Feasibility study on surface finishing of miniature V-grooves with magnetic compound fluid slurry

• We proposed a novel polishing technique for the high-precision surface finishing of structured surfaces with miniature V-grooves.
• The newly developed technique enables the good work-surface and form accuracy in the structured surfaces finishing process.
• The novel developed magnetic compound fluid polishing process demonstrated great potential for finishing the structured surface.

Towards the development of a novel polishing technique for the high-precision surface finishing of miniature V-grooves, the feasibility of finishing linear V-grooves generated on an oxygen-free copper substrate using a magnetic compound fluid (MCF) slurry was experimentally investigated, and the fundamental finishing characteristics were elucidated. First, a polishing apparatus was constructed by installing an MCF unit for generating a rotary magnetic field and rotating an MCF carrier onto a polisher, along with a wave maker used for vibrating the workpiece. Then, polishing experiments were performed to clarify the fundamental polishing characteristics, including the effects of the polishing time on the material removal, the form accuracy (i.e. the form retention rate and symmetry error), and the surface roughness at different polishing locations/positions in the polishing zone. Thereafter, the fundamental characteristics were examined by investigating the distribution of abrasive particles in the polishing zone, the relative velocity of abrasive particles compared to the V-groove, and the impact angle of abrasive particles against the V-groove side surface. Finally, the effect of the MCF carrier rotation speed nc on the characteristics was elucidated, and an appropriate value of nc was proposed. The main results can be summarized as follows. (1) At the majority of locations in the polishing zone, the surface quality Ra at higher positions on the V-grooves was better than that at lower ones. At locations where abrasive particles moved from the right/left side to left/right side of the grooves, the surface quality Ra on the right/left side was better than that at the left/right side. The final surface roughness after 150 min of polishing was in the range of 15–50 nm Ra, indicating that a mirror-like surface could be successfully achieved for a miniature V-groove using the proposed technique. (2) The V-groove form accuracy, i.e. form retention rate η and symmetry error ɛ, deteriorated during polishing, and the final form accuracy differed with the location. Nevertheless, the η and ɛ values at the location where the form accuracy was the lowest were greater than 99.47% and less than 0.17, respectively. (3) Increasing the MCF carrier rotational speed nc deteriorated the form accuracy but improved the surface quality Ra. Taking into account the balance between the form accuracy and surface quality Ra, nc should be set at 10 rpm under the experimental conditions in the current work.