Quantification of Surface Roughness Using Fringe Projection Profilometry for Metallic Machined Surfaces

The surface conditions of a machined part hold substantial significance in the manufacturing domain as they influence the overall tribological performance and structural characteristics of a service component. The quality control approach focuses on the assessment of surface roughness parameters to ensure the performance and reliability of components. This article presents an application of fringe projection profilometry (FPP) for three-dimensional (3D) surface roughness measurement, advancing beyond typical 3D mapping techniques in the field of surface metrology. FPP is a noncontact optical method with cost-efficient technology that can operate at a higher speed with precise accuracy and resolution. To address the issue of roughness criterion on metallic surfaces, a wide range of machined components were considered, viz., ground, milled, and electric-discharge machined surfaces, for the first time. The surface roughness assessment of these machined surfaces belonging to a roughness range of 0.2–15 µm has been carried out using a five-frame phase-shifting algorithm. Fringe patterns were captured at four different orientations (0 deg, 30 deg, 60 deg, and 90 deg), and the discrete cosine transformation technique was used to unwrap phase maps. The unwrapped phase maps were utilized to calculate the phase height profile, and eventually, the 3D roughness values of machined surfaces were computed. The results were validated using a mechanical stylus profilometer, and it was determined that R² values were above 0.9, which indicated the robustness of the analysis. The study of utilizing FPP contributes to advancements in optical metrology for modern manufacturing and quality control.