Development and application of a rotary smart toolholder for four-component milling force/torque measurement

To meet the demand for online cutting process monitoring in intelligent manufacturing and solve the problems of poor adaptability, high cost, insufficient stiffness and dynamic performance of existing sensors, this study developed a piezoresistive four-component intelligent tool holder for milling force/torque measurement. Based on the HSK-A63-ER32 standard holder, this design adopts the “tool holder as sensor” concept. Through the structural design of the tool holder, chip placement, and ingenious combination of bridges, it achieves independent measurement of four components. Semiconductor strain gauges form a Wheatstone bridge to decouple and measure three-dimensional cutting forces (F_x, F_y, F_z) and torque (T) without changing the main structure, and a wireless transmission module is integrated to solve the signal transmission problem in rotation. Finite element analysis shows a maximum stiffness loss of 10.6 % with safe stress. Performance tests revealed good accuracy, with repeatability, linearity, and hysteresis errors of 3.5 %, 0.97 %, and 0.27 %, respectively. The sensor exhibited a natural frequency of 2500 Hz, enabling dynamic milling force and torque measurements up to the theoretical safe spindle speed of 9375 r/min. Milling experiments verify its ability to monitor cutting states. With low cost, high stiffness, excellent static, dynamic and dynamic balance performance, it has good engineering potential and provides a reliable solution for intelligent machine tool cutting process perception.