Localized magnetic fluid finishing of freeform surfaces using electropermanent magnets and magnetic concentration

We report a novel magnetic concentration setup for localized finishing of freeform surfaces based on employing electropermanent magnet arrays configured using a recently developed magnetic concentration principle. The setup, without the use of any rotating or moving component, is capable of creating a localized spatiotemporal magnetic field variation a specialized magnetic fluid to polish a target 1.5 cm² area on the workpiece surface. Using a computational mechanistic model as well as experimental studies, we show that the current configuration of electropermanent magnets is capable of amplifying the magnetic strength by almost 3 times near the workpiece surface in comparison to no magnetic concentration. We also show that by modulating the strength, including toggling the polarity of electropermanent magnets, we demonstrate the sloshing motion of the fluid at a targeted region without requiring any rotating part. Experimental investigations on the localized removal of acrylic paint from a cylindrical workpiece surface suggest that the method can be used to polish localized, hard-to-access freeform geometries.