The basic composition of a CNC machine tool includes a processing program carrier, a CNC device, a servo drive device, the main body of the machine tool and other auxiliary devices. The basic working principles of each component are summarized below.
When a CNC machine tool is working, workers do not need to directly operate the machine tool. To control the CNC machine tool, it is necessary to compile a processing program. The part processing program includes the relative motion trajectory of the tool and the workpiece on the machine tool, process parameters (feed amount, spindle speed, etc.) and auxiliary motion. The part processing program is stored in a program carrier with a certain format and code, such as punched paper tape, cassette tape, floppy disk, etc., and the program information is input to the CNC unit through the input device of the CNC machine tool.
The numerical control device is the core of the numerical control machine tool. Modern numerical control devices all adopt the form of CNC (Computer Numerical Control). This kind of CNC device generally uses multiple microprocessors to realize numerical control functions in the form of programmed software, so it is also called Software NC (Software NC). The CNC system is a position control system, which interpolates the ideal motion trajectory according to the input data, and then outputs it to the execution component to process the required parts. Therefore, the numerical control device is mainly composed of three basic parts: input, processing and output. And all these tasks are reasonably organized by the computer system program, so that the entire system works in a coordinated manner.
Input the numerical control instructions to the numerical control device, and there are different input devices according to the different program carriers. There are mainly keyboard input, disk input, CAD/CAM system direct communication input and DNC (direct numerical control) input connected to a higher-level computer. There are still many systems that still retain the paper tape input form of photoelectric readers.
(1) Paper tape input method. The part program can be read in with a paper tape photoelectric reader to directly control the movement of the machine tool, or the content of the paper tape can be read into the memory, and the part program stored in the memory can be used to control the motion of the machine tool.
(2) MDI manual data input mode. The operator can use the keyboard on the operation panel to input the instructions of the processing program, which is suitable for relatively short programs. In the edit state of the control device (EDIT), use the software to input the processing program and store it in the memory of the control device. This input method can reuse the program. This method is generally used for manual programming. On the numerical control device with conversational programming function, you can select different menus according to the questions prompted on the display, use the method of man-machine dialogue, and input the relevant size numbers to automatically generate the processing program.
(3) Adopt DNC direct numerical control input method. Save the part program in the upper-level computer, and the CNC system receives subsequent program segments from the computer while processing. The DNC method is mostly used when using CAD/CAM software to design complex workpieces and directly generate part programs.
The input device transmits the processing information to the CNC unit and compiles it into information that can be recognized by the computer. After the information processing part stores and processes it step by step in accordance with the regulations of the control program, the output unit sends out position and speed commands to the servo system and The main motion control part. The input data of the CNC system includes: the contour information of the part (start point, end point, straight line, arc, etc.), processing speed and other auxiliary processing information (such as tool change, speed change, coolant switch, etc.). The purpose of data processing is to complete the insertion Preparation work before complement operation. The data processing program also includes tool radius compensation, speed calculation and processing of auxiliary functions.
The output device is connected with the servo mechanism. The output device receives the output pulse of the arithmetic unit according to the command of the controller, and sends it to the servo control system of each coordinate. After power amplification, the servo system is driven to control the machine tool to move as required.
In general, this article introduces the working principle of CNC machines. If you are interested in CNC machines and get more information, you can consult Ouke. Ouke is a professional manufacturer specializing in Fanuc servo motor, Siemens servo drive, Mitsubishi servo motor, Fanuc servo drive, Fanuc servo motor encoder, Fanuc circuit boards, and so on.
