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Research on the Key Technology of virtual Assembly in Automobile Panel Mould manufacturing - Dr. Jianxun Lu


Abstract: A set of product-based digital virtual assembly process specification is proposed to solve the difference between virtual assembly based on CAD model and actual assembly. The key links affecting the final results in the whole virtual assembly process specification are mainly studied. Based on the actual parts data, a set of guiding adjustment and assembly specifications are developed. Make the assembly more convenient, cost and precision to achieve an optimization.

Key words: dimension engineering virtual reality assembly sheet metal measuring specification

1. Dimensional engineering is a systematic and emerging engineering field.

A new system for standardizing and systematizing this kind of work is extracted from the traditional working methods in each 3-process manufacturing field. It aims to meet the quality requirements of customers. The core of automotive dimensional engineering is the dimensional precision of body assembly. Body size and common difference system were optimized from the aspects of body shape, structure, process, manufacturing, testing and management. According to the functional requirements of the product, the design department can design CAD model, and virtual assembly software can be used for virtual assembly.

2.1 Virtual Design Technology for Products (VDT)

Product virtual design technology (VirtualD esignT echnology) is based on the principle, structure and performance of the digital product model to design the product on the computer, simulate a variety of manufacturing schemes, analyze the structural performance and assembly of the product, in order to obtain the product design evaluation and performance prediction results. So as to optimize product design and process design, reduce the possible problems in the manufacturing process, to achieve the purpose of reducing costs and shortening the production cycle.

2.2 Virtual Manufacturing Technology (VMT)

Product virtual manufacturing technology (VirtualM manufacturing technology) is the use of computer simulation technology, according to the enterprise's existing resources, environment, production capacity and other parts of the processing method, process order, tooling and process parameters to select, on the computer to establish a virtual model, The simulation analysis of the processing technology, the assembly technology, the coordination between the fitting parts, the connectivity between the connecting parts, the movement of the moving components and so on. Through analysis, defects in processing and problems in assembly can be found in advance, so as to modify the manufacturing process until the whole manufacturing process is completely reasonable, so as to achieve the purpose of optimization. The virtual manufacturing technology of products mainly includes material hot working process simulation, assembly process simulation, sheet metal forming simulation, processing process simulation, mold manufacturing simulation, product trial imitation and so on.

2.3 Virtual Manufacturing System (VMS)

Virtual manufacturing system (VirtualM anufacturingS system) is to introduce the simulation technology into the NUMERICAL control model to provide a virtual environment to simulate the actual production process, that is, machine control model is used for simulation, so that enterprises can optimize the control of the manufacturing process on the basis of considering the workshop control behavior. With the advent of the network era, virtual manufacturing technology has been rapidly developed, and the research field is also more and more wide. In addition to virtual manufacturing itself contains information about the theoretical system of virtual manufacturing, design and production process of 3 d visualization and virtual environment system global optimal decision theory and technology, the open architecture of virtual manufacturing system, virtual product assembly simulation, virtual environment and human-machine collaborative, etc in the process of virtual manufacturing, At present, experts are investing a lot of time and energy in the research of virtual manufacturing technology integration system and related software development. A virtual environment VEDAM system for design and manufacturing has been developed by Washington State University in THE CAD/CAM system of PTC Pro/ Enginee:, which includes machining equipment modeling environment, virtual design environment, virtual manufacturing environment and virtual assembly environment. Using the Internet, expert system development tools, HTML/VRML and database systems, Lee and Noh et al at the National University of Singapore developed a virtual manufacturing prototype system as a test bed for engineering and production activities. Driven by the huge application demand, foreign software companies have launched a batch of software supporting virtual manufacturing, such as Deneb, Multigen, dVISE, World-Toolkit and EA1. Virtual manufacturing technology is a multi-discipline and multi-technology synthesis, its related technical support includes simulation technology, modeling technology, computer graphics, visualization technology, multimedia technology, virtual reality technology, etc. The integration and application of these technologies is the focus of current research.

The application of virtual manufacturing in automobile panel mould

The development of automobile cover parts mold is restricted by reliability, aesthetics, economy, manufacturability and maintainability. In the traditional development process of automobile cover parts mold, when the mold design and manufacturing is completed, it needs to go through repeated debugging and modification to get satisfactory automobile parts. In the debugging process, some forming defects, such as cracking, wrinkling, springback, Angle, etc., mainly rely on the experience of the mold bench engineer, through the cycle process of trying the mold, repairing the mold, and then trying the mold, and then repairing the mold to solve. This method not only reduces the production efficiency, but also produces the mold accuracy often can not meet the expected requirements, but also will lengthen the mold development cycle. Virtual manufacturing technology can greatly shorten this cycle. Because in the virtual reality environment, the design and manufacture of cars do not need to build a physical model, engineers can take advantage of the visualization of virtual "natural" environment, the structural analysis of automobile mold, virtual design, component assembly and performance optimization integration in the computer virtual manufacturing system. Based on the comprehensive consideration of the overall layout of the appearance of the automobile body parts and the interaction between the parts and other factors, the interactive rapid modeling and simulation analysis of the geometric size, technical performance, production and manufacturing of the mold, so as to avoid repeated mold repair, to ensure the accuracy of the mold requirements; And because the generated simulation model can be directly manipulated and modified, data can be used repeatedly, thus greatly shorten the cycle of die development cS-I21 virtual manufacturing technology and rapid prototyping technology, reverse design, reverse engineering, knowledge-based engineering design and other technologies have very good advantages. Because virtual manufacturing technology has a unique virtual design and manufacturing environment, can make the mould completely the entire development process in the "real" virtual environment, in terms of the performance of the desired quality for physical after manufacturing, to produce the mould one-time meet user requirements, greatly reduces the mold rejection rate, reduce the cost of development of the enterprise.

3.1 Development process of virtual manufacturing of automobile panel die

The virtual manufacturing development process of automobile cover parts mold is shown in Figure 1. Firstly, it starts from product demand analysis, then carries out conceptual design, and then from optimization design to system integration. By using relevant development software, the virtual model of the product is constructed in the virtual environment. This is a gradual process, based on the development of the product requirements, adopt the corresponding simulation analysis tools for virtual model of function and performance simulation analysis, simulation analysis was carried out on the behavior of the virtual model, and based on the results of the simulation analysis, through repeated modeling to simulation analysis to model improvements, until the virtual manufacturing of mould meet the expected design goal, We just started making the F1s7. The automobile cover parts mold has passed the virtual "actual environment" test before the life. The difficulties and unreasonable design that may be encountered in the actual manufacturing are all tested out, and then the design staff can modify or redesign until the whole manufacturing process can be completely reasonable and smooth. This can not only shorten the product research and development cycle, reduce the research and development costs of enterprises, but also improve the quality of products.

3.2 Key technologies in the virtual manufacturing of automobile panel die

In the virtual manufacturing process of automobile cover parts mold, there are many related technologies involved. The application of any technology will affect the final quality of the mold, which is also one of the reasons for the slow progress of the application of virtual manufacturing technology. Only if each technology is well mastered and applied, the virtual manufactured products can reach an agreement with the actual manufactured products, so as to reduce the development cost, shorten the development cycle and improve the quality of the mold. Among them, the more difficult but very critical techniques are:

(1) The establishment of a mathematical model to establish a simple and can reflect the dynamic manufacturing process of the mathematical model is the key to the application of virtual manufacturing technology in the automobile panel die. The mathematical model is not reasonable, then the virtual environment simulation of the manufacturing process will be different from the actual manufacturing process, can not play the role of optimizing the mold design, so as to shorten the development cycle and reduce the development cost. Therefore, a reasonable mathematical model must be established when using virtual manufacturing technology to develop automobile panel die. In the establishment of the mathematical model, we should carefully analyze the characteristics of the automobile cover parts die, according to the die function and manufacturing requirements, find out the main factors, and put forward reasonable assumptions. The established model must be able to reflect all the functions and manufacturing relations of the die, including the change of the force on the die surface and the change of the force shape of the stamping parts, so as to simulate the actual production relations, to predict the possible problems in production, to achieve the purpose of optimized design and manufacturing.

(2) System integration and scheme evaluation are the basis of the preliminary work in automobile die virtual manufacturing. System integration is an optimized comprehensive design, which needs a lot of technical support, including computer software, hardware, operating system technology, database technology, network information, etc. It needs to consider the relationship between subsystems from the global point of view, and study the interface relationship between subsystems. System integration to achieve the goal of optimal overall performance, that is, all components and components together after not only can work, and the whole system is low cost, high efficiency, symmetrical performance, extensible and maintainable system. But for the general enterprise, the purchase of complete simulation analysis of the software system is a high cost of investment, and there is no professional personnel is unable to make these software play the role of the most vividly.

Under the good simulated environment provided by computer virtual manufacturing system, the staff can evaluate and modify the virtual model. At this stage, the manufacturing process of the mold can be simulated to solve the feasibility and difficulty of each component manufacturing; The assembly process of the mold can be simulated to solve the connectivity and equipment between the components and the degree of difficulty in operation; Virtual testing can be carried out to verify the production capacity and production quality of the mold through testing. Evaluate the implementation difficulty, cost and time of each scheme among various schemes, and select the optimal production scheme which is most suitable for production conditions.

(3) Concurrent engineering is a systematic method to design products, components and related processes in an integrated and parallel way. This method requires the product developers to work together with other personnel, at the beginning of the design from the formation of the concept of the product to the disposal of all factors in the whole life cycle of the product, including quality, cost, schedule and user requirements. Concurrent engineering emphasizes that all the work of all staff should be carried out at the same time, and emphasizes the team work spirit. Therefore, everyone in the work chain has the right to review the designed products, and strive to make the designed products more convenient for processing, assembly and maintenance, with lower manufacturing cost and shorter manufacturing cycle. Auto mould virtual manufacturing engineering in the initial stage must also starting from the overall structure and function of auto mould, consider a virtual model between the parts of mutual connection and interaction relations, see them as an organic whole, implement internal data and resources sharing, to make the mould production meet the desired effect. Auto mould virtual manufacturing process, each part of the work are conducted by different personnel in parallel, but the function of each part activities and there are a lot of interdependent relationship, to ensure that each part of the staff work together smoothly between, group activities in the distributed environment can achieve information exchange and sharing, we must to carry on the dynamic adjustment and control, the design process The key to shorten the development cycle of virtual manufacturing die is to provide the working environment of concurrent design and ensure the smooth progress of concurrent design. The condition of concurrent engineering implementation is to have a computer network system and monitoring and mediation personnel to support the concurrent work of all aspects of personnel, even the remote work, so that information can be communicated between designers in real time and online, and conflicts can be found and mediated. A proper management mediator is an important software in concurrent engineering, and it is also the key for concurrent engineering to proceed smoothly.

(4) Simulation analysis and data processing is a difficult point in the virtual manufacturing of automobile die, and also an important factor hindering the large-scale use of virtual manufacturing technology in enterprises. Simulation analysis needs various technical support, data processing needs a huge database and professionals with professional knowledge, need to consider the relationship between subsystems from the global point of view, study the interface between subsystems. This technology requires the cooperation of professional simulation software in many fields, and requires the joint research and discussion of professionals. However, most enterprises are difficult to complete the required simulation analysis software and have the required professional personnel.

Toyota Motor Has successfully developed the New Toyota AVALON model using virtual manufacturing technology. Because in the early stage of production can predict the production of possible problems, so that the staff earlier to find and solve the problem, in the early stage of design to get more information, so as to reduce the development risk of the enterprise. Over the entire development process, the Toyota AVALON reduced development cycles by 10 months, reduced developers by 20%, reduced production samples by 70%, and reduced development costs by 35%; And the quality of cars produced has improved significantly. It can be seen that virtual manufacturing technology can not only shorten the product development cycle and reduce the development cost of enterprises, but also improve the product quality and the success rate of r&d.

4. Current development of virtual manufacturing

It has been more than 20 years since the virtual manufacturing was proposed, and its technology has been greatly developed and its application has been widely expanded. In foreign countries, there are many schools, research institutes, research units, large enterprises and so on are constantly researching and applying virtual manufacturing technology. In recent years, virtual reality technology has been widely applied in automobile development, and has initially formed a relatively complete application system integrating professional theory, engineering design, scientific experiment and so on. For example, the 1995 REPORT of the American Institute of Standards and Technology, "The Conceptual Design Plan for the National Advanced Manufacturing Laboratory", emphasizes the concept of decentralized, multi-node decentralized virtual manufacturing (DVM), or virtual enterprise; The National Research Council's report, "Information Technology in Manufacturing," addresses information technology issues such as product integration, process design, shop floor control, and virtual factories. Ford Motor Company also has plans to use virtual environment technology to design and develop vehicles. The company's Advanced Vehicle Technology group applies virtual manufacturing technology to assembly simulation and virtual shaping to improve aerodynamics, ergonomics, and surface modeling.

Caterpillar Inc., the world's largest manufacturer of excavators and construction equipment, is using virtual design technology to evaluate the visibility of new prototypes. The company also plans to use the technology to give customers "actual trials" of new products. Japan has also carried out a lot of research on the modeling and simulation technology of virtual manufacturing system and the construction environment of virtual factory. Several large automobile companies such as Mitsubishi, Toyota and Honda have made great achievements in the application of virtual manufacturing. In recent years, the holographic virtual reality system applied by Renault has a good visualization level, which pushes the application of virtual technology in automobile mold to a new level.

The technology research and practical application of virtual manufacturing in China are in the primary stage, and the knowledge of virtual manufacturing theory is not mature, so the technology is seldom applied to the development and manufacturing of automobile mould. Some universities and enterprises have done a lot of research on the theory of virtual manufacturing and developed many suitable technologies for Chinese enterprises. For example, the joint research of Tongji University and The Hong Kong Polytechnic University has made a lot of progress in the technology of decentralized networked manufacturing, remote design and manufacturing. In cooperation with Shanghai Zhenhua Port Machinery Co., LTD., the Intelligent Design and Manufacturing Institute of Wuhan University of Technology has developed a "Computer-aided Design and Simulation system for Container Loading Bridge". Tsinghua University has also made great progress in the research of virtual design environment software, virtual reality, virtual machine tool, virtual vehicle training system and so on. However, due to the constraints of basic software such as CAD/CAM/CAE/CAPP, simulation software and modeling technology, the research of virtual manufacturing technology in China is mostly some unit technology of virtual manufacturing. The contents of this study are virtual product assembly, virtual plastic forming, overall scheme design of machine tool, virtual testing, virtual sheet metal forming, virtual NUMERICAL control processing and virtual enterprise.

Virtual manufacturing technology is a technology with vitality. The research of virtual technology in foreign countries has reached the level that it can be well used in actual production, but our country has not developed software products to support virtual manufacturing technology, and there is no complete understanding and absorption of imported commercial software, so it can not be well used in actual production. Compared with foreign researches, most of China's researches stay on the system framework and overall technology, and the substantial application-oriented key technologies need to be further improved.

5 conclusion

The automobile mold occupies a very important position in the whole automobile industry, and the automobile industry occupies a very important position in the whole manufacturing industry. It used to take two or three years or more for a car to go from conception to production. In the computer industry is highly developed today, on the basis of CAD/CAM/CAE technology is becoming more and more mature, the use of virtual manufacturing technology can greatly shorten the car development cycle, but also can reduce the development cost of enterprises. Virtual manufacturing technology has a good application prospect in automobile die manufacturing, but in Our country, due to many constraints, virtual technology in automobile die is still relatively few, most of the research is still in the theoretical aspect; In the future research, we should do more research in the practical application of this aspect, virtual manufacturing technology and other digital technology together, using computers and the Internet, the advantages of virtual manufacturing technology better application.