A theoretical and experimental study of surface micro/nanostructure formation in ultraprecision diamond milling

Ultraprecision diamond milling (UPDM) is a very promising machining method, producing high-quality surface structures with nanometric surface roughness Sa and sub-micrometric form accuracy PV. Due to its high flexibility, it has been widely employed to fabricate complex freeform/structured surfaces. However, there exists little comprehensive understanding of its surface structure formation. Therefore, this study focuses on discussing surface structure formation in the UPDM process. Firstly, a geometric model was proposed for the relationship among the diamond tool with eccentricity, machining motion with tool tilt, and surface formation in the UPDM process. Secondly, the simulation for surface structure formation of UPDM was carried out for the proposed geometric model, considering different tool tilt angles. Finally, a series of UPDM experiments were conducted at the different tool tilt angles. By comparing with the simulation results, it was found that the simulation results were in good consistence with the experimental results. The simulation and experimental results indicated that in the UPDM process the diamond tool eccentricity would prominently induce the droplet-like microstructures on the machined surface, and the tilt angle would dramatically produce the hexagon-like nanostructures. Further, with the increase of the tool tilt angle, the micro/nanostructures' PV first increased, then decreased, and finally remained stable. Interestingly, UPDM could be directly modulated for the fabrication of micro/nanostructures. Significantly, the study gives a deep insight into surface micro/nanostructure formation of UPDM.