Step/Dir Servos

I a building a rotary table that needs to have very smooth motion at low speed (~1 RPM). Currently using a stepper motor, the steps are noticeable at slow speeds creating a jerky motion. I can smooth out the motion by microstepping, but that has limited my maximum speed (ideally ~100 RPM) to be too slow. I'm thinking that moving to a servo system would be the best way to smooth this motion and have been looking at the step/dir servo drives since they are reasonably priced. Does anyone have experience with these drives at low speed? Will I still experience the same type of motion at low speeds since the control is just like a stepper? Thanks for any feedback.

They work much like steppers, only more precise at high resolution (micro stepping with a stepper becomes less precise the finer you get), within reason (dependent on encoder resolution.) But you still will have the exact same imitations regarding step rates killing your top speed if you using soft ware step generation. The only way around that is to use hardware step generation. Another advantage of a servo is that they can usually spin alot faster with more torque than a step motor allowing for higher gear reduction.

Thanks, sounds like my first step should be to incorporate hardware step generation and see what kind of performance I get at high/low speeds.

What gearing does your rotary table have? What is the motor RPM at your desired speed? Mine is a 90:1 so full speed on a stepper is only about 4 RPM.

Perhaps you could consider adding a timing belt gearing drive to your RT.

There is some general advice on speed and gearing on this thread.
forum.linuxcnc.org/30-cnc-machines/31509...-loaded-pinion-drive

Look at the line of teknic clear path sd motors, They would be just the ticket for that rotary table. very smooth on the low end and very fast on the top end, google around about them,

What gearing does your rotary table have? What is the motor RPM at your desired speed? Mine is a 90:1 so full speed on a stepper is only about 4 RPM.

The rotary table is actually just a crossed roller bearing that will be driven by a timing belt. the pulley ratio will be about 7:1. To get 100RPM at the table the motor will be going about 700RPM. I am considering a geared motor to increase torque.

Look at the line of teknic clear path sd motors, They would be just the ticket for that rotary table. very smooth on the low end and very fast on the top end, google around about them,

I have had my eye on these for awhile. Definitely seem like a nice drop in replacement for steppers. Would you recommend these over Leadshine motors which are similarly priced?