Spindle-mounted self-decoupled force/torque sensor for cutting force detection in a precision machine tool

Cutting force detection is important in machine tools. In this study, a self-decoupled force/torque sensor mounted on a machine tool spindle is proposed, analyzed, fabricated and tested to detect the axial force and torque of the cutting force. The self-decoupled operation is fulfilled by two decoupling nodes: the first decoupling node is achieved by three guide bearings to eliminate the translational effect, and the second decoupling node is completed by a graphite gasket to eliminate the torsional effect. Two magnetostrictive materials are added to the force-sensitive and torque-sensitive zone as sensing elements to detect the axial force and torque, respectively. Passive and wireless characteristics are realized based on the Villari effect. A full-size prototype of the sensor was fabricated and tested, and calibration results show that the sensor achieves good self-decoupling with a maximum decoupling error of 0.44%. Cutting test results show that the sensor is consistent with industry standard sensors and can be applied to real machine-tool cutting processes. Compared with similar cutting force sensors, the proposed sensor performs better in decoupling method with regard to decoupling accuracy.