Ahsan Ali Khan

Cooling Effect on Electrode and Process Parameters in EDM

In electrical discharge machining (EDM), material is removed by a series of electrical sparks that develops a temperature in the range 8, 000°C–12, 000°C between the electrode and the workpiece. Due to the high temperature of the sparks, the workpiece is melted and vaporized. At the same time, the electrode material is also eroded by melting and vaporization. This erosion of the electrode is termed as electrode wear (EW). The EW process is similar to the material removal mechanism as the electrode and the workpiece are considered as a set of electrodes in EDM. Due to EW, electrodes lose their dimensions resulting in inaccuracy of the cavity formed by EDM. This paper reports on the study of the effect of electrode cooling during the EDM of titanium alloy (Ti-6Al-4 V). Investigation on the effect of electrode cooling on electrode wear was carried out. Current, pulse on-time, pause off-time, and gap voltage were considered as the machining parameters while EW is the response. Analysis of the influence of electrode cooling on the response has been carried out, and it was possible to reduce EW by 27% using this method.

Influence of electrical discharge machining process parameters on surface micro-hardness of titanium alloy:

The resistance of a material to an indentation on microscopic scale is an indication of its micro-hardness. To a lubrication engineer, micro-hardness is synonymous with surface wear resistance of a material. In this study, an attempt was made to enhance the surface micro-hardness of titanium alloy (Ti-6Al-4V) through modification of electrical discharge machining process parameters. These parameters are the electrode, the dielectric fluid and the electrical variables of the machine. Cu–TaC composite electrode produced through powder metallurgy method was used during the electrical discharge machining with different urea concentrations in distilled water as dielectric fluid. The electrical variables used were the peak current, the pulse duration and the duty factor. Electrical discharge machining was also conducted with copper (Cu) powder metallurgy electrode with distilled water dielectric fluid for comparison. The results showed that the micro-hardness of the electrical discharge machined surfaces with Cu–TaC electrode/urea dielectric fluid was generally higher than that of those with Cu electrode/distilled water dielectric fluid. The highest micro-hardness of 1795 Hv was attained with 10 g/L of urea concentration.

Influence of dielectric fluids on surface properties of electrical discharge machined titanium alloy

Dielectric fluid is one of the major components of electrical discharge machining. In this article, the influence of two dielectric fluids on the surface properties of workpiece was investigated. Machining was conducted on the titanium alloy (Ti-6Al-4V) with the new Cu-TaC composite electrodes under the two dielectric fluids, which are the urea solution and distilled water. Cu-TaC electrodes were produced from copper and tantalum carbide powders by powder metallurgy method with 50/50% composition at compacting pressure of 24.115 MPa. The main objective is to compare the effect of these dielectric fluids on the electrical discharge machined surface properties—microhardness (Mh) and surface roughness (Ra). The machining variables used to investigate the Ra and Mh were peak current and pulse duration. The surface roughness was found to be generally higher in the specimens machined with urea solution dielectric fluid, the highest being 19.05 µm. For the specimens machined with distilled water dielectric fluid, the highest Ra is 14.45 µm. The highest microhardness improvement ratio attained by the specimens electrical discharge machined with urea dielectric fluid is about 48% higher than those machined with distilled water. It is concluded that distilled water dielectric fluid gave better surface roughness, while the urea dielectric fluid provides the machined surface with higher microhardness.

Improving micro-hardness of stainless steel through powder-mixed electrical discharge machining

Powder-mixed electrical discharge machining (PMEDM) is the technique of using dielectric fluid mixed with various types of powders to improve the machined surface output. This process is fast gaining prominence in electrical discharge machining (EDM) industry. The objective of this investigation is to determine the ability of tantalum carbide (TaC) powder-mixed dielectric fluid to enhance the surface properties of stainless steel material during EDM. The properties investigated are the micro-hardness and corrosion characteristics of the EDMed surface. Machining was conducted with 25.0 g/L concentration of TaC powder in kerosene dielectric fluid. The machining variables used were the peak current, pulse on time and the pulse off time. The effects of these variables on the micro-hardness of the EDMed surface were determined. Corrosion tests were also conducted on the samples that exhibited higher hardness. Results showed that the EDMed surface was alloyed with elements from the TaC powder. The highest micro-hardness obtained with PMEDM is about 1,200 Hv. This is about 1.5 times that obtained without TaC powder in the dielectric fluid. The loss in weight during corrosion test was found to be 0.056 µg/min for the PMEDM which was much lower than the lowest value of 10.56 µg/min obtained for the EDM without powder dielectric fluid.

Surface modification using Electric Discharge Machining (EDM) with powder addition

Powder mixed electrical discharge machining (PMEDM) is one of the recent innovations for the enhancement of the capabilities of EDM process. In this study, the effects of powder addition on the surface modification of mild steel were investigated. Copper tungsten electrode was used in the machining. Two different powders namely TiC and Al2O3 were used in the study with kerosene as the dielectric medium. The powder types and currents were manipulated to study their effects on the machined surface. The results show that increasing the current leads to increase in recast layer thickness, and the cracks. The Al2O3 powder gave higher layer thickness than TiC powder. TiC Powder addition also produced higher hardness, more tool material and carbon depositions on the work surface than Al2O3 powder.

Formation of Nitrides and Carbides on Titanium Alloy Surface through EDM

In this investigation, electrical discharge machining (EDM) was done with Cu-TaC powder metallurgy (PM) electrode and urea solution dielectric fluid. The main objective is to improve the surface wear property of Ti-6Al-4V alloy through the formation of hard ceramic compounds on its surface during EDM. The experiments were conducted with peak current, Ip (3.5, 5.5 A) and pulse duration, ton (3.3, 5.3 µsec) as the machining variables. The outputs investigated are surface characteristics and micro-hardness. The formation of nitrides, carbides and oxides of tantalum and titanium on the EDMed surface was confirmed. The highest micro-hardness of 902.2 Hv was obtained with Ip of 5.5 A and ton of 3.3 µsec.

Electro-Discharge Machining of SUS 304 Stainless Steel with TaC Powder-Mixed Dielectric

Powder-mixed dielectric fluid is one of the innovations of electro-discharge machining (EDM) which seeks to improve the process outputs by addition of powders to the dielectric during machining. In the present study, the influence of TaC powder in kerosene dielectric fluid on EDM process outputs was investigated. Experiments were conducted with the outputs as material removal rate (MRR), surface roughness (Ra) and micro-hardness. During the EDM, the discharge current was varied between 2.5 and 6.5 A, while powder concentration ranges between 5.0 and 15.0 g/l. Results indicate that the highest MRR of 0.38 g/min was obtained with TaC concentration of 15 g/l at the current of 6.5 A. TaC powder addition does not affect both the MRR and Ra at lower current. However, the level of micro-hardness attained was influenced by TaC powder concentration in dielectric fluid, the highest being 1,040 Hv with 5.0 g/l at the current of 2.5 A.

Optimization of Process Parameters on EDM Milling of Stainless Steel AISI 304

Electrical Discharge Machining (EDM) is one of the most widely used non conventional machining processes for removing material from workpiece by means of a series of repeated electric discharges. This process is now one of the main techniques used in die production and has good accuracy and precision with no direct physical contact between the electrodes so that no mechanical stress is exerted on the workpiece. Electrical discharge milling (ED-milling) is an emerging technology where a cylindrical tool electrode follows a programmed path in order to obtain the desired shape of a part. The current investigation aims to optimize the process parameters during EDM milling of stainless steel by using copper electrode. The selected input parameters used for the study are voltage, rotational speed of the electrode and feed rate while the responses are material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (Ra). Response surface methodology is used in the study. The experimental design is formed by using design expert software. Central Composite design (CCD) is used to identify the optimum operating condition in order to obtain maximum MRR, minimum EWR and minimum Ra as response. The result shows that the machining parameter setting of voltage 120 V, rotational speed of electrode 1200 rpm and feed rate 4μm/s, gives optimized responses MRR 5.0259 x 10-3 mm3/min, EWR 53% and Ra 0.79 μm.

Experimental Investigation of Machining Parameters on Surface Roughness in Dry and Wet Wire-Electrical Discharge Machining

Wire electrical discharge machining (WEDM) is a thermal process in which the workpiece and the wire (tool) experience an intense local heating in the discharge channel. The high power density results in the erosion of a part of the material from both electrodes by local melting and vaporization. Whilst good surface finish and high material removal rate of the workpiece is a major requirement, the effect of EDM machining factors on these requirements cannot be overlooked. This study investigate the effect of two different machining methods of dry and wet WEDM process as well as the effect of on-time and voltage on the surface roughness of the workpiece. The machining factors used for this study are the pulse current, on-time and voltage. The results of the effect of the two machining methods on the responses are investigated and reported in this paper.

Influence of Electrode Cooling on Recast Layers and Micro Crack in EDM of Titanium

Electrical discharge machining (EDM) process is a manufacturing method for shaping hard metals and formation of deep and complex shaped hole by spark erosion in electrical conductive materials such as metals, metallic alloys, ceramics etc. EDM process is achieved by a series of recurring electrical discharges between the electrode and workpiece in the presence of dielectric fluid. EDM unique feature of using thermal energy to machine conductive materials irrespective of material hardness has been its major advantage in the manufacture of aerospace, surgical, mould, die, automotive and as well as sport components. The effectiveness of EDM process depends among other factors on the thermal properties of the electrode material. The objective of this study is to study the influence of electrode cooling on recast layers and micro crack in EDM of titanium. The machining parameters investigated in the present study are current intensity (I), pulse on-time (Ton), pulse off-time (Toff) and gap voltage (V), which are of great interest for EDM researchers. The copper electrode is used to EDM titanium workpiece at room temperature and at sub-zero temperature using liquid nitrogen. The influence of cooling of copper electrode on recast layers and micro crack on titanium were investigated using scanning electron microscope (SEM) and has been reported in this study.