Investigation of indices based on milling force for tool wear in milling

Abstract

In milling, the cutting force pulsates periodically as the inserts intermittently engage and disengage the workpiece with each revolution of the cutter. Several deterministic and stochastic factors contribute to the fluctuation in the cutting force. The resulting complex variations of the cutting force complicate attempts to correlate the tool wear with the measured force signal. Suitable techniques are required to derive effective indices of significant or severe milling tool wear from the cutting force. In this paper, three time series and statistical techniques used to determine tool wear indices from the milling force signals are discussed. From experimental tests in milling, it has been found that the flank wear of the insert is the prominent wear under normal cutting conditions. Hence, the standard criterion that determines significant flank wear of a cutting insert is used to set the corresponding threshold values for the tool wear indices derived from the cutting force signal. The effectiveness of the three techniques in providing reliable indices of significant tool flank wear under conditions of run-out, cutting transients, and changes of cutting conditions are compared over a range of milling conditions.