AN INTEGRATED ULTRASONIC SENSOR FOR MONITORING GRADUAL WEAR ONLINE DURING TURNING OPERATIONS

The condition of the tool and the cutting process are essential inputs to any productivity improvements through process optimization in conventional and unmanned machining. Tool replacement and tool wear compensation strategies, which are based on prior experience and/or tool history are, in general, under performing. Currently, the methods of tool condition monitoring are either time consuming, as in the case of off-line direct measurements of the tool, or are modestly successful, as in the case of the on-line indirect measurements, such as forces or acoustic emissions. This in part is due to the lack of suitable sensors and/or exact dynamic models, which relate the indirect measurements to the actual tool condition. This paper describes a promising ultrasonic method for on-line direct measurement of gradual wear in turning operations. An integrated (transmit and receive) single ultrasonic transducer operating at a frequency of 10 MHz is placed in contact with the tool. The change in the amount of the reflected energy from the nose and the hanks of the tool can be related to the level of gradual wear and the mechanical integrity of the tool. The experimental results show that under laboratory conditions, a correlation exists between the ultrasonic measurement and gradual wear and that it is tool dependent.