In-process tool wear detection by using tool-work contact resistance change for intermittent cutting process in face milling

This paper reports in-process detection of tool wear by using tool-work contact electric resistance as a sensor signal in face milling. The change in the tool-work contact resistance was estimated from the change in the tool-work contact area according to the progress of the tool flank wear by using Holm's contact theory. As a result, it has been understood that the tool-work contact resistance changes by several milli ohm due to the progress of the tool flank wear. We calculated the tool-work contact resistance by using Ohm's law from the tool-work thermo electromotive force (E.M.F.) and the tool-work thermal current. 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 progress of tool flank wear and tool-work contact resistance under several cutting conditions, it has been confirmed that this method is effective for tool wear detection, that is difficult to monitor in traditional external detection sensors under the finish intermittent cutting.