Research On Key Techniques Of Parametric Design For Stamping Die Face Of Auto Body Panel

Rapid development of china industry and individual demand put into a higher level for reform and regeneration of automobile-manufacturing enterprises, in the process of development of a new car type, the design and manufacture capacity of panel stamping die determines the circle and cost of development to a large degree. In order to reduce the development circle and lower the development cost of panel stamping die, one of the methods is that the CAE software for sheet metal forming be used in the process of die design. At the phase of design of panel stamping die, designer usually import the simulation model to the CAE software and simulates in the environment of CAE after some parameters is inputted, the simulation judges superior or inferior of the die design scheme and provides the preference for modify of die. Stamping die is designed on the base of geometry data of part model through mending holes, flange expansion, boundary smoothing and addenda. The stamping die that is created on the base of the geometry model of the part is defined as die-face design, so the die-face design is the key to design of stamping die.The related theories and key technologies of panel die face digital design are studied thoroughly based on CAE system. This paper has researched on the following several key technical issues. In order to realize the die-face design for stamping die, the related function of die-face design is analyzed and the key algorithm on ACIS platform is finished, the main content is as following:It is easy to make the error that non two edges form when the stamping die is transferred among the system of CAD styling. The defect, such as crack among the surface, appears due to the different of minimal tolerant, these defects hinder the simulation of pre-process of stamping parts, at the same time, the cracking stamping parts do not produce the finite element meshes that meet the simulation analysis. Therefore, the study of fixing technology at the process of the transformation of model has very important academic value of study. The study is made for the transformations defect of tamping model and the type and reason of transformation is analyzed, more important is, the study of manifold and topology re-building. The corresponding fixing method is proposed in view of different types.In order to realize the purpose of model parametric editing, through the InterOp of ACIS platform, the modification and editing of 3D model is studied, and some components for different editing purposes are also compiled, including the following functions: boundary re-building, local editing, blending and shell, etc. In accordance with the problem of possible multi-solutions, when the boundary re-building operation is executed, the analysis and solution are studied in this paper. The blending operation creates Coons surfaces, and according to the equal radius blending, variable radius blending and point blending, the corresponding programs are compiled. The topology of blending operation is also re-built.According to the finite element basis theory of one-step inverse forming and assumption conditions that constant volume of elastic-plastic remains, the premise of the consideration of physical properties, the rational expansion of surface is realized. In the algorithm of surface expansion, one-step inverse forming expansion overcame drawbacks of inaccurate size in the geometry expansion. Under the condition of proportional loading, the flange-face is expanded according to the theory of metal elastic-plastic and the expansion accuracy of surface is improved. Through the testing of flange-face expansion for typical stamping parts and dimension measurement, the accuracy of flange-face expansion algorithm is proved.The traditional algorithms of addenda design, which based on knowledge system and parameter, can realize the interpolation generation of addenda surfaces, but can not solve the following problems well: the continuity degree between addenda surfaces on the sharp corner of parts, the continuity degree between addenda surfaces and parts'surfaces or blank surfaces. Additionally, the continuity of addenda surfaces by traditional algorithms can only be realized by the experience of designer and setting parameters. And the traditional addenda design basing section curves need the designer to build several section curves on every edges of stamping parts for the interpolation generation, and this kind of method of construct interpolation surfaces basing several section curves will cause the continuity fault of addenda surfaces. The method of section curves and defined direction to build parametric blank surfaces are proposed in this paper, and these blank surfaces can fulfill the requirement of simulation of drawing. The method of using three parts of section curves during the construction of addenda surfaces is disused in this paper, and two alterable B-Splines with 6 controlling points are proposed as sections curves in this paper, and the method of construction boundary of interpolation surfaces basing section curves, boundary curves and connecting curves are also proposed in this paper. In order to fulfill the requirement of C1 continuity of addenda surfaces, the blending method with rolling ball is used to realize the smoothing of sharp corners and sharp edges.The parametric design of stamping die face module of KMAS/Die_Face includes the following basic functions: meshing, normal consistence, stamping direction optimizing, holes filling, flange hiding, symmetry operation, boundary smoothing, flange expansion, blank surface design, addenda surfaces design and draw bead design. But how to rational arrange and integration the above basic functions, and realizes fast and precise die face design is the kernel content of stamping die face design module. The basic functions of parametric design of stamping die face provide the premise of KMAS/Die_Face. Through the study of technology characteristics of stamping die face design, and the integration of corresponding basic functions, and the product characteristics of stamping parts, and the simulation results of forming, the fast design module of stamping die face is designed and realized, which includes the matching of parts model features and the prediction of forming results. This design module focus on the design according to the geometry characteristics and similarity of stamping parts, and the research of classify-algorithm, and construction of databank, and the construction of model characteristics templates, thus the fast design module of die face is realized.