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Machining method for controlling the behaviours of Bingham fluids in cluster magnetorheological polishing pads

Cluster magnetorheological finishing is a novel machining method for attaining super-smooth and even surfaces. The aim of the research is to strengthen the role of cluster magnetorheological polishing pads and improve the material removal rate (MRR) while attaining smooth and undamaged surfaces. To this end, a novel polishing disk with three-dimensional (3D) microstructures was formed by machining an array of holes on the surface of a polishing disk. The influences of the type of abrasives, geometric parameters of the holes, and polishing time on the roughness and MRR of the machined surface were explored. The test result showed that a polishing disk with multiple holes contributes to a higher MRR and a lower surface roughness relative to a smooth polishing disk, significantly improving the polishing effect; the diameter and distribution of multiple holes on the surface of the polishing disk exhibit a significant effect on the polishing process. The polishing effect with silica sols is most remarkably improved. The solid-state chemical reaction between sapphire and silica sols promotes material removal; relative to a smooth polishing disk, the MRR is increased by 107% and the surface roughness is decreased by 11%. The surface roughness is reduced from Ra 5.14 nm to Ra 0.24 nm by utilising the optimised technological parameters. Under the synergistic action of mechanical removal enhancement of polishing disks with multiple holes and chemical removal of silica sol sapphire can obtain super smooth undamaged surfaces efficiently.