Optical probing of acoustic emission from a rotating tool holder with a Sagnac interferometer

The development of the Sagnac interferometer to monitor the machining proce ss in high-value-added machining processes is described. The instrumental r equirements are non-contact measurement of acoustic emission, in the form o f 0.1-1.0 MHz out-of-plane vibration, with amplitudes in the subnanometre r ange. The instrument was designed to detect acoustic emission by probing th e surface of the rotating tool holder on the machine tool shaft. Experiment s leading to the instrument design, face milling and slot milling machine t ests and a comparison with earlier instrument designs are described.