Influence of discharge energy on dimensional accuracy and surface morphology during the µ-EDM of Ti-6Al-4 V

Micro-electrical discharge machining (µ-EDM) is a precision micromachining method widely used for producing micro-features in aerospace superalloys. However, unstable discharge pulses reduce dimensional accuracy and compromise µ-hole integrity. This study improves the dimensional accuracy of µ-holes machined in Ti-6Al-4V using copper electrodes by systematically identifying efficient and inefficient discharge pulses. A discharge pulse classification algorithm was developed using energy-signal analysis to distinguish pulse types. Based on defined pulse-energy thresholds, key µ-hole responses depth accuracy, material removal rate (MRR), and surface roughness were correlated with discharge behavior. The highest depth deviation (~49%) occurred at 2600 µJ and a feed rate of 50 µm/min, while the lowest deviation (~35%) was achieved at 3600 µJ and 100 µm/min. Transient arcing, arcing, and short-circuit pulses lower effective discharge energy, reducing machining efficiency and altering MRR. Overall, the proposed pulse classification approach clarifies how µ-EDM parameters govern pulse efficiency and machining performance in Ti-6Al-4V.