Electrical Discharge Machining System Research Articles

The Existence of Autonomous Chaos in EDM Process

The dynamical evolution of electrical discharge machining (EDM) has drawn immense research interest. Previous research on mechanism analysis has discussed the deterministic nonlinearity of gap states at pulse-on discharging duration, while describing the pulse-off deionization process separately as a stochastic evolutionary process. In this case, the precise model describing a complete machining process, as well as the optimum performance parameters of EDM, can hardly be determined. The main purpose of this paper is to clarify whether the EDM system can maintain consistency in dynamic characteristics within a discharge interval. A nonlinear self-maintained equivalent model is first established, and two threshold conditions are obtained by the Shilnikov theory. The theoretical results prove that the EDM system could lead to chaos without external excitation. The time series of the deionization process recorded in the EDM experiments are then analyzed to further validate this theoretical conclusion. Qualitative chaotic analyses verify that the autonomous EDM process has chaotic characteristics. Quantitative methods are used to estimate the chaotic feature of the autonomous EDM process. By comparing the quantitative results of the autonomous EDM process with the non-autonomous EDM process, a deduction is further made that the EDM system will evolve towards steady chaos under an autonomous state.

Dynamic behaviour of EDM system through mathematical model

Electrical discharge machining (EDM) is a stochastic machining process which widely used to generate dies and molds. However, information about the EDM process is still at the earlier stage which lead to experience many challenges for further developments. Experimental analysis is time consuming as well as a costly procedure, due to the highly stochastic and complex nature of the process. Therefore, process modeling is an alternative to reduce the experimental costs related to the technology. This research proposes method to design a mathematical model of electrical discharge machining (EDM) system. The model will be used to understand the effects of machining parameters into the dynamic behaviour of EDM system based on the sparking phases and pulse power generator.

Discharge analysis of EDM pulse generator

Electrical discharge machining (EDM) is a non-conventional manufacturing process used broadly in medical applications, aerospace industry and manufacturing in hard material fields. However, information about the process is still in an unfledged stage and it has been becoming a serious obstacle to its more improvements. In this paper, spark discharge condition is studied based on the simulated model of EDM spark pulse generator system equivalent form. Simulated model is verified by comparing with a series of experimental results. Frequency response is established through simplified model of EDM system. Influence of discharge time and stable discharge current on material removal rate (MRR) and stability of the system is analysed. This study is important to select the process parameters, and uses as a guidance to design the EDM spark pulse generator system.

Design of a Machine-integrated Optical Measuring System for Electrode Positioning for Electro-Thermal Precision Ablation

Besides traditional machining processes, unconventional machining by EDM (Electrical Discharge Machining) is used, especially when precise cavities with complicated shapes are required or hard to machine alloys need to be machined. For the production of a geometrically complicated workpiece, numerous differently shaped electrodes are required due to the variety of the single cavities and the tool wear. Due to the process-related tool wear, the electrodes can only be reused a few times. Thus, process chains consisting of milling electrode production, automated electrode changing and CNC-controlled erosion process are frequently used. After fabrication of the milling electrode, the electrode geometry is measured for quality control usually using a tactile measuring device. In order to assist in the orientation of the electrode in the EDM system, the consideration of measurement results with respect to a reference point would be helpful. However, the transfer of the measured coordinate parameters from the measurement system to the EDM system is not possible in most cases since there is no connection between the measurement system and the EDM system. In addition, the tactile electrode measurement is time consuming. With the help of a machine-integrated optical measuring system, it will be possible to save time for measuring the electrodes by automated optical measurements and thus replacing the tactile measuring method. The present study describes the technological development of a machine-integrated optical measuring system, which enables a qualitative optimization of the process chain from the production of the EDM electrode and the subsequent erosion process. The design of an optical measuring system consisting of CCD (Charge Coupled Device) sensors and a custom software for the evaluation of the results of the optical measurements are presented. The presented solution will prospectively be implemented into an industrial EDM-machine with the aim to achieve a more efficient process chain and to avoid incorrect machining.

Novel electrical discharge machining system with real-time control and monitoring for preparing nanoiron colloid

Nanoiron colloid is remarkably suitable for medical, engineering, and other applications because it exhibits excellent properties such as nontoxicity, biocompatibility, and high chemical stability. Because no studies have examined preparation of nanoiron colloid through electric spark discharge method, an electrical discharge machining system for preparing nanoiron colloid was developed in this study based on automated electric spark discharge method with real-time monitoring. An Arduino microcontroller, laser positioning technology, and closed-loop motor control were combined for automatic alignment of the two discharge electrodes. This electrode alignment method enabled achieving electrode alignment accuracy of 0.139 mm. The real-time monitoring applied the Ziegler–Nichols method with a proportional–integral–derivative controller for closed-loop control of the interelectrode gap that, compared with the manually tuned proportional–integral–derivative controller, increased the interelectrode gap discharge success rate from 22.25 to 28.99. A user-friendly interface and process parameters were realized through VisSim software, an Arduino microcontroller, and an RT/DAC4 PCI card. This design enabled obtaining data on process efficiency and providing real-time process diagnosis. Compared with colloids prepared using chemical methods, the nanoiron colloids prepared in this study contained only iron and oxygen; therefore, they would be safer for application in the human body. According to the UV-Vis and Zetasizer analyses, the absorbance peak of the nanoiron colloid prepared with this system ranged from 200 to 220 nm, and the zeta potential was approximately –11.6 mV with a diameter of approximately 155.9 nm. These results verified that this electrical discharge machining system can prepare nanoiron colloid featuring excellent suspension stability.

Non-linear mechanism in electrical discharge machining process

Electrical discharge machining (EDM) is an advanced non-traditional manufacturing technology that has many advantages over other machining methods. Many papers have discussed the machining mechanism and modeling of the EDM process. However, previous mechanism models have mainly been linear, which contradicts their precondition that EDM is a stochastic process. In this paper, a non-linear mechanism model is proposed for the EDM process. A threshold condition that leads to chaos is calculated using the Melnikov theory. The theoretical results indicate that the EDM system can generate varied chaos in the evolution of electrical discharge. To verify this conclusion, validation experiments are implemented. Several sets of complete EDM processes’ real-time series are analyzed by multiple chaotic numerical criteria, including power spectrum analysis, principle component analysis (PCA), correlation dimension analysis, and Lyapunov exponent analysis. The experimental results provide further qualitative and quantitative evidence that a complete EDM process has dynamical chaotic characteristics.

A comparative investigation on hybrid EDM for drilling small deep holes

For the use of electrical discharge machining (EDM) to drill small, deep holes, many studies have shown that tool electrode vibration and rotation and pump forced flushing can improve machining efficiency or quality. However, these factors are usually studied separately. In this study, a hybrid, rotary, ultrasonic EDM system was developed that used these three methods simultaneously. A comparative investigation on different combinations of the three methods was conducted for drilling small, deep holes in Inconel 718 and 41Cr4 workpieces. Results showed that, compared with other combinations for precision drilling under low discharge currents, combinations including these three methods simultaneously achieved more stable machining and higher material removal rates. In addition, the applied current greatly influenced hole depth and the effects of ultrasonics. When a high discharge current was applied, the electrode vibration contribution appeared weak.

The investigation of discharge restriction mechanism of the floating workpiece based electrostatic field-induced electrolyte jet (E-Jet) EDM

In this paper, issues concerning the discharge deviation of the electrostatic field-induced electrolyte jet (E-Jet) electrical discharge machining (EDM) have been discussed. To restrict the discharge deviations, the floating workpiece and the assisted tool electrode are introduced into the E-Jet EDM system. The experimental results have shown that the discharges can be restricted at the nearest point from the tip of the fine jet on the workpiece. The controllable cave and continuous homogeneous linear groove machined verified this method can prohibit the deviation of the discharges. The simulation results of electric parameters on the workpiece have demonstrated the induced electric potential, the electric field intensity and the electric displacement field intensity are distributed in concentric circles with the peak values at the centers and gradients sharply decreasing with the increase of distance away from the center. The simulation, together with the experimental results, has revealed the discharge concentration mechanism of this improved E-Jet EDM.

昆虫型マイクロロボットによる曲がり穴放電加工システムの開発

昆虫型マイクロロボットによる曲がり穴放電加工システムの開発

Effect of impregnated powder materials on surface integrity aspects of Inconel 625 during electrical discharge machining

In recent times, nickel-based super alloys are widely utilized in aviation, processing, and marine industries owing to their supreme ability to retain the mechanical properties at elevated temperature in combination with remarkable resistance to corrosion. Some of the properties of these alloys such as low thermal conductivity, strain hardening tendency, chemical affinity, and presence of hard and abrasives phases in the microstructure render these materials very difficult-to-cut using conventional machining processes. In this work, an experimental setup was developed and integrated with the existing electrical discharge machining system for carrying out powder-mixed electrical discharge machining process for Inconel 625. The experiments were planned and conducted by varying five different variables, that is, powder concentration, peak current, pulse-on time, duty cycle, and gap voltage based on the central composite design of response surface methodology. Effects of these parameters along with powder concentration were investigated on various surface integrity aspects including surface morphology, surface roughness, surface microhardness, change in the composition of the machined surface, and residual stress. Results clearly indicated that addition of powder to dielectric has significantly improved surface integrity compared to pure dielectric. Among the powders used, silicon has resulted in highest microhardness, that is, almost 14% more than graphite. Lowest surface roughness (approximately 50% less than pure kerosene) and least residual stress were obtained using silicon powder (approximately 8% less than graphite-mixed dielectric). Relative content of nickel was reduced at the expense of Nb and Mo after addition of powders like aluminum and graphite in dielectric during electrical discharge machining.

Scale effects and a method for similarity evaluation in micro electrical discharge machining

Electrical discharge machining(EDM) is a promising non-traditional micro machining technology that offers a vast array of applications in the manufacturing industry. However, scale effects occur when machining at the micro-scale, which can make it difficult to predict and optimize the machining performances of micro EDM. A new concept of “scale effects” in micro EDM is proposed, the scale effects can reveal the difference in machining performances between micro EDM and conventional macro EDM. Similarity theory is presented to evaluate the scale effects in micro EDM. Single factor experiments are conducted and the experimental results are analyzed by discussing the similarity difference and similarity precision. The results show that the output results of scale effects in micro EDM do not change linearly with discharge parameters. The values of similarity precision of machining time significantly increase when scaling-down the capacitance or open-circuit voltage. It is indicated that the lower the scale of the discharge parameter, the greater the deviation of non-geometrical similarity degree over geometrical similarity degree, which means that the micro EDM system with lower discharge energy experiences more scale effects. The largest similarity difference is 5.34 while the largest similarity precision can be as high as 114.03. It is suggested that the similarity precision is more effective in reflecting the scale effects and their fluctuation than similarity difference. Consequently, similarity theory is suitable for evaluating the scale effects in micro EDM. This proposed research offers engineering values for optimizing the machining parameters and improving the machining performances of micro EDM.

Simulation and Analysis of RC Type Relaxation Power Generator for Electrical Discharge Machines (EDM) in Laplace Transform

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes and controlled process where pulsed electrical discharge is used to erode metal in a workpiece. EDM pulsed power generator applies voltage pulse discharge occurs in a small gap between the work piece and the electrode and removes the unwanted material from the parent metal through melting and vaporization. The essential requirement for EDM system is to obtain the output waveform similar to the ideal EDM waveform. This paper seeks to discuss on the design and simulation based on RC (resistance-capacitance) power generator circuit. Based on the findings of the study, from the equation gained, the simulation is constructed through using electrical model in Matlab Simulink software and circuit analysis in Lapels transform in EDM system process. Also this procedure simulated in Matlab software.

Design of five-axis ultrasonic assistant compound machine tool

A compound machine tool was designed, which combined rotary ultrasonic assisted grinding, electrical discharge machining (EDM) and multi-axis milling. Experimental results indicated that its positioning accuracy was less than 5.6 µm and its repetitive positioning accuracy was less than 1.8 µm; the vibration amplitude of ultrasonic grinding system was uniform and stable, and the EDM system worked well and stably. A smooth surface of K9 optical glass component was achieved by the grinding method.

Dynamic Modeling of Electrical Discharge Machining (EDM) System Using Matlab

Electrical discharge machining (EDM) is a nonconventional milling in which holes or shape can be created without any contact between electrode and work piece during the material removal process. Throughout the machining process a series of stochastic sparks are produced when the gap between electrode and work piece is very narrow just about 10 to 50 microns. Controlling this gap in micro dimension not only depends on electrode position but also on work piece surface. So a combination of PID controller and EDM process is used to monitor the gap. In this study an indirect measurement of surface position is carried out by implementing voltage average gap model. And Simulink models have been done to simulate the dynamic behavior of EDM system.

Gap Response of Linear and Non-Linear Discharge Model in Electrical Discharge Machining System

In recent years, simulation-based research is highly appreciated. So many researchers use this way to investigate and solve some problems. Empirical model or behavioral model is used to bring the problems into computer or other computing devices. Selection and determination of the model is very important on the outcome of research. In Electrical Discharge Machining system, servo control system uses voltage drop between electrode and workpiece as a feedback signal. Discharge phenomenon convert gap or distance between electrode and workpiece to voltage. In this paper, two discharge models are simulated and compared. Simulation results show that there are behavior’s differences between these models.

Model of Pulse Power Generator in Electrical Discharge Machining (EDM) System

Electrical discharge machining (EDM) is a non-traditional manufacturing process of removing material. EDM system consists of a shaped tool and the work piece, which are connected to a power supply and placed in a dielectric fluid. EDM pulse power generator applies voltage pulses between the electrode and workpiece to generate sparks through the gap. The essential requirement for EDM system is to obtain the output waveform similar to the ideal EDM waveform. The design is based on transistor type pulse power generator circuit. This paper discuss in modeling of current and voltage gap waveform for EDM system.

Control Strategy for Electrical Discharge Machining (EDM) Pulse Power Generator

Electrical Discharge Machining (EDM) is a advanced machine that can control electrical spark to erode metal on the workpiece. In manufacturing, EDM is used on hard material parts that are extremely difficult to machine by conventional machining processes. EDM system consists of a shaped tool and the work piece, which are connected to a power supply and placed in a dielectric fluid. EDM pulse power generator applies voltage and current pulses between the electrode and workpiece to generate sparks through the gap. To obtain the optimum metarial removal rate (MRR), a good alternative is to improve the gap voltage and gap current. A proposed solution to these issue is combining ultracapacitor bank to the main power supply circuit for EDM machines. The control feedback of this research is designed to make sure that the current on DC bus is maintained at current setting during the machining processes.

Power Generator of Electrical Discharge Machining (EDM) System

Electrical Discharge Machining (EDM) is a non-conventional manufacturing process of removing materials. The uniqueness of EDM process is the removal of the unwanted materials without direct contact between the electrode and workpiece. EDM power generator provides power source of EDM system. It supplies voltage and current to produce spark erosion. Power supply and pulse generator are two important parts in EDM power generator. By choosing the proper power supply and pulse generator to the application, a great result for Material Removal Rate (MRR) can be achieved. Efficiency of EDM power generator depends on the configurations of power supply used. This study reviews and summarizes some previous development of EDM power generator and their effectiveness.

Influences of Machining Parameters on Electrode Wear in Piezoelectric Self-Adaptive Micro-EDM

To resolve such problems as higher electrode wear and low machining efficiency of micro-EDM, a new piezoelectric self-adaptive micro electrical discharge machining system (PSMEDM), based on inverse piezoelectric effect, was developed in this paper. In this new system, a piezoelectric actuator with high frequency response was applied as the micro feeding system to regulate the discharge gap. The machining mechanism and machining process were elaborated. The paper focus on the planning of PSMEDM process and the electrode wear problem. Special attention is paid on the influence of machining parameters such as open voltage, capacitance, resistance, spindle rotational speed and initial feed speed on machining efficiency by using signal to noise analysis method based on orthogonal experiment.

Simulation of Micro–EDM Servomotor for Machining Micro Pits on Hip Implant

Metal–on–metal articulation of hip implant suffers from friction due to the moving metal surface. Thus it would shorten the lifespan of the joint. One of the significant current discussions in biomedical field is to reduce the friction between the articulations surface. It was found that lubrication technique is applicable in order to reduce the friction. A surface texture which micro pits formation on the metal surface of hip implant then was found to benefits the lubrication performance. Due to many advantages offered by electrical discharge machining especially in micro machining, it is utilized for machining the micro pits in this research. Thus, this paper is proposing on machining and control method for this purpose in terms of workpiece placement, coordination and orientation related to the electrode of the electrical discharge machining system. In this paper, a design of motor control simulation has been made using DC motor, Proportional–Integral controller and particle swarm optimization in order to get a better performance of micro–machining positioning for this purpose. From the simulation, the result obtained showed that the model could give a better positioning when using particle swarm optimization technique.