On the application and development of CAD technology
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On the application and development of CAD technology
CAD processes digital and graphic information to realize automatic programming software for product design, modeling and NC machining, which has the characteristics of intensive knowledge, strong comprehensive land strength and large initial investment. Its popularization and application will profoundly change the traditional mode of architectural planning and design and mechanical product manufacturing, thus promoting the rapid development of construction industry and mechanical manufacturing technology, which is a frontier topic in the current international science and technology field. As a mature and popular technology, CAD technology has been widely used in enterprises. Starting with the meaning of CAD, this paper briefly introduces several mainstream CAD software at present. This paper mainly introduces the future development trend of CAD technology and the hot issues of CAD technology research.
Keywords: CAD application development
First, the meaning of CAD
CAD is computer aided design. Use computers and their graphics devices to help designers complete the design work. CAD for short. In engineering and product design, computers can help designers undertake tasks such as calculation, information storage and drawing. In design, computers are usually used to calculate, analyze and compare many different schemes to determine the best scheme; All kinds of design information, whether digital, literal or graphic, can be stored in the internal memory or external memory of the computer and can be quickly retrieved; Designers usually start with sketches, and the heavy work of turning sketches into working drawings can be handed over to computers. The design results automatically generated by computer can be quickly displayed graphically, which is convenient for designers to judge and modify the design in time; Computers can be used to process graphic data related to editing, enlarging, reducing, translating and rotating graphics. CAD can reduce the labor of designers, shorten the design cycle and improve the design quality.
1June, 972, international federation for information processing gave the following definition at the "Working Conference on CAD Principles" held in the Netherlands: CAD is a technology, in which people and computers, as a problem-solving group, combine together and cooperate closely to give full play to their respective advantages, thus making their work better than each other's, and providing the possibility for comprehensive cooperation in applying multidisciplinary methods. CAD is a general term for engineers and technicians to design, draw, analyze and write technical documents for products and projects with computers as tools.
CAD technology is an important part of electronic information technology. It is a method and technology that uses computer hardware and software system to assist people to design products or projects, including design activities such as design, drawing, engineering analysis and document making. It is a new discipline that combines the latest development of computer science and engineering design methods. Broadly speaking, CAD technology includes two-dimensional engineering drawing, three-dimensional geometric design, finite element analysis, numerical control processing, simulation, product data management, network database and the integration technology of the above technologies (CAD/CAE/CAM).
At present, CAD technology can realize most of the activities in design, but there are also some activities that are difficult to realize with CAD technology, such as demand analysis and feasibility study of design. The activities that can be realized by CAD technology in the design process are grouped together to form a CAD process. The relationship between the design process and the CAD process is shown in figure 1.
Second, the application scope of CAD
Early CAD is a widely used software. Generally speaking, there are two kinds of CAD design objects: one is mechanical, electrical, electronic, light industry and textile products; The other is engineering design products, that is, engineering buildings, which are referred to as AEC (architecture, engineering and construction) in foreign countries. Nowadays, the application scope of CAD technology has been extended to art, film, animation, advertising, entertainment and other fields, which has produced great economic and social benefits and broad application prospects.
CAD is the earliest and most widely used in machinery manufacturing. Using CAD technology to design products can not only make designers "get rid of drawing boards", update traditional design ideas, realize design automation, reduce product costs and improve the competitiveness of enterprises and their products in the market; It can also change the original serial operation into parallel operation, establish a brand-new design and production technology management system, shorten the product development cycle and improve labor productivity. Nowadays, the world's major aviation, aerospace and automobile manufacturing giants not only widely use CAD/CAM technology for product design, but also invest a lot of manpower, material resources and funds to develop CAD/CAM software, so as to maintain their leading position in technology and advantages in the international market.
Computer aided architectural design is the application of CAD in the field of architecture, which has brought a real revolution to architectural design. With the development of CAAD software from 2D general drawing software to 3D building model software, CAAD technology has been widely used, which can not only improve the design quality, shorten the project cycle, but also save 2% to 5% of the construction investment. In recent years, China's annual capital construction investment has reached hundreds of billions of yuan. If nearly ten thousand engineering design units in China adopt CAD technology, the investment benefit of capital construction can be greatly improved.
CAD technology is also used in textile and clothing industries. In the past, the pattern design, pattern coordination, color transformation, pattern color separation, sketch drawing and color matching of textiles and garments in China were all done by hand, which was slow and inefficient. At present, the requirements of the international market for textiles and garments are small batch, various colors, high quality and fast delivery, which makes China's textile products uncompetitive in the international market. The adoption of CAD technology has greatly accelerated the pace of China textile and garment enterprises entering the international market.
Nowadays, CAD technology has entered people's daily life and played a great role in the fields of movies, animation, advertising, entertainment and so on. CAD technology has been used in film shooting for more than ten years. Hollywood film companies in the United States mainly use CAD technology to construct scenes, and can use virtual reality to design scenes that cannot be completed manually. This can not only save a lot of manpower and material resources, reduce the shooting cost of the film, but also create a strange and unimaginable environment for the audience and get huge box office income. For example, Jurassic Park, Star Wars, ET and other sci-fi films in the United States, as well as Toy Story made entirely by three-dimensional computer animation, have all achieved great success. The blockbuster Titanic, which caused a sensation all over the world, used a large number of three-dimensional animations to simulate the whole process of Tektronix's voyage and shipwreck with computers. In addition, computer modeling technology is fully used in animation and advertising production, and it is also a virtual reality technology in essence. Virtual reality technology is also used for real-time roaming and entertainment games of various simulators and scenes.
In recent ten years, with the advancement of CIMS engineering and CAD application engineering, the application of computer-aided design technology has become more and more common in China, and more and more design units and enterprises have adopted this technology to improve design efficiency, product quality and working conditions. At present, there are dozens of CAD software imported from abroad in China, and some domestic scientific research institutions, universities and software companies have also developed their own CAD software and put it on the market. The application of CAD technology in China presents a thriving scene.
Third, the development history of CAD
The development of CAD technology has gone through four stages.
(A) the formation stage
1950, Massachusetts Institute of Technology developed a graphic display terminal with cathode ray tube (CRT), which realized the screen display of graphics, thus ending the history that computers could only process character data, and based on this, a new discipline-computer graphics was born.
(2) development stage
The light pen appeared in the late 1950s, and the history of interactive painting began.
In the early 1960 s, interactive drawing techniques such as screen menu pointing, function key operation, light pen positioning and graphic dynamic modification appeared one after another. 1962 IvanSutherland, an American, developed the first interactive graphic system-sketchpad. Since then, a large number of commercial CAD software systems have appeared. However, due to the high price of monitors, CAD systems are difficult to popularize. Until the end of 1960s, there was a breakthrough in display technology, the price of display dropped sharply, the cost performance of CAD system improved greatly, and the number of CAD users began to increase by 30% every year.
With the development of display technology, computer graphics has also been greatly developed. Throughout the 1970s, CAD systems based on 2D drawing and 3D wireframe graphics became the mainstream.
(3) Mature stage
The first SolidModeling experimental system was born in 1973, and the first generation of solid modeling software was introduced to the market in 1978. In 1980s and 1990s, solid modeling technology became the mainstream of CAD technology development and matured, and a number of CAD software systems with 3D solid modeling as the core appeared. The development and application of solid modeling technology greatly broadens the application field of CAD technology.
(4) integration stage
People have realized that CAD plays a great role in promoting the design process and manufacturing process. With the demand of design and manufacturing automation, the appearance of integrated CAD system is inevitable. By the 1990s, almost all CAD systems have realized system integration by developing or purchasing support modules by themselves.
Four, the main software of CAD at present
CAD technology has penetrated into every corner of people's daily life from the initial industrial design field, from machinery, electronics, aviation, aerospace, posts and telecommunications, ordnance, textiles, architecture, ships, geology, mining, to art, clothing, medical care, teaching, tourism, management and so on. It can be said that there are countless packages, and various commercial professional software developed based on CAD technology has exceeded 65,438+10,000. The following are the mainstream CAD software on the market at present:
(1)AutoCAD and MDT
AutoCAD system is an interactive drawing software developed by Autodesk Company of the United States for microcomputers. It is basically a two-dimensional engineering drawing software, with strong drawing, editing, drawing section lines and patterns, dimensioning and user-friendly secondary development functions, as well as some three-dimensional drawing and modeling functions. It is the most widely used CAD software in the world. MDT(MechanicalDesktop) is a microcomputer CAD/CAM software based on parametric feature solid modeling and surface modeling, which is introduced by Autodesk Company in mechanical industry.
(2) Specialty/Engineer
Pro/Engineer system is a product of American Parametric Technology Company (PTC for short). As soon as it came out (1988), it was welcomed by users for its advanced parametric design and entity modeling based on feature design. Subsequently, major CAD/CAM companies have also introduced parametric modeling modules based on constraints. In addition, Pro/Engineer is built on the workstation from the beginning, which makes the system independent of hardware and easy to transplant. The user interface of the system is concise and the concept is clear, which conforms to the design ideas and habits of engineers. The whole system of Pro/Engineer is based on a unified database and has a complete and unified model, which can integrate the whole design and production process. It has more than 20 modules for users to choose from. Based on the above reasons, Pro/Engineer has become the most attractive system in the field of three-dimensional mechanical design in recent years, and its sales volume and user base are still developing at the fastest speed.
(3)I-DEASMasterSeries5
I-Deamaster series is a new generation of mechanical design automation software launched by American SDRC (Structural Dynamics Research Company), from 1993. It is also the flagship product of SDRC in the field of CAD/CAE/CAM, which is famous for its high integration, powerful functions, easy learning and easy use. I-Deamaster Series 5 was first exhibited in the United States on June 20th this year. Its biggest breakthrough is the introduction of VGX technology, which greatly improves the intuition and reliability of interactive operation. In addition, this version also enhances the functions of complex part design, advanced surface modeling, finite element modeling and durability analysis. Recently, SDRC has also concentrated its superior strength and strengthened the development of CNC machining functions.
(4)CATIA
CATIA system is a product developed by the engineering department of DassaultSystems, a French aircraft company. The system was developed on the basis of CADAM system (originally developed by Lockheed Company of the United States and later merged into IBM Company of the United States). The source program of the original CADAM system is purchased in CAD, and the source program of the famous APT system is purchased in processing. After several years of efforts, a commercial system has been formed. CATIA system has developed into an integrated CAD/CAE/CAM system, which has a unified user interface, data management and compatible database and application interface, and has more than 20 independent pricing modules.
(5) Euclid
Euclid software is a product of the information department of MATRA company in France. It was developed by the French National Scientific Research Center for the supersonic passenger plane Concorde jointly developed by Britain and France. The software has a unified object-oriented distributed database, and there is no need to convert any data between 3D solid, complex surface, 2D graphics and finite element analysis model. Because the data are mutually referenced, rather than simply copied, when users modify a part of the design, other related data will be updated by themselves.
(6) Unigraphics
UG originated from the products of McDonnell Douglas (MD) Company in the United States, and was merged into the EDS branch of General Motors Company in June of 199 1. Today, EDS is the largest information technology (IT) service company in the world, and UG is developed by its independent subsidiary UnigraphicsSolutions. UG is a mechanical engineering auxiliary system integrating CAD, CAE and CAM, which is suitable for the design, analysis and manufacture of aerospace vehicles, automobiles, general machinery and molds.
(7)SolidWorks
SolidWorks is a Windows-based CAD/CAE/CAM/PDM desktop integrated system, which was developed by SolidWorks Company of the United States on June 1995 1 1, and the price is only a quarter of that of workstation CAD system. The software adopts the top-down design method and can dynamically simulate the assembly process. It adopts feature-based entity modeling, which is called 100% parametric design and 100% modifiability. At the same time, it has both Chinese and English interfaces to select its advanced feature tree structure, which makes the operation simpler and more intuitive.
Five, the development trend of CAD
With the development of computer hardware technology, especially the rapid development of graphics processing equipment, computer aided design/manufacturing (CAD/CAM) technology has developed at an alarming rate. Some experts commented: "If electronic technology is regarded as a revolution in industry, then CAD/CAM is another revolution in industry, and it is an important embodiment of computer's great promotion to human civilization in industry, with unlimited prospects." Focusing on the improvement of innovative design ability of enterprises and the popularization of network computing environment, the development direction of CAD technology mainly focuses on four aspects: standardization, openness, integration and intelligence.
1. Standardization
In addition to the gradual realization of ISO standards and industry standards by CAD supporting software, application-oriented standard parts (parts library) and standardization methods have also become necessary contents in CAD systems, and are developing towards the application direction of rational engineering design. Looking back on history, the formulation of international standards for CAD and computer graphics always lags behind the industrial standards in the market. CAD products are frequently updated. Whoever has the leading technical concept, the best performance, the most users and the dominant market is the de facto industry standard. The development of CAD technology is not a purely academic behavior, it is constantly advancing in the inherent fierce market competition of high-tech products, and it is endless. At present, standards are divided into two categories: first, public standards, mainly from national or international standard-setting units; The other is market standard, or industry standard, which is private. The former pays attention to the openness of standards and the advanced technology adopted, while the latter is market-oriented and pays attention to the consideration of effectiveness and economic benefits. The latter easily leads to monopoly and unnecessary standard war. Many standardization experts have recognized the existing problems by summing up decades of standardization work experience in this field, and put forward relevant views on reforming traditional standardization work.
Step 2 make it public
At present, CAD systems are widely established on the open operating systems Windows 95/98/NT and UNIX platforms, and there are also CAD products on the Java LINUX platform. In addition, CAD system provides a secondary development environment for end users, and even such an environment can develop their own kernel source code, allowing users to customize their own CAD system.
Step 3 synthesize
The integration of CAD technology is reflected in three levels: First, the generalized CAD function CAD/CAE/CAPP/CAM/CAQ/PDM/ERP has become an integrated solution for enterprises through various integration forms, which has promoted the process of enterprise informatization. At present, the integration of innovative design ability (CAD) and modern enterprise management ability (ERP, PDM) has become the focus of enterprise informatization. Secondly, the algorithms that can be used in CAD technology, even functional modules or systems, are made into special chips to improve the efficiency of CAD systems; Thirdly, CAD realizes the integration of heterogeneous systems among enterprises based on network computing environment. Virtual design, virtual manufacturing and virtual enterprise are the applications of this integration level.
Become smart
Design is a highly intelligent field of human creative activities, and intelligent CAD is the inevitable direction of CAD development. Intelligent CAD is not only a simple combination of existing intelligent technology and CAD technology, but also an in-depth study of the thinking mode of human design and its expression and simulation with information technology. This will not only produce an efficient CAD system, but also provide new theories and methods for artificial intelligence. This development trend of CAD will have a far-reaching impact on the development of information science.
Research and development hotspot of intransitive verb CAD technology
1. computer-aided conceptual design
According to relevant statistics, 70% of the product cost is decided in the product design stage. At the same time, once the conceptual design is determined, 60%-70% of the product design will be determined. In particular, no matter how good the detailed design is, it is difficult to make up for the defects in the conceptual design stage. In addition, product innovation and its competitiveness are basically determined in the conceptual design stage. Therefore, conceptual design is a very important stage in the design process and has become the commanding height of enterprise competition. Therefore, computer-aided conceptual design has been paid more and more attention. On the other hand, in the process of conceptual design, all kinds of knowledge about design requirements and constraints are often inaccurate, approximate or unknown, which means high complexity and brings great difficulties to CAD technology. The process of conceptual design is mainly a process of evaluation and decision-making, which involves factors such as product function, action and structure, and plays a decisive role in product cost performance, reliability and safety. It is precisely because there are many factors and goals to consider. Therefore, the evaluation and decision-making process is a very complicated and difficult process. At present, the methods of computer aided conceptual design can be divided into two categories: automatic generation scheme and interactive generation scheme. Of course, these two methods can be mixed in application.
At present, the automatic generation scheme of (1) mainly adopts artificial intelligence technology. In order to make computers effectively support conceptual design activities, two main problems need to be solved. That is, modeling problem and reasoning problem: A. The former is to model or express the complex relationship between the function, action and structure of the product. For example, the steam valve of a boiler is designed to prevent the boiler from exploding. Its function is to automatically open when a certain pressure difference is detected. Its structure is the layout of the actually used components and their connection relations, and the modeling results provide reasoning. B. The problem of reasoning is actually to generate and choose a suitable scheme.
The modeling problem is mainly the representation of modeling, and various representations have been put forward at present. Such as language, geometric models, graphics, objects, knowledge models and image methods. Language representation is a formal description method, which can ensure the computer to carry out reasoning effectively, and is called machine-oriented representation. Image representation is a highly visual representation (that is, visual thinking model), which focuses on providing a modeling environment that helps designers to innovate. It is called human-oriented representation, and the other representations listed above are in between.
The key point of reasoning problem is the transformation process, that is, mapping the user's requirements to some actual structures to realize a given set of requirements. The difficulty lies in generating and selecting the appropriate mapping method. For example, knowledge acquisition is a big problem in the field of artificial intelligence. In order to solve this problem, data mining technology can be used to automatically obtain the domain knowledge of interest from the existing design library.
(2) Generating a scheme through interactive technology Because of the complexity of conceptual design, it is very difficult to automatically generate a suitable scheme. Interactive technology is an important means before automatic generation and comparison schemes are mature. In the conceptual design stage, we can make full use of multimedia technology, such as effective information search technology, in order to find a large number of useful design examples on the Internet. Another example is to study collaborative conceptual design technology, so that group members can easily participate in conceptual design and make positive contributions.
2. Computer-supported collaborative design
Design work is a typical team work. Team members have both division of labor and cooperation. Therefore, group work consists of two parts: one is individual work, that is, group members have to complete their respective tasks of division of labor; The other is cooperative work, because group work cannot be decomposed into independent individual work, and there are interrelated problems among group members. Generally called interface problem, interface will inevitably appear contradictions and conflicts. If it is not found and solved in time, it will cause rework and loss. The traditional CAD system only supports the specific tasks that should be completed after division of labor. As for the interface between members, computers can't support it, and they mainly rely on interviews or some communication tools to discuss and solve it. However, these methods are difficult to negotiate and discuss in time and fully. Therefore, a big design task interface problem is bound to make mistakes, which is also the main reason why the design work will be revised repeatedly.
3. Storage, management and retrieval of massive information
More and more information is processed by CAD system, and it is multimedia information. Although the disk capacity is growing rapidly, it is still far from meeting the demand of rapid information growth. The storage, management and quick retrieval of massive information has become a worldwide concern. Besides relying on hardware to solve problems, DBMS is an important technology. Practice has proved that the traditional relational database management system EDBMS can no longer meet the requirements, and adopting the model of combining object-oriented and relationship may be a transitional solution.
4. Research on design methods and related issues.
Design is a complex and knowledge-intensive group activity. In order to improve efficiency, we must follow the correct design method. Although the research of design methodology has been more than half a century, the CAD-oriented design method is relatively new, which is called formal design flow method. It not only lets us know that design is a process, but also provides a basis for developing CAD tools. Therefore, understanding and identifying different aspects of the design process (that is, different design activities) is the key to developing a new generation of CAD systems.
5. Support design innovation
Innovation is the soul of product design. How to use computers to support innovation is a new topic. At present, we can only provide an enlightening method, such as storing a large number of multimedia design materials to facilitate designers to query through the network, which may produce unexpected innovative designs. Another example is to use CSCW tools to inspire each other through direct discussion, generate new design ideas and promote innovative design.
6. Intelligent and humanized user interface
The user interface of CAD system is the medium and dialogue interface for exchanging information between people and computers, and it is also an important part of CAD software system. User-centered, natural and efficient multi-channel interaction technology and ubiquitous computing is a long-term goal, and it is also a research hotspot of human-computer interaction at present. Using user-centered CAD software design method, product development and actual engineering evaluation are carried out to ensure the healthy development of CAD software technology and CAD software industry. Innovation has been made in improving software interface, simplifying operation steps and reducing operation difficulty.
7. Modeling technology
Realize the modeling method that has nothing to do with history, that is, the shape of product model no longer depends on the order of feature creation, which makes the 3D CAD system easier to operate and use. Fully support conceptual design and detailed design; Geometric modeling system can create arbitrary geometric shapes; It can better express the complete technical and production management information of products, support the feature modeling system of product life cycle, make product design work at a higher level, and lay the foundation for developing a new generation of CIMS integrated system based on unified product information model: it has the comprehensive ability of line segment, surface and solid mixed modeling and the function of three-dimensional dimensioning; Support the modeling function based on three-dimensional pixels to solve the assembly problem of large and complex products.
8. Enjoy product data * * *
Solve the problem that users in some mainstream CAD systems can open models from other CAD systems, share and exchange graphic data in different CAD systems, so that they can communicate with each other and achieve * * *, and try to avoid possible problems such as graphic distortion, loss of feature and constraint information during interaction. Product model data exchange standard. . STEP "will be used to solve the above problems with the help of 3D CAD graphics standards. For example, by combining the functions of Surfacer with UG and Pro/E, points and lines are processed in specific operations to obtain basic control curves, and then the data of control lines are introduced into surface modeling by UG and Pro/E.. Among them, Pro/E application modules mainly include Icemsurf, Pro/Designer (CDRS), and UG module mainly includes UG/ modeling and UG/ surface module. These design modules are often used in general CAD design. It should be noted that not all points have to be selected in the design process. Therefore, when determining the control curve of datum plane, it is necessary to find out which points or lines are available and which points or lines are some detailed features, which need to be used in the future design, rather than reflecting meters in the overall design. In fact, some features, such as cylinders and bosses, are generated by measuring the solid model and combining the scanned data after the overall outline is determined. At the same time, try to select some points or lines with good scanning quality for fitting.
Seven. Concluding remarks
The development of CAD technology develops with the demand of practical application. With the wide application of CAD technology, new demands are constantly emerging. In the future, the hotspot of CAD technology will further develop into integration and intelligence, so it will play an increasingly important role in various fields such as architectural planning and design and mechanical design.
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