Papers by Keyword: Electrical Discharge Machining

Abstract: The current research focuses on the viability of rotating, single tubular brass electrodes undergoing shallow cryogenic treatment (at -140°C) before micro-drilling austenitic stainless steel SS316L with the electrical discharge machining process. In order to study and achieve a better rate of material removal and a lower rate of electrode wear, the Taguchi L18 experimental matrix representing the four variables, current, duty cycle, capacitance level, and gap voltage was examined. Regular tap water served as the dielectric fluid to uphold the sustainability concept of the machining experiments and an integrated hybrid approach incorporating CRITIC (criteria importance through inter-criteria correlation) weight determination method and MOORA (multi-objective optimization by the ratio analysis) was applied for decision making. The weight fractions (significance) for MRR and EWR were found to be 0.5532 and 0.4467, respectively and the MOORA method converted multiple objective parameters into a single objective function with weight fractions assigned to each of them. An ideal parameter combination highlighting the dominant significance of duty cycle, pulse current, capacitance level and gap voltage with corresponding values of 70%-18A-1-34V was obtained and the results were substantiated with relevant confirmation experiments. The highest MRR achieved is 10.0961 mm³/min and the lowest EWR is found to be 3.9640 mm³/min. Moreover, the electrode tip regions, the micro holes, and the surrounding workpiece surfaces were also thoughtfully scrutinized and contrasted using scanning electron micrographs (SEM), which validates the worth and significance of cryogenically frozen electrodes in successful micro-drilling of SS316L material.

Abstract: Electrical Discharge Machining (EDM) is a non-conventional thermal energy based erosive process, which primarily applied for machining hard materials. Material Removal Rate (MRR) and surface roughness are the response parameters used to characterize the dielectric nature of the machined surface in EDM process. Addition of ingredients in the dielectric fluid improves the properties of fluid for better machining of the samples. The dielectric fluid medium plays a key role in controlling the electrical discharge and heat absorption, thereby removes the debris and cools the work piece during the machining process. In the current study, comprehensive work is done by investigating the effect of different dielectric fluid medium on machining parameters of EDM process with the addition of different powders in the dielectric fluid, which results in high precise and better topography in the machined part surface. Addition of powders such as Titanium (Ti), Silicon (Si), Graphite (Gr), Copper (Cu) and Aluminium Oxide (Al2O3) in dielectric fluid increases the convection property in the work piece tool interaction with increase in the micro-hardness of material. This work analyses the performance study of Electrical Discharge Machining (EDM) of Monel 400 alloys, which can be improved by adding metallic powder into the dielectric medium. Material Removal Rate (MRR) is measured in the samples machined out of EDM process. In addition, Taguchi L27 Orthogonal Array is formulated for conducting machining in a sequential order to understand the implications of machined process parameters on the material removal rate over different dielectric mediums. It is found that the Aluminium oxide, graphite powder mix with EDM oil gives better material removal rate and less machining time. Furthermore, the introduction of Cu powders in the dielectric fluid provides better machinability response parameters. But it is preferable to parts with high slenderness ratio especially holes.

Abstract: This research aims to study the influence of controlled parameters on the machining performance for small hole drilling by an electrical discharge machine. Tubular copper with an outside diameter of 1 mm was used as an electrode. JIS SKD 61 grade steel at a depth of 40 mm for machining was used as a workpiece. The experimental results show that machining speed and electrode wear drastically increased with the discharge current. The high machining performance with varied pulse on-time occurred in the range of 16 to 28 μs. The machining time and electrode wear ratio increased with a decreased pulse off-time. In addition, the lowest difference in the dimension of the entrance and exit of the drilled hole at approximately 0.030 mm appeared at the pulse off-time of 6 μs. However, the high machining speed and electrode wear ratio occurred at the low dielectric pressure of 20 kg/cm². Furthermore, the machining performance reduced and slightly fluctuated with the varied dielectric pressure in the range of 40 to 80 kg/cm².

Abstract: As a result of implemented modernization of known electrode composite material based on Cu-3% wt BN copper powder successfully used for electrical discharge machining of high-strength alloys, composite material (Cu - 3% wt BN) – 0.5 % wt Al – 0.25 % wt in the form of high-density long thin-wall plates for operations of electrical discharge cutting and piercing of hard-to-machine materials was obtained. The new material was obtained with the use of the method of reactionary mechanical alloying of initial powder components in the attritor. Tool electrodes made of the new material during electrical discharge piercing of rectangular holes in titanium alloy sheets ensure a 1.6 times higher machining rate comparing to tool electrodes made of the Cu-3% wt BN prototype material. After replacement of rolled copper in tool electrodes with the new composite material the machining rate will increase 4.1 times. The tool electrodes made of this material have significantly lower electrical discharge wear comparing to the wear of tool electrodes made of the prototype material and rolled copper.

Abstract: This paper introduces an experimental study on the influence of electrical discharge machining (EDM) cylindrical shaped parts made of 90CrSi tool steel. In this work, some experiments were designed and analysed based on Taguchi method. Also, four input parameters including the pulse on time, the pulse off time, the current, and the server voltage were investigated. The influence of these parameters on the surface roughness were estimated by analysing variance. In addition, the optimum input parameters were found for getting the minimum surface roughness.

Abstract: This paper introduces an optimization study on electrode wear when electrical discharge machining (EDM) cylindrical shaped parts made from 90CrSi. In the study, the experiments were performed and analyzed by using Taguchi method. The input parameters of the experiments were the pulse on time, the pulse off time, the current, and the server voltage. The effect of input parameters on the electrode wear were evaluated by analyzing variance. Also, the optimum values of the input parameter were proposed for getting the minimum electrode wear.

Abstract: 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.

Abstract: This study investigates the possibility of electrochemical removal of the defective layer formed on the surface of the product after its electrical discharge machining. A set of experiments was conducted in different electrolytes based on aqueous and aqueous-organic solvents. The experiments were to trace the influence of such settings of electrochemical machining as current density, electrolyte pumping speed, electrolyte temperature, and an electrode gap upon both the dynamics of metal removal and surface quality. Morphology of the obtained surface was examined by an Olympus BX-51Microscope. The dynamics of removing material (stock) from the work piece was inspected. Appropriate adjustments were made to the machining parameters during the machining of 65G steels, and a preferred composition was selected for the working medium. A sufficient design for production tools was proposed. Pitting corrosion was discovered on the surface of the samples in all studied modes of electrolysis. It was observed that switching from aqueous electrolyte to aqueous-organic electrolyte gave lower material removal rate and longer machining time accordingly. At the same time, a reduction in surface roughness was visualized, together with smaller pits and lower density of their distribution. The obtained results may be applied in operation design for electrochemical machining of steels with relatively high carbon contents.

Abstract: A new method was adopted in this study to machine C/SiC composite. The machinability was studied by processing some shapes in the material in this way. Small deep holes were machined firstly to test whether the copper electrode was suitable enough to be adopted in the Electrical Discharge Machining. Then holes of different diameters were processed by two kinds of electrodes to study the more appropriate electrode material by comparing machining efficiency of two electrodes. Then complicated shapes were machined based on these conditions. Finally, a simulation model was built up to study the influence of the fluid on the electrode and the workpiece in the Fluent 6.3. According to the study, Electrical Discharge Machining Technology is suitable enough to machine the hard and brittle materials like C/SiC composite and the accuracy that the error should not exceed 0.5 mm can also be guaranteed well.

Abstract: In this paper, response surface methodology (RSM) and non sorting genetic algorithm (NSGA-II) are used to optimize the multi-responses of electrical discharge machining of Aluminum Alloy 6061/10%SiC_p composite. Experiment is performed to evaluates the effects of process parameters namely peak current, pulse on time, pulses off time and gap voltage on the responses material removal rate (MRR) and tool wear rate (TWR). The central composite rotatable design (CCRD) is utilized to design the experiment using RSM. Analysis of Variance (ANOVA) test is performed to validate model and to further establish the mathematical relation between process parameters and responses. Results are analyzed using ANOVA models. NSGA-II is used to optimize two conflicting responses i.e MRR and TWR. Finally results are validated by confirmatory experiment.