Process compatibility analysis for hybrid electrochemical removal and accretion towards a multifunctional machine-tool: An application-oriented approach

The demand for multifunctional and multi-material parts has driven the development of hybrid manufacturing technologies. Laser-based additive and subtractive techniques offer design flexibility but are unsuitable for smart components, high-end aerospace and biomedical applications due to thermal defects. In contrast, electrochemical additive manufacturing (ECAM) and electrochemical machining (ECM) are non-contact in nature with minimal thermal load, which can preserve material properties while enabling material accretion and removal, respectively as governed by the Faraday's laws of electrolysis. However, sequential processing with ECM and ECAM is challenging to achieve on the same platform due to different compatible process windows, electrolytes, and localisation issues.

Therefore, this study presents successful hybridisation of maskless ECM and ECAM processes on a multifunctional machine-tool, enabling bi-directional feature fabrication (via ECAM) and shaping (via ECM) in one clamp, where the process localisation is achieved by an electrolyte confining air-column. The experiments examined the influence of process parameters and investigated process compatibility to demonstrate the potential of this hybrid technique. The air column at 1.1 bar improved process localisation by reducing the ECAM feature width by 60 % in comparison to no air-confinement (0 bar). Additionally, the best surface quality of ∼0.33 μm Sa with ECAM at 5 V was achieved at 50 % duty cycle with 20 μs pulse period as voltage pulsing allowed flushing of by-products from the interelectrode gap and shorter pulses reduced gas bubbles generation. Furthermore, it was possible to demonstrate layered manufacturing and mould repair applications using appropriate process parameters to avoid stray removal and accretion during bi-directional ECM and ECAM. These results represent a significant step in hybrid electrochemical manufacturing towards realising advanced multi-material and multi-functional component applications.