Stepper motor sizing help

I am getting ready to build a CNC router and need help deciding on the stepper motor's

My build will be

welded steel construction
Moving gantry with dual ballscrews
1000mm Ball screws and linear rails
Useable size should be about 32"x32" after accounting for the linear carriages.
Mostly working with wood and plastic but occasional aluminum
I am going to start with a router but will probably upgrade to a water cooled spindle in the future.



My normal practice is when in doubt throw more power at it and I was initially going to go with nema 23 425oz. but I have been reading that the larger torque motors turn quite a bit slower. So now I am wondering if I should be looking at the 269oz or the 179oz motors. Or possible a combination of them.

Look at the motors inductance. Look for one below 2.0 MH, then use controllers with higher voltage, there are good controllers that run on 60 to 80 VDC which will give you great performance with a motor having 2.0 or lower inductance.

High inductance motors lose torque rapidly as the motors RPM increase. Look for the motors torque chart and see how at just 500 rpm, their torque is unusable. Some low inductance motors can easily have usable torque well above 500 RPM when paired with 60 to 80v controllers.

Hope that this helps.

John Z

Sent from my SM-G991U using Tapatalk

No B.S. here. This is based on some experience and fails.

First off forget about the ebay kit types.
Get some nema24 motors of around 566oz/in and a maximum 3mh inductance level. As John said ideally you want as close to 2mh as poss
(You can get lower inductance but the prices can go up massively).
Now connect these to some DM860 digital stepper drivers.
Run them all off at least 60Vdc.

This setup will fly.


I have the DM860T drivers which can take up to 110vdc running my nema24's. I'm running off 80Vdc supply.