The basic components of CNC machine tool include process program carrier, CNC device, servo drive device, machine tool main body and other auxiliary devices. The following parts of the basic principles of the work were outlined. When the numerical control machine tool works, does not need the worker to operate the machine tool directly, must carry on the control to the numerical control machine tool, must compile the processing procedure. 

In the part processing procedure, including on the machine tool tool and the work piece relative movement track, the craft parameter (feed quantity spindle speed and so on) and the auxiliary movement and so on. The part processing program is stored on a program carrier with certain format and code, such as perforated paper tape, cassette tape, floppy disk, etc. , input program information to CNC unit.

Numerical control device numerical control device is the core of numerical control machine tool. 

The modern Numerical Control device adopts CNC (Computer Numerical Control) form, this kind of CNC device generally uses many microprocessors, realizes the Numerical Control function by the programmed Software form, therefore is also called the Software Numerical Control (Software NC) . CNC system is a kind of position control system, which interpolates the ideal movement track according to the input data, and then outputs to the executive part to process the required parts. Therefore, the numerical control device is mainly composed of three basic parts: input, processing and output. All of these tasks are reasonably organized by the computer's system program to make the whole system work in a coordinated way.

1) input device: the numerical control instruction input to the numerical control device, according to the program carrier different, corresponding different input device. There are mainly keyboard input, disk input, direct communication input of CAD  CAM system and DNC (direct numerical control) input connecting to superior computer. 

(1) paper tape input method. Can be used to read into the paper tape photoelectric reading machine parts program, direct control of machine movement, but also can read the paper tape content into memory, with the memory of the stored parts program control machine movement. 

(2) MDI manual data input mode. The operator can use the keyboard on the operation panel to enter instructions for the processing program, which is suitable for shorter programs. In the control device EDIT state (EDIT) , the software input process program, and stored in the memory of the control device, this input method can be reused program. This method is commonly used in manual programming. In the NC device with session programming function, according to the question on the display, select different menu, use man-machine dialogue method, input the relevant size number, can automatically generate processing program.

 (3) using DNC Direct numerical control input mode. The part program is saved in the superior computer, and the CNC system receives the following program segment from the computer while processing. DNC is often used for complex workpieces designed with CAD  CAM software and for the direct generation of part programs.

2) information processing: the input device transmits the machining information to the CNC unit, and compiles it into the information that can be recognized by the computer. The information processing part stores and processes the information step by step according to the regulation of the control program, and then sends the position and speed instructions to the servo system and the main motion control part through the output unit. The input data of CNC system includes the contour information (starting point, end point, straight line, ARC, etc.) , machining speed and other auxiliary machining information (such as tool change, speed change, coolant switch, etc.) . The data processing program also includes tool radius compensation, velocity calculation and auxiliary function processing.

 3) output device: the output device is connected with the servo mechanism. The output device receives the output pulse according to the command of the controller, and sends it to the servo control system of each coordinate. Servo and measurement feedback system