DEVELOPMENT OF CHATTER INDICES BASED ON MA- CHINING SOUND ANALYSIS

The chatter is a detrimental vibration that can happen during machining operations. The effects of chatter are mostly a defective surface and a considerable reduction in the tool life. A solution commonly adopted to avoid the problem is the analytical study of the stability of the process thanks to known approaches, able to provide a chatter-free set of machining parameters. However this approach is functional if the machining parameters, such as tool engagement or force cutting coefficient of the material, would remain constant during the whole machining process. However, due to the complex geometries that usually have to be machined, these parameters change continuously and this often causes the arising of chatter. The idea of this paper is to develop a method to detect on-line the presence of chatter in order to change as soon as possible the machining parameters to suppress the vibration. As long as the chatter vibrations could be associated to a typical noise, the general idea is to create an approach to highlight the arising of chatter thanks to the study of the sound emitted by the process. To meet this goal some different numerical indices are defined and their threshold has been experimentally set to highlight when the cutting would become unstable or not. The choice of the threshold is set up based on the correspondence between the value of each index and the chattermarks left on the surface.