FLOW OF WORKING MEDIA THROUGH THE CHANNELS IN THE BODY OF THE ELECTRODE-TOOL

Рассмотрен механизм течения жидких и газожидкостных рабочих сред через профильный инструмент для комбинированных методов обработки. Приведены типовые детали, для которых применимы электроды-инструменты с регулируемой подачей рабочей среды в зону обработки, обеспечивающей массовынос продуктов обработки из межэлектродного зазора. За счет применения аддитивных технологий решена проблема изготовления инструмента с внутренними каналами расчетного переменного сечения, обеспечивающими стабильную подачу жидкой (газожидкостной) среды и массовынос продуктов обработки. Предложены новые (на уровне изобретений) способ и электрод-инструмент с управляемой подачей по внутренним каналам рабочей среды, параметры которой рассчитаны с учетом специфики чистовой электроабразивной обработки по схеме копирования профиля детали. Расчетные зависимости для описания механизма течения рабочих сред и методы их использования позволили проектировать электроды-инструменты с профильными каналами, обеспечивающими применение технологических режимов для чистовой обработки инструментом с регулируемой подачей сред и выполнением критерия массовыноса продуктов обработки. Приведенные результаты расчета параметров течения рабочих сред через каналы в инструменте позволили расширить область эффективного использования аддитивных технологий и создать новые (на уровне изобретений) инструменты для электроабразивной обработки по методу копирования и высокопроизводительного одновременного профилирования нескольких поверхностей. Доказана возможность использования энергетической модели для расчета потенциальной составляющей энергии от реализации мощности, затрачиваемой на подкачку рабочей среды, и кинетической энергии от вращения инструмента для получения в зоне обработки требуемой скорости течения жидких (газожидкостных) сред We considered the mechanism of flow of liquid and gas-liquid working media through a profile tool for combined processing methods. We present typical parts for which electrodes-tools are applicable with an adjustable supply of the working medium to the processing zone, which ensures the mass removal of processing products from the interelectrode gap. Through the use of additive technologies, we solved the problem of making a tool with internal channels of a calculated variable cross-section, providing a stable supply of a liquid (gas-liquid) medium and mass removal of processing products. We propose a new (at the level of inventions) method and electrode-tool with a controlled feed through the internal channels of the working medium, the parameters of which are calculated taking into account the specifics of finishing electro-abrasive machining according to the pattern of copying the profile of the part. Calculated dependencies for describing the mechanism of flow of working media and methods of their use made it possible to design electrodes-tools with profile channels that ensure the use of technological modes for finishing with a tool with controlled supply of media and fulfillment of the criterion of mass removal of processing products. The presented results of calculating the parameters of the flow of working media through channels in the tool made it possible to expand the area of effective use of additive technologies and create new (at the level of inventions) tools for electro-abrasive processing using the copying method and high-performance simultaneous profiling of several surfaces. The possibility of using the energy model for calculating the potential component of energy from the implementation of the power spent on pumping the working medium and the kinetic energy from the rotation of the tool has been proved to obtain the required flow rate of liquid (gas-liquid) media in the processing zone

Selected Aspects of Electrochemical Micromachining Technology Development

The paper focuses on the fundamentals of electrochemical machining technology de-elopement with special attention to applications for micromachining. In this method, a material is removed during an anodic electrochemical dissolution. The method has a number of features which make it attractive technology for shaping parts with geometrical features in range of micrometres. The paper is divided into two parts. The first one covers discussion on: general characteristics of electrochemical machining, phenomena in the gap, problems resulting from scaling down the process and electrochemical micromachining processes and variants. The second part consists of synthetic overview of the authors’ research on localization of pulse electrochemical micromachining process and case studies connected with application of this method with use of universal cylindrical electrode-tool for shaping cavities in 1.4301 stainless steel. The latter application was conducted in two following variants: electrochemical contour milling and shaping carried out with sidewall surface of rotating tool. In both cases, the obtained shape is a function of electrode tool trajectory. Selection of adequate machining strategy allows to obtain desired shape and quality.

Current state and prospects of the development of electromechanical processing for gas-thermal coatings

The article presents an overview of the works on electromechanical processing of plasma coatings performed at the Institute of Metallurgy and Materials Science of the Russian Academy of Sciences and VolgSTU. The results of changes in the physical, mechanical and operational properties of plasma-sprayed coatings after electromechanical processing are analyzed. The main approaches in the field of electromechanical processing of gas-thermal coatings are outlined. The use of a cooling liquid to protect the zone of electric contact heating contributes to the preservation of the chemical composition of the coating. High rates of heating and cooling of the local area in the contact zone of the coating and the electrode tool lead to the fixation of the fast-quenched structure in the coating. An increase in the coating temperature as a result of resistive heating with simultaneous surface plastic deformation contributes to a decrease in surface roughness, compaction of the coating and the passage of diffusion welding along the boundaries of the sprayed particles. After electromechanical processing, the coating microhardness, cohesive and adhesive strength, corrosion and wear resistance are increased.

The influence of titanium alloys phase composition on the surface roughness parameters obtained in the process of wire EDM

The paper investigates a roughness of titanium α, α+β and β alloys, obtained by wire electrical discharge machining (EDM) with a brass electrode-tool in distilled water. The purpose of the article is to establish the relationship between the electrical parameters of wire EDM with the surface roughness α, α+β and β of titanium alloys, in particular with the group of parameters Rk. It was established by the method of contact profilometry that the phase composition of titanium alloys significantly affects the height parameters of the roughness of the treated surfaces. It was shown experimentally that the phase composition has a significant effect on the roughness parameters of the Rk group obtained in the process of EDM

Improving Electrical Discharge Machining Process for Bodies of Rotation

In modern mechanical engineering, electrical discharge machining (EDM) methods are widely used for machining bodies of rotation from difficult-to-machine materials. Those methods ensure sparing cutting and make it possible to machine any electrically conductive material irrespective of its physical and chemical properties, in particular hardness. There is a known method for dimensional machining of bodies of rotation with electric arc using a wire electrode tool that is pulled along in the machining area thus "compensating" for that tool's EDM wear and tear. The machining accuracy is therefore significantly heightened. However, when implementing this method, an effect of splashing the working fluid outside the working area of the machine and a pronounced luminous effect from the burning of the electric arc in the machining area are observed. That worsens the working conditions. In addition, when pulling the wire electrode tool along the convex surface of the electrode holder, the sliding friction arises, which eventually leads to mechanical destruction of the contact point. As a result, a deep kerf is formed on the electrode holder. When the depth of the kerf reaches the diameter of the wire electrode tool, the destruction of the electrode holder by the electric arc begins. Consequently, the durability of the electrode holder in the known method is unsatisfactory. A method of dimensional machining of bodies of rotation with electric arc using a wire electrode tool with the immersion of the machining area in the working fluid has been proposed, which makes it possible to improve the working conditions of the operator by eliminating the effect of fluid splashing and removing the luminous effect of arc burning in the machining area. In addition, it has been proposed to make the electrode holder in the form of a roller that rotates with a guide groove for the wire electrode tool, while the nozzle for creating the transverse hydrodynamic fluid flow has been proposed to be mounted in a separate fixed housing that is adjacent to the electrode holder. This technical solution replaces the sliding friction with the rolling one thus enhancing the durability of the electrode holder. Mathematical models of the process characteristics of the DMA-process (dimensional machining with electric arc) for bodies of rotation using a wire electrode tool with the immersion of the machining area in the working fluid have been obtained that make it possible to control the machining productivity, the specific machining productivity, the specific electric power consumption, and the roughness of the surface machined.

Measuring the Influence of Process Parameter on CuCr Electrode Tool Wear Rate for Biocompatible Zr-Based BMG Cutting Using Sinking-EDM

Subsequent processing through machining for biocompatible Zr-based BMG previously developed is needed in order to enlarge the material application, especially for medical devices. In this study the performance of CuCr tool on EDM process was investigated to cut biocompatible Zr-based BMG having low machinability nature. The experiment utilized volume loss technique to measure the TWR and consecutive SEM observation to reveal the tool wear mechanism of selected tool samples. The tool wear behavior was strongly characterized by the combination of discharge current and pulse-on time, where the larger TWR obtained by higher current and shorter pulse-on time. By SEM analysis, the irregular-shaped surface morphology with the presence of debris was observed on the tool wear region resulted by high discharge energy process. Additionally, the larger crater size, microvoids and numerous debris particles were also appeared on BMG workpiece surface machined using higher discharge energy.

COMPARATIVE ANALYSIS OF TWO METHODS OF ELECTROEROSION FIRMWARE FOR DEAF MICROHOLES

The paper presents the results of experimental studies of the significance of differences in the technological parameters of electroerosive micro-hole firmware for two variants of the micro-hole firmware series process: without facing the tool electrode and with the tool electrode facing after processing each hole. The significance of differences in the technological parameters of the firmware process is established: by the wear of the electrode-tool, by the productivity of the process and the efficiency of the process as a whole. Detailed statistical processing of data from two samples of eight duplicate (parallel) experiments in each sample is performed to accurately assess the significance of the differences between the two variants of the process of electroerosive firmware of microholes. Calculations are made of the limit values of parameters of the microholes' electroerosion firmware: the relative linear wear of the electrode-tool and the process performance. They allow identifying and excluding doubtful experiments (artifacts) from the results, i.e. experiments with sharply distinguished results. The results of such experiments should be excluded from the statistical series, since they significantly affect the results of the experiment. The paper uses an exact method for determining the required number of duplicate experiments developed at BSTU named after V. G. Shukhov. The conducted research clearly shows the feasibility of introducing the electrode-tool in manufacturing to reduce the wear of the electrode-tool and, therefore, increase the quality of products with deaf microholes, for example, in the mass production of atraumatic surgical needles, the volume of production of which is millions of pieces per year.