The rapid development of information technology and computer network technology, the continuous advancement of manufacturing technology and C AD/CAM technology have completely changed the traditional design, production and management methods of products. Practice has proved that the networking of CNC machine tools and the unified management of the central computer constitute the CNC production line is an effective way to improve the utilization rate of CNC machine tools and the labor productivity of single-piece small batch production. At the same time, on the basis of network, CAD/CAM and CNC system are integrated into one, and the Internet is used to realize centralized control of group control. At present, the hardware system of CAD/CAM in China has reached a practical stage, and the single technology of CAD/CAM is also becoming more and more mature, but the CAD/CAM integrated system is far from reaching the practical stage. Therefore, the development is based on the network and meets the requirements. An integrated system of modern manufacturing processes is imperative.
1 Characteristics and structure of network numerical control
Network numerical control is an emerging technology. It is based on advanced technologies such as numerical control technology, communication technology and computer technology. It integrates equipment related to the manufacturing process through the network to realize centralized control and management of manufacturing equipment and equipment. Information exchange between the device, the upper computer, and other workshops, and then through the international network and other enterprises. A system configuration of an example of network numerical control, which has integrated functional modules such as real-time communication system, NC machine information management system, and graphic automatic programming system.
A perfect network numerical control system integrates production management, process design and DNC network control. The integration of the system should be based on functional integration. It can share information with other CAD/CAM systems and integrate with open architecture. Production management system. As can be seen from the above, the system has a CAD/CAM interface, and therefore, it provides conditions for the development of a CAD/CAM integrated system.
2 Key technologies for CAD/CAM system integration
There are many ways to develop integrated CAD/CAM systems. In summary, there are four main types:
According to the actual situation of products and hardware devices, the designer develops the whole system of CAD, CAD and CAM, including the design and management system of the underlying graphics.
A method based on feature recognition.
A method based on feature design.
A method based on the STEP standard.
The first problem that CAD/CAM integration needs to solve is how to describe the product information completely and reasonably, so that the information between modules can be shared and minimally redundant. To solve this problem, the solution is to establish a relatively uniform product model within the scope of CAD/CAM, and based on this model, use product data exchange technology to realize data exchange and sharing between CAD and CAM. Therefore, establishing a unified product model has become one of the key technologies for CAD/CAM integration.
In addition, the current CAD/CAM system integration, mainly through the file to achieve data exchange. In order to improve data transmission efficiency and system integration, and to ensure data consistency, reliability and data sharing between systems, an engineering database management system should be used to manage integrated data, so that information can be directly exchanged between systems to achieve real CAD/CAM integration in the sense. Therefore, integrated data management is also a key technology for CAD/CAM system integration.
Finally, CAD/CAM integration requires a large amount of data exchange, so a unified product data exchange standard is required. Currently, international exchange standards are only for geometric figures, such as IGES, DXF, etc. There is no uniform standard for data exchange between the entire product design and manufacturing process. It is often the software developer's own data exchange protocol based on product conditions and hardware and software environment. The CAD model will have quality defects when it is created, causing problems in subsequent applications such as CAM. Some defective models are used in the same system without problems, but as long as they are received and applied by other fields through data exchange, the problem will be exposed, and it is difficult to determine where the error occurred and sometimes it has to be Recreate the CAD model. Since the “auxiliary geometry elements†made during the model generation are often invisible, the auxiliary geometry elements and the real product information are difficult to separate after the exchange. Therefore, all non-products should be deleted before the model is sent. A geometric entity that does not retain multiple representations of the geometric entity in the model.
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