Synergetic approach to improve the efficiency of machining process control on metal-cutting machines

OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. No. 3 2021 Fig. 3. Areas of stability of the “frozen” system at different values of wear w 0 : 1 – w 0 = 0.05; 2 – w 0 = 0.1; 3 – w 0 = 0.15 a b area always expands. It was previously shown that, as the speed increases, parametric self-excitation is also observed in the system [11–13]. Therefore, when the velocity increases, there is its range, in which the stability margin is maximum. At the third stage , the trajectories that provide a minimum tool wear intensity are selected from the set L ( ) Ψ . It is taken into account [29–32] that as the work is done, there is an evolutionary restructuring of the properties of the cutting process, including the intensity of tool wear. Moreover, each evolutionary diagram is unique. It depends on the initial parameters, modes and perturbations. Therefore, even its small variations correspond to excellent diagrams of wear and changes in the geometric characteristics of the workpiece surface formed by cutting. Results and discussion During cutting, there are changes in the properties of the dynamic system, determined by two reasons. Firstly, changes in the parameters of interacting subsystems: its stiffness, variations of the allowance, etc. These factors are a priori given. Secondly, the change in the properties of the dynamic coupling formed by cutting, which combines the subsystems, as well as the development of tool wear. These factors are determined by the capacity of irreversible transformations of the energy supplied to the cutting. It is important to emphasize that the properties of the dynamic cutting system during processing change even when the parameters of the subsystems (matrix of m , h and c ) remain unchanged. Therefore, it is necessary to coordinate the TEE of the machine (the CNC program) with the changing cutting properties. Depending on a priori set laws of variation of the system parameters, it is possible to determine the set of desired TEEs of the machine, at which the output requirements to the cutting process are provided and to select from this set asymptotically stable, i.e. attractors. The given example of selecting the trajectory of the longitudinal feed rate when processing a shaft, the change in the stiffness of which is set, allowed us to identify a number of properties. 1. If the dynamic cutting system is unperturbed and stiffness variations are the only parameter varying in space, the elastic strain displacements can be stabilized by software methods with high accuracy. In this case, stabilization of cutting forces leads to even larger diameter errors than uncontrolled machining at constant modes (Fig. 3). This is due to the self-regulating properties of the cutting process, in which the generated forces, represented in the state coordinates, play the role of an internal regulator of the machining diameter with negative feedback formed by the cutting process itself. If the main variable parameter is