Generic three-dimensional model of freeform surface polishing with non-Newtonian fluids

Non-Newtonian fluids are being increasingly considered for application in manufacturing. Their combination with compliant polishing techniques offers a promising approach for ultraprecision finishing of freeform surfaces. However, in-depth understanding of the underlying material removal mechanism and its link with slurry rheology has not been disclosed yet. In this study, a comprehensive three-dimensional dynamic modeling framework is presented, which enables accurate prediction of stress distribution, rheological flow, compliant deformation in 3D, as well as material removal behavior on curved workpieces. Supported by experimental tests and theoretical analysis, it is demonstrated that the viscosity peak gets shifted to a higher frequency by mixing starch and polymer, which makes high speed polishing with improved material removal rate possible. Meanwhile, it is found that the polymer additive prevents large size starch agglomeration and has high affinity with fine abrasives, both of which greatly contribute to the obtained scratch-free and nanoscale surface finish. Finally, the controllability and predictability of the process are demonstrated by polishing a bi-sinusoidal freeform surface onto a planar workpiece coated with nickel.