Development of a magnetostrictive torque sensor for milling process monitoring

This paper deals with a sensor system based on the magnetostrictive effect which is installed in a tool holder for sensing cutting torque in order to monitor the milling process. Changes in the magnetic permeability of ferromagnetic alloy layers formed onto a rotating shaft due to torque are detected by coils as changes in impedance without contacting the rotating shaft. By mounting the magnetostrictive sensor on a tool holder, it has become possible to detect cutting torque as close to the cutting point as possible. The accuracy of the proposed sensor system is confirmed through static and dynamic evaluation tests. In order to investigate the relationship between tool failure and cutting torque, cutting tests were performed. As the results, the possibility of estimating flank wear and tool fracture from cutting torque detected by the proposed sensor system is recognized.