CNC machine tools are an important basic equipment for machine tool manufacturing, so its development has been receiving much attention. In recent years, China's machine tool manufacturing industry has not only faced the opportunity of the development of manufacturing equipment, but also encountered the pressure of market competition. From a technical point of view, accelerating the advancement of CNC technology will be a key to solving the sustainable development of the machine tool manufacturing industry. At present, the world's advanced manufacturing technology is constantly emerging, the application of ultra-high-speed cutting, ultra-precision machining and other technologies, the rapid development of flexible manufacturing systems and the continuous maturity of computer integrated systems, put forward higher requirements for CNC machining technology. Today's CNC machine tools are moving in the following directions.
1. Maximize reliability
The reliability of CNC machine tools has always been the main indicator of users' most concern. The CNC system will use a more integrated circuit chip, using large-scale or ultra-large-scale dedicated and hybrid integrated circuits to reduce the number of components to improve reliability. Softwareized by hardware functions to meet the requirements of various control functions, while adopting the modularization, standardization, generalization and serialization of the hardware structure of the machine tool body, it not only improves the hardware production batch, but also facilitates the organization of production and quality control. It also realizes fault diagnosis and alarm for hardware, software and various external devices in the system by automatically running various diagnostic programs such as startup diagnosis, online diagnosis, and offline diagnosis. Use alarm prompts to eliminate faults in a timely manner; use fault-tolerant technology to adopt “redundant” design for important components to achieve fault self-recovery; use various testing and monitoring technologies to produce over-travel, tool loss, interference, power failure, etc. When an accident occurs, the corresponding protection is automatically performed.
2. Control system miniaturization
The miniaturization of the numerical control system facilitates the integration of the machine and the electric device. At present, it mainly adopts ultra-large-scale integrated components and multi-layer printed circuit boards, and adopts a three-dimensional installation method to enable high-density installation of electronic components, and to reduce the occupied space of the system by a large scale. The replacement of the conventional cathode ray tube with a new type of color liquid crystal thin display will further miniaturize the numerical control operating system. This makes it easy to install it on machine tools, making it easier to use the CNC machine.
3. Intelligent
Modern CNC machine tools will introduce adaptive control technology, which automatically adjusts the working parameters according to the changes of cutting conditions, so that the best working condition can be maintained during the machining process, resulting in higher machining accuracy and smaller surface roughness. Improve tool life and equipment productivity. With self-diagnosis and self-repair function, the system performs self-diagnosis and inspection on the CNC system itself and various devices connected to it at any time during the whole working state. In the event of a fault, immediately take measures such as shutdown, and perform a fault alarm to indicate the location and cause of the fault. It is also possible to automatically take the failed module offline and switch on the standby module to ensure the requirements of the unmanned working environment. In order to achieve higher fault diagnosis requirements, the trend is to use artificial intelligence expert diagnostic systems.
4. CNC programming automation
At present, CAD/CAM graphic interactive automatic programming has been applied more and is a new trend in the development of numerical control technology. It is a part processing drawing drawn by CAD, and then calculated and post-processed by the tool path data in the computer, thereby automatically generating NC part processing program to realize the integration of CAD and CAM. With the development of CIMS technology, there is a fully automatic programming method of CAD/CAPP/CAM integration. The biggest difference between it and CAD/CAM system programming is that the processing parameters required for programming do not have to be manually involved, directly from the system. The CAPP database is obtained inside.
5. High speed and high precision
Speed and accuracy are two important indicators of CNC machine tools, which are directly related to machining efficiency and product quality. At present, the numerical control system uses a processor with a higher number of bits and a higher frequency to improve the basic operation speed of the system. At the same time, the use of ultra-large-scale integrated circuits and multi-microprocessor structures to improve the data processing capabilities of the system, that is, improve the speed and accuracy of the interpolation operation. The linear servo feed mode of the machine table is directly driven by a linear motor, and its high speed and dynamic response characteristics are quite superior. The feedforward control technology is used to greatly reduce the tracking hysteresis error, thus improving the machining accuracy of corner cutting.
6. Multi-functional
All kinds of machining centers equipped with automatic tool changers (tools with a capacity of more than 100) can simultaneously perform milling, boring, drilling, turning, reaming, reaming, tapping, etc. on the same machine. In the process of processing, modern CNC machine tools also use multi-spindle and polyhedral cutting, which means that different parts of a part can be cut in different ways at the same time. Due to the multi-CPU structure and hierarchical interrupt control mode, the CNC system can simultaneously process and program parts on a single machine to achieve the so-called “foreground processing, background editing”. In order to meet the requirements of flexible manufacturing systems and computer integrated systems, CNC systems have long-distance serial interfaces, and even can be networked to realize data communication between CNC machine tools, and can also directly control multiple CNC machine tools.
In order to meet the requirements of ultra-high-speed machining, the CNC machine tool adopts a structural form in which the spindle motor and the machine tool spindle are combined into one, and realizes the integration of the variable frequency motor and the machine tool spindle. The bearing of the spindle motor adopts a magnetic floating bearing, a hydrodynamic bearing or a ceramic rolling bearing. form.
CNC machine tools have attracted worldwide attention with its excellent flexible automation performance, excellent and stable precision, and agile and diversified functions. It has pioneered the development of mechanical products to mechatronics, so CNC technology has become an advanced manufacturing technology. A core technology. On the other hand, through continuous research, the deepening application of information technology has promoted the further improvement of CNC machine tools.
