Research On The Key Technologies For Accurate Design Of Automotive Body Panel Stamping Die

The design and manufacture of large automobile panel is one of the key technologies in automobile industry, which also restricts the development of automobile industry in China. The dynamic fitting accuracy between punch and die is reflected through matching-ratio, and guarantees the operation stability of stamping under high frequency conditions. Traditionally, the matching-ratio is measured and improved during die modification stage, and it directly results in heavy labor cost and severely restricts the development duration.With the application of fine design technology, the compensation amount is obtained in early design stage on the basis of studying the influencing factors of matching-ratio. Then, the die surface is modified to meet the requirement of fitting accuracy, which has the capacity to reduce both labor forces and production circle and improve the quality of stamping dies.A methodology to predict and improve the matching-ratio based on sheet metal forming simulation and die structure analysis is proposed considering two key influencing factors, the blank thinning and the elastic deformation of tooling. The presented method mainly includes three countermeasures: the compensation calculation caused by blank thinning based on sheet metal forming simulation, the compensation calculation caused by die elastic deformation based on structure analysis and the linear superposition of these two compensations and surface modification.The calculation flow and key algorithms on compensating the blank thinning is discussed here by using Autoform and LS-DYNA on detail. The compensation amount induced by blank thinning is obtained from extracting the data of blank thinning quantity or the information of surface meshes through stamping simulation. In addition, it is available to modify the die surface meshes with iterative calculation when using LS-DYNA. The developed load mapping algorithm maps the contact forces obtained from stamping simulation to the die structure analysis model as force boundary conditions. Then the compensation amount due to the die elastic deformation is calculated after processing the output data of die surface deformation. The proposed methodology also establishes the compensation rule for the linear superposition to intergrate two compensation amounts to comprehensively modify the die surface.The traditional and improved measurements for matching-ratio are summarized and key influencing factors of matching-ratio are analyzed. On the basis of the compensation amount calculation and numerical simulation, the matching-ratio measurement for automobile stamping dies is presented here.Based on the methodology and the proposed algorithms, a software tool is also developed using C++. A fender drawing die and an inner panel drawing die are regarded as two study cases to verify the proposed method and the developed software.