NC machine tools is the typical standard of mechatronics products. Although its mechanical structure has many similarities with the ordinary machine tools, it is not simply equipped with numerical control system on the ordinary machine tools. Comparing to the ordinary machine tools, the structure of NC machine tools are improved in the following aspects:
1. The main transmission adopts the finfinitely variable speeds or section variable speed methods, and the change of the spindle's direction and speed can be controled by procedure so that the main transmission has a wider range for speed's change. Some NC machine tools begins to adopt the electrical main transmission with compact structure and excellent performance.
2. The feed device adopts widely the precision seamless ball and lead screw for movements along X,Y axis and precision gear drive, reducing the frictional force via plastic coated guideway or hydrostatic guideway so that to improve its transmission precision. Some NC machine tools's feed devices are drived directly by linear motion actuator to achieve high speed and high sensitivity of Servo driver.
3. Bed, column, cross girder and some main braces adopt reasonable section shapes together with some measures for distortion, which make the NC machine tools has high structural rigidity.
4. There are tool storage and automatic tool changers in the processing center for multiple operation and facet machining, which improve the productivity greatly.