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Journal of Materials Processing Technology 140 (2003) 264–268 A material removal analysis of electrochemical machining using flat-end cathode H. Hocheng ∗ , Y.H. Sun, S.C. Lin, P.S. Kao Department of P ower , Mechanica l Engineering , National Tsing-Hua University, 300 Hsin-Chu, Taiwan , ROC Abstract Electro che mical mac hin ing (ECM) has bee n increa sin gly rec ogn ize d for the pot ential for mac hin ing, whi le the pre cis ion of themachined profile is a concern of its application. A process to erode a hole of hundreds of micrometers on the metal surface is analyzed in the current pap er. A the ore tica l and comput ationalmodel is pre sen ted to illu stra te how the mac hin ed pro file ev olv es as the time ela pse s. The ana lys is is based on the fundamental law of electrolysis and the integral of a finite-width tool. The paper also discusses the influence of experimental variables including time of electrolysis, voltage, molar concentration of electrolyte and electrode gap upon the amount of material removal and diameter of machined hole. The results of experiment show the material removal increases with increasing electrical voltage, molar concentration of electrolyte, time of electrolysis and reduced initial gap. The time of electrolysis is the most influential factor on the produced diameter of hole. © 2003 Elsevier B.V. All rights reserved. Keywords: Electrochemical machining; Material removal; Time; Gap; Anode profile 1. Introdu ction Elec troch emica l mach ining (ECM) is among the well recognized non-traditional manufacturing processes in in- dustry. An electrical current passes through an electrolyte solution between a cathode tool and an anode workpiece. The workpiece is eroded in accordance with Faraday’s law of electrolysis. Since the first introduction of ECM in 1929 by Gusseff, its industrial applications have been extended to electrochemical drilling, electrochemical deburring, electro- chemical grinding and electrochemical polishing [1]. ECM was found particularly advantageous for high-strength al- loys. For example, the semi-conductor industry frequently requires the machining of components of complex shape and high-s tre ngt h alloys hence ECM is a maj or pro cess candidate for semiconductor devices and thin metallic films [2–4]. ECM processes were also adopted in the aerospace and ele ctronic ind ust rie s for sha pin g and fini shi ng ope rat ion s of a variety of parts of the opening windows that are a few microns in diameter [5]. The accuracy of machining can be improved by the use of pulsed electrical current. Controlling the wave pattern of pulsed current and the time of pulsed on/off is effective [6,7]. Among the often considered elec- ∗ Corresponding author. Tel.: +886-3-5715131x3748; fax: +886-3-5722840. E-mail address: [email protected] (H. Hocheng). trolytes, the current efficiency is nearly 100% for NaCl. The current efficiency depends on the current density in use of NaNO 3 [8]. The desi gn of ele ctr ode in ECM is a maj or concer n. Keylov presented the inverse problem of Cauchy for tool de- sign in Laplace equation and, using complex analysis, was able to solve the problem exactly for a limited number of an- ode geometries based in analytical fashion [9,10]. Another well known approach is the cos θ method for cathode shape design. This approach assumes that the distance between the workpiece and the tool to be inversely proportional to cos θ, where θ is the angle between the tool feed direction and the normal of the workpiece surface. The method is valid only as a first-order approximation for small values of θ, while highl y curved anode shapes cannot be accur ately treated [11]. A few numerical analyses have been applied to the cathode design in ECM. An example is a boundary element method to solve Laplace equation within the inter-electrode gap and tested three different formulations to update the cathode boundary position [12]. The above research focused on the effect of electrical field, while the gap changing with time was not considered. The authors proposed an analytical model of electrochem- ical erosion to predict the machined profile of the workpiece. The prediction describ es the dev elopment of the erosi on profile as a function of time and the changing gap opening. The resul ts can be use d for bot h dimensional control of 0924-0136/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0924-0136(03)00791-X
