Contactless inspection of castings: analysis of alignment procedures

In foundry industries as well as in many other sectors, inspection practice has been facing a gradual revolution through the introduction and development of optical scanners in recent years. The main advantage of contactless quality control is that the external geometry of the cast tool or cast part can be completely inspected in short times by retrieving the coordinates of hundreds of thousands of points. The role and importance of the alignment operation in part inspection is undeniable since any error leads to an unreliable inspection of the part. Therefore, the definition of part reference systems on scan data for computer aided inspection is a crucial operation. The aims of this paper are to highlight this issue and to point out how an improper procedure for part alignment can lead to an incorrect evaluation of real part deviations, especially when the accuracy of the scan data is low.