Acoustic emission monitoring for the diamond machining of oxygen-free high-conductivity copper

The fabrication of high-quality optical lenses and reflectors demands the ultraprecision cutting of materials using micron to submicron uncut chip thicknesses (ac). At this scale, surface topography is influenced significantly by the interaction between the cutting tool and grain orientation and boundary effects. In the past, several researchers verified this effect using techniques and sensors such as scanning electron microscopy (SEM) and force sensors. In this study, micro-scratching tests on coarse-grained, oxygen-free high-conductivity (OFHC) copper were performed using both increasing and constant depths of cut. The topography of the surfaces was characterized and verified using SEM and optical microscopy after micro-etching of the workpiece. Acoustic emission (AE) was used to explore the grain orientation and grain boundary effect in the precision cutting process. Due to its high signal-to-noise ratio at very low depths of cut, AE is a leading sensing technology for monitoring precision machining processes. In this investigation, differences in material properties such as change in grain orientation and grain boundary crossing are monitored during diamond cutting of OFHC copper using AE sensing. The results show that AE has excellent sensitivity and can indicate the local change in material characteristics.