Originally Posted by
sploo
Thanks. It's a torque and HP issue.
A 60W 3000rpm servo should produce around 0.2Nm of torque (at max speed). Assuming it's constant HP then if run at 1500rpm it'll produce 0.1Nm of torque, and only 0.02Nm at 300rpm (the torque should reduce linearly with a reduction in rpm).
If you instead gear the servo down by 10:1 for a 300rpm output (when running at 3000rpm) then it should produce around 10 times the output torque; i.e. 0.2Nm x 10 = 2Nm.
However, the datasheet for the CNC Router Parts 960 oz in stepper shows that it produces 3.6Nm of torque at 300rpm, so you're getting much more torque at lower rpm speeds without needing gearing; the downside is obviously that it won't spin at 3000rpm (should that be required).
For my application, I need a very low output rpm, so it seems sensible to go with a stepper + small reduction in gearing, vs a servo with larger reduction (given that low backlash gearboxes with high reduction ratios tend to be expensive).