Near-Field Electromagnetic Sensors for Noncontact Monitoring and Workpiece Classification During WEDM Process

Wire electrical discharge machining (WEDM) is a stochastic process incorporating electrical discharges to cut conductive materials. Various sensors have been reported for discharge detection and process monitoring. This study investigates the use of electric (E) and magnetic (H) near-field probes for noncontact WEDM monitoring by distinguishing electrical discharges through their electromagnetic (EM) signatures. Furthermore, the probes’ potential for workpiece identification has also been explored. Based on numerical simulations, a 6 mm long (h) E probe and an 8.5 mm radius (a) H probe were fabricated for operation within 1–100-MHz range, with their electrical lengths ${h}/\lambda $ and ${a}/\lambda $ kept below ${0}.{003}$ . Their EM measurement capabilities were characterized using a 50- $\Omega $ quasi-transverse EM transmission line, with sensitivity values of 2 mV/V/m (E probe) and 4.5 V/A/m (H probe) at 100 MHz. Probe measurements gathered during WEDM of Ti6Al4V, EN32 steel, tungsten carbide (WC), and printed titanium (printed Ti) demonstrated their ability to capture near-field emissions during electrical discharges. The spectral content was predominantly within 1–4.5-MHz and 1–30-MHz range for H and E probes, respectively. Spectral domain features were analyzed using linear discriminant analysis (LDA) for workpiece identification. The model achieved classification accuracy exceeding 97.4% and 87.9% for H and E probe data, respectively. This study proposes that near-field probes are effective for WEDM monitoring and workpiece identification. Further research on the effect of machining parameters and plasma characteristics on different materials is required for sensor optimization and data fusion for monitoring WEDM process.