An in-situ high-cylindricity micro-hole finishing technique

This study presents the development of an in-situ hybrid micro-manufacturing process for making a novel micro-tool for the fabrication of a high-precision micro-hole of 200-μm in diameter in difficult-to-machine material. The hybrid techniques approach consists of rotary micro-EDM, micro-EDM peck-drilling, codeposition, reverse micro-w-EDM, and micro-honing, which can all be conducted on a single machining center allowing for in-situ micro-manufacturing. A novel micro grinding-tool which has an invert-tapered forked microstructure with central-symmetry and radial-elasticity is designed and fabricated using the hybrid processes. By applying the principle of cantilever beam support, the micro grinding-tool is employed for honing a micro-hole on SKD11 cold-working steel, achieving micro-scale material removal. All working coordinates are recorded during the process, the micro-tool and -workpiece do not need to be unloaded and repositioned until all planned tasks are completed. Experimental results demonstrate that flatness of the hole-wall, circularity, cylindricity and surface roughness of the honed micro-hole are 1μm, 0.5μm, 1μm and Ra0.032μm, respectively. It is expected that the approach will significantly contribute to the high-precision industry and to future micro fabrication techniques.