I just stumbled into a matched set of brushless AC servo motors and drives!
Until now, I've been struggling to find an affordable set (3) of servo motors powerful enough for my 4'x4' gantry mill project. I want to hit 500 IPM and calculated that servos with a 1/2 HP continuous rating should be plenty powerfull. So when this set of monster 2HP servos fell into my lap, I could hardly believe my good fortune!!
But now it begs the question (and I still can't believe I'm asking it): Have I perhaps got motors that are overkill to the extreme? They are rated at 2HP continuous and can peak at 200% of power and torque ratings. They're much bigger than Nema 34, weighing 19.5 pounds! The mounting flange is about 6" square.
The servo amps are matched to the motors and have a lot of sophisticated programming options. For instance, I can program the amp to understand ratios between the motor rotation and linear travel (i.e. 0.2000" per rotation). And I can select how many steps pulses per rotation (up to 4096 per rotation, which is the resolution of the resolver). So I have a lot of flexibility to change the speed and resolution of the motor. And even though the motors are 3 phase, 240v, the servo amp runs off of single phaase. Not to mention that they are matched sets and I have 3 of them.
So, of course, I really want to use them. But when I start adding up the z-axis weight, I'll be pushing around the a 19 pound motor plus 2hp spindle motor and all the usual linear slides and ballscrew. Is this wasteful? It seems that this should not be a real problem since the x and y axis motors are also 2hp servos and should be able to overcome this greater inertia.
Another concern is that the frame may be underdesigned. Until now, I had planned to use 3"x3" sections of 80/20 extrusions for the frame. Does anyone have practical experience building machines with that size frame members? Do you think it would be rigid enough?
Or looking at it another way, (and this is the real question I am asking myself): What size machine should I be building to do justice to these motors?
I have a picture and would love to post it. Can anyone tell me how I go about doing that? (I'm new to this forum).
Opinions, warnings, advice and any other comment is welcomed!
-D