SYNTHESIZING ANDEVALUATION OFNEWCOPPER-TUNGSTEN BASED EDM ELECTRODE FOR MACHINING HARDENED MATERIALS

By using Electrical discharge machining (EDM) it is possible to machine any
materials that are difficult to machine by using conventional machining technique as
long as it is electrically conductive. The performance of EDM is highly depending on
the type of electrode being used, the power supply system, and the dielectric system.
Copper-Tungsten electrode is the higher in wear resistance but it is difficult to
manufacture due to variation of melting point and zero miscibility of copper (Cu) with
Tungsten (W). Thus, new modified Copper-Tungsten electrodes were synthesized
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milling was used to synthesize the new electrode material and Taguchimethod is used
to design and analyse the experiment. Material removal rate (MRR) and electrode
wear (EW) are the main parameters used for testing the performance between the
existing Copper-Tungsten (Cu-W) electrode and the new developed electrode.
Machining variables selection show that the gap voltage, peak current and pulse on
time are the most important ones that contribute on material removal rate, electrode
wear and surface roughness (Ra). Results of milling process indicate a clear change in
the thickness of crystalline and d-spacing of the milled powder after five hours
milling time. The performance of Cu-WC-Si electrode shows an improvement in
MRR by an average of 22.5% when milled for 5 tolO hours. The EW of 10 to 20
hours milled Cu-WC-Si improvedby an average of 62% from that achieved by using
Cu-W electrode. The performance of Cu-WC-Ti and Cu-WC-Ti-Si electrode show
clear improvement in the electrode wear but at the expense of MRR. It is reduced by
an average of 86% for Cu-WC-Ti and by 70.1% compared with that achieved by
using Cu-W electrode. Si additive improve TWR of Cu-WC-Si electrode where it
shows the lowestTWR (10%)compared with that achieved by Cu-WC-Ti (466%) and
Cu-WC-Ti-Si (37%). The contribution of milling variables on the performance of the
new developed electrodes shows that milling time is the most important variable.