Showing 13 results for Electrical Discharge Machining
Behzad Jabbaripour, M Sadeghi, , ,
Volume 11, Issue 2 (9-2011)
Abstract
Due to outstanding properties of γ–TiAl intermetallic such as high resistance against fatigue, oxidation, corrosion, creep, dynamic vibration, high working temperature and also its application in aerospace and automotive industry, turbojet engines and blade manufacturing; in this paper, electrical discharge machining (EDM) of γ–TiAl intermetallic by means of three kinds of tool electrodes including copper, graphite and aluminum is investigated, to compare the output characteristics of the machining process such as material removal rate, tool wear ratio, surface roughness and topography and EDS elemental analysis of machined surfaces. The results indicate that major elements in chemical composition of γ–TiAl machined surfaces are including titanium, aluminum, carbon and oxygen. The variation of tool material has not significant effect on formation of different chemical compounds and phases or in other words surface modification of machined surface. While it mainly affects other aspects of output characteristics such as material removal rate, tool wear ratio and surface roughness.
Behzad Jabbaripour, , , ,
Volume 12, Issue 5 (1-2013)
Abstract
γ–TiAl intermetallic has outstanding properties such as high resistance against fatigue, oxidation, corrosion, creep, dynamic vibration and high working temperature. These intermetallics are applied in aerospace and automotive industry, turbojet engines and blade manufacturing. In this paper, powder mixed electrical discharge machining (PMEDM) of γ–TiAl intermetallic by means of different kinds of powders including Al, SiC, Gr, Cr and Fe is investigated to compare the output characteristics of the process such as surface roughness, tool wear rate, material removal rate and surface topography with each other. This is an experimental investigation, by means of die sinking EDM machine and a special tank for machining. The results indicate that, aluminum powder as the most appropriate kind of powder in the optimum particle concentration of 2 g/l, improves the surface roughness about 32% comparing with conventional EDM, decreases the tool wear rate about 19%, but decreases the material removal rate about 7.5% and also the Al powder leads to improving the machined surface topography and decreasing the surface defects and micro cracks.
, Behnam Khosrozadeh, Babak Sadizadeh, Hamed Kakoulvand,
Volume 13, Issue 12 (2-2014)
Abstract
In this study the interaction of material and ultrasonic vibration of workpiece at different pulse on times (Ti) and discharge currents (I) in the electrical discharge machining (EDM) has been studied. The materials of machined samples were AISI H13 tool steel and FW4 weld steel. The results show that ultrasonic vibration of workpiece, independent of workpiece material increase material removal rate (MRR) and reduce tool wear ratio (TWR) and surface roughness. Also the results indicate that the effect of ultrasonic vibration on the material removal rate increase of FW4weld steel is higher than AISI H13 tool steel, and the reduction of tool wear ratio of FW4 weld steel is more than AISI H13 tool steel.
, , , ,
Volume 14, Issue 1 (4-2014)
Abstract
One of the fundamental problems of Electrical Discharge Machining (EDM) process is tool electrode wear. In this study, ultra fine grains (UFG) structure of pure copper was used to improve performance and also increase the electrical wear resistance of tool electrode. Equal Channel Angular Pressing (ECAP) was used to reduce the crystal size of pure copper. Samples were processed through ECAP die up to 8 passes, and then used as electrode in EDM process. The effect of electrodes grain size, discharge current, and machining time on the metal removal of the work piece and electrical wear of the electrodes were investigated. In addition, the microstructure, and electrical conductivity of copper tool electrodes were examined. By applying the ECAP on pure copper a fine, approximately 50-200 nm grain size, microstructure was obtained after 8 passes. The results show that for finer crystalline structure of copper electrodes, electrical wear decreases but material removal rate is somehow constant.
Mohammad Reza Shabgard, Babak Roushangar Zineh,
Volume 16, Issue 3 (5-2016)
Abstract
This paper experimentally investigated the effects of electrical discharge machining processes parameters on fatigue resistance of 16MnCr5 alloy steel. 16MnCr5 alloy steels have good wear resistance. For this purpose, pulse current and pulse time have been considered as variables in the process. The selected EDM parameters were pulsed current (8, 16 and 32A) and pulse time (25, 100 and 400µs). Tests were conducted in full factorial mode and the R. R. Moore fatigue test machine was used to determine the fatigue life of components. The results show that by increasing the spark current and pulse duration 16MnCr5 alloy steel fatigue life is reduced. Respectively, the greatest resistance to fatigue achieved at current of 8A and pulse time of 25 microseconds and lowest resistance to fatigue achieved at pulse current of 32A and pulse time of 400 microseconds. Resistance to fatigue crack depends on cracks density on the surface of the workpiece and heat-affected zone, where the density of cracks increase resistance to fatigue will be reduced. Also in the specimens that have low resistance to fatigue, fatigue cracks are initiated from multiple points of the cross-section. It seems the reason for this phenomenon is the high surface roughness in the samples. EDM machining with high energy sparks can decrease the fatigue strength of 16MnCr5 by as much as factors of 3-5.
Behzad Jabbaripour, Mehrdad Motallebpouralishahi,
Volume 17, Issue 12 (2-2018)
Abstract
The intermetallic compound of gamma titanium aluminide is a kind of recently developed material which has outstanding potential for utilization in high temperature structural applications due to higher ratios of strength to density and also elasticity modulus to density. In this study with considering two dielectric fluids of kerosene and de-ionized water, the effects of the most important input parameters of electrical discharge machining including pulse current and pulse on time on the output characteristics of material removal rate, tool wear ratio, some surface integrity criteria such as surface roughness and cracks, are investigated. The results indicate that, rough machining of titanium aluminide in contrary to finishing of this material, is performed efficiently. As the result of more thermal conductivity coefficient of water comparing with kerosene, the energy dissipation or loss and also plasma channel radius expansion in water is noticeably more than kerosene. This issue leads to more concentration and higher rates of thermal energy on the machined surface in the case of kerosene. Consequently, the density of surface cracks, surface roughness and intensity of surface topography alterations for the machined surface in kerosene is more than the samples which are machined in de-ionized water, but in contrary, the material removal rate with kerosene is much more than MRR in de-ionized water and also the tool wear ratio during machining process by means of kerosene is significantly less than the de-ionized water.
Mohammadreza Shabgard, Ahad Gholipoor,
Volume 17, Issue 12 (2-2018)
Abstract
Electric discharge machining is one of the most widely used non-traditional machining techniques which use thermal energy for machining in small dimensions, machining complex shapes and machining hard materials with high strength such as ceramics and heat-treated steels. In this study the ultrasonic vibrations and magnetic field assisted EDM process as a new hybrid process was introduced and used for machining of AISI H13 too steel, to solve the EDM process limitations such as low material removal rate. In this investigation, several experiments were designed and performed based on full factorial method by selecting pulse current and pulse duration as most effective parameters of EDM process in order to study the effects of applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance of EDM process, simultaneously, on material removal rate and tool wear rate. According the results, applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance of EDM process, simultaneously, despite the increases of tool wear rate, increases the material removal rate as compared with EDM (60%), ultrasonic vibrations assisted EDM (40%) and magnetic field assisted EDM processes (55%) in all pulse durations and pulse currents except in pulse current of 32 A. In pulse current of 32 A, because of the interference of the influences of applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance, the material removal rate and tool wear ratio are decreased.
, Hamed Tavanaei, Behnam Khosrozadeh,
Volume 18, Issue 3 (5-2018)
Abstract
Ti-6Al-4V alloy due to excellent mechanical properties mainly is used in the aerospace, automobile and biomedical industries. Electrical discharge machining (EDM) are used extensively for machining of this alloy. Due to the thermoelectric nature of this process, unwanted changes happen on machined surface such as development of residual stresses and the change in the corrosion resistance. The aim of this study is the experimental investigation of the effect of input parameters (discharge current and pulse on time) on the amount and distribution of residual stresses and corrosion resistance changes of the machined surface in EDM process of Ti-6Al-4V alloy. For this purpose, samples of Ti-6Al-4V alloy were machined by EDM process and residual stresses induced successive sparks in different setting (different discharge currents and pulses on time) were measured by nanoindentation method and SEM images of machined surface used to better assess of samples surface integrity. TOFL measurement method used to determine the corrosion resistance of the samples. Results indicate that at this process tensile stresses is formed on surface and mentioned stresses increase with depth initially and after reaching a maximum dropping out and eventually leads to pressure stress. By increasing pulse on time and discharge current, maximum tension residual stress only slightly increases and is near ultimate tensile strength of work piece material. Comparison of corrosion results indicated that the corrosion resistance of EDMed samples, was less than the not machined specimens.
, Ahad Gholipoor, Mousa Mohammadpourfard,
Volume 18, Issue 7 (11-2018)
Abstract
Despite the unique usage of electrical discharge machining process at machining in small dimensions, machining complex shapes and machining of high-strength parts such as ceramics and heat treated steels, which can’t be machined by traditional machining methods, low machined surface integrity achieved by electrical discharge machining process is one of the most important limitations of this process. In this investigation the machined surface integrity will be improved by applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance of electrical discharge machining process, simultaneously. So several experiments were designed and performed based on full factorial method by selecting pulse current and pulse duration as the most important input parameters, in order to study the effects of pulse current and duration on surface integrity of workpiec machined by this hybrid process and to investigate the effects of tools ultrasonic vibrations and external magnetic field on machined surface roughness and integrity of machined surface. According the results, machined surfaces roughness is increased by applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance of electrical discharge machining process, simultaneously, while the SEM pictures of machined surfaces showed that the, amount of created surface cracks, blowholes, globules and beads of debris are decreased and integrity of machined surfaces by EDM process is improved by applying ultrasonic vibrations to tool electrode and external magnetic field around gap distance, simultaneously.
M.r. Shabgard , A. Gholipoor , M. Mohammadpourfard ,
Volume 19, Issue 1 (1-2019)
Abstract
In this investigation, finite element method was used to model single discharge of ultrasonic vibrations and magnetic field assisted electrical discharge machining (MUEDM) process. Regarding good correlation between theoretical recast layer thickness obtained by process modeling and experimental recast layer thickness obtained by experiments with maximum error of 8.6%, the developed numerical model was used to find the temperature distribution at workpiece surface and predict the created craters dimensions on workpiece surface. The influences of applying ultrasonic vibrations to tool electrode simultaneous with applying external magnetic field around gap distance of electrical discharge machining (EDM) process, on plasma flushing efficiency, recast layer thickness and created craters dimensions were found by numerical and experimental analysis. The experimental and numerical results showed that applying magnetic field around gap distance and ultrasonic vibrations to tool electrode, simultaneously, at EDM process increases plasma flushing efficiency and decreases recast layer thickness. Also, applying magnetic field around gap distance and ultrasonic vibrations to tool electrode, simultaneously, at EDM process, leads to higher depth and volume of created craters on machined surface and lower craters radius.
M. Nasri, E. Rouhani Esfahani,
Volume 19, Issue 6 (6-2019)
Abstract
Near dry Electrical Discharge Machining (EDM) is one of the advanced methods for removing materials environmentally friendly. Combining the minimum quantity of lubricant (MQL) and vegetable oil not only reduces health and costs, but also improves the process. This research has been conducted on Mo40 steel and the mixture of vegetable oil and air has been used as dielectric. The effect of electric current variables, open circuit voltage, pulse on and off time and air pressure were studied on material removal rate (MRR), tool wear rate (TWR), and surface roughness (Ra), using the method of designing the central composition of the response surface. The results showed that the increase in ampere, pulse on time and open circuit voltage increase the MRR; also, increase of the pulse time improves washing of the environment that prevent short-circuit and all had an effect on the MRR. Also, increasing the ampere and open circuit voltage leads to an increase in the TWR and increasing the pulse on time, as well as the increase in pulse time, reduces the TWR. Increasing the air pressure reduced the dielectric density and increased the TWR. On the other hand, the increase in the ampere and the pulse on time as well as the open circuit voltage increased Ra and increase in the pulse time and the air pressure reduced Ra. This method has led to an increase of 200% in MRR, 30% reduction in TWR, and 60% reduction in Ra compared to the kerosene immersion method.
S. Oskueyan , V. Abedini , A. Hajialimohammadi ,
Volume 20, Issue 6 (6-2020)
Abstract
In this study, the effect of using of aluminum oxide and silicon oxide nanoparticles simultaneously into dielectric has been investigated in the process of electrical discharge machining of titanium alloy Ti-6Al-4V. After analyzing the parameters affecting the process of the electrical discharge machining using nanoparticles, intensity of the current, concentration, pulse on time, and particle composition were considered as input parameters. The effect of each parameters has been investigated on three levels; the material removal rate (MRR), the tool wear rate (TWR) and the surface roughness (SR) of the work piece. With respect to the development of the industry in the use of environmentally friendly dielectrics, deionized water was used as the dielectric fluid. Also, Design Expert software has been employed for the design of the experiments, analysis of the results and optimization of the parameters. The results showed that the best surface morphology is obtained by machining with the addition of nanoparticles in the relative composition of 50%. In this percentage of the composition, the surface roughness has the least value of the crack and the recast layer. In addition, the maximum value of the MRR and minimum value of TWR can be achieved in 12A of current intensity, 100µs of pulse on time and 75% of relative composition.
S. Dinarvand, B. Jabbaripour,
Volume 20, Issue 7 (6-2020)
Abstract
Modern intermetallic compound of gamma titanium aluminide (γ-TiAl) due to its low density, high elastic modulus, high resistance to oxidation, corrosion, and ignition has recently been considered in the aerospace and automotive industries. Traditional machining of this alloy is so difficult. In the current study, electrical discharge machining of γ-TiAl samples is investigated using different tool electrodes of graphite, copper, and aluminum. The results show that when using aluminum electrodes, tool wear rate is averagely 3.2 times more than copper and 5.8 times more than graphite tools. In addition, when using graphite electrodes, the average material removal rate is 4.2 times more than copper and 7.7 times more than aluminum. Machining by aluminum tool leads to formation of Al2O3 and TiO2 oxide compounds on the work surface but in machining by graphite electrode, TiC and Ti8C5 carbide phases are created on the work surface. In machining by graphite due to formation of hard carbide compounds in the recast layer, the microhardness is higher than the machined sample by the aluminum tool, where oxide compounds exist on the surface and the hardness of recast layer in the machined sample by copper electrode is less than the other two electrodes, because of existing phases such as copper oxide with less hardness. The highest electrochemical corrosion resistance belongs to the machined specimen using graphite tool and the lowest corrosion resistance is related to the machined sample by aluminum electrode. Reducing oxide and aluminum compounds and increasing carbide phases enhance the corrosion resistance of γ-TiAl machined samples.
