Chatter Detection Using the Main Cutting Force

摘要

The coherence function between two crossed accelerations is used in the reference material to identify chatter in turning. The accelerations are in two directions, axial X and vertical Z, measured by two accelerometers mounted on the tool shank. In the frame of an experiment, focused on the monitoring of a lathe, the accelerations of the cutter-holder was registered, for different cutting wear classes (c1 ÷c6), where c6 means "Chatter". Twelve monitoring indices were calculated, among: x_5 → F_2 variation range; x_6 → number of inter-sections of oscillogram F_z with its average value F_z, . The histograms of the column matrices corresponding to the monitoring indices x_5 and x_6, shown for each class, underline the accurate use of these indices values for chatter detection. The coherence function between the accelerations in the directions Y and Z was calculated, by using the function COHERE from MATLAB. The class recordings c6 (Chatter) falls, with one exception, under the criterion from reference material, but it can be seen that 75 % recordings from the class c2 take the maximum value of the coherence function equal to or greater than 0.91. For these recordings the first 6 monitoring indices were calculated. According to a new criterion (which operate with the monitoring indices x_5 and x_6), these recordings are not within the class c6, but class c2. As a conclusion, we believe that the new criterion is much more efficient than those at reference material.