whats the maximem rpm a stepper motor can turn?
It will vary greatly depending on a lot of things. At it's maximum speed, whatever it may be, it will have virtually no torque at all, since a stepper motors torque drops off as rpm's increase. The voltage supplied also has a lot to do with it. Typically, a stepper will be able to spin it's fastest with the highest voltage possible supplied to it. However, the higher the voltage, the hotter the motor will run. Run it too hot and you will destroy the motor.
Larger motors will typically not spin as fast as smaller ones. For a machine use, NEMA 23 motors will usualy be able to spin faster than Nema 34's.
The drive used also factors in, as well as what you're using to create the step and direction pulses. A lot of times that is the limiting factor.
For a given application, your best bet is to figure out houw much torque you need at a given speed, and pick a motor who's torque curve fits the application.
Just a guess, but I'd say most use their steppers at 1000-1500 rpm max, and a lot use them even slower.
As for the Max a stepper can spin, I've heard of steppers spinning at 10,000 rpm while being tested in a lab, but has no bearing on their use in a machine.
Mach3 2010 Screenset
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)