CNC Machine Stepper or Servo

With the advancement of the technology and the maturity of skill, CNC machine is increasingly being applied to various fields of industrial production. The most important areas are: general woodworking, panel furniture manufacturing, European furniture manufacturing, woodworking decoration industry, sign-making industry, metal cutting industry, mold manufacturing industry and so on. In the fierce competition, more and more production companies began to adopt a development strategy of replacing the labor with a machine. As a newbie, how to select a cnc machine, stepper or servo? In this post, let’s looking at the difference in the working principle between the two.

What is a stepper motor?

Step motor is a DC motor. The rotation of it is performed step by step at a fixed angle (called the step angle), which is characterized by no accumulation error. The control method is open loop control. The run of the stepper motor is performed by a stepper driver. It converts the pulse signal from the cnc controller into the angular displacement of the stepmotor. Or, we can say, each time the controller sends a pulse signal, the stepper motor is rotated by one step angle through the driver. Therefore, the the stepper motor speed is proportional to the frequency of the pulse signal. Therefore, the motor speed can be controlled accurately via controlling the frequency of the pulse signal; the motor can be precisely positioned via controlling the quantity of the pulse signal.

What is a servo motor?

Servo motor is an AC motor. The rotor inside the electric servo motor is a permanent magnet, three phase electricity U/V/W (controlled by servo pack) formed electric magnetic field. The rotor turns under the action of this magnetic field. At the same time, the servo motor encoder feeds back the signal to the servo driver, and the driver compares the feedback value with the target value to adjust the angle of the rotor rotation. Therefore, its control method is closed-loop controlled. The cnc controller will know how many pulses are sent to the servo motor, and how many pulses are returned at the same time, so that the rotation of the motor can be controlled very accurately, thus achieving accurate positioning. Its positioning accuracy can reach 0.001mm.

There is a question, is it that the cnc machine using the AC servo motor must be closed-loop control?

Not certainly. This depends on what kind of CNC controller the linear servo motor is equipped with. Not all controllers support closed-loop control. In other words, to achieve closed-loop control, two conditions must be met: one is to use an AC servo motor, and the other is equipped with a CNC controller that supports closed-loop control. For example, cnc servo motor with RichAuto A11 DSP controller is not closed-loop, because A11 does not support closed-loop control.

Origin post from Jinan EagleTec Machinery Co.,Ltd.

Repost to indicate the source.