OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 4 4 2 If we follow the work [58], as the cutting speed increases, a redistribution of physical interactions in the interface areas of the tool and cutting zone (adhesion, fatigue, abrasion, tribochemical, diffusion, etc.) is observed. Transition from prevailing adhesion to diffusion interactions corresponds to the minimum of wear intensity. This range corresponds to the minimum power of irreversible transformations of the energy input to the cutting [56]. When machining steel 45, the region of this transition is located in the range 1.0–2.0 m/s. In addition, with increasing Ω there is a critical value of Ω, starting from which parametric effects begin to appear, including parametric self-excitation [45]. Therefore, there is a critical value of Ω, exceeding which is unacceptable and it is necessary to take into account the restrictions imposed on the system the peculiarities of its dynamics. Results and discussion One of the currently developing ways to increase the effi ciency of machining parts, the stiffness of which varies along the tool path is the coordination of external control (from the CNC system) with internal control of elastic deformations, determined by the dependence of forces on deformation displacements and TEE. The synergistic problem of interaction between the external control and the internal control [3–7], formed by the dependence of cutting forces on deformation displacements and TEE set by the CNC system, is solved on the basis of matching the external control with the internal dynamics of cutting. To do this, fi rstly, when defi ning the CNC program, a set of desired paths of the forming motions, which include both the TEE and the deformations of the tool tip relative to the workpiece, is constructed. The desired paths are defi ned on the basis of the requirements to the parts quality. All intermediate paths of the dynamical system up to the CNC program are subject to these paths. Thus, the currently existing principle of subordination is replaced by the principle of interaction of subsystems according to the direction of goal achievement. Secondly, from the obtained set of paths obtained at different technological modes, a path is selected, at which the intensity of tool wear is minimal. The depth of cutting is usually set a priori, so when selecting the modes, it is necessary to determine the cutting speed, at which the desired path of the forming motions is asymptotically stable, from the conditions of physical optimality. The performed verifi cation of the effectiveness of the method in the longitudinal turning of the fuel pump nozzle showed that by reducing the number of passes, it is possible to increase the productivity of part manufacturing up to two times in machine time. The increase in productivity is achieved, fi rstly, by reducing the number of passes. According to the basic technology, after drilling the central hole D = 2.5 mm, which is performed on a specialized machine, the workpiece is installed in the centers and the longitudinal turning of the shaft is performed in the beginning for the entire length up to D = 27 mm. Then the main surface of the shaft is turned in three passes with depths of cut tP (0) = 1.5 mm; t P (0) = 0.7 mm; and t P (0) = 0.3 mm. Such transitions provide the required diameter accuracy until the back edge wear reaches 0.6 mm. The cutting modes remain unchanged. When using the synergistic concept due to the coordination of TEE with the changing parameters of the workpiece stiffness along the tool motion coordinates, coordination of TEE with the evolutionary changes in the properties of the dynamic relationship formed by cutting, as well as determining the optimal coordinates of switching (readjustment) of machining cycles, it is possible to reduce the number of passes from four to two. Besides, it is possible to increase the batch of parts before tooling system readjustment by 1.5 times. The optimal switching coordinates were determined according to the method stated by us earlier [59]. It is important to emphasize that the increase in productivity was achieved by software methods, without additional material costs. Conclusion One of the promising directions of manufacturing a batch of parts of a set quality while minimizing the reduced costs is the use of the synergistic principle of matching the external control (CNC program) with the internal dynamics of the system. The given example of manufacturing a part, the stiffness of which
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