Robust design of a sheet stamping process: approaches to control the inner process variability

The robustness investigation has become a crucial issue in the sheet metal forming. The uncontrollable effects of some noise variables influence the process, often evolving up to the failure of the design. Tools able to handle such variability are worth developing to minimize the scattering of the performances. The stamping operations are usually characterized by conflicting objectives and a set of Pareto solutions is obtained instead of a global optimum. The question becomes how the noise effects influence the Pareto solutions. And, which is the most robust operative window? The stamping of the IFU Hishida part is designed by the calibration of the blank holder force to minimize thinning and wrinkling. Coil to coil variation of the material properties is accounted for. Two robust approaches are applied on a multi-objective sheet stamping process: a hybrid deterministic-stochastic and a stochastic framework. The former integrates Finite Element simulation, Response Surface Methodology and Monte Carlo simulation. A probability distribution of the performances is achieved and the robustness of a Pareto solution is evaluated. The latter applies a Dual Response Surface approach: the Pareto solutions are obtained under the influence of the noises. Their capabilities of robust design and variability investigation are finally compared.