The use of in-situ surface metrology for advanced electrochemical polishing applications

Additively manufactured (AM) metallic parts have issues of inherently rough surface texture, which negatively impacts the precision potential functionality and ultimately limits applications. To make the workpieces functionally suitable and - improve the part aesthetic qualities, post-processing the additively printed parts is very much required. There are various methods of post-processing AM surfaces, of which the electrochemical polishing (ECP) methods have garnered significant attention recently due to their non-contact nature. ECP processes are subtractive and are in theory an easily controllable processing technique. While the electrochemical post-processing improves the part surface by reducing the roughness via a polishing process, it is essential to assess whether the part has achieved the desired surface quality to be deemed fit for the purpose. Current assessment methods involve offline measurement of parts, making the whole process less efficient and requiring removal and replacement of parts. Integration of metrology directly into the manufacturing platform would enable rapid inspection, making manufacturing more efficient and controllable. In this research work, we investigate the focus variation (FV) measurement principle for the implementation of in situ surface metrology within the electrochemical polishing system. A performance study of focus variation optical metrology compared against the stylus measurement was carried out to assess the FV potential. The test surface was a standard Rubert &Co Microsurf 334 comparator plate and a range of actual workpieces produced by AM and electrochemical polishing. Additionally, the - focus variation setup was developed, and the measurement output was compared with state-of-the-art optical surface metrology for performance verification, the system's robustness in the manufacturing environment.