Manufacturing of three-dimensional optical functional surfaces by diamond engraving of RSA 905

Abstract Functional surfaces have been investigated widely due to different applications in industries. In this paper, the surface functionality was the contrast generated by surfaces orthogonally textured with micro ridges. The principle to generate contrast was the anisotropic reflection led by the bevel surfaces of micro ridges. The surface quality of the micro bevels determined the reflection of the features. In the authors’ previous work, such a functionality was successfully achieved on flat and cylinder surfaces of tool steel samples by micro milling. However, due to the limitation of micro milling process for microstructure fabrication, this study investigated the manufacturing of 3D functional surfaces of RSA 905 by diamond engraving. The 3D surface was shaped with hierarchical structures of micro bricks and micro ridges on the bricks: the surface was divided into micro grids then each grid was machined into a flat basic cell by using a round-tipped tool; the micro ridges were engraved on the basic cells with a sharp-tipped tool. In order to determine the feasibility of the microstructures to achieve contrast generation on 3D surfaces, a data matrix consisting of such micro ridges was patterned on a spherical concave and a freeform surface. The surface integrity was evaluated by measuring the surface roughness of the bevels on the micro ridges, characterizing the burr formation and detection of possible defects left on the micro features that affect the surface functionality. The successful scanning of the data matrix proved the microstructures successfully generated enough contrast to form readable codes. Furthermore, the contrast generated by the microstructures was quantified for process optimization by using a customized robotic measuring system.