How to choose the right stepper motor for small CNC engraving machine
First, the holding torque is also called the static torque, which refers to the moment at which the stator locks the rotor when the stepping motor is energized but not rotated. Since the torque of the stepping motor at low speed is close to the holding torque, the torque of the stepping motor is rapidly attenuated as the speed increases, and the output power also changes with the increase of the speed, so the holding torque is a measure of the stepping. One of the most important parameters of the motor load capacity.
First, choose to maintain torque
First, maintain the torque
Also called static torque, it refers to the torque that the stator locks the rotor when the stepper motor is energized but does not rotate. Since the torque of the stepping motor at low speed is close to the holding torque, the torque of the stepping motor is rapidly attenuated as the speed increases, and the output power also changes with the increase of the speed, so the holding torque is a measure of the stepping. One of the most important parameters of the motor load capacity. For example, a stepper motor of 1N.m is generally mentioned without explanation, and it can be understood that the holding torque is 1N.m.
Second, choose the number of phases
Two-phase stepping motor has low cost, minimum step angle of 1.8 degrees, high vibration at low speed, fast torque drop at high speed, suitable for high speed and low precision and stability requirements; three-phase stepper motor step The angle is at least 1.2 degrees, the vibration is smaller than the two-phase stepping motor, and the low speed performance is better than the two-phase stepping motor. The maximum speed is 30 to 50% higher than that of the two-phase stepping motor, which is suitable for high speed and accuracy and stability requirements. In higher cases, the 5-phase stepping motor has a smaller step angle, and the low-speed performance is better than that of the 3-phase stepping motor, but the cost is high, which is suitable for the middle and low speed sections and requires high precision and stability.
Third, choose stepper motor
The principle of selecting the motor after selecting the motor should be followed, firstly, the load characteristics should be clearly defined, and then the static torque and the torque frequency curve of the different types of stepping motors can be compared to find the stepping motor that best matches the load characteristics; when the precision requirement is high, the machine should be used. The deceleration device is used to operate the motor in the most efficient and lowest noise state; avoid operating the motor in the vibration zone, and if necessary, by changing the voltage, current or increasing the damping;
In terms of power supply voltage, it is recommended that 57 motors adopt DC 24V-36V, 86 motors adopt DC 46V, and 110 motors adopt higher than DC 80V;
For large moment of inertia load, the motor with larger frame number should be selected. When the high inertia load and working speed are high, the motor should adopt the gradual upsizing and speed increase to prevent the motor from losing the step, reduce the noise and improve the positioning accuracy when stopping. In view of the fact that the stepping motor torque is generally below 40 Nm, beyond this torque range, and the running speed is greater than 1000 RPM, the servo motor should be considered. The general AC servo motor can operate normally at 3000 RPM, and the DC servo motor can operate normally at 10000 RPM.
Fourth, select the drive and the number of subdivisions
It is best not to choose the whole step state, because the vibration is larger in the whole step state; try to choose a small current, large inductance, low voltage driver; use a driver larger than the working current, and use subdivision when low vibration or high precision is required. Type drive, high voltage type drive for large torque motors for good high speed performance;
In the case where the actual rotational speed of the motor is usually high and the accuracy and stability are not high, it is not necessary to select a high subdivision drive to save cost; in the case where the actual rotational speed of the motor is usually low, a larger subdivision should be selected. The number is to ensure smooth operation and reduce vibration and noise. In short, when selecting the subdivision number, the actual running speed of the motor, the range of load torque, the setting of the reducer, the accuracy requirement, the vibration and noise requirements should be considered.
