With the continuous improvement of the productivity, the improvement of the machine tool structure, the expansion of the processing range, the speed and power of the spindle is also increasing, the spindle speed range is also expanding, the spindle's constant power speed range is larger, and there is automatic change of the spindle of the main stop function.
In order to realize the above requirements, the spindle drive should be driven by stepless speed-regulating system. In general, the spindle drive only speed control requirements, a small number of position control requirements, so the spindle control system only speed control ring.
Because the spindle needs constant power speed range, the use of permanent magnet electric machine is unreasonable, often using his excitation DC servo motor and cage-type induction AC servo motor.
The main rotational motion of NC machine tool does not require a screw or other linear motion mechanism, and the spindle drive of the machine tool differs greatly from the feed drive.
In the early years, the NC machine tool adopts the DC spindle drive system, but because of the commutation limit of the DC motor, the constant power speed range of most systems is very small. With the development of microprocessor technology and high-power transistor technology, the spindle drive system of CNC machine tool has been applied in the early 1980s. At present, the new production of CNC machine tools at home and abroad are basically used AC spindle drive system, AC spindle drive system will completely replace the DC spindle drive system. This is because the AC motor is not like the DC motor in the high speed and large capacity constraints, and the AC spindle drive system performance has reached the DC drive system level, even in the noise has been reduced, the price is lower than the DC spindle drive system.