Tip-based vibration carving of shape-customized convex microstructures: principle, modeling, and experiments

Convex structures are a crucial type of surface functional structure whose shape significantly affects their performance. Tip-based machining and vibration texturing are two groups of state-of-the-art subtractive fabrication methods for micro/nano structures, each offering distinct advantages: tip-based machining excels in achieving small feature sizes, whereas vibration texturing improves production efficiency. This study aims to combine these methods to create a more powerful micromachining technique, namely tip-based vibration carving (TVC), particularly suited for fabricating shape-customized convex microstructures. In TVC, the vibration trajectory and nominal carving motion of the tip tool are parallel to the workpiece surface. In each vibration cycle, the tip tool removes some material while the remaining material becomes one convex microstructure. Therefore, the shape of convex microstructures can be customized by the design of vibration trajectories. By adopting high-frequency vibration, the production rate of convex microstructures can be highly efficient. Based on the fundamental principle of TVC, three types of TVC methods—sine-shape, O-shape, and U-shape TVC—are proposed, each employing distinct vibration trajectories. A prediction model for surface generation of convex microstructures is established based on the fusion of process mechanism and experimental data. Finite element simulations are conducted to analyze the material removal and deformation processes during TVC processing. Surface texturing tests are performed on the aluminum workpieces to verify the efficacy of the proposed TVC in producing various shapes and hybrids of convex microstructures. The experimental results also validate the accuracy of the developed prediction model of the surface morphology of generated microstructures. In addition, the feasibility of TVC on various materials, tool wear after processing, subsurface change of carving, and surface wettability are investigated.