Basic composition of CNC machine tools

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The basic components of CNC machine tools include processing program carriers, CNC devices, servo drive devices, machine body, and other auxiliary devices. Below is an overview of the basic working principles of each component.
Processing program carrier
When CNC machine tools are working, workers do not need to operate them directly. To control the CNC machine tool, a processing program must be developed. In the part processing program, it includes the relative motion trajectory of the tool and workpiece on the machine tool, process parameters (feed rate, spindle speed, etc.), and auxiliary motion. Store the part processing program in a certain format and code on a program carrier, such as perforated paper tape, cassette tape, floppy disk, etc., and input the program information into the CNC unit through the input device of the CNC machine tool.
CNC device
CNC devices are the core of CNC machine tools. Modern CNC devices all adopt the form of CNC (Computer Numerical Control), which generally uses multiple microprocessors to achieve CNC functions in the form of programmed software. Therefore, it is also known as Software NC. The CNC system is a position control system that interpolates the ideal motion trajectory based on input data, and then outputs it to the executing component to process the required parts. Therefore, CNC devices are mainly composed of three basic parts: input, processing, and output. And all these tasks are organized reasonably by the computer system program, enabling the entire system to work in a coordinated manner.
1) Input device: Input CNC commands to the CNC device, and there are different input devices according to the different program carriers. There are mainly keyboard input, disk input, direct communication input in CAD/CAM systems, and DNC (direct numerical control) input connected to higher-level computers. Many systems still retain the paper tape input form of photoelectric readers.
(1) Paper tape input method. The paper tape photoelectric reader can be used to read the part program and directly control the machine tool movement, or the paper tape content can be read into the memory and the part program stored in the memory can be used to control the machine tool movement.
(2) MDI manual data input method. The operator can use the keyboard on the operation panel to input instructions for the processing program, which is suitable for shorter programs.
In the control device editing state (EDIT), input the processing program using software and store it in the control device's memory. This input method can reuse the program. This method is commonly used for manual programming.
On CNC devices with session programming function, different menus can be selected according to the prompts on the display, and the machining program can be automatically generated by inputting relevant size numbers through human-machine dialogue.
(3) Adopting DNC direct CNC input method. Save the part program in the superior computer, and the CNC system receives subsequent program segments from the computer while processing. The DNC method is often used for complex workpieces designed using CAD/CAM software and directly generating part programs.
2) Information processing: The input device transmits processing information to the CNC unit, compiles it into information that can be recognized by the computer, and the information processing section gradually stores and processes it according to the control program. After that, the output unit sends position and speed commands to the servo system and the main motion control section. The input data of the CNC system includes: contour information of the parts (starting point, ending point, straight line, arc, etc.), machining speed, and other auxiliary machining information (such as tool change, speed change, coolant switch, etc.). The purpose of data processing is to complete the preparation work before interpolation operations. The data processing program also includes tool radius compensation, speed calculation, and processing of auxiliary functions.
3) Output device: The output device is connected to 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, it drives the servo system to control the machine tool to move according to the specified requirements.