2.1.1 Overall structure of CNC system
To process parts on a CNC machine tool, first, a processing program must be prepared according to the geometric data and process data of the parts to be processed in accordance with the specified code and program format, and then the program instructions are input into the CNC system of the CNC machine tool. The CNC system then decodes the program (code), processes the data, and performs interpolation operations, and sends information and instructions to the servo mechanism and auxiliary control device of each coordinate of the CNC machine tool, Drive all moving parts of CNC machine tool, control the required auxiliary movement, and finally process qualified parts. These information and instructions include: feed speed, feed direction and feed displacement of each coordinate axis, and control signals of each state.
Modern CNC system consists of hardware and software. The hardware part includes the computer and its peripherals. Peripheral equipment mainly includes: display, keyboard, panel, programmable logic controller (PLC), I/O interface, etc. Display is used to display information and monitor; The keyboard is used to input operation commands, input and edit processing programs, input setting data, etc; The operation panel is used for the operator to change the working mode, manual operation, operation processing, etc; PLC is mainly used for the control of switching value/ O interface is the bridge between CNC device, servo system and machine tool. The software part consists of management software and control software. The management software mainly includes input/output, display, self diagnosis and other programs; The control software mainly includes decoding, interpolation, tool compensation, speed control, position control and other programs.
The core of numerical control system is numerical control device, which is a special computer composed of hardware (general hardware and special hardware) and software (special), so modern numerical control system is also called CNC system. The system software runs under the support of hardware, and cannot work without software and hardware.
With the development of computer technology, the performance of numerical control device is getting higher and higher, and the price is getting lower and lower. Some or all of its control functions are realized through software. As long as the control program is changed, the control function can be changed without changing the hardware circuit. Therefore, CNC system has greater advantages in universality, flexibility, scope of use, etc. Table 2-1 describes the advantages of CNC system in detail.
Table 2-1 Advantages of NC System
|
Serial No. |
Advantage | Detailed description |
| 1 | Flexible and versatile | The functions of CNC system are mostly realized by software, and the software and hardware adopt modular structure, which makes the modification and expansion of system functions more flexible. The basic configuration of CNC system is universal. Different CNC machine tools are only configured with corresponding specific functional modules to achieve specific control functions |
| 2 | Rich NC functions | ① Interpolation function: quadratic curve, spline curve, spatial surface interpolation ② Compensation function: motion accuracy compensation, random error compensation, nonlinear error compensation, etc ③ Man machine dialogue function: dynamic and static tracking display of processing, advanced man machine dialogue window ④ Programming function: G code, graphic programming and some automatic programming functions |
| 3 | High reliability | The CNC system uses highly integrated electronic components and chips to ensure its reliability. Many functions are implemented by software, reducing the number of hardware. Rich fault diagnosis and protection functions (mostly implemented by software) can reduce the frequency of system faults and the repair time after faults |
| 4 | Easy to use and maintain | ① Convenient operation: users can operate correctly only according to the menu prompts ② Convenient programming: it has multiple programming functions, automatic program verification and simulation functions ③ Convenient maintenance and repair: part of the daily maintenance work is carried out automatically (lubrication, regular inspection of key components, etc.), and the self diagnosis function of the CNC machine tool can quickly and accurately locate the fault |
| 5 | Easy to realize electromechanical integration | The volume of the control cabinet of the numerical control system is small (with computers, the number of hardware is reduced; the integration of electronic components is getting higher and higher, and the volume of hardware is decreasing), which makes it possible to physically combine it with the machine tool, reduce the floor area, and facilitate operation |
