Band-limited cutting force control in ultra-precision turning

Ultra-precision cutting has recently attracted attention to produce optical parts such as lenses without a grinding and a polishing process. It is well known that unstable fluctuation in cutting force has a significant influence on a machined surface roughness and shape quality. Therefore, it is considered essential to control the cutting force in the ultra-precision machining. The sensor-less cutting force control based on the disturbance observer is a practical approach because it does not require any additional sensors. A cutting force is estimated by using the servo information. When the estimated cutting force is fed back to the controller, the sensor-less cutting force control is realized. In this study, the sensor-less cutting force control is applied at a certain range of frequency, and a position control is simultaneously employed. The effect of the proposed control method is evaluated by face turning tests.