The difference between stepper motor and servo motor of engraving machine

Engraving machine Drive can be divided into stepper motor and servo motor, many people do not know what the difference between stepper motor and servo motor, do not know how to choose, the following IGOLDENCNC for everyone to say the engraving machine stepper motor and servo motor difference.

1. Different control accuracy

Servo motor better than stepper motor, their precision is different, two-phase hybrid stepper motor step angle is generally 3.6°, 1.8°, five-phase hybrid stepper motor step angle is generally 0.72°, 0.36°; the control precision of servo motor is guaranteed by the Rotary encoder on the back end of motor shaft, For motors with standard 2500-line encoders, the four times-octave technique is used in most drives and its pulse equivalent is 360°/10000=0.036°. For a motor with a 17-bit encoder, the drive takes a lap of 217 = 131,072 pulses per receiver, i.e. its pulse equivalent is 360°/131072=9.89 seconds. Is 1/655 of the pulse equivalent of a stepper motor with a 1.8° angle.

Simply put, the servo motor's minimum control accuracy is 600 times more than the stepper motor. In the case of low speed (generally refers to 600 rpm) stepper motor precision as high as the servo motor, in the case of high speed (generally refers to 1200 RPM) stepper motor due to its own characteristics torque drop will cause the loss of step so the precision is not servo high, stepper used in relatively low-speed occasions, servo used in high-speed.

2. the low-frequency characteristics are different

Engraving machine Stepper motor at low speed easy to appear low-frequency vibration AC servo motor running very smoothly, even at low speed will not appear vibration phenomenon Stepper motor output speed is lower than the servo motor, stepper motor speed is unstable, 300 to 600 floating, servo motor for constant force output, 2000 or 3000. The output torque of stepper motor decreases with the increase of rotational speed, and it decreases sharply at higher rotational speed, so its maximum working speed is generally 300~600rpm. AC servo motor for constant torque output, that is, in its rated speed (generally 2000RPM or 3000RPM) within, can output rated torque, at rated speed above for constant power output.

3. overload ability is not the same

Engraving machine Stepper motor generally does not have overload capacity. AC Servo motor has strong overload ability. Stepper motor generally does not have overload ability. AC Servo motor has strong overload ability, it has the ability of speed overload and torque overload. The maximum torque is three times times of the rated torque, which can be used to overcome inertia moment of inertia load in the starting moment. Stepper motor Because there is no such overload capacity, in the selection of the often need to choose a larger torque of the motor, and the machine in the normal working time does not need so large torque, it appears a moment of waste phenomenon.

4. the performance of the operation is not the same

Operating performance is different (servo motor will not appear to lose or overshoot the phenomenon of high stability) the internal composition of the position ring and speed loop, generally do not appear stepping motor of the phenomenon of loss or overshoot, control performance more reliable. Stepper motor for Open-loop control, start-up frequency is too high or too large load prone to drop or plug the phenomenon, stop the speed is too high prone to overshoot phenomenon, so in order to ensure its control accuracy, should handle a good rise and spin down problems. AC Servo Drive system for closed-loop control, the driver can be directly to the motor encoder feedback signal sampling, the internal composition of the position ring and speed loop, the general will not appear stepping motor of the phenomenon of loss or overshoot, control performance more reliable.

5. the speed response performance is different

Engraving machine stepper motor from static acceleration to working speed (generally hundreds of rpm per minute) requires 200~400 milliseconds. AC servo system has a better acceleration performance, with Panasonic MSMA 400W AC servo motor, for example, from static acceleration to its rated speed of 3000RPM only a few milliseconds, can be used to require rapid start and stop control occasions.

6. control mode

Engraving machine Stepper motor is Open-loop control, there is no feedback, so the control is simple, only need to be equipped with a driver, control part of the pulse, servo motor control is relatively complicated.

7. Price: Stepper motor cheap, servo motor expensive

The engraving machine servo system is superior to the stepper motor in many performance aspects. But in some low demand occasions also often use stepper motor to do the implementation of motor. Therefore, in the design process of the control system to take into account the control requirements, costs and many other factors, the use of appropriate control motor.