A New Technique for Identification and Evaluation of Wear in Cupper Electrodes in Electrical Discharge Machining Using Acoustic Emission Signals

Abstract Electrical Discharge Machining (EDM) is an unconventional machining process based on removing material by successive electrical discharges. The tool electrode wear must be kept as minimal as possible to produce high precision components. This scope proposes the development of a new technique for identifying wear on electrodes and its evolution using acoustic emission (AE) signals. Therefore, EDM tests were performed on H13 steel parts with electrolytic copper tool electrodes under two different conditions with concomitant AE signals measurements. The following parameters were used in the first EDM test: voltage pulse duration time (𝑡𝑒) of 150 𝜇s; the time interval between two successive voltage pulses (𝑡𝑜) of 14.84 𝜇s; electrical current of 33 A; and positive polarity electrode. For the second test: duration of the voltage pulse (𝑡𝑒) of 2 𝜇s; the time interval between two successive voltage pulses (𝑡𝑜) of 4.90 𝜇s; electrical current of 18 A; and negative polarity electrode. In this way, a wear rate 28.3 times higher was obtained in the electrolytic copper electrode in the first test, more aggressive due to its parameters, for the same machining time compared to the second test. Finally, the wear of the tool electrodes was related to the AE signals from machining, initially in this study, the workpiece's mass loss was not verified. These signals were analyzed using the Short-Time Fourier Transform techniques and Spectral Entropy. The results showed that the signals using the new technique of relation respond to wear and are sensitive to the electrode's wear rate.