Monitoring of the tool condition with acoustic emission signal analysis using wavelet packets

The acoustic emission (AE) phenomenon is useful for monitoring machining processes. AE is directly related to the tool condition, since it is generated by plastic deformation, abrasion, debris fracture, and crack propagation. In this paper, several AE parameters were measured during the wear of a tool insert in turning tests. While some of these parameters are indicative of the wear degree, their applicability in industrial activities is limited. This occurs because the establishment of a control threshold value strongly depends on the process variables. For this reason, parameters obtained from the Wavelet Packet (WP) transform coefficients, were employed. They were the Power and the Entropy of the WP coefficients, both in the 300 kHz 600 kHz frequency range. These two parameters were found to be adequate and specific for the determination of the tool condition.