Parametric Optimization of PMEDM Process with Chromium Powder Suspended Dielectric for Triangular Electrodes

Dr Rajiv Kumar Garg1, a, Dr Kuldeep Ojha2,b 1IPE Department, Dr B R Ambedkar National Institute of Technology, Jalandhar, Punjab, India

2Mechanical Engineering Department, Lakshmi Narain College of Technology, Bhawrsala, Revati Range, Sanwer Road, Indore, MP, India-453331

agargrk@nitj.ac.in, bkojha.gvc@gmail.com,

Keywords: PMEDM, MRR, SR, Optimization

Abstract. In this article, parametric optimization for material removal rate (MRR) and surface

roughness (SR) study on the powder mixed electrical discharge machining (PMEDM) of EN-8

steel has been carried out. Response surface methodology (RSM) has been used to plan and analyze

the experiments. Average current, duty cycle, diameter of electrode and concentration of micro-

nickel powder added into dielectric fluid of EDM were chosen as process parameters to study the

PMEDM performance in terms of MRR and SR. Experiments have been performed on newly

designed experimental setup developed in laboratory. Most important parameters affecting selected

performance measures have been identified and effects of their variations have been observed.

Introduction and Literature Review

Electrical discharge machining is an important manufacturing process for tool mould and die

industries. This process is finding an increasing application for because of its ability to produce

geometrically complex shapes and its ability to machine materials irrespective to their hardness.

However, poor surface finish and low machining efficiency limits its further applications. Many

researchers have explored the EDM field and presented their novel findings [1-8] still there are

developing areas in this field. Powder mixed electrical discharge machining (PMEDM) one of the

relatively new material removal processes applied to improve the machining efficiency and surface

finish in presence of powder mixed dielectric fluid.

Kansal et al. [9] and A. Kumar et al. [10] presented a comprehensive literature review of the

published literature on EDM mixed with additives in dielectric. PMEDM process and electrode

design for EDM application is one of the major areas of interest of EDM researchers and many

recent research findings reveal its importance [11-25].

In present research work, different parametric combinations of average current, duty cycle,

diameter of electrode, and powder concentration of chromium in dielectric has been explored for

EN- 8 steel. Literature review reveals that this combination has not been explored yet. Also

electrode diameter has been chosen as one design factor to develop some guidelines for electrode

design.

Experimentation and Optimization

Experimentation has been performed on newly developed experimental setup. Commercial copper

has been chosen as electrode and kerosene oil as dielectric. The response variables selected are

MRR and SR. Cr powder has been mixed in dielectric at different concentration levels. The results

for experimentation have been summarized in Table 1.

The perturbation curve has been plotted as shown in Figure 1 helps to compare the effect of all

the factors at a particular point in the design space. Since duty cycle is not there because of its

insignificance, its variation is not included in perturbation graph. The graph shows that surface

roughness is most sensitive to average current and powder concentration. Optimization of

parameters with the help of Design Expert 8.0.4 software. The constraints applied on the design

space have been shown in Table 2. The optimization results are shown in Table 3.

Advanced Materials Research Vols. 816-817 (2013) pp 23-27Online available since 2013/Sep/23 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.816-817.23

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Table 1 Experimental design matrix and collected data

Run no

Coded values Natural values Responses

X1 X2 X3 X4 A

(A)

B

(%)

C

(g/l)

D

(Degree)

MRR

(mm3/min)

TWR

(mm3/min)

SR

(µm)

1 0 0 0 0 6 63 4 90 8.61 0.04 5.68

2 +1 0 0 0 8 63 4 90 7.78 0.035 7.31

3 0 0 0 +1 6 63 4 130 5.83 0.033 4.75

4 -1 -1 -1 -1 4 54 2 50 1.72 0.03 3.95

5 0 0 0 0 6 63 4 90 8.64 0.031 5.43

6 0 0 -1 0 6 63 2 90 8.01 0.022 4.37

7 -1 0 0 0 4 63 4 90 7.98 0.029 4.53

8 +1 +1 -1 +1 8 72 2 130 6.66 0.021 5.25

9 +1 +1 -1 -1 8 72 2 50 5.42 0.036 5.97

10 0 0 0 0 6 63 4 90 7.89 0.028 5.75

11 +1 +1 +1 +1 8 72 6 130 13.41 0.034 6.43

12 +1 -1 -1 +1 8 54 2 130 3.25 0.039 5.11

13 -1 -1 +1 +1 4 54 6 130 3.31 0.016 5.32

14 -1 -1 -1 +1 4 54 2 130 2.74 0.013 4.19

15 +1 -1 -1 -1 8 54 2 50 8.72 0.041 6.35

16 +1 +1 +1 -1 8 72 6 50 9.02 0.033 5.63

17 0 0 0 0 6 63 4 90 7.76 0.031 6.03

18 +1 -1 +1 -1 8 54 6 50 11.01 0.035 5.03

19 +1 -1 +1 +1 8 54 6 130 10.31 0.032 5.87

20 0 -1 -1 0 6 54 4 90 7.79 0.034 6.43

21 0 +1 -1 0 6 72 4 90 6.52 0.026 5.21

22 -1 +1 -1 -1 4 72 2 50 1.54 0.016 4.02

23 -1 +1 +1 +1 4 72 6 130 2.09 0.02 4.23

24 0 0 +1 +1 6 63 6 90 6.65 0.032 5.12

25 -1 +1 +1 -1 4 72 6 50 3.28 0.033 4.86

26 0 0 0 0 6 63 4 90 7.53 0.026 5.31

27 -1 -1 +1 -1 4 54 6 50 2.75 0.025 5.97

28 0 0 0 0 6 63 4 90 7.98 0.031 5.46

29 0 0 0 -1 6 63 4 50 5.87 0.035 6.31

30 -1 +1 -1 +1 4 72 2 130 1.59 0.019 3.12

Figure 1 Perturbation graph for MRR

24 Manufacturing Science and Technology (ICMST2013)

Table 2 Constraints in design space

Name Goal Lower

limit

Upper

limit

Lower

weight

Upper

weight Importance

A:Current Is in range 4 8 1 1 3

B: Duty cycle (%) Is in range 54 72 1 1 3

C:Powder concentration Is in range 2 6 1 1 3

D:Tool angle Is in range 50 130 1 1 3

MRR Maximize 1.54 13.41 1 1 3

TWR Minimize 0.013 0.041 1 1 3

SR Minimize 3.12 7.31 1 1 3

Following solution has been suggested by software for optimum parameter settings.

Table 3: Optimum value in design space

Parameter/performance measure Values

A:Current 4.00

B: Duty cycle (%) 63.39

C:Powder concentration 2.00

D:Tool angle 95

MRR 4.7155

TWR 0.022

SR 3.648

Desirability 0.532

Conclusions

In this article, quantitative analysis of machinability of EN-8 steel in PMEDM process has been

carried out. Cr powder particles are mixed in EDM dielectric fluid. RSM has been applied for

analysis. Optimum results have been found as suggested by software.

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Advanced Materials Research Vols. 816-817 27

Manufacturing Science and Technology (ICMST2013) 10.4028/www.scientific.net/AMR.816-817 Parametric Optimization of PMEDM Process with Chromium Powder Suspended Dielectric for

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