The difference between stepper motor and servo motor - the latest guide

We all know that the drive system of CNC router is an important part of machine operation, and the core of the drive system lies in the motor. Motors are divided into stepper motors and servo motors. The same is the motor, so what is the difference between the two?

Below, I will take you to understand what is a stepper motor, a servo motor and what is the difference between them, and what is the impact on the CNC router.

What are stepper motors and servo motors?

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Servo motor: refers to the engine that controls the operation of mechanical components in the servo system, and is an auxiliary motor indirect speed change device. The servo motor can control the speed and position accuracy very accurately, and can convert the voltage signal into torque and speed to drive the control object.

Servo Motor Woodworking Machine

Stepper motor: Stepper motor is an open-loop control motor that converts electrical pulse signals into angular displacement or linear displacement. It is the main executive component in modern digital program control systems and is widely used. The speed and acceleration of motor rotation can be controlled by controlling the pulse frequency, so as to achieve the purpose of speed regulation.

Stepper Motor CNC Router

What's the difference between the two?

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The difference between a stepper motor and a servo motor is:

1. The control precision is different.

The more the number of phases and beats of the stepping motor, the higher its accuracy. The servo motor is based on its own encoder, and the more scales of the encoder, the higher its accuracy.

2. Different control methods. 

One is open-loop control and the other is closed-loop control.

3. Different low-frequency characteristics. 

Stepper motors are prone to low-frequency vibrations at low speeds. When they work at low speeds, damping technology or subdivision technology is generally used to overcome low-frequency vibrations. The servo motor runs very smoothly, and there will be no vibrations even at low speeds. The AC servo system has a resonance suppression function, which can cover the lack of rigidity of the machine, and the system has a frequency analysis function (FFT) inside the system, which can detect the resonance point of the machine to facilitate system adjustment.

4. The moment-frequency characteristics are different. 

The output torque of the stepper motor will decrease with the increase of the speed, and the AC servo motor has a constant torque output.

5. The overload capacity is different. 

Stepper motors generally do not have overload capability, while AC motors have strong overload capability.

6. The running performance is different. 

The control of the stepping motor is an open-loop control. If the starting frequency is too high or the load is too large, it is easy to lose steps or stall. When the speed is too high when it stops, it is easy to overshoot. The AC servo drive system is closed-loop control, and the driver can directly control the motor. The feedback signal of the motor encoder is sampled, and the internal position loop and speed loop are formed. Generally, there will be no step loss or overshoot of the stepping motor, and the control performance is more reliable.

7. The speed response performance is different.

It takes hundreds of milliseconds for a stepper motor to accelerate from a standstill to a working speed, while the acceleration performance of an AC servo system is better, generally only a few milliseconds, and can be used in control occasions that require fast start and stop.

To sum up, the servo motor system is superior to the stepper motor in many aspects of performance, but the price ratio is not the same. The above is the difference between servo motor and stepper motor. If you have any questions, please consult Superstar CNC.