Development of current sensor for cutting force measurement in turning

The importance of monitoring cutting forces in turning has been well recognized in machine tool communities. This paper proposes a new method to measure the cutting forces in turning using inexpensive current sensors and the cutting force model. First, the relationship between the various factors, which affect the performance of the spindle and feed drive systems, and the models of the spindle and feed drive systems are analyzed. Then, some reliable and inexpensive Hall-effect current transducers are employed to sense the current signals of the ac servomotor in a computer numeric control (CNC) turning center; the tangential (F_t) and axial (F_a) cutting forces in turning are estimated by applying a neuro-fuzzy technique. Finally, the normal cutting pressure (K_n) and effective friction coefficient (K_f) are calculated through the cutting mechanical model, so the axial cutting forces (F_r) can also be estimated based on the model of cutting force. Experimental results demonstrate that the method proposed can measure tangential, axial, and radial cutting forces with an error of less than 10%, 5% and 25%, respectively.