When did cad originate?

In the modern machinery manufacturing industry, the mold industry has become the basic industry in the national economy. The development and production of many new products depend on the mold manufacturing technology to a great extent, especially in automobile, light industry, electronics, aerospace and other industries. The strength of mold manufacturing ability and the level of mold manufacturing have become one of the important symbols to measure the technical level of a country's machinery manufacturing, which directly affects the development of many departments in the national economy. Mold CAD/CAM is developed on the basis of the separate development of mold CAD and mold CAM, which is a new leap in the comprehensive application of computer technology in mold production. The rapid development of CAD/CAM technology and the further improvement of software and hardware level have provided strong technical support for the mold industry, brought a qualitative leap to the development of product design, manufacturing and production level of enterprises, and become the best choice for information, integration and networking of modern enterprises.

1 Features and applications of popular CAD/CAM software in China.

1. 1 foreign software

1. 1. 1 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. UG is a CAD/CAM/CAE mechanical engineering auxiliary system developed by its independent subsidiary UnigraphicsSolutions, which is suitable for design, analysis and manufacturing engineering in aviation, aerospace, automobiles, general machinery, molds and other fields. UG combines excellent parameterization and variant technology with traditional solid, wireframe and surface functions, and also provides secondary development tools such as GRIP, UFUNG and ITK, allowing users to expand the functions of UG.

1. 1.2 AutoCAD

AutoCAD is a drawing software developed by Autodesk Company in the United States, which has interactive and powerful two-dimensional functions, such as two-dimensional drawing, editing, drawing section lines and patterns, dimensioning and secondary development, and some three-dimensional functions. AutoCAD software is the most widely used CAD software in the world at present, accounting for about 37% of the whole CAD/CAE/CAM software market, and has an absolute advantage in the 2D drawing CAD software market in China.

1. 1.3 MDT (mechanical desktop)

MDT is a CAD/CAM software of Autodesk Company based on parametric feature solid modeling and surface modeling. Based on 3D design, MDT integrates design, analysis, manufacturing and document management to provide users with an integrated solution from design to manufacturing. It is said that more than 20,000 sets have been installed and nearly 1,000 sets have been sold in China.

1. 1.4 SolidWorks

SolidWorks is a full parametric feature modeling software based on Windows platform, which was developed by SolidWorks Company of the United States in June 1995 1 1. SolidWorks is a software system which is widely used by users all over the world and full of technological innovation, and has become the standard of three-dimensional mechanical design software. It can easily realize solid modeling, complex assembly and engineering drawing generation of complex three-dimensional parts. The graphical interface is friendly and easy for users to learn and use. SolidWorks software was officially introduced to China by Shengxin International Co., Ltd. in August 1996, and it has been widely used in machinery industry. At present, its users have expanded to more than 300 thousand units.

1. 1.5 Specialty/Engineer

Pro/Engineer is a product of American Parametric Technology Company (PTC for short), and 1988 came out. Pro/E has the characteristics of advanced parametric design, solid modeling based on feature design and easy transplantation of design ideas. The user interface of the software is friendly and conforms to the mechanical design idea of engineers and technicians. The whole system of Pro/Engineer is based on a unified and complete database and complete and diverse models. Because it has more than 20 modules for users to choose from, it can integrate the whole design and production process. In recent years, Pro/E has become the most attractive software in the field of 3D mechanical design, and has been widely used in China Mould Factory.

1.2 domestic software

1.2. 1 PICAD

PICAD system and series software are CAD software with independent intellectual property rights jointly developed by Case Software Group of China Academy of Sciences and Beijing Case Bohong Application Engineering Company. The software is intelligent, parameterized and open, and can automatically capture and dynamically navigate feature points and coordinates. The system provides local graphics parameterization, parameterized pixel assembly and extensible parameter symbol library; Provide an open secondary development tool in an interactive environment, and users can add functions or develop professional application software at will. PICAD is the earliest commercial CAD support platform and the largest interactive engineering drawing system in China. Since the advent of 199 1 the first commercial 2D CAD system in China, users of PICAD have spread all over industries and provinces and cities, and the installed capacity has exceeded tens of thousands.

1.2.2 Gao Hua CAD

Gaohua CAD software includes mechanical design and drawing system GHMDS, computer-aided drawing support system GHDrafting, process planning system GHCAPP, product data management system GHPDMS, three-dimensional geometric modeling system GHGEMS and automatic numerical control programming system GHCAM. Among them, GHMDS is a CAD/CAE/CAM integrated system based on parametric design, which has functional modules such as full navigation, graphic drawing, list processing, full constraint parametric design, parametric pixel assembly, dimension marking, standard parts library and image editing.

1.2.3 CAXA

CAXA electronic drawing board is an efficient, convenient and intelligent general Chinese design and drawing software, which can help designers design part drawings, assembly drawings, process drawings, plane packaging and so on. It is suitable for all occasions that need two-dimensional drawing, so that designers can concentrate on design ideas and get rid of drawing boards completely to meet the design needs of related industries.

CAXA-ME is a set of NC programming and 3D machining software, which has powerful modeling function and can quickly build various complex 3D models. It provides an integrated solution for NC machining industry from modeling, design to machining code generation, machining simulation and code verification. CAXA Injection Mold Design (CAXA-IMD) is a set of Chinese professional CAD software for injection molds, which provides the standard mold base and parts library of injection molds, as well as the database of design parameters such as plastics, mold materials and injection molding machines, and can be queried and retrieved at any time. And can automatically convert the cavity size and make various calculations for the mold. Using this software, designers can easily design molds without looking through the design manual.

1.2.4 GS-CAD98

GS-CAD98 is a feature-based parametric modeling system software developed by Zhejiang Datian Electronic Information Engineering Co., Ltd. It is a three-dimensional CAD system with completely independent intellectual property rights based on Chinese Windows95/NT platform. The software is developed on the basis of the national key research in the Seventh Five-Year Plan and the development results of 863/CIMS theme target products, and draws lessons from the user interface style and main functions of SolidWorks. Including solid, sketch, parametric feature modeling and advanced surface modeling technology, using adaptive parameter correlation technology to ensure the consistency of all links from design to manufacturing.

1.2.5 honeysuckle system (Lonicera)

Honeysuckle system is a CAD/CAM system based on STEP standard developed by Guangzhou Di Hong Technology Co., Ltd.. This system is the latest research achievement of the "Ninth Five-Year Plan" 863/CIMS project of the State Science and Technology Commission. This is a CAD/CAM system based on STEP standard. This software is mainly used for the design and manufacture of mechanical products. It can realize the integration and automation of design/manufacturing. The software adopts object-oriented technology, advanced entity modeling, parametric feature modeling, two-dimensional and three-dimensional integration and SDAI standard data access interface technology; Have the functions of mechanical product design, process planning and design and automatic generation of NC machining program; At the same time, it also has a variety of standard data interfaces, such as STEP and DXF. Support product data management. At present, the series products of honeysuckle system include: mechanical design platform MDA, numerical control programming system NCP, product data management PDS and process design tool MPP. MDA 1.7 version of mechanical design platform has been listed, and MDA99 version has also been released, with the goal of issuing a strong challenge to foreign 3D CAD software.

1.2.6 Mu Kai CAD

Mu Kai CAD is a CAD and drawing management software with independent intellectual property rights developed by School of Mechanical Engineering, Huazhong University of Science and Technology, which is oriented to practical engineering applications. Mu Kai CAD follows the principle of descriptive geometry in design idea, directly imitates the thinking mode and drawing method of engineers and technicians when drawing by hand, and supports the dimension analysis and driving module driven by full constraint, over constraint and under constraint to meet the various needs of users. Support the block and layer functions of AUTOCAD to ensure full compatibility with AUTOCAD; It has powerful and flexible functions of parts labeling and parts list design, and it is more handy to customize the size style, parts labeling style, online and intelligent navigation tools flexibly.

2 Secondary development of current CAD/CAM software

As mentioned above, many commercial CAD/CAM systems have been widely used in the mold industry. However, because these CAD/CAM systems are designed as general mechanical design and manufacturing software, they are not specially designed for molds. In order to improve the efficiency and accuracy of mold design, they need to be redeveloped. In the aspect of developing CAD/CAM software on microcomputer platform, the starting point in China is similar to that in foreign countries, and software development is carried out by using tools such as VisualC++ or OpenGL. On this basis, many domestic universities, software companies and enterprises have developed advanced CAD/CAM software or modules with their own characteristics and in line with the habits of China users, and some of the achievements have been popularized [7]. For example, Huazhong University of Science and Technology introduced the HSC2.0 injection mold CAD/CAE/CAM integrated system in 1997. The system is based on AutoCAD software package, including mold structure design subsystem, structure and process parameter calculation and checking subsystem, and plastic flow and cooling subsystem. 3-D parametric injection mold system IPMCADV4.0 based on AutoCAD and MDT in Hefei University of Technology. In addition, many scientific research units and enterprises have also developed many plug-ins and modules for specific applications. For example, Wuhan University of Automobile Technology has developed a 3D standard parts library based on SolidWorks and 3DPARTLIB.

Three principles to be followed in the development of mould CAD/CAM software

1) User-friendly software is developed for application, so whether users can master it easily becomes the basic standard for evaluating software. A friendly user interface should include: easy to use, familiar interface, flexible tips and help information, good interactivity and good error handling.

2) Follow the method of software engineering. Software engineering is an engineering science that guides the development and maintenance of computer software. That is, the concepts, principles, technologies and methods of engineering are adopted to develop and maintain software. In software engineering, the life cycle method is used to time warp the development and maintenance of software, and the software life cycle is divided into several stages and developed in stages.

3) Parametric CAD For products with high serialization, generalization and standardization, the mathematical model and product structure adopted in product design are fixed. The difference is only the difference in structural size, which is caused by the different values of the same quantity and type of known conditions in product design of different specifications. For this kind of products, the known conditions and other basic parameters changing with product specifications can be replaced by corresponding variables, and then according to these known conditions and basic parameters, the computer can automatically query the graphics database, or the corresponding software can calculate all the data needed for drawing, and the special drawing generation software can automatically design the graphics on the screen. This method is called parametric CAD.

4) Group CAD Although the product structure of many enterprises is different, they are all similar. According to the similarity of product structure and manufacturability, the parts are divided into a limited number of parts libraries by group technology, and the corresponding CAD general software is compiled according to the structural characteristics of all parts in the same part family for the design of all parts in the family. This is called "group CAD".

5) Some work in intelligent CAD engineering design is non-computational and needs reasoning and judgment, including process decision of design process content and technical decision of specific design. Therefore, the design efficiency and quality depend on the designer's practical experience, creative thinking and sense of responsibility. Using expert system can guide designers to do what to do next, existing problems, propose solutions and recommend solutions, or simulate human wisdom and propose reasonable solutions according to problems. Using expert system can improve the design quality and efficiency. Intelligent CAD is a combination of expert system and CAD technology.

4 mold CAD/CAM technology development trend

The basic characteristics of mold manufacturing industry in 2 1 century are high integration, intelligence, flexibility and networking. The goal is to improve product quality and production efficiency, shorten design cycle and manufacturing cycle, reduce production cost, maximize the adaptability of mold manufacturing industry and meet the needs of users. Specific performance for the following characteristics.

1) standardized CAD/CAM system can establish standard parts library, non-standard parts library and mold parameter library. Parts in standard parts library can be called at any time in CAD design and produced by GT (Group Technology). Although the parts stored in the non-standard parts library are not the same as the structures needed for design, they can be easily modified by using the system's own modeling technology, thus speeding up the design process. The typical mold structure library is realized on the basis of parametric design, and similar mold structures can be modified according to the requirements of users to generate the required structures.

2) Integration technology Modern mold design and manufacturing system should not only emphasize the integration of information, but also emphasize the integration of technology, people and management. The concept of "multi-integration", that is, information integration, intelligent integration, series-parallel working mechanism integration and personnel integration, is emphasized when developing mold manufacturing system, which is more suitable for the needs of future manufacturing systems.

3) Intelligent technology The application of artificial intelligence technology realizes the intelligence of all links in the product life cycle (including product design, manufacturing and use), the intelligence of all links in the production process (including organization, management, planning, scheduling and control) and the intelligence of mold equipment, and also realizes the integration of people and systems and the full play of people's intelligence.

4) Network technology applies network technology, including the integration of hardware and software, various communication protocols and manufacturing automation protocols, information communication interfaces, system operation control strategies, etc. , which is the basis of realizing the automation of various manufacturing systems. At present, there have been successful examples of cross-border mold design through the Internet.

5) Multidisciplinary and multifunctional integrated product design technology The future product development and design not only uses the theory and knowledge of mechanical science, but also uses the knowledge of electromagnetism, optics and control theory. In product development, multi-objective and full-performance optimization design should be carried out in order to pursue the best combination of dynamic and static characteristics, efficiency, accuracy, service life, reliability, manufacturing cost and manufacturing cycle of mold products.

6) Application of reverse engineering technology In many cases, some products do not come from design concepts, but from other products or objects. In order to manufacture products, it is necessary to design and manufacture molds only with product prototypes or physical models without product drawings. At this time, it is necessary to measure the physical object, and then use the measured data to reconstruct the CAD geometric model of the physical object. This process is called RE (Reverse Engineering). Reverse engineering can shorten the cycle from design to manufacturing, and it is a powerful tool to help designers realize modern design concepts such as concurrent engineering. At present, it is widely used in engineering.

7) Rapid Prototyping Technology Rapid Prototyping &&; Manufacturing) is based on the principle of layered manufacturing, regardless of the geometric complexity of parts, to quickly produce product prototypes, especially in the manufacturing of products with complex surfaces. Not only can the prototype for design evaluation, assembly verification and function test be manufactured quickly, but also the product mold (such as electrode for EDM, casting mold as mold core, etc.) can be manufactured quickly and economically through shape replication. ), thus avoiding the time-consuming and high-cost NC machining of traditional mold manufacturing, so RPM technology plays an increasingly important role in mold manufacturing.

5 main shortcomings of CAD/CAM technology

There are still many shortcomings in the application of mold CAD/CAM technology in China, such as:

1) Many enterprises' understanding of CAD only stays in the drawing stage, so that the benefits generated by CAD have not been fully exerted.

2) 2) The application personnel of CAD/CAM software are uneven, so it is impossible to make efficient application of CAD software.

3) The imported mould CAD/CAM technology tends to be blind.

4) The secondary development of imported mold CAD/CAM system can't keep up, which leads to the low efficiency of imported software.

5) The domestic mold CAD/CAM technology level is still in the transition period of high-tech integration and industrialization and commercialization, and the commercialization degree of the self-developed mold CAD/CAM system is not high enough, and its function and stability are still far from those of foreign advanced software.

6 conclusion

After decades of development, China's mold CAD/CAM has made great progress, and mold CAD/CAM technology has been widely used in Chinese enterprises. The development level of mold CAD/CAM software in China is gradually approaching the advanced level abroad. With the strong support of the government, a number of advanced mold CAD/CAM demonstration enterprises have emerged, and universities and enterprises have also trained a large number of mold CAD/CAM software development and application talents. But generally speaking, China's current mold CAD/CAM software has a big gap with developed countries in product development level, commercialization and marketization. The technical level of mold CAD/CAM is still in the transition period from high-tech integration to industrialization and commercialization. The developed software still lags behind developed countries in reliability and stability. At present, there is no targeted software, but generally general software. But we should not only see our own disadvantages clearly, but also see our own advantages. Compared with foreign software, our advantages are: understanding the domestic market, convenient to provide technical support, relatively cheap and so on. In addition, we have the strong support of the government, and major universities have also trained a large number of talents for the development of CAD software. Under these preconditions, China's mold CAD/CAM industry should not only keep up with the trend of the times, the latest international trends, and abide by various international norms to form its own unique advantages, but also develop its own unique CAD/CAM software based on domestic conditions and facing the needs of domestic economic construction.