In-Process Machining Process Monitoring Method Based on Impedance Model of Dielectric Coating Layer at Tool-Chip Interface

In this study, we investigated a novel approach that enables the in-process machining process monitoring at the tool-chip interface (TCI) by utilizing the impedance characteristics of the dielectric coating layer of the cutting tool. This study first analyzes the Nyquist diagram that characterizes the impedance response of a few micrometer-thick dielectric layers coated on the surface of the cutting tool by using an impedance analyzer under various temperature conditions for establishing the relationship between the relative permittivity of the dielectric layer and temperature. Consequently, the impedance of the dielectric layer was subject to change according to given temperature conditions. Thus, under its temperature-dependent impedance characteristics, the machining processes could be in-situ tracked and analyzed by directly probing the localized TCI, the so-called cutting hot spot, during the machining. The current source was implemented with the machining system and the variations of impedance at TCI were monitored during the facing process. As a result, impedance responses were remarkably changed under various machining conditions. The impedance was further characterized under the varying depth of contact and the impedance was decreased as the depth of contact increased. Therefore, the preliminary study demonstrated that an electrical impedance model of the dielectric coating layer may be applied for an in-process machining process monitoring method to analyze and assess the phenomenon of the machining process at the local TCI region. This study is expected to potentially provide utilization in advanced manufacturing to improve final part quality and productivity.