A Comprehensive Investigation on Micro-Drilling Performance and Hole Quality of Ti6Al4V Alloy Fabricated by Electron Beam Melting

Abstract The application of additive manufacturing is increasing in the production of metal components, while machining processes, such as micro-drilling, are essential to ensure the successful completion of the manufacturing process. This paper experimentally investigated the drilling performance and hole quality assessment of Ti6Al4V alloy manufactured via Electron Beam Melting (EBM), considering various drilling strategies, spindle speeds and feed rates. Thrust force, vibration, hole quality, tool temperature and wear were considered as evaluation criteria. The process parameters were optimized primarily based on hole geometry, and the obtained optimal conditions were subsequently validated for each evaluation criterion. A similar trend was observed between thrust force and vibration, with both increasing at higher feed rates and spindle speeds. In pilot hole drilling, the maximum thrust force and vibration frequency were significantly lower at approximately 130 N and 1049 Hz, respectively. The increase in thrust forces resulted in the deterioration of hole quality. The best hole quality was obtained using the pilot hole strategy and the parameters of 7500 rpm and 5 µm/rev. Surface roughness values (Ra) were measured between 2.3 μm and 3.5 μm. The maximum tool temperature and wear were observed at the highest feed rate during direct drilling strategy, measured at 323 °C and 19.2 µm, respectively. These results provide valuable data for industry, potentially aiding the production of high-quality micro-drilled components at lower production costs. It is suggested that various cutting strategies can be applied to minimize defects at holes during micro-drilling of Ti6Al4V alloy.