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A Study of Multiobjective Parametric Optimization of Silicon Abrasive Mixed Electrical Discharge Machining of Tool Steel a
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Anil Kumar , S. Maheshwari , C. Sharma & Naveen Beri a
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Research Scholar , University School of Engineering and Technology , GGSIPU, Delhi, India
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Division of Manufacturing Processes and Automation Engineering , Netaji Subhas Institute of Technology , Dwarka, New Delhi, India c
Department of Mechanical and Automation Engineering , Indira Gandhi Institute of Technology , Kashmiri Gate, Delhi, India Published online: 13 Dec 2010.
To cite this article: Anil Kumar , S. Maheshwari , C. Sharma & Naveen Beri (2010) A Study of Multiobjective Parametric Optimization of Silicon Abrasive Mixed Electrical Discharge Machining of Tool Steel, Materials and Manufacturing Processes, 25:10, 1041-1047, DOI: 10.1080/10426910903447303 To link to this article: http://dx.doi.org/10.1080/10426910903447303
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Materials and Manufacturing Processes, 25: 1041–1047, 2010 Copyright © Taylor & Francis Group, LLC ISSN: 1042-6914 print/1532-2475 online DOI: 10.1080/10426910903447303
A Study of Multiobjective Parametric Optimization of Silicon Abrasive Mixed Electrical Discharge Machining of Tool Steel Anil Kumar1 , S. Maheshwari2 , C. Sharma3 , and Naveen Beri1
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1 Research Scholar, University School of Engineering and Technology, GGSIPU, Delhi, India Division of Manufacturing Processes and Automation Engineering, Netaji Subhas Institute of Technology, Dwarka, New Delhi, India 3 Department of Mechanical and Automation Engineering, Indira Gandhi Institute of Technology, Kashmiri Gate, Delhi, India
In this article, a technique for optimization of abrasive mixed electrical discharge machining (AEDM) process with multiple performance characteristics based on the orthogonal array with grey relational analysis has been studied. The process input parameters, i.e., concentration of silicon abrasive powder in dielectric fluid, peak current, pulse-on time, and duty factor, were chosen to study process performance in the form of MRR and surface roughness. The research outcome identifies significant parameters and their effect on process performance on EN-24 tool steel using copper electrode with silicon powder (2 g/l) suspended in kerosene dielectric. The optimum process conditions have been verified by conducting the confirmation experiments. Keywords Abrasive mixed electrical discharge machining (AEDM); Grey relation theory; Material removal rate (MRR); Orthogonal array (OA); Surface roughness (SR).
Introduction Electrical discharge machining (EDM) is one of the earliest and most popular nontraditional machining processes. In this process, material is removed by controlled erosion through a series of electric sparks of short duration and high current density between the tool (electrode) and the workpiece. It can be successfully employed to machine electrically conductive materials regardless of their hardness and toughness and has made machining of intricate shapes relatively simple. This machining process is being used extensively in press tools and dies, aerospace, automotive, and surgical components manufacturing industries [1, 2]. In spite of remarkable process capabilities, limitations such as low volumetric material removal rate (MRR) and poor surface quality are associated with conventional electrical discharge machining. To address this problem, an innovative new hybrid technique, i.e., abrasive mixed electrical discharge machining (AEDM) has emerged as one of the advanced techniques in direction of enhancement of capabilities of electrical discharge machining [4, 5]. In this technique, material is removed by series of electric discharges and ploughing action of abrasive particles in dielectric medium with an objective of improving MRR and enhancing surface qualities. In AEDM, abrasives in powder form are mixed in the dielectric fluid and, for better circulation, a stirring system is employed, which also avoids particles setting. The electrically conductive metallic
Received July 20, 2009; Accepted October 4, 2009 Address correspondence to Anil Kumar, Department of Mechanical Engineering, Beant College of Engineering & Technology, Gurdaspur, Punjab, India; E-mail:
[email protected]
powder reduces insulating strength of dielectric fluid and increases spark gap between electrode and workpiece. As a result, the process becomes more stable, thereby improving machining rate and surface finish. The process condition scheme of AEDM is well explained by star model as shown in Fig. 1. The main factors that influence machining in AEDM are electrical parameters (like pulse frequency, duty cycle, pulse on time, spark gap, current, and voltage), material properties of electrode, workpiece and dielectric fluid, and properties of abrasive powders (like melting point, specific heat, thermal conductivity, grain size, and concentration) [3, 6]. Like other machining processes, the quality of machined parts is significantly affected by input process conditions. Therefore, promoting the quality of the process by developing a thorough understanding of the relationship between these parameters for better machined surfaces has become a major research concern. The mechanism of AEDM is different from conventional EDM [5]. Under the influence of high potential intensity, the particles become charged, accelerated, move in a zigzag fashion, and may act as conductors. These conductive particles lower the breakdown strength of insulating dielectric fluid [7] which causes early explosion in the gap. As a result, a series of discharges starts under the electrode area. Abrasive particles lead to increase in gap size between workpiece and electrode, whereas the actual spark gap decreases as spark takes place because of breakage somewhere in the stagnation chain connecting the electrodes as a result of which the process becomes more stable thereby increasing MRR and improving surface roughness [8]. Erden and Belgin [9] were the first who studied the effect of impurities (copper, aluminium, iron, and carbon)
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Figure 1.—Process condition scheme of abrasive mixed electrical discharge machining (AEDM) (Star Model).
in EDM of brass steel and copper steel pair, and reported increase in machining rates with increase in concentration of impurities. It was further observed that machining becomes unstable at an excessive powder concentration due to the occurrence of short-circuits. Since then a lot of research work has been done in the area of AEDM and has shown great effect on process performance in terms of MRR, surface qualities, wear ratio, etc. Jeswani [10] investigated the effect of suspended fine graphite powder in dielectric medium of EDM on tool steel and reported that an additional about 4 g of fine graphite powder (10 m in average size) per liter of kerosene increased MRR by 60% and tool wear rate by 15%. Mohri and coworker [11] studied the effect of silicon powder in dielectric medium. Particles size of 10–30 m were mixed with dielectric fluid, and machining was performed at low discharge current and very short discharge time (
