Investigation on metrological performances in CT helical scanning for dimensional quality control

For many industrial applications, workpieces characterized by high surface roughness are scanned; this is the case for example of parts produced by additive manufacturing. Surface roughness has a strong influence on CT dimensional measurements, causing relevant measurement errors with respect to reference tactile measurements, especially for parts characterized by high surface roughness. It comes that surface roughness effects on CT dimensional measurements must be quantified. In the present work, the influence of surface roughness on CT dimensional measurements, and the relation between tactile CMM and CT measurements are studied. Effects of larger as well as smaller surface roughness are taken into account. Experimental results prove the presence of a systematic error between tactile and CT measurements, due to surface roughness. The possibility to correct this systematic error to enhance the accuracy of CT measurements is outlined.