Development of CAD technology for auto panel die

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The development of Auto Panel Die CAD technology i. the development status of Auto Panel Die CAD technology at home and abroad. This research began with the design of automobile body. On this basis, the design method of complex surface has been developed. Major automobile companies have successively established their own cad/cam systems and applied them to mold design and manufacturing. The rapid development of computer software and hardware technology has created conditions for the development and application of mold cad/cam to a higher level

in terms of geometric modeling, the CAD system based on wireframe model was first developed and applied by aircraft and automobile manufacturers. For example: 20% discount for American locsamt members (membership fee: RMB 400/person/year); Lecture teacher: RMB 1300/person; The CAD system, CADD system and AD2000 system of khaad aircraft company, McDonnell Douglas Aircraft Company and general motor automobile company all promote the development of mold CAD technology

Since the 1970s, the technology of surface modeling and solid modeling has developed rapidly. The new generation of CAD software are both solid modeling and surface modeling systems, which can be applied to the design and manufacturing of complex molds and have been widely used in the mold industry. For example, the mold cad/cam part included in the cad/cam system of Ford Automobile Company of the United States replaces manual design and manufacturing. In terms of design, human-computer interaction is used for three-dimensional graphic processing, process analysis and design calculation. The two-dimensional drawing of toothpaste contains a large number of high molecular compound drawings, and production part drawings, material lists, processes, quotas, costs and other documents are generated. The system also includes some professional software, such as the design of process supplementary surface, the analysis of elastic-plastic deformation, the Springback Control and the development of curved part shape, and so on. Some of them have been used in production, and some are still under research and improvement. Japan Toyota automobile company has developed a cad/cam system for automobile panel dies since 1980. This system includes die face software for processing panel die surface and Tinca software for machining convex and concave dies. The data obtained from the measurement of the physical model is sent to the computer by the coordinate measuring machine. After processing, these data are used in the design of automobile panels, mold design and manufacturing. The three-dimensional graphics function of the system is strong, and the surface shape can be modified repeatedly on the screen, so that the workpiece will not produce various process defects during stamping forming, so as to ensure the workpiece quality; Die CAD system developed by diecomp company has shortened the whole production preparation cycle from 18 weeks to 6 weeks

at the same time, some European countries have also made great progress in the research and application of stamping die cad/cam. For example, Renault of France has used Euclid software system as the leading software of cad/cam. At present, 95% of the design workload has been completed with this software, and Renault has also developed many modules suitable for the needs of the automotive industry on the basis of Euclid leading software, Such as megavision for interference inspection and optris for sheet metal forming analysis

at present, many enterprises in China have adopted mold CAD technology, and have gained rich experience and skills in computer automatic programming technology, which has greatly improved mold accuracy and productivity. A batch of drawing software represented by AutoCAD imported from Autodesk company of the United States is gradually popularized in the mold industry, and computer drawing is gradually replacing manual drawing. A number of large and medium-sized domestic enterprises (mainly in the automobile and home appliance industries) have successively introduced a considerable number of CAD systems from abroad and configured some special software for design and analysis, which has achieved obvious economic benefits. However, due to various reasons, many enterprises are still at the stage of manual mold design. Although some units have lost the drawing board and realized no drawing design, a considerable part of their mold CAD work only uses computer aided draft and two-dimensional design. Only a few enterprises' automobile mold design and manufacturing capabilities are close to the international advanced level. In 1989, Chengdu Chengfei automobile mould center successfully designed and manufactured a complete set of external main models of IVECO automobile body by using foreign cad/cam technology, NC machining and NC measurement technology, focusing on digital transmission

in addition, some domestic software with independent copyright, such as the cold stamping die CAD system developed by the national mold CAD Engineering Research Center of Shanghai Jiaotong University, the plastic injection mold cad/cae/cam system hsc2.0 developed by the State Key Laboratory of mold technology of Wuhan Huazhong University of technology, and the cad/cam system CAXA developed by the Huazheng Mold Research Institute of Beijing University of Aeronautics and Astronautics, have solved some problems in production, But it has not been well promoted and used

at present, it takes 48 months for Europe and America to launch a new model, and only 30 months for Japan. China lags behind in the development and design of new automobile models, especially car models. One of the important reasons is the low design efficiency of panel dies. The traditional domestic mold design method can not meet the needs of the development of the automotive industry. The introduction of foreign panel mold products will not only cost a lot of foreign exchange, but also seriously hinder the upgrading of automotive products. To solve these problems, we must research and develop our own die CAD technology. At the same time, it is undoubtedly a necessary and effective means to introduce foreign advanced general modeling software for secondary development

2. technical characteristics of Auto Panel Die CAD

(1) characteristics of auto panel die surface CAD

generally, the forming of auto panel should go through several processes, such as drawing, trimming, shaping, flanging and punching. The first process, that is, the most important part of the drawing process, is the design of the process supplementary surface. The design of process supplementary surface directly affects whether the designed mold can pull out qualified parts, reduce the time of debugging the mold, and shorten the production cycle of the whole mold

2) characteristics of CAD for automobile panel die structure

large die structures are generally complex. A pair of large panel dies have hundreds of parts, and the overall dimensions of the dies are also relatively large. Mold structure design can generally be divided into two kinds: two-dimensional design and three-dimensional design. The two methods have their own advantages and disadvantages

computer two-dimensional design is similar to manual drawing board design and belongs to plane drawing. Its advantages are fast design speed, small computer memory occupation and low requirements for computer hardware configuration. It is a method with small investment and quick results; Its disadvantage is that design errors are not easy to be found, and can not be directly used for analysis and processing. 3D design has many advantages, such as parameterization, feature-based, full correlation, etc., which makes the product easy to modify in the design stage, and also makes concurrent engineering possible. The three-dimensional design is visual and intuitive, and whether the design structure is reasonable is clear at a glance. At the same time, the automatic dimensioning of 3D design reduces human design errors, but there are also some problems in 3D mold design, such as low computing speed of computer, large space of hard disk and memory occupied by software, many projection lines of mold structure, slow design speed, etc

3. the main problems existing in the CAD application of automobile panel die at present

body panels occupy an important position in the whole automobile, and the panel die is the main process equipment for producing panels, which plays a decisive role in the quality of the body. At present, the development of cad/cam technology for automobile panel dies abroad has entered a substantial application stage, which not only comprehensively improves the quality of die design, but also greatly shortens the production cycle of dies. In recent years, China has also made remarkable progress in the application of CAD technology for automobile panel dies, but there are still some problems as follows:

(1) low design efficiency

due to the late start of CAD technology in China, the low level of professionals, and the lack of talents who are familiar with cad/cam application software technology, the development ability is poor, the quality of independently developed CAD software is not high, and the design efficiency is low

(2) low degree of standardization

due to the standards of various industries and enterprises, certain design and manufacturing specifications have not been formed among mold manufacturers, the integration and intelligence of the existing panel die cad/cam system are relatively low

(3) poor specificity of existing CAD software

at present, there are few independently developed CAD software in China, while most foreign advanced software introduced by most manufacturers are general-purpose software, and the specificity is poor without development

(4) the development means of panel stamping die cad/cam technology is relatively backward, the developed cad/cam system is difficult to guarantee in quality and reliability, and the development cycle is long

(5) the man-machine interface of the existing stamping die CAD system can not meet the requirements of many users

(6) CAD is mainly used for two-dimensional design, and most of them stay on the basis of replacing manual drawing with computer drawing

II. The future development trend of automobile panel die CAD

die technology is one of the fastest developing technologies in the manufacturing industry, which is characterized by a large number, a small batch and a very fast generation. Theoretically speaking, it is the field where CAD technology can give full play to its advantages. However, at present, the achievements of mold CAD in China are not very significant, especially in the application of automobile overlay: the great potential of this technology has not been fully brought into play in the application of CAD technology to the experimental cover mold at low temperature. The key to solve this problem is to improve the design efficiency of the mold. At present, there are several trends in the development of mold CAD technology:

1. parametric modeling method of mold CAD is an advanced modeling method in CAD technology, and also an effective means to improve the efficiency of CAD. Aiming at the characteristics that the overall structure of various stamping dies generally has a more standardized form, it establishes the corresponding parameter variables for the basic dimensions of each part, and establishes the relationship between the elements of each part on the basis of the actual geometry and topology. When the die part size changes due to different die structures, change the value of relevant variables in the parameter file, and the corresponding dimension values in the related part model will also change. After being processed by the dimension drive module, the part with the size in line with the actual dimension can be generated

2. intellectualization of die CAD

the difficulty of die design for stamping parts mainly lies in the incompleteness of design theory and the expression and utilization of expert experience that can only be understood but difficult to be explained. Just like manual design, when using general CAD software (including new integrated CAD software) to design panel dies, it must rely on the intervention of die experts to a large extent. In order to realize the automation of mold structure design and reduce the dependence on mold experts, it is necessary to develop a special intelligent software for mold structure design of automobile panel, apply the successful experience of previous design and manufacturing to mold design, form a knowledge base and intelligent base in the computer, and generate an expert system, so that the CAD system can be competent for the work of mold design experts, Design the automobile panel die that meets the requirements, which is the so-called intelligent die CAD

intelligent CAD is based on the cognitive theory of human thinking and integrates the logic

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