Effect of tool vibration trajectory on vibration-assisted diamond-cutting structural color

Nano-gratings induced structural color is of great value in various anti-counterfeiting and decoration applications. Despite the attractive rendering performances, the manipulation strategy for vibration-assisted diamondcutting structural color is far from complete due to the intrinsically limited tool trajectory designs. The novelty of this paper lies in the precise generation and control of non-harmonic triangle and trapezoidal two-dimensional vibration trajectories to shape typical blazed nano-gratings and nano-grating with specific duty cycles. A twodegree-of-freedom non-resonant vibration tool with closed-loop control was employed to reveal the effect of tool vibration trajectory on the machined nano-grating topography, and establish a sound framework for diamond-cutting structural-color to manipulate color attributes through innovative tool trajectory designs. Triangle and trapezoidal vibration trajectories are utilized for the first time to generate nano-gratings, which will be systematically compared to the common utilization of elliptical vibration trajectory throughout the trajectory generation, kinematical modelling and finite element analysis. Then, various vibration-assisted diamond cutting experiments were carried out to validate the identified differences of nano-grating topography induced by different tool vibration trajectories. The results show that smooth triangle and trapezoidal trajectories can be accurately generated for texturing nano-gratings with typical sawtooth topography and specific duty cycle, which can hardly be achieved using conventional elliptical trajectory. Ultimately, the manipulation of structural color effect via varying tool vibration trajectory was successfully demonstrated using the comparisons of color palette and diffractive spectrum. The revealed effects of tool vibration trajectory are beneficial to guide the process parameter designs for deterministically manipulating the vibration-assisted diamond-cutting structural color effect.