raise 456 lbs, which equals my thrust calculation (I used this to back into the screw efficiency value, just to double-check my math).
My gantry could end up weighing around 200 lbs. I realize that I'm not "lifting" the gantry, but just "pushing" it on low-friction linear rails. I will be lifting the z-axis, but that should weigh around 35-40 lbs.
I'm more worried about inertia.
Is this motor going to work?
Thanks,
Chris