Monitoring the effect of runout on a Diamond-Coated Burrs’ wear progression with Acoustic Emission

Recent Tool Condition Monitoring (TCM) approaches aim to optimise tool replacement by reducing unutilised Remaining Useful Life (RUL) and preventing unexpected failures of Diamond-Coated Burrs (DCBs). Acoustic Emission (AE) has been established as an indirect monitoring method for DCB wear through precision tool measurements. This study assesses the impact of changing initial runout on both wear progression and AE-based monitoring. Twelve wear tests were conducted using an adjustable tool-holder to vary initial runout between 1–78 µm, with AE and frequent on-machine surface measurements collected throughout. Results show that increased initial runout negatively affects total tool life and introduces greater variability in wear behaviour under identical conditions. Using a Renishaw NC4+ Blue (NC4) system, a high frequency of measurements enabled tracking of each DCB’s progression through the three wear phases. Surface crater formation and circumferential wear band expansion were consistently observed in the final wear phase of all DCBs. AE proved effective in monitoring both runout severity and the wear progression of the tool’s high spot. AE features also identified key wear points throughout the tool’s life, regardless of initial runout. These findings highlight the critical influence of runout on small-diameter DCB performance and support AE as a reliable, indirect, on-machine sensing method for tool wear monitoring, capable of identifying varying initial tool conditions.