Use of wire bunch electrodes in electric discharge machining

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Use of wire bunch electrodes in electric discharge machining
Kadir Dursun and Can Cogun
Department of Mechanical Engineering, Faculty of Engineering and Architecture, Gazi University, Ankara, Turkey
Abstract Purpose – In electrical discharge machining (EDM) process, the production of separate electrodes for rough, semi-rough and finish machining of dies and moulds having complex surfaces,results in high cost and long lead-time in manufacturing. The purpose of this paper is to describe the machining performance of electrodes formed by using copper wire bunches (WBs) positioned to conform the surface to be machined was experimentally and theoretically analyzed. In the study, the variations in the machining rate, electrode wear rate, relative wear and workpiece surface roughness wereexamined for various discharge current and pulse-time settings. Design/methodology/approach – Copper WBs positioned to conform the surface to be machined in electric discharge machining. The variations in the machining rate, electrode wear rate, relative wear and workpiece surface roughness were examined experimentally for various discharge current and pulse-time settings. The WB electrodes (WBEs) areproven to be satisfactory as electrodes for roughing operations in electric discharge machining. Findings – The increase in number of wires and pulse energy result in decrease of relative wear for each wire in the electrode. The increase in number of wires in electrodes causes increase in machining area and in machining time in WBE method. With the increase of discharge current and pulse time,the electrode wear rate and material removal values increase and machining time decreases. By using the mathematical models obtained from the result of the experiments, the electrode wear rate, material removal rate, relative wear and the set length of wires for the desired cavity profile can be calculated. The labor cost of electrode manufacturing in the WBE method is lower compared to conventionalsolid electrodes. The use of WBE method for rough machining decreases machining cost and time. The use of WBE method decreases both the number of the electrodes required and the delay in starting machining due to the preparation of electrode in EDM. Originality/value – This paper introduces the benefits of using WBE in electric discharge machining; wear and material removal characteristics of WBEsare introduced; the surface roughness characteristics of surfaces produced by WBEs are examined experimentally; and the effect of number of wires used in WBEs given (experimental findings). Keywords Electric discharge machining, Wire bunch electrode, Machining performance Paper type Research paper

1. Introduction
Electrical discharge machining (EDM) is based on the fact that a tiny section isremoved by being melted from the surface of the workpiece through the controlled electrical discharges provided by the conductive electrode immersed the dielectric fluid and the workpiece (Pandey and Shan, 1980). EDM is commonly used to machine the materials which have a high strength and complex surfaces and those are enduring to the high temperatures, much more rigid and harder to be machinedunder the normal conditions. EDM is used for the production of injection, forging, extrusion and powder compression dies in the manufacturing industry (Uhlman et al., 2005; Masuzawa, 1993; Ho and Newman, 2003; Valantincic et al., 2006; Altan et al., 1993). Moulds and dies to be machined in EDM need an electrode which is the similar of the positive or negative volume to be machined. In the case thatvolumes to be
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machined are complex; the number of the electrodes to be used is increasing (Altan et al., 2001; Arthur et al., 1996; Prasad et al., 1999; Ding et al., 2000, 2002). It is known that the electrode manufacturing occupies 50 percent of the cost and of the lead time of the...
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