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.

On the Forecasting of Lathe Cutting Dynamics(1)

“…with a minimum E E at, can be completed among ARMA (3,2), ARMA (4,3),etc... exhaustively. 1 The minimization in (b) is not a straightforward operation to carry out. Starting from time =l: a = 0 because there is no related data to this residual term 1 a, = 0 j = 2,3...n for the same reason…”

“…E at. 1 It is shown in the literature [9] that in general for the dynamic systems the most agreeable form has m =n -1, so that the search for the most suitable order of ARMA (n,m), N 2 i.e. with a minimum E E at, can be completed among ARMA (3,2), ARMA (4,3),etc... exhaustively.…”

“…There are number of causes of such oscillations, for instance the ground motion, inhomogeneous workpiece, chatter, etc. Especially the chatter phenomenon being a controllable event constituted a focus of attraction for numerous researches [1][2][3][4][5][6]. Very widely spoken form of the chatter, among others is the "Regenerative Chatter", which emanates from the action of overlapping cuts on the previously generated wavy surfaces.…”

A new process damping model for chatter vibration

“…Penetration force and variations of cutting force that occurs from penetration into wavy workpiece surface of the tool have been studied [2][3][4][5]. Also, variable cutting force which occurs from shear angle (u) variation because of oscillation of tool has been studied [6][7][8][9]. Comprehensive modeling of the dynamic cutting forces and, its effects in the chatter vibration have been studied [10][11][12][13][14][15] where dynamic cutting coefficients are obtained.…”

Lathe stability charts via acoustic emission monitoring

“…A closed-loop model of the metal-cutting system as discussed by Merrit [1] is shown in Fig The existence of unique relationships between the cutting force and tool displacements has also been used to predict the onset of self-excited chatter. Scrinivasan and Nachtigal [10] have described 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 method as described in their paper can only be an off-line identification technique because of the difficulties of measuring relative displacements in actual production and the undesirability of applying an impulsive input to the workpiece during machining.…”