Stable and efficient polishing of sapphire surface damage layers using polyurethane polishing wheel based on central supply polishing fluid

During the polishing of hard and brittle material, a polyurethane polishing tool rotating around a single axis often produces an irregular tool influence function (TIF). This phenomenon is closely related to the polishing particle states within the contact region. Under the condition of external supplying polishing fluid, this study first selected two polyurethane polishing wheels with different surface roughness levels. Fixed-spot polishing of sapphire material was then performed to demonstrate the resulting irregular TIFs, and to reveal that the material removal process primarily relies on the polishing particles carried by independent peak features or continuous peak-surface features. Subsequently, staged polishing process using specific peak features on the surface of polyurethane polishing layer were conducted to thoroughly reveal that the formation of irregular TIFs is attributed to the non-uniform consumption behavior of polishing particles. Furthermore, a third polishing wheel was designed to optimize the polishing slurry supply method, allowing for the timely replenishment and renewal of polishing particles in the key contact region. This, in turn, promoted the generation of a regular TIF. Finally, planar polishing was conducted on sapphire surface with a certain defect layer thickness using the three types of polishing wheels. This further validated the stable and efficient polishing capability of the optimized polyurethane polishing wheel when dealing with surface defects of a specific thickness.