In-process tool flank wear detection by using changes in the tool-work electrical contact resistance

This paper reports in-process detection of tool wear by using tool-work contact electric resistance as a sensor signal in face milling. By observing tool-work thermo-electromotive force (E. M. F.) in the case of using a single cutting edge, E. M. F. at the beginning of cut increased slowly corresponding to the width of tool flank wear. We assume this phenomenon is due to variations in electric resistance by increase of the contact area between the workpiece and the tool, so electric current between tool and workpiece was also detected. The variations of contact electric resistance calculated from both the E. M. F. and the electric current reveal that the electric resistance decreases as the tool flank wear progresses because contact areas between tool and workpiece increase. We developed an in-process measurement system of variations of the contact resistance during face milling process. From the result in relation between progress of tool flank wear and tool-work contact resistance by change the cutting conditions, it has been understood that this method is effective for tool wear detection, that is difficult to monitor in traditional external detection sensors under the finish intermittent cutting.