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

Author(s):  
R Rajeswari ◽  
MS Shunmugam

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.

2015 ◽  
Vol 14 (03) ◽  
pp. 189-202 ◽  
Author(s):  
V. Vikram Reddy ◽  
P. Madar Valli ◽  
A. Kumar ◽  
Ch. Sridhar Reddy

In the present work, an investigation has been made into the electrical discharge machining process during machining of precipitation hardening stainless steel PH17-4. Taguchi method is used to formulate the experimental layout, to analyze the effect of each process parameter on machining characteristics and to predict the optimal choice for each electrical discharge machining process parameters namely, peak current, pulse on time and pulse off time that give up optimal process performance characteristics such as material removal rate, surface roughness, tool wear rate and surface hardness. To identify the significance of parameters on measured response, the analysis of variance has been done. It is found that parameters peak current and pulse on time have the significant affect on material removal rate, surface roughness, tool wear rate and surface hardness. However, parameter pulse off time has significant affect on material removal rate. Confirmation tests are conducted at their respective optimum parametric settings to verify the predicted optimal values of performance characteristics.


Author(s):  
Gurpreet Singh ◽  
DR Prajapati ◽  
PS Satsangi

The micro-electrical discharge machining process is hindered by low material removal rate and low surface quality, which bound its capability. The assistance of ultrasonic vibration and magnetic pulling force in micro-electrical discharge machining helps to overcome this limitation and increase the stability of the machining process. In the present research, an attempt has been made on Taguchi based GRA optimization for µEDM assisted with ultrasonic vibration and magnetic pulling force while µEDM of SKD-5 die steel with the tubular copper electrode. The process parameters such as ultrasonic vibration, magnetic pulling force, tool rotation, energy and feed rate have been chosen as process variables. Material removal rate and taper of the feature have been selected as response measures. From the experimental study, it has been found that response output measures have been significantly improved by 18% as compared to non assisted µEDM. The best optimal combination of input parameters for improved performance measures were recorded as machining with ultrasonic vibration (U1), 0.25 kgf of magnetic pulling force (M1), 600 rpm of tool rotation (R2), 3.38 mJ of energy (E3) and 1.5 mm/min of Tool feed rate (F3). The confirmation trail was also carried out for the validation of the results attained by Grey Relational Analysis and confirmed that there is a substantial improvement with both assistance applied simultaneously.


Author(s):  
Arun Kumar Rouniyar ◽  
Pragya Shandilya

Magnetic field assisted powder mixed electrical discharge machining is a hybrid machining process with suitable modification in electrical discharge machining combining the use of magnetic field and fine powder in the dielectric fluid. Aluminum 6061 alloy has found highly significance for the advanced industries like automotive, aerospace, electrical, marine, food processing and chemical due to good corrosion resistance, high strength-to-weight ratio, ease of weldability. In this present work, magnetic field assisted powder mixed electrical discharge machining setup was fabricated and experiments were performed using one factor at a time approach for aluminum 6061 alloy. The individual effect of machining parameters namely, peak current, pulse on time, pulse off time, powder concentration and magnetic field on material removal rate and tool wear rate was investigated. The effect of peak current was found to be dominant on material removal rate and tool wear rate followed by pulse on time, powder concentration and magnetic field. Increase in material removal rate and tool wear rate was observed with increase in peak current, pulse on time and a decrease in pulse off time, whereas, for material removal rate increases and tool wear rate decreases up to the certain value and follow the reverse trend with an increase in powder concentration. Material removal rate was increased and tool wear rate was decreased with increase in magnetic field.


Author(s):  
Vikas Gohil ◽  
Yogesh M Puri

Electrical discharge turning is a unique form of electrical discharge machining process, which is being especially developed to generate cylindrical forms and helical profiles on the difficult-to-machine materials at both macro and micro levels. A precise submerged rotating spindle as a work holding system was designed and added to a conventional electrical discharge machine to rotate the workpiece. A conductive preshaped strip of copper as a forming tool is fed (reciprocate) continuously against the rotating workpiece; thus, mirror image of the tool is formed on the circumference of the workpiece. The machining performance of electrical discharge turning process is defined and influenced by its machining parameters, which directly affects the quality of the machined component. This study presents an investigation on the effects of the machining parameters, namely, pulse-on time, peak current, gap voltage, spindle speed and flushing pressure, on the material removal rate (MRR) and surface roughness (Ra) in electrical discharge turning of titanium alloy Ti-6Al-4V. This has been done by means of Taguchi’s design of experiment technique. Analysis of variance as well as regression analysis is performed on the experimental data. The signal-to-noise ratio analysis is employed to find the optimal condition. The experimental results indicate that peak current, gap voltage and pulse-on time are the most significant influencing parameters that contribute more than 90% to material removal rate. In the context of Ra, peak current and pulse-on time come up with more than 82% of contribution. Finally, the obtained predicted optimal results were verified experimentally. It was shown that the error values are all less than 6%, confirming the feasibility and effectiveness of the adopted approach.


2012 ◽  
Vol 445 ◽  
pp. 994-999 ◽  
Author(s):  
Mohammad Reza Shabgard ◽  
Mirsadegh Seyedzavvar

This paper details the correlation between the input parameters with the tool material on the machining response in comparison of two different combinations of toolworkpiece material, namely copper-H13 and graphite-H13. The considered machining input parameters included pulse current and pulse on-time, and the investigated characteristics of the machining response were the material removal rate, tool wear, and surface roughness of the workpiece. Furthermore, differences in pulse shapes and process stability between the copper-H13 and graphite-H13 combinations were investigated.


2015 ◽  
Vol 1115 ◽  
pp. 3-6 ◽  
Author(s):  
M.A. Moudood ◽  
Abdus Sabur ◽  
Mohammad Yeakub Ali ◽  
I.H. Jaafar

Electrical discharge machining (EDM) is a non-conventional machining technique which can be used to machine non-conductive ceramics. This technique removes materials from the workpiece by thermal energy exerted from series of electrical sparks. Using copper foil as assisting electrode (AE), machining of Al2O3 is done successfully. In this investigation, experiments were performed to study the effect of gap voltage and pulse-on time on material removal rate (MRR) for EDM of Al2O3. The results showed that the lowest and the highest values of gap voltage were 12 V and 14 V, respectively, with a fixed peak current of 1.1 A and pulse-on time of 8 μs. Beyond these two voltage values, material cannot be removed due to insufficient pyrolytic carbon layer generation. Similarly, pulse-on time is varied from 6 μs to 8 μs when gap voltage is fixed at 14 V and peak current at 1.1 A. MRR, in this case, is increased almost 20 times from a lowest value of 0.006 mm3/min to a highest value of 0.119 mm3/min for the specified gap voltage and pulse-on time.


Author(s):  
Hardik Beravala ◽  
Pulak M Pandey

In the present research work, an attempt has been made to develop the mathematical model to predict the material removal rate in the electrical discharge machining process when the assistance of air and magnetic field is provided together. The proposed model incorporates the physical phenomenon occurred during electrical discharge machining such as the plasma column expansion and reduction in the mean free path of electron in the plasma column due to magnetic field. In addition, the model incorporates the effect of air on the material removal rate. The developed model correlates the material removal rate with the process parameters such as the peak current, pulse duration, duty cycle, air pressure and magnetic flux density. The experimental data were used to evaluate the constants for district processing conditions. The relation between air pressure and breakdown voltage in the liquid-air mixed dielectric has been established experimentally. The obtained expression of material removal rate has been validated for the experimental conditions other than that used for obtaining constants. The results show less than 10% error in the prediction by the model over the respective experimental values.


2013 ◽  
Vol 393 ◽  
pp. 246-252 ◽  
Author(s):  
A. Sabur ◽  
Mohammad Yeakub Ali ◽  
M.A. Maleque

Electro discharge machining (EDM) technique, a noncontact machining process, is applied for structuring nonconductive ZrO2 ceramic. A conductive layer of adhesive copper is applied on the workpiece surface to initiate the sparks. Kerosene is used as dielectric for creation of continuous conductive pyrolytic carbon layer on the machined surface. Experiments are conducted by varying the peak current (Ip), pulse-on time (Ton), pulse-off time (Toff) and gap voltage (Vg). Correlating these variables a mathematical model for material removal rate (MRR) is developed using Taguchi method. The optimized parametric conditions are determined for higher MRR through ANOVA and signal to noise (S/N) ratio analysis. The results showed that the Ip and Ton are the significant parameters of MRR in EDM for nonconductive ZrO2 ceramic. The model also showed that MRR increases with the increase of Ip and Ton, but the process is controlled by Ip as a whole.


ROTASI ◽  
2019 ◽  
Vol 21 (1) ◽  
pp. 1
Author(s):  
Petrus Londa

Electrical Discharge Machining (EDM) adalah non-conventional machining process. EDM dapat memotong semua jenis benda kerja yang bersifat penghantar listrik, terutama digunakan pada benda kerja yang sangat keras dan memiliki bentuk yang rumit, yang tidak dapat dipotong oleh mesin konvensional. Penelitian ini menggunakan metode Taguchi untuk menentukan variabel pemesinan yang secara signifikan mempengaruhi proses pemotongan pada beberapa material elektroda (tembaga, kuningan, alumunium) dan benda kerja dari bahan K460 (amutit S). Taguchi L25 Orthogonal standard arrays dan analysis of variance (ANOVA) dapat menentukan performa variabel pemotongan (PON, POFF, GAP, QDON, SERVO dan LT) dengan variabel yang diteliti adalah Electrode Wear Rate (EWR), Material Removal Rate (MRR) dan Diameter Overcut (DOC). Hasil dari penelitian ini ditampilkan dalam bentuk tabel-tabel dan grafik yang menunjukan variabel pemesinan yang signifikan mempengaruhi proses pemotongan sesuai dengan jenis material elektroda yang digunakan.


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