Pressure and Draw-In Maps for Stamping Process Monitoring

This paper presents two tooling-integrated sensing techniques for the in situ measurement and analyses of pressure distribution at the tool-workpiece interface and material drawin during the stamping processes. Specifically, the contact pressure distribution is calculated from the measurements by an array of force sensors embedded in the punch, whereas sheet draw-in is measured by custom-designed thin film sensors integrated in the binder. Quantification of the pressure distribution from spatially distributed sensors has been investigated as a regularization problem and solved through energy minimization. Additionally, a Bayesian framework has been established for combining finite-element analysis (FEA) based estimates of the pressure distribution with experimentally measured evidence, to achieve improved spatiotemporal resolution. A new data visualization technique termed pressure and draw-in (PDI) map has been introduced, which combine spatiotemporal information from the two sensing techniques into an illustrative representation by capturing both the tool-workpiece interaction (dynamic information) and resulting workpiece motion (kinematic information) in a series of time-stamped snap shots. Together, the two separate yet complementary process-embedded sensing methods present an effective tool for quantifying process variations in sheet metal stamping and enable new insight into the underlying physics of the process.