Plakhotnyi O. Scientific principles of the combined technology of wire electrodischarge and electrochemical machining

The work is devoted to further development of scientific and technological princi-ples of combined wire electrical discharge and wire electrochemical machining (WEDM and WECM), creation of a system of multifactor calculation of equipment parameters and technologies to achieve maximum technological characteristics of the process and obtain controlled surface formation with new geometric and physicochemical parameters. The work deals with the establishment of physical and technological patterns of material removal using electrical discharges and the formation of near-surface layers of electrodes by discharges of short duration and energy. Based on the analysis of known results of experimental and theoretical studies, simplifying assumptions are formulated that allow to conduct computational experiments using a threedimensional model of thermal processes of electrode material removal based on the numerical solution of threephase thermal conductivity problem without significant loss of adequacy of a mathematical model of real physical processes, which occur in the area of the spark discharge. The method of determining the depth of the HAZ and the parameters of surface roughness formed by the sequence of discharges typical for WEDM cutting is proposed and substantiated. The work presents the results of studies of the nearsurface anodic dissolution processes during electrochemical machining with microsecond current pulses. The complex of experimental researches has specified the values of current efficien-cy coefficients depending on the pulse current density and the structure formed by preliminary heat treatment of the material during the electrochemical dissolution of ARMCO iron and steels H12F1, U8А, SchH15, Steel 45. The use of the size of the dissolution zone and the excesses of the current density distribution for WECM technologies as criteria for estimating the localization of the anodic dissolution process is proposed and substantiated. Based on the comparison of the obtained electrolyte flow velocity distribution and the accurate analytically presented current distribution on the anode surface, a method of coordinating the hydraulic modes of electrolyte flow with the amplitude-time parameters of the power supply is proposed. The use of this method allows for each case of the height of the part, the size of the interelectrode gap, the parameters of the electrolyte supply to design the amplitude-time parameters of the current pulses, which ensure uniformity and stability of dissolution throughout the machining height. Experimental verification has confirmed the effectiveness of the practical use of the obtained research results and their contribution to improving the stability and predictability of electrochemical dimensional machining with a wire electrode as a technology. An improved method for calculating quantitative parameters of the process of anodic dissolution of WEDM-modified surface with uneven in depth electrochemical character-istics is proposed, which allows to specify the numerical values of the coefficients of elec-trochemical dissolution of steel surfaces` layers and can provide a significant increase in the accuracy of calculations of parameters of the processes of electrochemical modification of surfaces by a wire electrode. The work is devoted to the development of methods that ensure the accuracy of the formation of elements of complex contour surfaces by a combined technology of electrical discharge and electrochemical machining with a wire electrode. On the basis of a complex of experimental and theoretical researches, the computational-experimental technique is offered. Also the equations for calculation of the value of the distributed external load applied to a wire during cutting of certain groups of steels and hard alloys are obtained. The obtained results allow at the design stage of technological process to calculate the actual shape of the wire electrode and, taking it into account, to build the machining technology and the corresponding trajectory of machine drives. A method of mathematical computer calculation of technological current density distribution in threedimensional formulation for flat anode and cylindrical cathode configuration has been developed and tested, which helps to predict the accuracy of shaping when designing the machining process of combined technology of sequential application of WEDM and WECM cutting.