Harmonic-based-on analysis to discriminate different mechanical actions involved in the machining of hard-to-cut materials

Cutting force monitoring may be established as a functional control system for machining processes, helping determine the optimal time for tool change since a relationship between tool wear and milling forces exists. However, these forces result from various effect, including chip removal, friction, and vibrations. Predicting the end of functional tool life becomes challenging due to these complex interactions. In this study, it is proposed a decomposed action methodology based on force analysis using the fast Fourier transform and harmonic analysis. In pursuit of a comprehensive understanding of cutting forces during milling process, it is proposed a methodology to capture the signal given by a rotary dynamometer in selective cutting tests directed to discriminate and isolate external friction and other effects. The methodology has been tuned for slot milling of Ti48Al2Cr2Nb titanium aluminide using a single uncoated tungsten carbide insert, under different combinations of depth of cut and feed per tooth, for a fixed cutting speed value. The friction force in the tool flank zone has been demonstrated as the main action due to the small chip section removed, which leads to explain the rapid tool wear in titanium aluminides machining. Friction coefficients ranging from 0.412 to 0.579 have been found in real cutting conditions. This methodology will allow the evaluation of different tool geometries to reduce tool-workpiece friction and wear phenomena, enhancing the tool life.