The key factor of quality in precision sheet metal forming is to satisfy the requirements for part size and shape. Together with tearing and wrinkling, problem of unflatness is encountered frequently in sheet metal forming, which is one of the main causes of the tool modification. This study focuses on estimating the amount of unflatness using finite element method so that the tools can be designed to remove the unflatness. Finite element analyses of forming process and springback have been carried out for two sample cases, box drawing and coining. To reduce the computation time, explicit scheme was used for the box drawing and rigid plastic finite element method for the coining. Estimation of springback was done by linear static analysis because removal of tools causes vibration or divergence of the solution. For the analysis box drawing, shell elements were used and the final stresses obtained in the forming analysis were converted into equivalent thermal expansion coefficients to generate the initial thermal stresses for the springback analysis. For the coining, solid continuum element were used and the final external forces obtained in the forming analysis were set to zero by applying reverse forces to calculate the amount of springback. The results showed some differences from the experimental results but they were still good enough to be used for the design of tools. When the methodology developed in this study was applied to the design of new tools for box drawing, it succeeded to produce the parts without any modification of the tools.
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