Abstract

The metrological inspection of additively manufactured ceramic components is particularly challenging due to the complexity of the manufacturing process and the potential for significant dimensional and geometrical deviations. Non-contact digitisation techniques offer advantages in terms of acquisition speed and data density; however, their measurement reliability depends on the surface characteristics of the part.

This study evaluates the metrological performance of conoscopic holography (CH) for digitising alumina (Al₂O₃) spheres manufactured by stereolithography (SLA). The reference diameter and form error of the spheres were first determined using a high-precision coordinate measuring machine (CMM). Selected artefacts were then digitised using a ConoScan 4000 sensor, and the resulting point clouds were filtered to remove outliers before comparison with the reference measurements.

The results revealed diameter deviations of approximately 60 μm and form-error deviations of up to 280 μm relative to the CMM measurements. Furthermore, the signal quality indicators, namely the signal-to-noise ratio (SNR) and the Total parameter, frequently fell below the thresholds required for reliable measurements. In particular, the surface finish of the SLA-manufactured ceramic spheres prevented the sensor from consistently achieving the minimum SNR of 50%.

These findings highlight the limitations of CH for the metrological inspection of SLA-manufactured ceramic components and emphasise the need to consider surface characteristics and signal quality when assessing the suitability of optical digitisation systems.

Keywords

Conoscopic holography, 3D sensor, Additive manufacturing, Stereolithography, Alumina