CNC machine generally consists of input and output devices, CNC equipment, PLC, servo system, test feedback device and host machine, etc. 
1, input/output device input device can be different processing information in the computer.At the beginning of the CNC machine produce, input device for the punched tape, now tend to be eliminated;At present, using the keyboard, disk, etc., greatly facilitate the input for the job.Output refers to output the internal working parameters (including the original parameters of machine tool, the ideal work normally, the fault diagnosis parameters, etc.), usually at the beginning of machine tool working state to the output of these parameters for record keeping, after a period of time to work, then the output with the original data for comparison, contrast, can help to determine whether a machine work to maintain normal. 

2, numerical control device of nc device is the core of the nc machine tool and dominant, complete all processing and data processing, the calculation work, eventually realizing the function of nc machine tools each command.It consists of microcomputer circuit, all kinds of interface circuit, CRT monitors and other hardware and corresponding software. 
3, programmable controller PLC, it on the spindle unit control and rotational speed of the program for processing and controlling spindle speed;Management of knife library, automatic tool change, accumulative used times of way choice knife, cutting tool, cutting tool residual life and tool sharpening times management;Control the spindle positive &negative and stop, stop, cutting fluid switch, chuck clamping loosen such action, from mechanical hand off the edge of the sword;Also machine tool for external switch (trip switch, pressure switch, temperature control switches, etc.) to control;The output signal (knife library, manipulator, rotary table, etc.). 
4, test feedback device is composed of detecting element and the corresponding circuit, mainly detection speed and displacement, and information feedback to the CNC device, achieve closed-loop control to guarantee the precision nc machine tool.