The Differences Between Servo Motor And Stepping Motor

One of the crucial components of all CNC machines are the servo or stepping motors. These parts play an integral role in the overall operation and functionality of the machines. Knowing the importance of these components, it is no wonder that manufacturers take great care in choosing and installing the appropriate motors for their CNC machines. Without them, the machines would not be able to accurately and efficiently produce the desired output. Therefore, it is essential to understand the significance of the servo and stepping motors and how they contribute to the overall performance of the CNC machines.

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When it comes to the output characteristics of stepping and servo motors, there are noticeable differences that you should take note of. Stepping motors have a lower output rotational speed compared to servo motors. Additionally, the output torque of stepping motors tends to steeply decline, especially at high rotation speeds. In contrast, servo motors have constant torque output, ensuring that the output torque is rated below a certain rotary speed, typically around 2000RPM or 3000RPM. Furthermore, the output power of servo motors is also constant under a rated rotary speed. While stepping motors may have a higher highest rotation speed reaching 300 to 600 rpm, their output torque will not remain constant at these speeds. On the other hand, servo motors offer consistent output characteristics that ensure stability and reliability in their performance.

The running performance of a servo motor is distinct from that of a stepper motor. This is due to the presence of a position loop as well as a speed loop within the servo motor, which works together to prevent instances of steps losing or being overthrown. In comparison, stepping motors are prone to such issues, making them less reliable in certain applications.

Servo motors are known for their good overload capacity, whereas stepping motors typically do not possess such capability.

5. Different Response Performance to Speed

Stepping motors can take anywhere from 200 to 400 milliseconds to return to their working speed, which often ranges from several hundred rpm per minute. Comparatively, servo motors only require a few milliseconds to reach their rated speed. This quick response time is necessary in scenarios where there is an urgent need to stop or start.

6. Different Control Accuracy.

Stepping motors and servo motors exhibit similar levels of accuracy at low speeds, typically around 600rpm. However, as the rotary speed increases to 1200rpm, the low torque of stepping motors can result in steps being lost. Therefore, stepping motors are commonly utilized in applications that require low rotary speeds. It is important to note that the low torque of stepping motors may limit their performance in high-speed scenarios.

Stepping motors are controlled using an open-loop system, which means that they don't receive any feedback. As a result, they are much simpler to control and require only one driver. In contrast, servo motors are operated using a more complicated control system. Controllers send control signals to the motor, which are then compared to feedback signals received from the motor. If there are any differences between the two signals, servo motors will send out an alarm or take corrective action. This makes servo motors much more sophisticated than stepping motors.

Servo motors are more expensive compared to stepping motors, primarily due to differences in their construction and functionality.