Metrological interpretation of a six-sigma action for improving the online optical measurement of the turbocharger dimensions in the automotive industry

In this paper, a synergy between metrological concepts and six sigma methodology has been developed, in order to increase and consolidate improvements of a DMAIC intervention with reference to on line control procedure of critical geometrical dimensions of high performance turbocharger for automotive applications. The metrological support is intended not only in terms of rigorously quantifying and validating the improvement effects. Concepts and approaches typical of measurements are used with the aim of justifying and physically explaining the motivations of problems and of the obtained improvements. The consistency of the measured parameters with the production process steps is used as a peculiarity and newness of this approach. Sensitivity analysis to interfering inputs, uncertainty budget, modeling of the measurement process are used by a bottom-up approach to set coherent actions able to strongly and consciously improve six sigma performance indicators.