Manufactura

j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 1 ( 2 0 0 8 ) 570–573

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Copper and graphite electrodes performance in electrical-discharge machining of XW42 tool steel
C.H. Che Haron ∗ , J.A. Ghani, Y. Burhanuddin, Y.K. Seong, C.Y. Swee
Department of Mechanical and Materials Engineering, Faculty ofEngineering, National University of Malaysia, 43600 Bangi, Selangor, Malaysia

a r t i c l e
Keywords: EDM Current

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a b s t r a c t
Electrical-discharge machining (EDM) is a process of utilizing the removal phenomenon of electrical-discharge in dielectric, therefore, the electrode plays an important role, which affects the material removal rate and the tool wear rate. In this paper themachining characteristics were investigated when machining XW42 tool steel at two current settings (3 A and 6 A), three diameter sizes (10, 15 and 20 mm) and kerosene as the dielectric. The results show that the material removal rate is higher and the relative electrode wear ratio is lower with copper electrode than graphite electrode. The increase in the current and electrode diameter reduced toolwear rate as well as the material removal rate. © 2007 Elsevier B.V. All rights reserved.

Material removal rate Electrode wear rate

1.

Introduction

An electrical-discharge machining (EDM) is based on the eroding effect of an electric spark on both the electrodes used. To obtain the maximum metal removal with minimum wear on the tool electrode, the work material and the tool must be setat positive and negative electrodes, respectively. EDM is commonly used in tool, die and mould making industries for machining heat-treated tool steel materials. The heat-treated tool steels material falls in the difficult-to-cut material group when using conventional machining process. The high rate of tool wear is one of the main problems in EDM. The wear ratio, defined as the volume of metallost from the tool divided by the volume of metal removed from the work material, varies with the tool and work materials used (Boothroyd, 1981; McGeough, 1988). High tool wear rates result in inaccurate dimension. Due to these reasons, a suitable combination between workpiece and tool materials has been studied by previous researchers. Bhattacharyya et al. described influence of rise in the surfacetemperature on both the electrode and the workpiece (Bhattacharya et al., 1981). Patel et al. stated that

the anode erosion rate increases as the current increases, but decreases as pulse time increases (Patel et al., 1989). Che Haron et al. studied the correlation between current and the machinability of the AISI 1045 tool steel with the hardness 230 HB, using copper electrodes (Che Haron etal., 2001). Singh et.al investigated the material removal rate, tool wear, surface quality and diametric over-cut on En-31 tool steel, in detail and concluded that copper and aluminium electrode resulted in the best machining rate (Singh et al., 2004). Ho and Newman stated that research areas in EDM could be arranged into three major headings: machining performance measures, the effects of processparameter and design and manufacture electrode. They concluded that machining performance depends on the wear and surface quality (Ho and Newman, 2003). This paper describes the wear behaviour of copper and graphite electrodes when machining XW42 tool steel. The material removal rate and the electrode wear rate were selected as the machinability factors to be investigated. The results will beutilised to select an optimum electrode and work material combination

Corresponding author. Tel.: +603 8921 6516; fax: +603 8925 9659. E-mail address: chase@vlsi.eng.ukm.my (C.H. Che Haron). 0924-0136/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2007.11.285

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