Now, numerical control technology is also called computer numerical control technology. At present, it is a technology that uses computers to realize digital program control. This technology uses a computer to perform the control function of the equipment according to the pre-stored control program. Because the computer is used to replace the original numerical control device composed of hardware logic circuITs, the storage, processing, operation, logical judgment and other control functions of input data can be realized by computer software.
The application of numerical control technology not only brings revolutionary changes to the traditional manufacturing industry, but also makes the manufacturing industry a symbol of industrialization. With the continuous development of numerical control technology and the expansion of application fields, it has made great contributions to some important industries (IT, automobile, light industry, medical care, etc.) of the national economy and people's livelihood. Judging from the current development trend of numerical control technology and its equipment in the world, its main research hotspots are as follows.
1. The new trend of high-speed and high-precision machining technology and equipment
Efficiency and quality are the main parts of advanced manufacturing technology. High-speed and high-precision machining technology can greatly improve efficiency, improve product quality and grade, shorten production cycle and improve market competitiveness. Therefore, Japan Advanced Technology Research Association listed it as one of the five modern manufacturing technologies, and CIRP identified it as one of the central research directions in the 21st century.
In the field of car industry, the production cycle of 3, cars per year is 4 seconds, and multi-variety processing is one of the key problems that car equipment must solve. In the field of aviation and aerospace industry, the machined parts are mostly thin-walled and thin ribs with poor stiffness, and the materials are aluminum or aluminum alloy. Only under the condition of high cutting speed and small cutting force can these ribs and walls be machined. Recently, the method of "hollowing out" large integral aluminum alloy blank is adopted to manufacture large parts such as wings and fuselage, instead of assembling many parts through numerous rivets, screws and other connection methods, so that the strength, rigidity and reliability of the components are improved. All these put forward the requirements of high speed, high precision and high flexibility for processing equipment.
according to the exhibition of EMO21, the feed speed of high-speed machining center can reach 8m/min, or even higher, and the idle running speed can reach about 1m/min. At present, many automobile factories in the world, including Shanghai General Motors Company in China, have partially replaced modular machine tools with production lines composed of high-speed machining centers. The feeding speed of HyperMach machine tool of CINCINNATI company in the United States is 6m/min at maximum, 1m/min at high speed, 2g at acceleration and 6r/min at spindle speed. It takes only 3 minutes to process a thin-walled aircraft part, while it takes 3 hours to process the same part in a general high-speed milling machine and 8 hours in a general milling machine. The spindle speed and acceleration of the double spindle lathe of German DMG company are 12* respectively! r/mm and 1g.
in terms of machining accuracy, in recent 1 years, the machining accuracy of ordinary CNC machine tools has been increased from 1μm to 5μm, and that of precision machining centers has been increased from 3 ~ 5μ m to 1 ~ 1.5μ m, and the ultra-precision machining accuracy has begun to enter the nanometer level (.1μm).
in terms of reliability, the MTBF value of foreign numerical control devices has reached more than 6 h, and the MTBF value of servo system has reached more than 3h, showing very high reliability.
in order to realize high-speed and high-precision machining, the supporting functional components such as motorized spindle and linear motor have developed rapidly, and their application fields have been further expanded.
2. 5-axis linkage machining and rapid development of compound machining machine tools
Using 5-axis linkage to process three-dimensional curved surface parts, cutting with the best tool geometry can not only improve the smoothness, but also greatly improve the efficiency. Generally speaking, the efficiency of one 5-axis linkage machine tool can be equal to that of two 3-axis linkage machine tools. Especially, when milling hardened steel parts with superhard materials such as cubic boron nitride, 5-axis linkage machining can bring more benefits than 3-axis linkage machining. However, in the past, its price was several times higher than that of the 3-axis CNC machine tool because of the complex structure of the 5-axis CNC system and the host computer, and the programming technology was difficult, which restricted the development of the 5-axis CNC machine tool.
At present, due to the appearance of motorized spindle, the structure of compound spindle head for 5-axis linkage machining is greatly simplified, its manufacturing difficulty and cost are greatly reduced, and the price gap of CNC system is narrowed. Therefore, it promotes the development of compound spindle head type 5-axis linkage machine tool and compound machining machine tool (including 5-face machining machine tool).
at EMO21, the 5-face machining machine tool of nippon industrial machinery co., ltd. adopted the compound spindle head, which can realize the machining of 4 vertical planes and any angle, so that 5-face machining and 5-axis machining can be realized on the same machine tool, and the machining of inclined surfaces and inverted cone holes can also be realized. DMUVoution series machining centers exhibited by German DMG Company can be used for 5-face machining and 5-axis linkage machining under one clamping, and can be controlled directly or indirectly by CNC system or CAD/CAM.
3. Intelligentization, openness and networking have become the main trends in the development of contemporary numerical control systems.
The numerical control equipment in the 21st century will be a certain intelligent system, and the intelligent content includes all aspects in the numerical control system: in order to pursue the intelligentization of machining efficiency and machining quality, such as adaptive control of machining process, process parameters will be automatically generated; In order to improve the driving performance and the intelligence of easy connection, such as feedforward control, adaptive operation of motor parameters, automatic identification of load, automatic selection of model, self-tuning, etc. Simplify programming and simplify the intelligence of operation, such as intelligent automatic programming and intelligent man-machine interface; There are also intelligent diagnosis, intelligent monitoring, convenient system diagnosis and maintenance, etc.
In order to solve the problems existing in the closed traditional numerical control system and the industrialized production of numerical control application software. At present, many countries study the open CNC system, Such as NGC (the next generation work-station/machine control) in the United States, OSACA (open system architecture for control within automation systems) in Europe, Osec (open system environment for controller) in Japan, ONC(Open Numerical Control System) in China, etc. The opening of CNC system has become the future of CNC system. The so-called open CNC system means that the development of CNC system can be oriented to machine tool manufacturers and end users on a unified operating platform. By changing, adding or cutting structural objects (CNC functions), serialization can be formed, and users' special applications and technical know-how can be easily integrated into the control system, so as to quickly realize open CNC systems of different varieties and grades and form brand-name products with distinct personality. At present, the architecture specification, communication specification, configuration specification, running platform, CNC system function library and CNC system function software development tools of open CNC system are the core of current research.
networked numerical control equipment is a new highlight of the international famous machine tool Expo in recent two years. The networking of CNC equipment will greatly meet the demand of information integration of production lines, manufacturing systems and manufacturing enterprises, and it is also the basic unit to realize new manufacturing modes such as agile manufacturing, virtual enterprise and global manufacturing. Some well-known CNC machine tools and CNC system manufacturing companies at home and abroad have introduced related new concepts and prototypes in recent two years, such as "CyberProduction Center" (abbreviated as CPC) exhibited by Mazak Yamazaki in EMO21; Okuma Machine Tool Company of Japan exhibited "IT plaza" (Information Technology Plaza, referred to as IT Plaza); The Open Manufacturing Environment (OME) exhibited by Siemens in Germany reflects the trend of NC machine tool processing towards networking.
4. Pay attention to the establishment of new technical standards and specifications
(1) Specifications for the design and development of CNC systems
As mentioned above, open CNC systems have better versatility, flexibility, adaptability and expansibility. The United States, Europe, Japan and other countries have implemented strategic development plans and carried out open architecture CNC system specifications (OMAC, OSACA, OSEC). In 2, China also began to research and formulate the standard framework of ONC CNC system in China.
(2) About numerical control standards
Numerical control standards are a trend in the development of manufacturing informatization. In the 5 years after the birth of CNC technology, the information exchange is based on ISO6983 standard, that is, G and M codes are used to describe how to process, and its essential feature is to face the machining process. Obviously, it can no longer meet the needs of the rapid development of modern CNC technology. Therefore, a new CNC system standard ISO 14649 (Step-NC) is being studied and formulated internationally, which aims to provide a neutral mechanism that does not depend on specific systems and can describe a unified data model in the whole product life cycle, thus realizing the standardization of product information in the whole manufacturing process and even in various industrial fields.
the emergence of step-NC may be a revolution in the field of numerical control technology, which will have a far-reaching impact on the development of numerical control technology and even the whole manufacturing industry. First of all, STEP-NC puts forward a brand-new manufacturing concept. In the traditional manufacturing concept, NC machining programs are all concentrated on a single computer. Under the new standard, NC programs can be distributed on the Internet, which is the direction of open and networked development of NC technology. Secondly, the STEP-NC system can greatly reduce the processing drawings (about 75%), the programming time (about 35%) and the processing time (about 5%).
at present, European and American countries attach great importance to the research of STEP-NC, and Europe initiated the IMS plan of STEP-NC (from January 1, 1999 to December 31, 21). Twenty CAD/CAM/CAPP/CNC users, manufacturers and academic institutions from Europe and Japan participated in this program. STEP Tools, an American company, is a global developer of manufacturing data exchange software. He has developed a Super Model for information exchange of NC machine tools, with the goal of describing all machining processes with a unified specification. At present, this new data exchange format has been verified on the prototype equipped with SIEMENS, FIDIA and European OSACA-NC numerical control system.
1. programming methods for CNC machine tools
there are three programming methods for CNC machine tools: manual programming, automatic programming and CAD/CAM.
1. Manual programming
Part pattern analysis, process treatment, numerical calculation, program list writing and program input and inspection are completed manually. It is suitable for point-to-point machining or parts with less complicated geometry, but it is very time-consuming and easy to make mistakes when compiling complex parts.
2. Automatic programming
It is very convenient for complicated parts to use a computer or a programmer to complete the process of programming parts.
3. CAD/CAM
Using CAD/CAM software, automatic programming of modeling and images is realized. The most typical software is Master CAM, which can complete the programming of milling two-coordinate, three-coordinate, four-coordinate and five-coordinate, turning and wire cutting. Although this kind of software has single function, it is easy to learn and low in price, and it is still the choice of small and medium-sized enterprises at present.
2. Contents and steps of programming for CNC machine tools
1. Main contents of programming for CNC machine tools
Analyze part drawings, determine machining process, carry out mathematical treatment, write program list, make control media, carry out program inspection, input programs and try cutting workpieces.
2. Steps of CNC machine tools
1) Analysis of part drawings and process treatment
According to the drawings, the geometric dimensions and technical requirements of parts are analyzed, the processing contents and requirements are defined, and the processing scheme, processing sequence, fixture design, tool selection, reasonable tool path and reasonable cutting dosage are decided.
At the same time, we should also give full play to the functions of the CNC system and the capabilities of the CNC machine tool itself, correctly select the tool alignment point and cutting mode, and minimize the auxiliary time such as tool changing and indexing.
2) Mathematical processing
Before programming, a workpiece coordinate system is established according to the geometric characteristics of the part, and the machining path is worked out according to the requirements of the drawing of the part. On the established workpiece coordinate system, the tool trajectory is first calculated. For parts with simple shapes (such as parts composed of lines and arcs), only the coordinate values of the starting point and ending point of geometric elements, the center of the arc, and the intersection or tangent point of two geometric elements need to be calculated.
3) Write the parts program list
After the processing route and process parameters are determined, write the parts program list according to the specified code and program segment format specified by the CNC system.
4) program input
5) program verification and first piece trial cutting
3. structure of NC machining program
1. program composition: composed of multiple program segments.
O1； O (Fanuc-O, Ab84-P, Sinumerik 8m-%) can specify program numbers, and each program number corresponds to a machined part.
N1 G92 X Y； semicolon