Determination of the optimal metal processing mode when analyzing the dynamics of cutting control systems

Abstract

Introduction. In numerous experimental studies of metal cutting processes on metal-cutting equipment, the existence of some optimal processing mode is noted, which was most vividly formulated by A.D. Makarov in his point on the existence of an optimal cutting temperature (processing speed). Here, by the authors from Russia, the emphasis is on the description of the optimality of cutting processes related to the properties of the processed material and the properties of the tool used in this process. However, there is another opinion in the Western scientific literature, which is generally based on the regenerative nature of vibrations in cutting dynamics. Vibration regeneration is associated with the dynamics of the cutting process, which is significantly affected by a lagging argument reflecting the variability of the cut layer. The connection of these two approaches is seen through the analysis of the stability domain of the dynamic cutting system in the parameter space: cutting speeds and tool wear values. Subject. Based on this, the paper considers the question of the relationship between the optimal according to A.D. Makarov the processing mode and the dynamics of the cutting process, including the regeneration of tool vibrations during metal turning. To do this, two research hypotheses are formulated and numerical modeling is performed in order to determine its reliability. Purpose of the work: to consider the position of A.D. Makarov on the existence of an optimal cutting mode, from the point of view of the stability of the dynamics of metal turning. For this purpose, two hypotheses are put forward in the work to be analyzed. The paper investigates: a mathematical model describing the dynamics of vibration oscillations of the cutting wedge tip, taking into account the dynamics of the temperature formed in the contact zone and its influence on the forces that prevent the forming motions of the tool. Research methods: a series of field experiments was carried out on a metalworking equipment using the capabilities of the measuring stand STD.201-1, the purpose of which was to determine the effect of the thermal expansion of metals on the value of the buoyant force. Based on numerical simulation of the initial nonlinear mathematical models, as well as simulation of models linearized in the vicinity of the equilibrium point, an analysis of the stability of the cutting system with variations in the cutting speed and the amount of tool wear along the flank is conducted. The results of the work. The results of field experiments are presented, which showed a significant linear increase in the force pushing out the tool with an increase in temperature in the contact zone of the tool and the workpiece. The results of simulation of the state and the corresponding phase trajectories when the cutting wedge is embedded in the workpiece, as well as the forces decomposed along the axis of deformation of the tool, are presented. The results of modeling the Mikhailov vector hodograph for a linearized model of the dynamics of the cutting process are presented. Conclusions: The research results have shown that only the second hypothesis put forward by the authors makes it possible to adequately interpret the point put forward by A.D. Makarov. The main addition to the description of the point of A.D. Makarov, the authors consider it necessary to take into account changes in the pushing force with an increase in the temperature of the contact zone of the tool and the workpiece.