The servo driver used in CNC machine tools is mostly dedicated DC servo motor, such as improved DC motor, small inertia DC motor, permanent magnet DC servo motor, brushless DC motor, etc. Since the middle of 20th century, AC transmission based on AC asynchronous motor and permanent magnet synchronous motor has been developed rapidly. It is the direction in which the machine tool is driven.
The machine feed servo driver includes a speed control loop and a position control loop. Feed servo driver is the most demanding servo system in the control of machine tools. It can complete the feed movement of machine coordinates and has the functions of positioning and contour tracking. No screws or other linear motion devices are required to achieve the infinitely variable speed of the spindle and to provide torque and power during cutting.
The use of feed servo drive in the machine tool greatly saves the PLC programming in the numerical control system, better meets the machining accuracy of the workpiece, and is more conducive to the use and maintenance of users.
Because CNC machine tools put forward strict technical requirements for servo system, servo drive also put forward strict requirements for its own actuator - motor.
1, the motor can run smoothly from the lowest speed to the highest speed, torque fluctuation is small. Especially at low speed (such as O.1R/min) or low speed, there is still a stable speed, no crawling phenomenon.
2, the motor should have a large overload capacity to meet the requirements of low speed and large torque. The average DC servo motor requires 4 to 6 times the overload in a few minutes without damage.
3, the motor can run smoothly from the lowest speed to the highest speed, torque fluctuation is small. Especially at low speed (such as O.1R/min) or low speed, there is still a stable speed, no crawling phenomenon.
4, the servo motor should be able to withstand frequent start, brake and reverse.