A comprehensive methodology for designing a magnetic deflection system for a technological electron gun is proposed. The feasibility of using deflection systems with an internal magnetic circuit and toroidal coil sections to form deflection fields that ensure azimuth beam rotation with a constant angle of deviation from the vertical axis is substantiated. The potential of computer modeling is shown both at the stage of calculating the deflection field and beam displacement and at the stage of creating the design of the system frame for its subsequent manufacture based on 3D printing. The main coil parameters are determined, and the circuit diagram of a current stabilizer with external control from a digital-to-analog converter is developed. Dependences are presented showing the relationship between control signals and deflection angles in the developed unit prototype. It is shown that the proposed technique is universal and can be used to create electron-optical gun elements providing deflection, scanning, parallel transfer or adjustment of technological electron beams.

The structure is considered for a typical system to control electron beam welding deposition with supplying feed (wire). This approach is used today to implement additive technologies. The main features of the process are described. It is shown that the temperature of the underlying layer changes during surface deposition; therefore, it destabilizes the process through changing the temperature of the melt bath as well as the transverse dimensions of the formed layer. The need to use a feedback control system to stabilize the temperature of the welded layer is substantiated and an approach to its technical implementation is described. The results obtained for a prototype of a temperature stabilizer based on a microcontroller are presented. The fundamental potential is demonstrated to ensure the repeatability of the height of the welded layer and to prevent the wire from detaching the liquid melt bath during welding deposition of a multilayer cylindrical contour made of 316L steel.

The structure of a typical control system for the wire-based electron-beam surfacing process, which is used today for the implementation of additive technologies, is considered, and the main regularities of the process are described. It is shown that the temperature of the underlying layer, which changes during surfacing, is a destabilizing factor affecting the pool temperature and the transverse dimensions of the formed layer. The necessity of using a feedback control system to stabilize the temperature of the deposited layer is substantiated and its technical implementation is described. The results of using the developed prototype of a temperature stabilizer based on a microcontroller are presented, and the fundamental possibility of ensuring the repeatability of the height of the deposited layer and eliminating the separation of the wire from the liquid pool during surfacing of a multilayer cylindrical contour made of 316L steel is shown.

The mathematical formulation of electron beam melting and liquid metal transfer model in wire-based additive manufacturing with temperature dependencies of thermophysical properties is described. A description of the model algorithmic implementation based on the use of numerical methods for solving the Navier-Stokes equations system and the Volume of Fluid (VOF) method for tracking the free surface of a liquid on the cubic mesh cells is given. An iterative method for calculating the pressure field that ensures the fulfillment of the incompressibility condition for a viscous fluid is described. The paper also paid attention to the description of methodology for calculating the forces acting on the free surface of the melt, including surface tension forces and metal vapor pressure forces. One of the key elements of the proposed model is method for volumetric distribution of electron losses calculating, considering their scattering during the interaction of an electron beam with a curved melt surface. Electron beam focusing influence on the distribution of energy losses and the dynamics of penetration channel formation has been studied. An algorithm for visualizing the free surface of the melt based on the use of the Gaussian function, is described.

Проведен анализ структуры каналов управления установки для реализации процессов электронно-лучевого аддитивного формообразования на базе серийных электронно-лучевых сварочных установок. Рассмотрена актуальность решаемой задачи и описан метод ее решения. Предложен программно-аппаратный способ синхронизации каналов управления ЧПУ с каналами управления током пучка на базе программируемого контроллера ATmega328, который позволяет синхронизировать во времени каналы управления перемещения электронной пушкой и током пучка. Описан принцип работы разработанного устройства сопряжения, а также проведены эксперименты, показывающие работоспособность устройства. Проведены серии экспериментов по наплавке одиночных валиков из сплава ВТ6 и приведены осциллограммы параметров источников питания пушки, которые демонстрируют работоспособность разработанного метода.

A mathematical model, proposed by the authors to study the processes of nonlinear heat transfer during electron-beam deposition with direct feeding of filler material into the heating source influence zone, is described. The model is implemented in the form of a computer program based on numerical methods for solving the energy equation with moving boundary conditions. An algorithm is described that makes it possible to take into account the latent heat of melting when calculating the temperature field. Using this descriptive model and a discrete model of PID-controller, a quasi-normative model has been developed that allows analyzing closed-loop control processes to stabilize the deposited layer temperature. The fundamental possibility of using PI- and PID-controllers for heating source power controlling in multilayer deposition process of a straight wall made of AISI 316L steel is shown, as well as the need to turn off feedback when passing from one layer to another.

Molten pool free surface shape calculation and its evaluation in time for analysis of electron beam melting and welding processes is a very important problem. Unfortunately, experimental methods can provide only a part of the necessary information. Electron beam heating creates the conditions for intense metal transfer, and pool surface shape affects the energy absorption efficiency. This paper reports the method which combines the Monte-Carlo simulation for spatial and energy parameters of heating source calculating with the Volume of Fluid algorithm for liquid free-surface numerical evaluation. The velocity and pressure field technique calculation in a molten pool with the action of surface tension forces and vapor recoil pressure is described. It is shown that the proposed simulation method allows to study heat and mass transfer transient processes, including deep penetration channel formation. Model validation was carried out. Simulation results are shown to be consistent with experimental data obtained using a high-speed camera.

In the last decade, great interest has been shown in the introduction of additive technologies, in which wire is used as a feed material. Such technologies are characterized by high productivity, low cost of the filler material and provide the possibility of forming large-sized products. The relevance of closed control systems development for additive manufacturing processes with filler wire feeding is justified. It is shown that despite the availability of publications devoted to the development of methods for controlling of the deposited layer temperature, there are currently no applying process control systems with feedback. The most rational method of developing such systems is mathematical modeling using. The paper represents a descriptive mathematical model of the additive manufacturing process based on the energy equation numerical solution. It is shown that this model can be supplemented by an algorithm for temperature stabilization that implements one of the laws widely used in control theory, which is PI, or PID–law. The results of computational experiments have shown the fundamental possibility of creating closed systems for additive manufacturing processes controlling with filler material feeding in the form of a wire.

One of the most actual problems during electron beam welding of metal materials is the determination of the laws of primary electrons interaction with a gas (vapor) flow, taking into account existing and generated (by charged particles) electric fields. The paper is devoted to the development of computer simulation method for the process of electron beam passage through a layer of evaporated metal. The analysis of simulation results showed a significant effect of ionization process on electric field in a gas-vapor channel. It was established that at the initial stage of the process, a region with a positive potential is formed in the lower part of gas-vapor channel, and in its upper part, on the contrary, potential decreases.

The urgency of solving the problem of determining the deposited layer’s height for controlling the process of additive forming products from metallic materials in a vacuum is substantiated. A scheme of electron-beam additive manufacturing process with wire feed is shown. A method for controlling the distance between deposited bead and electron gun by the signal taken from a collector of backscattered electrons is proposed. The analysis of the signals recorded during the process of deposited metal bead scanning has been carried out, and technical feasibility of this method has been substantiated. The technical solutions to introduce a method for continuous monitoring and control of additive forming process are proposed. A series of computational experiments at using the Monte Carlo method were carried out. They confirmed the relevance of the proposed method for controlling the distance between the electron gun and deposited bead. The calculation of beam energy fraction absorbed by the collector made it possible to substantiate the need for using a signal preamplifier. Based on the analysis of the results of experimental studies conducted on the ELA-15I power complex, the relevance of the proposed method for measuring the working segment and the possibility of using it as part of a process control system was confirmed.

This work analyzes the manufacturing process of an electron-beam additive form by heating as a result of remelting the supplied filler wire as a control object. Control actions and output values are designated that can be used in constructing a control systems with feedback. A mathematical modeling technique is used to study heat transfer in a nonstationary formulation, taking into account the influence of the latent heat of fusion. The transient processes of temperature changes were studied at points, whose values can be used to estimate the extension of the weld pool and the degree of metal overheating. An analysis of the results of computational experiments is carried out, and the range of variations of control actions are shown. The possibility of an independent temperature control in the range of the beam and the extension of the liquid bath is also justified. Recommendations are given for the technical implementation of the system and the option of implementing local regulators, types of sensors, and their installation.

The development of a mathematical model provides an analysis of heat transfer and metal flow during wire-based electron-beam additive manufacturing described. The procedure for solving the heat equation for the metal in the solid phase and the Navier–Stokes equations in the liquid phase, based on the use of the finite-difference method and the predictor–corrector procedure, is described. An algorithm for numerical approximation of the motion of the free surface of the melt, using the concept of the volume of fluid (VOF) is described. The original method for calculating the effect of surface tension forces, based on the numerical calculation of the surface curvature index, is proposed. The results of simulating the melting of a wire element localized above a substrate made of 316L steel are described. Experiments showed the predominant role of surface tension force in the formation of deposited layer and also that metal’s flow has a laminar structure. These results were obtained by simulating a short-time beam exposure (t = 0.1 s) with a power of 6 kW. Thus, even when the wire and the substrate are exposed with a more intense beam than often used in practice, the metal transfer is not characterized by the formation of intense vortex flows. This can simplify the solution of the problem of additive manufacturing modeling in the future.

The need of measuring the wire feed speed in the process of electron-beam additive manufacturing instead of measuring the drive rollers rotation speed is proved. Factors that have a negative effect on the result of the technological process are listed. A new method for measuring the wire feed speed, based on image processing from a photo-detector array, is proposed. The possibility of implementing this method with using industrial technical solutions, applied in human interface devices, is shown. The transient characteristics of wire speed control channel, obtained experimentally with the help of raw input technology, have been studied. The workability of this method and the possibility of its application for building a feedback sensor for the wire feed speed control loop in additive technology are substantiated.

This paper presents a method of control of the metal-transfer mode during electron-beam surfacing with a filler-wire feed based on simultaneous recording of the potential of the wire and article connected with the apparatus frame through the resistors. The main metal-transfer modes are specified that are observed with a change of the energy-input rate. The importance of the solved problem for additive technologies is shown. A scheme of experimental investigations carried out at the ELA-15I apparatus is given, and the obtained oscillograms are presented. The relation of the characteristics of the registered signals with the operation modes of the equipment and transfer parameters is shown. It is noted that, with a change of only the filler-wire feed rate, a changeover from drop metal transfer to the scattering mode can be triggered. The possibility of detecting the mode of appearance of the shot metal, as well as emergency modes related with stopping the filler-wire feed or excessive increase of its feed rate, is substantiated. The influence of the plasma processes on the registered signals in the developed scheme is analyzed, and it is also shown that, to reduce the influence of these processes, it is necessary to decrease the resistance of the measuring circuit. Photographs of the process corresponding to the certain oscillogram intervals are given.

The urgency of the development of mathematical modeling tools that allow calculating the shape of free surface of the melt during the analysis of surfacing processes, introduced in additive production, is shown. A mathematical formulation of the problem is presented, which corresponds to Lagrangian description of liquid medium. It includes equation of motion and energy equation. A numerical algorithm for solving this problem is described, based on Smoothed Particle Hydrodynamics method, and the corresponding equations are given. The analysis of the results of solution of test problems is carried out and comparison of experimental results of the process with well-known data and physical representations is given. The conclusion is made about the possibility of applying this modeling method for development of additive production and creation of automatic control systems for the processes of shaping.

The structure, composition, and characteristics of a device for feeding a filler wire to an electron beam additive manufacturing unit are described. The analysis of the results of experimental technological processes is carried out and the relevance of considering the wire feed channel as one of the main control channels is proved, for the effective use of which feedback speeding is required. The analysis of existing methods of measuring feed speed is carried out and a noncontact measurement method based on the use of a multi-element matrix sensor and infrared illumination is proposed. A measurement scheme is described, which includes a computer, as well as a module for data collection and control. The experimentally obtained dynamic characteristics of the control channel of wire feed speed are presented. The analysis of the obtained oscillograms of the armature winding voltage and the signal of the wire feed speed is carried out, and the possibility of using the proposed sensor for constructing feed speed stabilization system is justified.

An experimental technique for the acquisition of current-density distributions of continuously operating electron beams with an electron energy of 60 keV is proposed. The measurement results for different cross-sectional areas of the beam with a power of 2.1 kW and a current density around 1 × 10 5 A/m 2 are given.

Предложена экспериментальная методика получения распределений плотности тока непрерывно действующих электронных пучков с энергией электронов 60 keV. Приведены результаты измерений для различных поперечных сечений пучка мощностью 2.1 kW с плотностью тока порядка 1·105 A/m2. DOI: 10.21883/PJTF.2017.21.45156.16916