On-machine non-contact roughness verification system based on Conoscopic holography

Abstract

The surface quality verification of mechanical components is an essential activity in many applications where surface performance plays an important role in the functional behaviour of the part. Although many of the verification techniques commonly employed are based on the use of contact roughness profilometers, there are some limitations related to the morphological filtering effect associated to the stylus tip radius, as well as the difficulty in using these type of styli to carry out on-machine surface verification. The use of non-contact digitizing techniques helps to overcome some of these drawbacks, although the verification of surface quality using these non-contact systems still requires the development of scanning and data processing procedures similar to those described in the international standards for contact probing techniques. This work analyses the use of a non-contact sensor, based on Conoscopic Holography and integrated in a 3-axis machining centre, applied to the verification of the surface roughness of parts machined by face and cylindrical milling processes. After the calibration of the integrated system, a high-frequency noise filtering procedure specifically designed for roughness verification is proposed. The results demonstrate the feasibility of the system for verifying surface roughness grades from N5 to N12 in the two milling processes. Finally, specific filtering recommendations for each roughness grade of both milling processes as well as a surface verification procedure are provided.