Tool pre-failure monitoring in intermittent cutting operations

Tool failure remains one of the most challenging phenomena in machining that affects the productivity and product quality, and hence the cost. In high feed rough milling operations of hard-tocut materials, chipping and breakage have been observed as the dominant failure modes of the end mill cutters. Most of the work in the open literature is focusing on either detecting the complete tool breakage after it takes place or detecting the progressive tool wear. Detecting the abrupt/sudden tool failure due to tool chipping before it takes place, which is essential to avoid any damage to the machined part, has not been addressed. Therefore, the main objective of this research work is to investigate the ability of using the process monitoring signals in order to detect the tool pre-failure and failure by chipping/breakage in intermittent cutting operations. A method was devised to induce impact load on the cutting tool tip to study the features of signals collected by various sensors due to unstable crack propagation and chipping, while ensuring minimal tool wear effect. The acoustic emission (AE) signal features were able to successfully capture tool pre-failure, while other signals could detect the failure occurrence only.