Research On Die Surface Quality Improvement And Spring-back Control For The Automobile Fender

To manufacture auto body drawing part of high quality has become one of the most important topics in the field of sheet metal cold stamping. In order to improve the surface quality of parts, stamping process must be arranged reasonably. Different kinds of defects and flaws on each working procedure should be eliminated. In this dissertation, the defects and flaws of fender on stamping, trimming, flanging and reshaping procedure were focused on.In this dissertation, theory of sheet metal forming and finite element method were used to analysis surface quality and springback flaws of fender on each working procedure. Besides that, targeted research was carried out on these defects and multiple solutions were proposed to control deficiency. The forming process of four working procedure was developed through analyzing the structure of fender. The initial shape of stamping blank was reversed by using "one-step" finite element method, and the shape of blank was optimized on the basis of the trimming line. The deep drawing process model of fender was preliminary designed according to the design principles of addendum and binder surface. The satisfactory simulation results were got by adjusting the stamping process parameter and repeated simulation. In order to eliminate the defects of wrinkle on primary surface in deep drawing process, the drawing depth of local die surface was fixed through tracking the local material flows.The actual structure of drawbead was designed according to the parameters of the virtual drawbead, and the modular drawbead was designed to eliminate wrinkle of binder surface on the basis of traditional design so as to improve the quality of fender mold surface. The defects of the large sliding distance was solved by the scheme of die surface compression treatment, and the situation of die clearance when die closed was analyzed to optimize the value of surface compensation. The problems of burrs and surface deformation during the trimming process were focused. A new plan of precisely matching edge line during side trimming process was put forward to solve the defects of trimming, and the feasibility of the scheme was confirmed by the theoretical analysis. In this dissertation, some new structures for flanging and reshaping were projected to eliminate the wrinkling problem of fender on flanging and reshaping process. Besides that, plastic deformation of parts was increased, thus the springback of parts was reduced to a certain extent. The springback compensation was used to reduce the springback of fender forming, and the value of compensation of different position of surface was determined by iteration. Finally, the springback value was controlled in the range of allowable error.