Removal characteristics and performance of brick-shape permanent magnet-assisted magnetorheological lapping

A brick-shape magnet-assisted magnetorheological (MR) lapping was proposed for ultra-smooth flat surface finish, where a straight ribbon was produced to enhance polishing efficiency. Finite element analysis was performed to understand the magnetic property of the brick-shape magnet. Polishing marks and surface topographies were compared with the removal functions and distributions to reveal effects of translational oscillation, period ratio, work gap, eccentricity and trough speed on surface finish. Trajectories were calculated for kinematical analysis. Polishing performances on K9, sapphire and GaN showed that the polishing area was expanded to 1100 mm(2) by the brick-shape magnet. Surface planarity as 1 mu m in PV with sub-nanometric roughness were obtained on sapphire, GaN and K9 substrates from removal rates of 0.019, 0.037 and 0.437 mu m/min respectively.