The performance of electrical discharge machining for drilling holes decreases with machining depth because the conventional flushing and electrode cannot completely eliminate debris particles from the machining area. In this study, a modified electrode for self-flushing in the electrical discharge machining process with a step cylindrical shape was designed to improve machining performance for deep hole drilling. The experimental results of the step cylindrical electrode showed that the material removal rate increased by approximately 215.7%, 203.8%, and 130.4%, and the electrode wear ratio decreased by approximately 47.2%, 63.1%, and 37.3%, when compared with a conventional electrode for the diameters of 6, 9, and 12 mm, respectively. In addition, the gap clearance and concavity of the side wall of the drilled hole was reduced with the step cylindrical electrode. The limited high flank of the electrode led to an increase in the escape area of the debris that was partially removed from the machining area, and the limited secondary spark on the side wall of the electrode resulted in a reduction in machining time.
This research aimed to study the machining efficiency of AISI P20 steel by Electrical Discharge Machining (EDM) using rod copper electrode to machining material by 50 mm depth of machining was mainly assessed from Materials Removal Rate (MRR) and Electrode Wear Ratio (EWR). From the experiment designed to use Taguchi technique of data analysis and suitable parameter prediction, the highest MRR was at on-time of 150 μs, off-time of 2 μs and electric current level was at 15 A or 0.25 A/mm2. Predicted value was at 19.2395 mm3/min which was equal to real experiment, showing Materials Removal Rate of 19.647 mm3/min (with error of 2.12 percent) .Moreover, it was found that gap would increase with the size of electrode and depth of machining caused by movement of particles removed from side surface of electrode, which cause micro sparks at the side of the material workpiece.
This article aims to show the effects of the EDM process that influences the surface hardness by comparing the hardness values before and after the spark on the plastic mould steel AISI P20. Divided by the heat treatment, there were three different hardness levels: 1) the plastic mould steel AISI P20 through the process of quenching with the hardness value in the range of 690-710 HV; 2) the steel through the process of quenching and then annealing with the hardness value in the range of 470-490 HV; and 3) the non-heat treatment steel (raw material) with the hardness value in the range of 300-320 HV. The condition of EDM spark on the surface workpiece was 3 mm of depth and 10 mm of diameter copper electrode. The experiment was carried out under the cover of hydrocarbon, using dielectric cooling, and removing debris by the side flushing through the 6 mm of diameter pipe with the flow rate of 15 liters per minute. The experiment parameters included on-time duty factor variable, off-time duty factor variable, and current. Based on the experiment, it was found that when the duty factor increased, the hardened workpiece showed the less surface hardness value. At the same time, the annealed, and the non-heat treatment workpieces showed that the hardness values were proportional to the duty factor and the current of the EDM process.
In this study, experiments were performed to study the effects of electrode materials mixed with nickel in electrical discharge machining (EDM) of SUS 304 material. Experiments were constructed using parameters consisting of pulse-on time, pulse-off time, discharge current and electrode polarity, respectively. The analysis of structural features of the surface was accomplished using a scanning electron microscope (SEM) as well as an element analysis created on the surface, after the EDM process, by using Energy-dispersive x-ray spectroscopy (EDS). The results of the experiments found that nickel elements in the electrode material have an effect on the working performance of material removal rate and electrode wear ratio. The electrode wear ratio reduces when nickel elements increase. Moreover, the surface roughness had the lowest level at electrode 15 % nickel element. Thus, electrode wear during the EDM process of nickel element from electrodes and other elements, combined with surface metalworking, becomes a recast layer of nickel.
In this paper, preheating temperature was investigated for the laser assisted machining (LAM) of Inconel 718 under different conditions for the milling test. The experimental results show that the requirement of laser power for the particularly preheating temperature proportionally increased with the table speed. The resultant cutting force for sufficient shearing work material in LAM was lower than conventional machining (CM) approximately 11, 21 and 28% for the cutting speed of 30, 50 and 75 m/min, respectively. The tool wear in LAM could be improved at relatively high cutting speed of 75 m/min and the hardness of machined surface in LAM was slightly higher than CM.
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