Which is better for the drive motor of the engraving machine?
The engraving machine has an important part, which is equivalent to the human heart, and the source of the driving power of the entire engraving machine is here. There are currently two mainstream motors in the market, namely stepper motors and AC servo motors.
machine. Which of the two motors is better is always a problem that puzzles our buyers. The stepper motor is a discrete motion device that is intrinsically linked to modern digital control technology. In the eyes
Among the former domestic digital control systems, stepper motors are widely used. With the advent of all-digital AC servo systems, AC servo motors are increasingly used in digital control systems.
. In order to adapt to the development trend of digital control, stepping motor or all-digital AC servo motor is mostly used as the execution motor in the motion control system. Although the two are similar in control style (
Pulse train and direction signals), but there are large differences in performance and application. Now compare the performance of the two.
First, from the perspective of the motor, the two low frequencies are different.
Stepper motors are prone to low frequency vibration at low speeds. The vibration frequency is related to the load condition and the performance of the driver. It is generally considered that the vibration frequency is half of the take-off frequency of the motor no-load. This kind
The low frequency vibration phenomenon determined by the working principle of the stepper motor is very detrimental to the normal operation of the machine. When the stepper motor works at low speed, damping technology should generally be used to overcome the low frequency vibration.
For example, add a damper to the motor, or use a subdivision technique on the drive. The AC servo motor runs very smoothly, and vibration does not occur even at low speeds. AC servo system
Resonance suppression function can cover the lack of rigidity of the machine, and the system has a frequency analysis function (FFT) inside, which can detect the mechanical resonance point and facilitate system adjustment.
Second, from the perspective of accelerated start-up, the acceleration response capability of the two is not comparable.
It takes 200 to 400 milliseconds for the stepper motor to accelerate from standstill to the operating speed (typically several hundred revolutions per minute). AC servo system has better acceleration performance, with Panasonic MSMA 400W AC servo
For example, it takes only a few milliseconds to accelerate from standstill to its rated speed of 3000 RPM, which can be used in control situations where fast start-stop is required.
Third, the overload capacity of the two is different.
Stepper motors generally do not have overload capability. The AC servo motor has a strong overload capability. Take the Panasonic AC servo system as an example, it has speed overload and torque overload capability. Its maximum turn
The moment is three times the rated torque and can be used to overcome the moment of inertia of the inertia load at the moment of starting. Because there is no such overload capability for stepper motors, in order to overcome this moment of inertia during the selection, often
It is necessary to select a motor with a large torque, and the machine does not need such a large torque during normal operation, and a phenomenon of wasted torque occurs.
Fourth, compared to the output torque of the two, the moment frequency is not in a grade.
The output torque of the stepping motor decreases as the speed increases, and it drops sharply at higher speeds, so the maximum operating speed is generally 300-600 RPM. AC servo motor is constant torque input
Out, that is, within its rated speed (generally 2000RPM or 3000RPM), the rated torque can be output, and the constant power output is above the rated speed.
5. From the step angle analysis, the control accuracy difference between the two is large.
The two-phase hybrid stepping motor step angle is generally 3.6 °, 1.8 °, and the five-phase hybrid stepping motor step angle is generally 0.72 °, 0.36 °. There are also some high performance stepper motor steps
The angle is smaller. For example, a stepping motor for a slow wire-cutting machine produced by Sitong has a step angle of 0.09°; a three-phase hybrid stepping motor produced by BERGER LAHR
The step angle can be set to 1.8°, 0.9°, 0.72°, 0.36°, 0.18°, 0.09°, 0.072°, 0.036° by the DIP switch, which is compatible with two-phase and five-phase hybrid stepping motors.
Step angle. The control accuracy of the AC servo motor is guaranteed by the rotary encoder at the rear of the motor shaft. Take Panasonic's all-digital AC servo motor as an example. For motors with standard 2500 line encoders.
Since the driver uses quadruple frequency technology inside, the pulse equivalent is 360°/10000=0.036°. For motors with 17-bit encoders, the drive receives 217 = 131072 pulses per
The machine turns one turn, that is, its pulse equivalent is 360°/131072=9.89 seconds. It is 1/655 of the pulse equivalent of a stepping motor with a step angle of 1.8°.
Sixth, there is a certain gap between the performance of the two.
The control of the stepping motor is open-loop control. If the starting frequency is too high or the load is too large, it may be lost or blocked. When the speed is too high, the overshoot may occur, so to ensure its control.
Accuracy should deal with the problem of rising and falling speed. The AC servo drive system is closed-loop control. The driver can directly sample the motor encoder feedback signal, and internally form a position loop and a speed loop.
As a result, there is no loss or overshoot of the stepping motor, and the control performance is more reliable.
In summary, the AC servo system is superior to the stepper motor in many performance aspects. However, in some occasions where the requirements are not high, stepper motors are often used to perform the motor. So, in the control system
In the design process, we must comprehensively consider the control requirements, cost and other factors, and choose the appropriate control motor. The choice of the engraving machine driving method is mainly determined by the customer's production situation.
Choosing the right motor is more conducive to the smooth operation of the engraving machine, efficient operation and greater production value. The specific analysis of the so-called specific problems, I hope to provide a certain reference for your purchase.
