Fabrication of Hierarchical Freeform Surfaces by 2D Compliant Vibration-assisted Cutting

Abstract In this paper, instead of the commonly used fast tool servo method, a two degrees-of-freedom (2D) vibration-assisted machining method is proposed to enable the efficient generation of freeform surfaces with hierarchical micro/nano-structures. With this method, the freeform component of the surface is realized by 1D vibrations in the depth-of-cut direction, whereas the hierarchical micro/nano-structures are generated by elliptical vibrations at high frequency and small vibration amplitudes. The determination of the tool vibration path, considering tool geometry and the interference between the tool's flank surface and the machined surface, is presented and used as the basis to propose a surface generation algorithm for topography prediction. Using a developed 2D vibration compliant cutting system, experiments were conducted to machine hierarchical sinusoidal and discontinuous cubic surface arrays for demonstration. The results show a high consistency between the simulated and generated topographies demonstrating the effectiveness of the proposed method for the efficient machining of hierarchical freeform surfaces. In addition, wettability tests were undertaken to demonstrate that larger wetting angles can be obtained on hierarchical freeform surfaces as compared to their smooth counterparts.