With the rapid development of the national economy and the substantial improvement of people’s living standards, people’s demand for automobiles is increasing, and the market competition for automobile molds is becoming more and more fierce. “Good quality”, “high precision”, “low price”, and “short delivery time” are the basic requirements for modern automobile molds. However, the automobile mold is a large-scale mold, which is large in size, complex in structure, high in dimensional accuracy and surface roughness, and it is quite difficult to manufacture. Moreover, the thin-walled structure with hollowed out base used to reduce the weight of the mold and the mosaic structure used for the middle profile for easy maintenance have brought greater difficulties to design and manufacturing. Generally speaking, an automobile covering part requires 3 or more processes to complete, that is to say, at least 3 or more molds are required to produce an automobile covering part. If the actual manufacturing situation is not considered during the design of the automobile cover parts, the designed mold may not be able to be processed at all during manufacturing, or the manufactured mold may not be able to produce the expected product, which will lead to the scrapping of the mold. , Extend the product development cycle, this kind of economic loss is unimaginable. However, in the design stage of the mold, it is impossible to predict the difficulties that will occur in the manufacturing process. Virtual manufacturing technology is a kind of software technology, which is a higher stage of CAD/CAE/CAM/CAPP and simulation technology. It can realize the whole process of mold design, manufacturing and inspection on the computer. According to the simulation process of the virtual model, it can be Modify the mold design based on the “actual” processing conditions on the computer, avoiding possible problems in the mold manufacturing process, so as to shorten the mold development cycle, reduce development costs, and improve production efficiency. Therefore, it is an automobile mold. Develop one of the most promising, most practical and effective technologies.
Virtual manufacturing (VM)
Virtual Manufacturing (Virtual Manufacturing), also called virtual manufacturing, is a new idea first proposed by the United States in the late 1980s. It uses information technology, simulation technology, computer technology, etc. The manufacturing process is comprehensively simulated to discover possible problems in manufacturing, and preventive measures are taken before the actual production of the product, so that the product is successfully manufactured at one time, so as to achieve the purpose of reducing costs, shortening the product development cycle, and enhancing the competitiveness of the enterprise. In virtual manufacturing, the entire production cycle of the product from initial appearance design, production process modeling, simulation processing, model assembly to inspection is simulated and simulated on the computer, without the need to actually produce the product to verify the mold design Reasonableness, therefore, can reduce the troubles caused by the early design to the later processing and manufacturing, and can avoid the scrapping of molds, so as to achieve the purpose of improving the primary yield of product development, shortening the product development cycle, and reducing the manufacturing cost of the enterprise.
Since the emergence of virtual manufacturing, people have tried to give it a unified definition, but the scope of knowledge involved in virtual manufacturing is very wide. Different researchers have different starting points and focuses, so their understandings are also very different. As a result, virtual manufacturing has remained so far. There is no exact definition. In different definitions, we can understand virtual manufacturing as a technical synthesis of the three key technologies of product virtual design technology, product virtual manufacturing technology and virtual manufacturing system.
1 Product Virtual Design Technology (VDT)
The virtual design technology of the product (VirtualD esignT echnology) is to design the product on the computer based on the principle, structure and performance of the digital product model, simulate a variety of manufacturing schemes, analyze the structure performance and assemblability of the product, and obtain the design of the product Evaluation and performance prediction results, thereby optimizing product design and process design, reducing possible problems in the manufacturing process, in order to achieve the purpose of reducing costs and shortening the production cycle.
2 Product Virtual Manufacturing Technology (VMT)
The virtual manufacturing technology of the product (Virtual Manufacturing Technology) is to use computer simulation technology to select the processing method, process sequence, tooling and process parameters of the parts according to the existing resources, environment, production capacity of the enterprise, etc., and to establish a virtual model on the computer. Perform simulation analysis of processing technology, assembly technology, fit between mating parts, connectivity between connecting parts, and kinematics between moving components. Through analysis, defects in processing and problems in assembly can be found in advance, so that the manufacturing process can be modified accordingly until the entire manufacturing process is completely reasonable to achieve the goal of optimization. The virtual manufacturing technology of products mainly includes material thermal processing technology simulation, assembly technology simulation, sheet forming simulation, machining process simulation, mold manufacturing simulation, product trial simulation and so on.
3 Virtual Manufacturing System (VMS)
Virtual Manufacturing System (VirtualM anufacturingS ystem) introduces simulation technology into the numerical control model to provide a virtual environment that simulates the actual production process, that is, the machine control model is used for simulation, so that the company can optimize the manufacturing process based on the control behavior of the workshop. Control, its goal is to optimize the process in actual production, better configuration manufacturing system. With the advent of the network age, virtual manufacturing technology has developed rapidly, and the field of research is becoming wider and wider, except for the virtual manufacturing field itself. Manufacturing theoretical system, design information and three-dimensional visualization of production process, system global optimal decision-making theory and technology in virtual environment, open architecture of virtual manufacturing system, virtual product assembly simulation, virtual environment and virtual manufacturing process In addition to human-machine collaboration and other content, experts at this stage are investing a lot of time and energy in researching virtual manufacturing technology integration systems and related software development. Washington State University in the United States has developed a design and manufacturing-oriented virtual environment VEDAM system on PTC’s Pro/enginee: CAD/CAM system, which includes processing equipment modeling environment, virtual design environment, virtual manufacturing environment and virtual assembly environment. Lee and Noh from the National University of Singapore used the Internet, expert system development tools, HTML/VRML and database systems to develop a virtual manufacturing prototype system as a test bed for engineering and production activities. Driven by huge application demand, foreign software companies have also successively launched a batch of software supporting virtual manufacturing such as Deneb, Multigen, dVISE, World-ToolKit, EA1. Virtual manufacturing technology is a multi-disciplinary and multi-technology integration. Its related technical support includes simulation technology, modeling technology, computer graphics, visualization technology, multimedia technology, virtual reality technology, etc. The application of these technologies is The focus of current research.
Application of virtual manufacturing in automobile panel molds
The development of automobile panel molds is subject to many constraints such as reliability, aesthetics, economy, manufacturability, and maintainability. In the traditional automotive panel mold development process, after the mold design and manufacturing are completed, it needs to undergo repeated adjustments and modifications to obtain satisfactory automotive parts. During the debugging process, some forming defects, such as cracks, wrinkles, springbacks, angles, etc., are mainly based on the experience of the mold fitter through the cyclical process of mold trial, mold repair, mold retry, and mold repair. solve. This method not only reduces the production efficiency, but the precision of the produced molds often fails to meet the expected requirements, and it will also lengthen the development cycle of the mold. The virtual manufacturing technology can greatly shorten this cycle. Because in the virtual reality environment, designing and manufacturing cars do not need to build physical models, engineers can take advantage of the visualization advantages of the virtual “natural” environment to integrate the structural analysis, virtual design, component assembly and performance optimization of automobile molds into computer virtual In the manufacturing system, on the basis of comprehensive consideration of the overall layout of the car body parts and the interconnection and interaction between the parts, interactive rapid modeling of the mold geometry, technical performance, production and manufacturing, etc. And simulation analysis, thereby avoiding repeated mold repairs and ensuring the accuracy requirements of the mold; and because the generated simulation model can be directly manipulated and modified, and the data can be used repeatedly, the cycle of mold development is greatly shortened. Cs-i21 virtual manufacturing technology Compared with rapid prototyping technology, reverse design, reverse engineering, knowledge-based engineering design and other technologies, it has very good advantages. Because the virtual manufacturing technology has a unique virtual design and manufacturing environment, the entire mold development process can be carried out completely in a virtual “real” environment, and physical manufacturing can only be started after the expected performance and quality requirements are met, so that the manufacturing The mold meets the needs of users at one time, greatly reduces the scrap rate of molds, and reduces the development cost of the enterprise.
1 Development process of virtual manufacturing of automotive panel molds
The virtual manufacturing and development process of automobile panel molds is shown in Figure 1. First, it starts with product demand analysis, then conceptual design, and then from optimization design to system integration. Through the use of related development software, the virtual environment of the product is constructed. Model. This is a cyclical and gradual process. Based on the development requirements of the product, the corresponding simulation analysis tool is used to simulate the function and performance of the virtual model, and the behavior of the virtual model is simulated and analyzed. Based on the results of the simulation analysis, through repeated construction Mold ~ simulation analysis ~ model improvement, until the virtual manufactured mold meets the expected design goals, the physical manufacturing F1s7 is started. It can be seen from Figure 1 that the automotive panel mold has passed the virtual “real environment” test before it is put into production, and all the difficulties and design irrationality that may be encountered in actual manufacturing are tested, and then the design work Personnel modify or redesign until the entire manufacturing process can be completed reasonably and smoothly. This will not only shorten the product development cycle, reduce the company’s research and development costs, but also improve the quality of the product.
Figure 1 The general process of virtual manufacturing of automotive panel molds
2 Key technologies in the virtual manufacturing of automotive panel molds
In the virtual manufacturing process of automotive panel molds, there are many related technologies involved. The quality of any technology application will affect the final quality of the mold. This is also one of the reasons for the slow progress in the application of virtual manufacturing technology. Only when each technology is well mastered and applied, can the virtual manufactured products reach agreement with the actual manufactured products, and achieve the purpose of reducing development costs, shortening development cycles, and improving mold quality. Among them are the more difficult and critical technologies:
(1) Establishment of mathematical model
Establishing a simple mathematical model that can reflect the dynamic manufacturing process is the key to the application of virtual manufacturing technology in automotive panel molds. If the mathematical model is unreasonable, the manufacturing process simulated under the virtual environment will be different from the actual manufacturing process, and it will not play the role of optimizing the mold design, thus failing to achieve the purpose of shortening the development cycle and reducing the development cost. Therefore, when using virtual manufacturing technology to develop automobile panel molds, a set of reasonable mathematical models must be established. When establishing the mathematical model, it is necessary to carefully analyze the characteristics of the automobile panel mold, find out the main influencing factors and put forward reasonable assumptions according to the mold function and manufacturing requirements. The model established must be able to reflect all the functions and manufacturing relationships of the mold, including the changing relationship of the force of the mold surface and the changing relationship of the force shape of the stamping part during work, so that the actual production relationship can be simulated and the production possibility can be predicted. The problems that arise can achieve the purpose of optimizing design and manufacturing.
(2) System integration and program evaluation
This is the basis for the preliminary work in the virtual manufacturing of automotive molds. System integration is an optimized comprehensive overall design, which requires a lot of technology
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