In-Process measurement of tool displacement in ultrasonic vibration superimposed turning of bronze

Abstract Ultrasonic vibration-superimposed turning can be used to improve the performance of components by enabling a surface microstructuring in finish machining. Even though the benefits are numerous, control of the vibration amplitude and operating frequency during machining proves difficult as mechanical and electrical resonance frequencies do not always match, limiting their efficiency and use in industrial applications. This highlights the need for improvement of conventional control systems. Measuring mechanical vibrations close to the cutting tool might offer benefits regarding the precision of displacement control compared to conventional approaches like phase-locked loop. To examine the usability and the information content of physical measurands, a sonotrode is designed to enable the measurement of acceleration, strain and temperature during machining. For this an accelerometer, fiber-optical sensors and a passive piezoelectric disk in the ultrasonic transducer are considered. Experiments during free vibration and in an ultrasonic vibration-superimposed turning process were carried out and compared to numerical results. Turning experiments were conducted at feeds of 0.05 mm and 0.10 mm and cutting speeds of 120 m/min and 480 m/min. Additionally, power levels of the ultrasonic system and tool flank wear land width were varied. Also, possible sources of deviations between the manufactured and predicted surface were analyzed.The results demonstrate correlations between the sensor data and the surface topography. Thus, the sensors provide meaningful information regarding the dynamic behavior of the system during operation, enabling a process monitoring close to the tool and showing a possible use for a future control system.