In the late 1960s, people began the research and development of CAPP. The earliest countries that studied CAPP technology were Norway and the former Soviet Union. However, a milestone in the history of CAPP development is the CAPP (CAM-I's Automated Process Planning) system developed by CAM-I, an international organization based in the United States, in 1976. The earliest developed CAPP system in China was Tongji University's revised TOJICAP system and Northwestern Polytechnical University's innovative CAOS system. Its time of completion was in the early 1980s.
After more than 20 years of development, CAPP technology has been extensively studied and researched both at home and abroad. Progress has been made in both depth and breadth of research.
However, compared with computer-aided technologies such as CAD and CAM, CAPP is still a weak link in application. On the one hand, this is determined by the complexity and characteristics of the process design problem; on the other hand, it is also influenced by the background and guiding ideology of CAPP development. Therefore, despite the continuous emergence of new concepts and methods in CAPP research at home and abroad, the lack of a solid practical foundation for the development of CAPP is a recognized fact.
From the perspective of the application of CAPP, this article reviews the development process of CAPP and discusses the future development of CAPP in order to provide some ideas for the application of CAPP in manufacturing informatization.
Second, based on the revision of automation ideas / CAPP system
In the traditional CAPP research and development, people divided the CAPP system into two categories based on process decision-making methods: revised (also known as derived) CAPP system and generative (generative) CAPP system. According to the technical development and actual development requirements, there are also hybrid systems that are compatible with the above two methods, as well as CAPP expert systems that are more influential in applying artificial intelligence (AI) and expert system (ES) technologies. This kind of system takes the automation as the only goal, in order to replace the craftman in the process design, therefore, has caused many problems in the development and application: The system development cycle is long, the cost is high, the difficulty is great; The craftworker uses in interactive input a large number of parts Information is troublesome and error-prone. It is difficult to grasp the use of the system. The system has a limited range of functions and applications (large limitations). It lacks the flexibility and adaptability to adapt to changes in the production environment, making it difficult to popularize and apply.
In order to solve the above problems, the development of development tools (including expert system development tools), application of object-oriented (OO) technologies, and CAD/CAPP integration applications have been continuously explored at home and abroad, but the practical use of CAPP has not been effectively promoted. .
Third, a practical CAPP system based on computerized thinking
Since the 1990s, the practical application of CAPP has attracted the attention of researchers and enterprise technicians, and the realization of the computerization of process design as a goal or the practical application of CAPP system, which emphasizes the role of computers in CAPP applications, has become a new topic. These practical CAPP systems, either dedicated development or application development based on commercial systems, can be roughly divided into the following two categories.
1. Process Card Filling System Based on Word/Excel/AutoCAD and Other Graphic Systems
Due to the problems existing in the revision/general-purpose CAPP application with automation as the goal, many companies fill in the system based on general software development process card such as Word/Excel/AutoCAD. Many of these systems are based on simple template computer cards and have only achieved certain application results. However, many of them have been developed on the basis of standardization and standardization of the process and have spent a lot of manpower and material resources. The effect of the application.
Since 1997, several commercial CAPP systems have been introduced in China, many of which are based on AutoCAD and other graphics systems. This type of system emphasizes the "what you see is what you get" process design. It completely uses the document as the core, ignoring the importance of product process data in the enterprise informatization, and it is difficult to guarantee the accuracy, consistency, and integration of process information for the product process data. Fatal problem. Such systems are managed in the form of files. Although some claim to be database management, they are in fact managed based on the concept of file packaging. The accuracy, consistency, and process information integration of product process data cannot be solved.
2. CAPP system based on structured data
From the perspective of information system development, analyze the data/information involved in the product process documentation, establish a structured data model, and use the model-driven process design. The dedicated CAPP system developed by some companies basically belongs to this type of system, and most of them use a general-purpose database management system for development. As a commercial CAPP application framework, CAPPFramework is based on object-oriented analysis and information modeling, adopts ODBC technology to adapt to various relational database systems, and realizes a â€œwhat you see is what you getâ€ process design interface driven by the model. The reliable and effective integration of information and the deep application of CAPP have laid a good foundation.
Although some of the commercially available CAPP systems introduced in the country also emphasize the importance of product process data, they still use documents as their core organizational data. Therefore, the degree of data structure is low. This type of system can only be called a CAPP system based on semi-structured data.
The development trend of the practical CAPP system seems to be a retreat to the initial stage of the development of the CAPP system, but it is actually not the case. In the process of development and application of practical CAPP systems, their goals are very different from traditional goals. Such CAPP systems have been applied in more and more domestic enterprises and have achieved significant results in a few short years. At present, the development of CAPP is gradually embodying modern advanced manufacturing concepts and the development of manufacturing process information systems that integrate process design and process management.
Fourth, product-oriented CAPP application and manufacturing process information system
In manufacturing companies, the process design of the final product throughout the entire life cycle usually involves product assembly process, mechanical processing technology, sheet metal stamping process, welding process, heat treatment process, blank manufacturing process, rework processing process and other processes Design, in the general product of the mechanical processing technology usually involves the rotary body parts, box parts, bracket parts and other parts types. Obviously, if the CAPP application model with the component as the main subject is adopted, the application of CAPP in the enterprise can only be a partial application, and the application of CAPP lacks the breadth required, thus making the development of CAPP lack a solid practical foundation. From the long-term perspective of corporate development, it will inevitably cause inconsistencies and inconsistencies in the process management of the company, which will fundamentally hinder the application and development of CAPP. The application of CAPP should be based on the partial application of the main component of the component to the overall application of the entire product, the integration of product process design and management, and the establishment of the enterprise manufacturing process information system.
1. Product-Oriented CAPP Methodology
The basic content of the product-oriented CAPP methodology is: The CAPP system should first be an interactive computer application system integrating process design and information management centered on product process data, and gradually integrate multiple process decisions such as retrieval, revision, and innovation. Hybrid technology and multi-artificial intelligence technology to realize the integration of human-machine hybrid intelligence and people, technology and management, and gradually and partially automate the process design and management, and improve the process personnel from many aspects such as design and management. The work efficiency, and the accumulation of process designer's experience in the application.
(1) The CAPP system should first be an interactive computer application system. Under the interactive CAPP system model, the craftsman is the main body of process decision-making. The system adopts multi-process decision-making hybrid technologies such as retrieval, revision, and innovation and multiple labors. Intelligent technology will focus on the automation of local process decision-making functions, and as a means to improve the work efficiency of process personnel as a whole, rather than simply automate the whole process of process decision-making, and it should not become the only thing that CAPP needs to implement or main target.
(2) Product process data is the central product of the CAPP system. Process data is an important part of product data, and it is also a collection of production information. The integrity and consistency of product process data and the integration and sharing of enterprise product process information are of great significance for enterprise informationization. Process cards, which are formatted representations of process data, can be automatically generated by the system. On this basis, CAPP can also automatically complete the tooling equipment, materials, key parts of the process, external parts and components, process time quotas, auxiliary materials, and key processes at all levels (product level, component level, and part level). Such as various statistical summary functions, and automatically generate summary statistical reports (details), this can not only greatly improve the efficiency of the preparation of process documents, but also minimize unnecessary human errors.
(3) Integration of product process design and management From the point of view of enterprise management, various statistical collections such as tooling equipment, materials, process critical parts, outsourcing products, working hours quotas, auxiliary materials, and key processes, and product process documents The process management of the product such as change and filing management occupies a very important position; some of the repetitive work such as the aggregation, calculation, and transcription of enterprise process data account for 50-60% of the total workload. A large part of the craftsman's time is used for repetitive work such as summary statistics of process data. Not only is the work efficiency low, but it is difficult to ensure the accuracy and consistency of the process documentation.
With the emergence and development of new production methods and philosophies such as CIMS and agile manufacturing, in the environment where companies adopt these new technologies in order to enhance market competitiveness and respond quickly to changes in the market, it is difficult to satisfy only the computerization of the establishment of technological regulations. Enterprise information needs. In addition to the convenient computer-aided process specification development functions, it is necessary to include rapid and effective management of the company's manufacturing process information and process workflow, to achieve product process design and management integration, and to establish a complete enterprise manufacturing process information system.
2. Manufacturing Process Information System
In the enterprise, the complete manufacturing process information system must be based on computer-aided design of various professional processes to realize basic process information management, manufacturing-oriented product structure management, material quota compilation, process division and process design process management, and product process data. Integrated management and other process management functions and integration with CAD/PDM, ERP and resource sharing.
V. Knowledge-based CAPP Integrated Intelligence
The establishment of an interactive CAPP-based manufacturing process information system does not exclude efforts in the direction of CAPP intelligence. On the basis of building a rich knowledge base of the process, applying various artificial intelligence decision-making techniques to achieve various effective and intelligent online assistance in various stages is still an important goal of CAPP development.
In the early stage of an enterprise CAPP application, interactive design is the main design method. With the accumulation of process data and knowledge, not only the efficiency of interactive design will be greatly improved, but more importantly, it will provide good conditions and basis for the development of various intelligent decision functions.
1. Computer-aided process standardization and standardization
The application of CAPP will greatly promote the standardization of the process; in turn, the standardization of the process is an important aspect of improving the application of CAPP, and will fundamentally improve the quality of process design. Whether it is the early group process or the standardization work carried out within the company, due to the limitations of computer application, the actual results obtained are limited. In the product-oriented CAPP application mode, the standardization and standardization of the process can be applied throughout the CAPP application process, and computer-aided tool software with standardized and standardized processes can be developed.
2. Automatic retrieval of similar processes based on instances
The use of similar technology search techniques can not only greatly reduce the work intensity of the craftworkers and the reliance on experienced craftsmen, but also improve the inheritance and reuse of the product technology and promote the standardization of the craft. In the development of the traditional revised CAPP system, it takes a lot of manpower, material resources, and financial resources to prepare parts such as coding and preparation of standard process rules in advance. In the product-oriented CAPP application mode, the automatic retrieval of similar processes is an automatic retrieval of similar processes based on instances. Group technology (GT), case-based technology, fuzzy logic, etc. are the basis for automatic retrieval of similar processes based on instances.
3. Automatic acquisition of process knowledge
Learning is an important feature of intelligence. Machine learning is an important aspect of CAPP intelligence. At home and abroad, many researches have been done on the application of ANN and other artificial intelligence technologies to the automatic acquisition of process knowledge. However, due to limitations of training samples, there are certain limitations. With the wide application of CAPP, companies will accumulate a rich product technology database. Data mining and knowledge discovery technologies will provide new ways to make full use of these companies' valuable wealth to improve the degree of intelligence in CAPP systems.
Obviously, the product-oriented CAPP application provides a solid practical foundation for the development of various effective intelligent on-line aided decision-making functions in various stages, and will also push CAPP's intelligence to a new stage.
Sixth, concluding remarks
Process design is a typical complex problem, which includes analysis, selection, planning, optimization and other various functional requirements of different nature. The scope involved is very wide, the amount of information used is quite large, and the specific production environment and individual The level of experience is closely related. For a long time, research and development of CAPP has neglected the in-depth research and exploration of the basic tasks, methods, and data involved in process preparation activities. It lacks an overall understanding of process business activities and is too limited to certain local links. This has led to difficulties in the development and implementation of specific application systems, and has also led to the lack of application and theoretical foundation for the adoption of new concepts, new technologies and new methods. Therefore, starting from the demand for process work in the entire product life cycle of modern manufacturing, with the future virtual enterprise and networked global manufacturing as background, based on the comprehensive application of CAPP, a process information system integrating process design and management is established. It is an important basis for the informatization of manufacturing companies.