scholarly journals Study on Fe-Based Metallic Glass Micro Hole Machining by Using Micro-EDM Combined with Electrophoretic Deposition Polishing

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 96
Author(s):  
Hai-Ping Tsui ◽  
Shih-Yu Hsu
Keyword(s):  
Metallic Glass ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
High Hardness ◽  
Duty Factor ◽  
Machined Surface ◽  
Inner Surface ◽  
Micro Hole ◽  
Pulse On Time ◽  
Hole Machining

Fe-based metallic glass possesses high hardness and brittleness. It is a hard-to-cut metal material and difficult to machine by conventional methods. Although electrical discharge machining (EDM) has advantages in machining hard-to-cut metal materials, recast layer, pores, and micro cracks will form on the machined surface after machining. The study used a helical tool for the micro electrical discharge drilling (µ-EDD) process on Fe-based metallic glass. The influence of processing parameters, including the pulse on time, gap voltage, duty factor, and spindle rotational speed on the micro hole machining quality characteristics was investigated. The helical tool with SiC electrophoretic deposited (EPD) film was used to polish the inner surface of the electrical discharged micro hole. The findings show that the best micro hole accuracy, tool wear length, and inner surface were obtained at the spindle rotation speed of 1150 rpm, pulse on time of 5 μs, gap voltage of 30 V, and duty factor of 40%. The inner surface roughness can be reduced to 0.018 µm by using EPD tool. The inner surface was polished up to form a mirror surface.

Modeling of Recast Layer in Micro-Electrical Discharge Machining

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
P. C. Tan ◽  
S. H. Yeo
Keyword(s):  
Numerical Model ◽  
Electrical Discharge ◽  
Prediction Models ◽  
Electrical Discharge Machining ◽  
Performance Measure ◽  
Recast Layer ◽  
Micro Edm ◽  
Machined Surface ◽  
Functional Layer ◽  
Pulse On Time

The thickness of recast layers produced during electrical discharge machining (EDM) is an important process performance measure as it may indicate an extent of crack propagation in a machined surface or thickness of a functional layer alloyed onto a machined surface. Thus, the availability of the recast layer thickness prediction models is needed to allow better control of machining outcomes, which becomes more vital for micro-EDM due to the microscale of machined features. The proposed numerical model, based on a multiple discharge approach for recast layer prediction, is developed to fill an existing gap in micro-EDM. The multiple discharge approach accounts for the overlapping nature by which craters are generated on the machined surface and considers the recast layer to be a combination of individual recast regions from individual craters. The numerical analysis, based on finite element methods, is used to determine the melting isotherms due to heat inputs on overlapping crater profiles. Then, a hemispherical-capped crater profile is estimated by applying a recast plasma flushing efficiency to the amount of molten material bounded by the melting isotherm. Finally, the recast region is defined to be bounded by the melting isotherm and crater profile. The model, developed for a peak discharge current of 1.45 A and pulse on time between 166 ns and 606 ns, predicted recast layer thicknesses of between 1.0 μm and 1.82 μm. It is then validated at pulse on time settings of 244 ns and 458 ns, which generated average recast layer thicknesses of 1.18 μm and 1.56 μm, respectively. Thus, the numerical model developed using the multiple discharge approach is suitable for estimation of recast layer thicknesses in micro-EDM.

Surface Study in a Non-conventional (Electrical Discharge Machining) Process for Grade 6 Titanium Material

2014 ◽  
Vol 68 (1) ◽  
Author(s):  
Md. Ashikur Rahman Khan ◽  
M. M. Rahman
Keyword(s):  
Surface Roughness ◽  
Process Parameters ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Machining Process ◽  
Machined Surface ◽  
Titanium Material ◽  
Pulse On Time ◽  
Pulse Off Time ◽  
Off Time

Electrical discharge machining (EDM) produces complex shapes and permits high-precision machining of any hard or difficult-to-cut materials. The performance characteristics such as surface roughness and microstructure of the machined face are influenced by numerous parameters. The selection of parameters becomes complicated. Thus, the surface roughness (Ra) and microstructure of the machined surface in EDM on Grade 6 titanium alloy are studied is this study. The experimental work is performed using copper as electrode material. The polarity of the electrode is maintained as negative. The process parameters taken into account in this study are peak current (Ip), pulse-on time (Ton), pulse-off time (Toff), and servo-voltage (Sv). A smooth surface finish is found at low pulse current, small on-time and high off-time. The servo-voltage affects the roughness diversely however, a finish surface is found at 80 V Sv. Craters, cracks and globules of debris are appeared in the microstructure of the machined part. The size and degree of craters as well as cracks increase with increasing in energy level. Low discharge energy yields an even surface. This approach helps in selecting proper process parameters resulting in economic EDM machining. 

Comparative evaluation of powder-mixed and ultrasonic-assisted rough die-sinking electrical discharge machining based on pulse characteristics

2019 ◽  
Vol 233 (14) ◽  
pp. 2515-2530 ◽  
Author(s):  
R Rajeswari ◽  
MS Shunmugam
Keyword(s):  
Material Removal Rate ◽  
Electrical Discharge ◽  
Material Removal ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
Graphite Powder ◽  
Machining Process ◽  
Machined Surface ◽  
Ultrasonic Assisted ◽  
Pulse On Time

Electrical discharge machining is used in the machining of complicated shapes in hardened molds and dies. In rough die-sinking stage, attempts are made to enhance material removal rate with a consequential reduction in cycle time. Powder mix and ultrasonic assistance are employed in the electrical discharge machining process to create gap conditions favoring material removal. In the present work, experiments are carried out on hardened D3 die steel using full-factorial design based on three levels of voltage, current and pulse on time. The gap phenomena in graphite powder-mixed and ultrasonic-assisted rough electrical discharge machining are studied using a detailed analysis of pulse shapes and their characteristic trains. Two new parameters, namely, energy expended over a second ( E) and performance factor ( PF) denoting the ratio of energy associated with sparks to total discharge energy, bring out gap conditions effectively. In comparison with the conventional electrical discharge machining for the selected condition, it is seen that the graphite powder mixed in the dielectric enhances the material removal rate by 20.8% with E of 215 J and PF of 0.227, while these values are 179.8 J and 0.076 for ultrasonic-assisted electrical discharge machining with marginal reduction of 3.9%. Cross-sectional images of workpieces also reveal the influence of electrical discharge machining conditions on the machined surface. The proposed approach can be extended to different powder mix and ultrasonic conditions to identify condition favoring higher material removal.

A Discharge Separation Model for Powder Mixed Electrical Discharge Machining

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Bülent Ekmekci ◽  
Hamidullah Yaşar ◽  
Nihal Ekmekci
Keyword(s):  
Electrical Discharge ◽  
Discharge Channel ◽  
Electrical Discharge Machining ◽  
Complete Separation ◽  
Dielectric Liquid ◽  
Material Transfer ◽  
Machined Surface ◽  
Machining Conditions ◽  
Main Discharge ◽  
Pulse On Time

Added powders in a dielectric medium substantially influence the features of electrical discharges due to altered interelectrode conditions during the electrical discharge machining (EDM) process. The main discharge channel is disturbed due to the added powders in dielectric liquid and leads formations of secondary discharges. Such altered discharge conditions generate a unique topography on the machined surface and consequent subsurface microstructure beneath it. Ti6Al4V work material machined using SiC powder mixing in de-ionized water for an extensive set of pulse-on duration and pulse currents. Then, different forms of secondary discharges were identified from the resultant surface features and corresponding subsurface microstructures. The results pointed out that generation of unevenly separated secondary discharges increased the material transfer rate from the powder mixed dielectric liquid to the machined surface by means of the decomposed ions in the plasma channel. Complete separation of the main discharge channel into evenly distributed secondary discharges is possible under specific machining conditions that suggested minimal deformation of the machined surface regarding microcracks, roughness, and heat affected layer thickness. Under such machining conditions, another means of material transfer mechanism is activated that lead a powder particle build-up process on the machined surface. Consequently, five different discharge forms were proposed to describe the resultant surface topographies and subsurface microstructures. The material migration phenomena and the mechanisms are discussed in relation to the pulse-on time and pulse current.

scholarly journals Optimization of the Material Removal Rate and Electrode Wear Ratio in Electrical Discharge Machining of Reaction-bonded Silicon Carbide by Response Surface Methodology

2020 ◽  
Vol 9 (4) ◽  
pp. 2116-2120
Keyword(s):  
Silicon Carbide ◽  
Response Surface Methodology ◽  
Response Surface ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
High Hardness ◽  
Electrode Wear ◽  
Good Surface ◽  
Pulse On Time

Reaction-bonded silicon carbide (RB-SiC) is widely used as moulding dies material in many industries thanks to its excellent properties. Nevertheless, because of its high hardness and brittleness, it is extremely hard to be machined with high accuracy and good surface finish. Therefore, electrical discharge machining (EDM) has been chosen as an alternative method to machine the RB-SiC. In the present study, an experimental investigation has been conducted to optimize and validate the EDM parameters on the MRR and EWR of low conductivity RB-SiC in EDM. The new Cu – 1.0 wt. % CNF composite electrode that fabricated via powder metallurgy (PM) process was used as the electrode. The experiments were systematically conducted by face-cubic centre (FCC) approach of response surface methodology (RSM). The mathematical models for MRR and EWR were developed in this study. In addition, analysis of variance (ANOVA) was also figured out to check the significance of the models. Three experiments were conducted as the confirmation test to determine the error percentage of MRR and EWR. Based on the results, only 3.06% and 3.93% errors were determined for both MRR and EWR, respectively. The optimum conditions for multi responses (MRR and EWR) were found to be at a current of 6A, voltage of 22V, and pulse on-time of 12µs. The findings of this study provide an important reference to the manufacturing industries, especially mould and die industry.

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

2014 ◽  
Vol 228 (18) ◽  
pp. 3374-3380 ◽  
Author(s):  
Zakaria Mohd Zain ◽  
Mohammed Baba Ndaliman ◽  
Ahsan Ali Khan ◽  
Mohammad Yeakub Ali
Keyword(s):  
Stainless Steel ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Tantalum Carbide ◽  
Dielectric Fluid ◽  
Micro Hardness ◽  
Machined Surface ◽  
Surface Machining ◽  
Pulse On Time ◽  
Pulse Off Time

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.

Optimization of machining parameters in chromium-additive mixed electrical discharge machining of the AA7075/5%B4C composite

2021 ◽  
pp. 095440892110317
Author(s):  
Vineet Dubey ◽  
Anuj K Sharma ◽  
Balbir Singh
Keyword(s):  
Surface Roughness ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Process Condition ◽  
Dielectric Fluid ◽  
Optimum Process ◽  
Machining Parameters ◽  
Machined Surface ◽  
Pulse On Time ◽  
Pulse Off Time

The present study establishes the optimum process condition for additive mixed electrical discharge machining of Al7075–5%B4Cp metal matrix composite by performing experimental investigation. The suspension of chromium particles in a dielectric fluid is used as an additive. The input process parameters selected for experimentation are specifically pulse on-time, gap voltage, pulse off-time and peak current, for analysing their influence on wear of the tool along with surface roughness of the composite. Comparative study of the machined surface is done by analysing microstructures, cracks and recast layers formed at different settings of input parameters using a scanning electron microscope. Rise in amount of current and pulse on-time led to increased height of the recast layer generated on the surface of the machined workpiece. Furthermore, a confirmatory experiment was performed at the optimal setting. The result revealed an error of 5.5% and 7.5% between experimental and predicted value of tool wear rate and surface roughness.

Performance Evaluation on Cryogenic Cooling of Electrode in Electrical Discharge Machining in AISI D2 Steel

2013 ◽  
Author(s):  
M. Pradeep Kumar ◽  
S. Vinoth Kumar
Keyword(s):  
Surface Roughness ◽  
Current Pulse ◽  
Discharge Current ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Electrode Wear ◽  
Machined Surface ◽  
Aisi D2 ◽  
Pulse On Time ◽  
D2 Steel

This research has been conducted to evaluate the performance of the Liquid Nitrogen (LN2) cooling of copper electrode in electrical discharge machining (EDM) on AISI D2 steel. The experimental process parameter such as discharge current, pulse on time and gap voltage were varied to explore their effects on machining performance, including the electrode wear and surface roughness. It was found that for electrode wear, discharge current, pulse on time, and gap voltage has the most significant effect, while the pulse on time and discharge current have the most significant effect on surface roughness. Analysis on the influence of cooling responses has been carried out and presented in this study. It was found that the electrode wear reduced up to 18% during LN2 cooling. Surface roughness was also significantly reduced while machining with LN2 electrode cooling. Scanning electron microscope (SEM) analysis was carried out to study the surface characteristics of machined surface. EDMed machined surface was also acceptable in LN2 cooling of the electrode.

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