The status of CAPP and its application technology
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The derivative CAPP system is based on the group technology (GT). Its basic principle is to use the similarity of parts, that is, similar parts have similar technological regulations. The process specification for a new part is obtained by retrieving the process specifications of similar parts already in the system and screening or editing them. Stored in the computer are some standard processes and standard processes. From a design point of view, the analogy with conventional Dingyi is the same, that is, the computer-simulated artificial design method, which inherits and applies the standard process. The derivative system must have a certain amount of model (standard) process documents, modify and generate new documents based on the existing documents. The process specification of the Generative CAPP System Generative System is generated based on the decision logic and manufacturing engineering data information reflected in the program. This information is mainly related to the capabilities and objects of various machining methods, and the application of various equipment and tools. Range and a series of basic knowledge. The various decision logics in the process decision are stored in a relatively independent process knowledge base for the main program to call. After inputting the information of the parts to be processed into the generative system, the system can automatically generate various process specification files, and the user does not need to modify it or slightly. The generatrix system does not require the template process document in the derivation method. In the creation system, only the decision logic and rules are required. The system must read the comprehensive information of the part, and then automatically generate the process document according to the logic rules specified by the program. Comprehensive CAPP system The integrated system is a combination of derivative, generative and artificial intelligence. It can be seen from the way the process files are generated in the above three CAPP systems that the derivative system must have template files, so its application scope is very limited. It can only produce process documents for certain similar parts. In a company, this part is only a part, and then the process file derivative system of other parts cannot be solved. Although the generative system is based on the expert system and automatically generates the process documents, it needs to input comprehensive parts information, including the information processing of the process information is in great demand, extremely comprehensive, the system must determine the processing route of the parts, positioning reference, clamping method Etc. From the specificity of process design and its individualized analysis, the expression and reasoning of these knowledge cannot be well implemented; it is precisely because of the “matching conflict†between knowledge expression “bottleneck†and theoretical reasoning that cannot be solved so far. Due to the poor self-optimization and self-improvement functions, the CAPP expert system method still remains at the stage of theoretical research and simple application. The domestic commercialized CAPP system uses Word, Excel, AutoCAD, or the currently-developed CAPP system. The process files generated by such CAPP systems exist in the form of text files, and cannot generate process data, let alone process data management. Conventional database management systems, process cards use Form, Report, or CAPP system to draw cards on AutoCAD. The CAPP system generated by the CAPP system is generated by the program design, and the filling in of the process card can not achieve what you see. The card format needs to be updated and the original program needs to be changed. The CAPP system that focuses on the generation of cards, but has weaker management functions for process data The process data of such CAPP systems is dispersed in various process cards, and it is difficult to achieve centralized management of process data. Using the "see what you get" interactive form filling method + process data management, integrated integrated CAPP system The filling form of this type of CAPP system is more in line with the working habits of the process design staff, and is easily integrated with the enterprise PDM system. The product's process data, and provide effective production and management process data for MRPII, MIS and other systems. 3 The significance of developing CAPP technology A good process design engineer must have the conditions to have a wealth of production experience; familiar with the company's various equipment usage; familiar with the company's various production processes and methods; familiar with the company's various production and processing related Norms; familiar with the various rules and regulations related to production management; able to maintain friendly cooperation with all parties concerned. Process engineers with extensive experience often feel under-represented in developed countries. In the United States, craftspeople are generally over 40 years of age and have extensive experience working in production workshops; in the United Kingdom. The average age of a process engineer is 55. The statistics of age data reflect that the process design requires process engineers to have many years of practical experience in production. The disadvantages of the traditional process design have a high requirement for the process designer. The traditional process design is manually designed by the craftsman. The rationality, operability and length of the process documentation mainly depend on the experience and skill of the craftsman. degree. This inevitably leads to the fact that the design cycle and quality of the process documentation are not easily guaranteed. Therefore, the traditional process design requires the craftsman to have a wealth of production experience. The workload is large and the efficiency is low. The process design requires the generation of a large number of process documents. These process documents are often manually processed in the form of forms and cards. : The craftman designs the art process according to the parts; fills in the craft card, draws the process sketch, etc.; Proofreads; Audits; Writes; Traces; Sew maps; binds into a booklet In addition, the craftman also carries on the massive summary work, for example: The tooling summary, Equipment summary and so on. This is a lot of work and it takes a long time. Unable to use CAD's graphics and data With the implementation of the National Science and Technology Commission's "Rescue and Drawing Board Project," the application of two-dimensional CAD technology in the enterprise has become very popular. All departments communicate with each other through electronic drawings. However, due to the process design department The manual design is still used, so that CAD graphics and data cannot be used effectively. It is difficult to guarantee the accuracy of data. Process design requires a lot of graphic information and data information, and produces a large number of process documents and process data through the process design. The traditional design method requires manual processing of graphics and data information, due to the variety of data and dispersion. Therefore, it is cumbersome and error-prone. Information cannot be shared With the deepening of enterprise computer applications, data generated by various departments can be exchanged and shared by computers. If the technology department still uses manual methods, the data of other departments can only be searched manually, and the work efficiency is low and easy. Errors; The resulting process data can not be easily communicated and shared with other departments. The current application of computer technology has been applied to various fields of factory and enterprise. When designing a process, such as using a computer to design a process, it is bound to greatly Improve work efficiency and quality of work in process departments. Improve information processing capabilities and information exchange capabilities among various departments of enterprises. The application of CAPP technology will shorten the design cycle and respond quickly to changes and changes in design; the experience of process personnel can be fully accumulated and inherited; the workload of the preparation of process documents can be reduced and the possibility of error can be reduced and a computer manufacturing system can be established. basis. 4 The current status of domestic enterprises applying CAPP technology through surveys conducted by some domestic design institutes and enterprises. The application of most CAPP systems by most companies is not optimistic. The status quo of enterprise application CAPP system The process design of most enterprises still adopts manual design, and the application of CAPP is still blank. Enterprises in more remote areas, especially those small and medium-sized enterprises, not only have a blank application of CAPP, but also have concerns about the application of computers. After some enterprises have become more popular in computer technology and CAD applications, process design has become a weak link for enterprises. Some companies draw a blank form of a process card on Word, Excel, or AutoCAD by themselves and design the process specification on this basis. This kind of design method also uses the computer to carry on the auxiliary craft design, therefore, may also be called CAPP, but this kind of CAPP produces the technological procedure exists in the form of the text file, the craft department only produces the text file, the enterprise cannot be able to the craft data Effective management. Some companies have fully realized the importance of process design and purchased some commercially-available CAPP systems. However, because companies still have some misunderstandings about CAPP, the application of CAPP is still not satisfactory. At present, most enterprises have realized the necessity of CAPP technology application, but there are still many misunderstandings and greater blindness in the selection and application of CAPP systems in enterprises, mainly manifested in the blind pursuit of design automation, optimization, It does not pay attention to the preparation of basic data, the steady development of basic technologies and the improvement of the quality of personnel. The misunderstanding of enterprise application of CAPP believes that CAPP is a computer automatically generated process specification. First, Dingyi design is a typical complex problem. The factors involved are numerous and complex. It involves parts information, manufacturing resources, and process experts. The organization and management of many kinds of information (data), such as knowledge, involves not only simple numerical operations but also complex data such as images, characters, tables, etc. Therefore, the core and difficulty of CAPP system is the processing of data. Second, because process design has a great dependence on the use environment, and many process knowledge in process design do not have precise definitions and strict mathematical models, many problems are non-deterministic, and process design is still in the stage of empirical decision making. This leads to the dynamic and empirical process design. It is for these reasons that the automated CAPP system can currently only target a specific part. Such as the slewing body; General automation CAPP system can only be in the research stage, and can not be applied to the actual. Currently, A in CAPP is Aided rather than Autometie. It is believed that CAPP is based on parts only and not necessarily based on the product structure in the enterprise. All production activities are carried out around the product structure. The production process of a product is actually the generation process of all attributes of the product. Although each process document is aimed at a specific part or component, as one of the properties of the product, the process document should also be developed around the product structure under the guidance of the process design plan, so that the assembly of the product can be clearly described. Relationships, and can directly read the product schedule data file The CAD product design data will be automatically brought to the CAPP system. Therefore, the CAPP system based on product structure is more suitable for the production environment of the enterprise. It is believed that CAPP only solves the filling and generation of process cards, but does not pay attention to the generation and management of process data. The filling and generation of process cards is a problem that CAPP system must solve, but CAPP is connected between CAD and CAM in computer integrated manufacturing system. Bridges and ties. The integrated CAPP system should be able to directly receive CAD part information, carry out process planning, generate relevant process documents, and use the results of process design and part information as basis, after appropriate post-processing, generate NC programs to achieve CAD/ The integration of CAPP/CAM system and its core is database. Therefore, the CAPP system must be able to generate process data and manage it rather than just complete the process card. Requirements for data management among departments, distribution, assignment of tasks, etc., which should be completed by PDM The CAPP system completes the CAPP system to solve the entire process of enterprise process design, and prepares data for the other systems of the company. As far as the manufacturing environment of domestic companies is concerned, the management and transmission of post design data are most suitable to be solved by the PDM system. 5 Conclusion In conclusion, the implementation of the CAPP system should improve the quality of process design, shorten the production preparation cycle, and liberate process designers from a lot of cumbersome and repetitive labor. However, companies should fully consider their actual situation to choose CAPP software. In summary, the CAPP system adapted to the current production situation of the enterprise should have the following characteristics: From multiple aspects: design, management, integration, etc. to solve the process design problem of the enterprise; and from the process design platform (data platform) to solve the process design problem, and It is not around the process card (graphical platform); it adopts the “seeing and gaining†interactive operation method, which conforms to the style and habit of using Windows; it can intelligently use the enterprise's manufacturing resources to solve the utilization and management of the process data; adopt an open system Structure, convenient for users to carry out secondary development; Based on the database, can integrate with other systems, share product database and authority database. When selecting a CAPP system, an enterprise should not only consider the functions that the system should have, but also take into consideration the unified planning and step-by-step implementation of the individual circumstances of the enterprise to ensure the effective use of funds.