New methods for tool failure detection in micromilling

A major issue in micromilling is unpredictable tool life and premature tool failure. The specific acoustic footprint and very small removal rates during machining as well as the use of small diameter cutters makes the detection of tool breakage a very difficult task. Thus, it is essential to develop new tool monitoring systems to increase the process productivity, reduce machining costs, and at the same time improve the precision and quality of machined components. This paper analyses three cost-effective and reliable methods for tool breakage detection: an on-line laser system, an on-line tool-workpiece voltage monitoring system, and a programming solution employing an off-line laser system. In order to verify the capability of these three methods, a series of experiments were conducted on an ultra-precision micromilling machine. This involved the machining of test parts in brass, aluminium, steel, and polymethylmethacryate (PMMA) with cutters from 0.5 mm down to 0.1 mm in diameter. The results of these tests are analysed and the technological capabilities of the three studied monitoring approaches are then compared. In addition, the possibility of developing an integrated solution that combines the capabilities of these three monitoring methods is discussed and conclusions made about the feasibility of such an approach.