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Computed tomography (CT) is progressively assuming an important role in metrology applications and great efforts are being made in order to turn it into a reliable and standardized measuring technology. CT is typically used for non-destructive tests, but it is currently becoming very popular for dimensional metrology applications due to its strategic advantages such as the capability of performing measurements on both the component's surface and volume, allowing inspection possibilities to otherwise non-accessible internal features. This paper focuses on the dimensional verification of two micro-injection moulded components, selected from actual industrial productions, using CT metrological tools. For this purpose, several parts have been measured with two different CT machines, and the results have been compared with the measurements obtained by other measuring systems. The experimental work carried out and the analysis of the results provide valuable conclusions about the advantages and drawbacks of using CT metrology in comparison with other measuring systems when these techniques are employed for the quality control of micro-moulded parts.

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Among the multiple factors influencing the accuracy of Computed Tomography measurements, the surface extraction process is a significant contributor. The location of the surface for metrological applications is generally based on the definition of a gray value as a characteristic of similarity to define the regions of interest. A different approach is to perform the detection or location of the surface based on the discontinuity or gradient. In this paper, an adapted 3D Deriche algorithm based on gradient information is presented and compared with a previously developed adapted Canny algorithm for different surface types. Both algorithms have been applied to nine calibrated workpieces with different geometries and materials. Both the systematic error and measurement uncertainty have been determined. The results show a significant reduction of the deviations obtained with the Deriche-based algorithm in the dimensions defined by flat surfaces.