[109jb]

What I did for an estimate on for the 30MV was take my hardest material to cut, SS 304 for me, and guessed at my the toughest cut. I used https://fswizard.com/www/ to get some rough numbers and if you click the blue bar on top you get cutting force. I am not sure if it is radial and axial combined but I assumed worst case it was all radial, came out to about 180#.

Put that in a lead screw calculator. https://www.amesweb.info/Screws/Lead...meThreads.aspx and got about 800 oz in.

I knew I wanted Teknic Clearpath SDSK motors so my choice was easy and went with 1100 oz in on all 3 axis knowing that my X and Y are overpowered for 80% of my jobs. I am sure the 640 oz in would have been find but it was $20 more for the bigger motor and I am a sucker for a cheap upgrade.

I am sure this isn't the best method and I would love to hear what others have done to size their motors.

That link is for calculating the force produced by an ACME screw. The OP has ballscrews which are much more efficient. Here is a calculator for ballscrews. For efficiency, a ballscrew is about 90% efficient.

My G0704 has the 570 oz-in steppers on all axes and has proven sufficient in X and Y but I would like a bit more on Z due to drilling forces. The ballscrew calculator says a 570 oz-in motor on a 0.196" (5mm) lead screw at 90% efficiency will give 1027 pounds of linear force. Using your 180 pound cutting force requirement there is a healthy margin. However, for a stepper design, the desired rapid speed may be the driver for motor sizing. This is because stepper torque drops off with increasing RPM and there will be a speed where the stepper will stall. For the 570 oz-in motors I can rapid reliably at about 150 IPM with double spring preload ball nuts. With single ball nuts that speed is closer to 200 IPM