Electrical Current Measurements for Process Monitoring in Wire Arc Additive Manufacturing

A measurement framework for the evaluation and online quality estimation of the wire arc additive manufacturing process based on cold metal transfer (WAAM-CMT) is presented here. Although several monitoring approaches have been proposed for WAAM, the identification of reliable noninvasive indicators capable of capturing process stability in real time remains challenging due to the highly nonstationary nature of arc current signals. A noninvasive monitoring strategy based on electrical current acquisition was implemented, using a clamp-type sensor to acquire the electrical current signal during the welding process. The acquired current signals were analyzed in both the time and frequency domains. To address the inherent variability of the current waveform, a wavelet coherence (WC) approach was adopted, enabling localized time-frequency correlation analysis between the measured current and a reference waveform. From this representation, a mean global WC (MGWC) index was derived as a quantitative indicator of process stability. The proposed methodology showed effectiveness in distinguishing between stable and unstable deposition regimes, linking signal irregularities to the geometric quality of the deposited tracks. In addition, measurement uncertainty was explicitly evaluated by combining probability density functions derived from instrument specifications with Monte Carlo propagation, enabling the estimation of the confidence level associated with the monitoring indicator. The resulting framework integrates electrical current sensing, time-frequency signal analysis, and uncertainty quantification, providing a scalable and noninvasive solution for real-time monitoring and quality assessment in WAAM-CMT processes.