Flow field design and process parameter experiments in electrochemical machining of involute internal spline

Machining complex internal structures in high-hardness materials poses significant challenges, as conventional cutting methods often suffer from excessive tool wear and extended production cycles. This study introduces a hybrid approach that combines rough electrochemical machining (ECM) with precision slotting to efficiently shape involute internal splines in intricate high-hardness components. To enhance electrolyte distribution and stabilize the spline ECM process, the electrolyte flow direction was first evaluated to identify the most effective orientation. Based on this preliminary assessment, three flow field optimisation methods—guided flow head, cathode working teeth, and circular rectifier—were developed and validated through simulation. Experimental setups featured two distinct cathode designs and a dedicated ECM fixture and system. Key process parameters, including electrolyte concentration and composition, machining voltage, and cathode feed rate, were experimentally evaluated to determine optimal conditions for spline ECM. The results demonstrated that an electrolyte concentration of 8% NaNO3, a machining voltage of 12 V, and a cathode feed rate of 3.0 to 3.5 mm/min yielded optimal outcomes. Following precision slotting, the maximum tooth profile deviation was 20.7 μm and the maximum helical deviation was 8.5 μm, both meeting target accuracy requirements. Furthermore, the cumulative processing time per piece remained under 1 h, achieving high precision and efficiency in shaping semi-blind hole involute internal splines. This study provides valuable insights into flow field design and process parameter optimisation in spline ECM, highlighting the potential of this combined process for the scalable production of intricate internal cavity components from hard-to-machine materials.