I. In the retrospective, the term "functional components" was derived from the 1980s. It uses some very important component "functions" to locate its role in the mainframe. This is more than the name of the "machine tool accessory". Appropriate and more accurate. The functional components that play a key role in CNC machine tools include: CNC system, spindle unit (including electric spindle), ball screw pair, rolling linear guide pair, rotary servo motor, linear servo motor, knife