Stepper Motor And Servo Motor

The Stepper motor and servo motor are widely used on various cnc machinery. Whats the different between stepper motor and Servo motor? I am trying to explain the difference by my own words with my limited knowledge.

1.Control Mode  

The stepper motor is with open loop control mode while the servo motor is with close loop control.  What is Open Loop and what is Close loop? In a word, the Open loop control is without signal feedback while close loop control is with control signal feedback.With Control signal back, the Operating system can control the motor more precisely and Wisely.

2.Low Frequency Characteristic

 Vibration will be existed for stepper motor work with low frequency which cant be eliminate. The AC Servo can work much stable even in low frequency at low speed. With Resonance suppression, the Mechanical rigidity can be enhanced.

3. Torque and Speed

Torque of the stepper motor will be smaller if rotate speed become higher. That is why mostly the Max speed of stepper motor is at 300r/600r per minutes. The Servo motor is with constant torque within its rated speed (2000r/min~3000r/min). And with constant power output when Servo motor works out of rate Torque.

4.Overload Capacity 

It is with low overload capacity for the stepper motor while servo motor is with high overload capacity. Which enables the Servo motor works  more durable and stable.