Process monitoring in stamping operations through tooling integrated sensing

This paper introduces a new sensing method for stamping process monitoring based on the measurement of contact pressure distribution across the sheet metal-tooling interface, by means of an array of tooling-integrated force sensors. The role of numeric surface methods in estimating the contact pressure distribution on the sheet metal-tooling interface has been studied through finite element analysis and experiments. A finite element model is set up to model the contact interactions, based on the geometry of a customized stamping test fixture. Discrete samples of contact pressure taken from the FE model have been used to recreate continuous-pressure surfaces based on the Thin Plate Splines (TPS) and Bezier surface algorithms. It is shown that the temporal–spatial contact pressure distribution across the sheet metal-tooling interface can be effectively reconstructed through interpolation using spatially discrete sensor data. Comparison of surface-based pressure estimates with the FEA field solution indicates that the TPS-based method is more accurate than the Bezier method. The effectiveness of the surface modeling scheme is also evaluated experimentally by comparing the net press force calculated from numerical integration of the TPS surfaces with the experimentally measured value under different press speeds. The effectiveness of the new sensing method is further demonstrated by detection of slide misparallelism through analysis of the tooling interface pressure distribution. The study presents a new approach to enhancing process observability in manufacturing operations.