Intelligent procedures for workpiece inspection: the role of uncertainties in design, production and measurement phases

The actors involved in the manufacturing process need a common technical language from ideation to verification. The Geometrical Product Specification and Verification standards, defined by ISO/TC 213, lay the groundwork for a new operator based language (ISO/TS 17450-2), able to manage a verification coherent with specifications, and, therefore, to reduce the total uncertainty, arising during the product lifecycle. Manufactured parts are necessarily affected by size and form errors, whose control relies on the analysis of the manufacturing technological signature and the evaluation of the associated uncertainty. In order for the study to be unscathed by the impossibility to know the actual shape of a workpiece before measuring it, five roundness profiles, affected by systematic deviation, have been simulated. The impact of simplified verification operators, the relative uncertainty contribution to measurement uncertainty and the ability to properly assess roundness deviation have been evaluated. Then, since literature proposes different approaches for the evaluation of implementation uncertainty, but a standardized method has not been yet achieved, an analysis of the various elements to be considered when choosing a specific approach has been carried out. The most common manufacturing signatures have been considered, together with the number of points necessary for a reliable estimation of implementation uncertainty [2]. Finally, in the case of flatness, a statistical predictive model combined with adaptive sampling strategies has been implemented, as the best “simplified verification operator”, in order to obtain accuracy in the estimation of the flatness error of a clamp for an industrial air cushion guide [1]. Only the most relevant points have been measured, instead of inspecting the whole surface, as required by the “perfect verification operator”, defined in the ISO standards. This consistent reduction is due to the effectiveness of the adaptive methods in presence of technological signatures.