NEMA23 vs NEMA34
 

I know I am showing my ignorance, but could someone please enlighten me as to why NEMA23 size motors, which are smaller physically, are not a good idea for a 'full size' CNC rig, like MechMate where we specify NEMA34's.

This is assuming we can get equivalent torque and number of steps per rotation.

Thanks for your patience with this newbie! (And yes, I understand the MechMate plans are set up for NEMA34, and am not suggesting any changes.)

Jack first off, getting the same torque might be a problem, check carefully all ratings are not equal. There will be no problem with the steps. I think the main deal will be the diameter of the shaft, 1/4" on the 23s and 1/2" on the 34s

Hi Jack. You haven't considered all of the variables. You may get equivalent torque and steps per revolution, but you won't get equivalent voltage, amperage, and impedance electrically, and you won't get equivalent shaft side loading strength or rotational intertia mechanically.

A NEMA34 in comparsion to an "equivalent" NEMA23 will have a shaft twice the diameter, a body that is 2-3 times shorter than the "triple stack" required to meet the torque in a NEMA23, and many, many fewer winding turns to be driven. This, for a variety of reasons discussed in threads on this forum, results in a far less efficient motor for the torque range a mechmate requires.

To use a really crude analogy, are three 650cc twin motorcycle engines sharing a common driveshaft the equivalent of one V6 1950cc automobile
engine?