A study of the consistency of tool wear characteristics and the criteria for the onset of tool failure

Abstract

Research on tool wear monitoring has shown that there is a good correlation between the dynamic cutting force and flank wear. A characteristic peak can be observed when the dynamic force is presented in the frequency spectrum. Studies have shown that the origin of the peak frequency remains substantially constant throughout the life of the cutting tool. The amplitude of the dynamic tangential force shows a trend whereby it increases as the flank wear increases, and decreases on approaching tool failure. Tests performed on AISI 4340 and AISI 1148 workpieces using P30 tungsten carbide tool inserts suggested that two criteria could be used to predict tool failure, these two criteria being: (i) the threshold value of the percentage drop in the dynamic tangential force from its maximum; and (ii) the negative gradient of the curve of the dynamic force with time. Further tests conducted on AISI 4140 workpieces and the use of P30 coated inserts confirmed a similar trend in the dynamic force results as the tool wore. The percentage drop in the dynamic tangential force from its maxima for a P30 coated tool insert is significantly larger than for the P30 uncoated tungsten carbide tool insert. A software program is being developed currently to track the dynamic force signals and predict the tool failure. © 1993.