Exploration of morphological evolution of surface array microstructures in die-sinking micro-EDM with composite material electrodes

Die-sinking micro-electrical discharge machining (micro-EDM) utilizing a composite material electrode (CME) is an innovative technology ideal for mass-producing surface array microstructures. The CME is fabricated by layering and integrating micro sub-electrodes with different wear rates in an array form, and the initial electrode working surface only needs to be cut flat. After several rounds of die-sinking micro-EDM with the same feed depth, the electrode working surface progressively wears, achieving a stable structure. Nevertheless, the composition of the sub-electrodes and their adjacent relationships significantly impact the development of the machining structure morphology. Therefore, addressing the fundamental scientific problem of die-sinking micro-EDM with CMEs is essential. In this study, a theorem was derived for die-sinking EDM with CMEs, illustrating that CMEs could conduct batch machining, unlike homogeneous electrodes. This theorem served as a universal principle applicable to die-sinking micro-EDM with both CMEs and homogeneous electrodes. This paper analyzed the adjacency effect, which decisively impacted sub-electrode wear rates. Based on the above theorem, a simulation iterative model was developed to determine the wear rates of sub-electrodes influenced by adjacency effects. The evolution of the structural morphology of both the CME working surface and the workpiece processing surface was simulated for each round until convergence and stability were attained. A description formula rule for CMEs and a bidirectional stacking process of connecting foil sub-electrodes with double-sided conductive tape were proposed, and a two-dimensional configuration method was developed for processing wear rates, thus achieving efficient batch manufacturing of various surface array microstructures.