Direct Measurement of Transient Temperature at the Tool–Chip Interface Using a 3-D-Printed Sensor-Integrated Cutting Tool

Due to the extreme thermal-mechanical stress at tool-chip interface, built-in sensors in the cutting tool are prone to failure during machining process despite their high sensitivity. Eroding thermocouple (ETC) can operate at high stress and high wear conditions; however, traditional adhesive bonding methods introduce significant thermal inertia because the low-thermal-con-ductivity bonding materials reduce response speed and cause sys-tematic measurement errors. In this study, we demonstrate for the first time the integration of an ETC at the tool–chip interface using a solid-state diffusion-bonding approach, which creates direct joints between the sensor and substrate materials. A 3D-printed stainless-steel tool was co-sintered with the ETC, achieving seam-less bonding, rapid response, and robust temperature monitoring based on solid-state diffusion. The performance of this sensor-in-tegrated cutting tool was first evaluated through calibration ex-periments and subsequently verified through real cutting tests. To process the measurements, an extended Kalman filter was em-ployed to filter and regulate the data into an equivalent first-order model. Experimental results demonstrate that the proposed sensor exhibits superior response speed and robustness compared with the conventional sensor, achieving a 67.8% mean reduction in thermal time constant and improving quasi-steady-state robust-ness by as much as 36.2%. Furthermore, the method enhances measurement accuracy, as evidenced by a distinctly narrowed un-certainty band.