Investigation of the Cutting Process Dynamics in Turning Operations

Abstract

There exist a great number of variational cutting force models for the case of plunge cutting but the analytical prediction of the parameters in these models is still elusive at best. The case of traverse cutting is even more intractable from an analytical point of view. A knowledge of the coefficients in the variational cutting force model is necessary to predict the borderline of chatter stability in machining operations. This paper describes the application of a sequential equation error minimization technique to determine empirically the optimum parameter values in a predetermined set of force component models from dynamic cutting data. The identification technique was verified on an analog computer simulation of the dynamic behavior of a machine tool system. The identified parameter values were compared with the actual simulated values. Even in the presence of noise inputs, the identification was accurate to within two to three percent. Experimental plunge cutting tests were performed on an aluminum workpiece. The results of the identification technique applied to these tests were analyzed against the backdrop of the simulation results. Conclusions drawn from the cutting tests were for the most part consistent with other researchers’ results and with intuition. The important contributions of this work are not the conclusions drawn from the cutting tests but the methodologies developed for obtaining results such as these. Specifically, no special inputs are required as in frequency response testing. Identification for both wave generating cuts and wave removing cuts is carried out in the same test. This situation is more indicative of a real cutting situation than either wave generating cuts or wave removing cuts considered separately.