Abstrak

Kembali

Electrical Discharge Machining (EDM) is a well-established noncontact machining technique for manufacturing geometrically complex shapes on hard but electrically conductive materials that are extremely difficult-tocut by conventional processes. EDM has low material removal rate and Powder-Mixed Electrical Discharge Machining (PMEDM) is one of the latest techniques that has emerged to improve material removal rate and electrode wear ratio among other performance characteristics. However, its utilization in the manufacturing industry is very low because many fundamental issues of this new development are not well understood. In this study, the performance of the PMEDM process was evaluated in terms of Material Removal Rate (MRR) and Electrode Wear Ratio (EWR) with respect to peak current and pulse-on time. Experiments were carried out at a duty cycle of 0.5, peak current of 21A and pulse frequency of 10 KHz. Peak current and pulse-on time were varied from 3-21A and 45 – 135μs, respectively for pure (distilled water) and distilled water suspended with diatomite (powder-mixed dielectric fluid) at a concentration of 2 g/l. Graphite tool electrode was used to machine mild steel workpiece submerged in dielectric fluid. Each of the experimental set was conducted for 10 minutes and analysis of variances on MRR and EWR were performed using Statistical Analysis of System (SAS) software at 5% level of significance. Completely randomized design was used to plan and analyze the experiments which were performed on Toolcraft A25 sinker electrical discharge machine with retrofitted dielectric fluid circulation system. This study has found that variations of peak current and pulse-on time in diatomite powder-mixed dielectric fluid have significant influence on material removal rate and electrode wear ratio. Material removal rate increases to a maximum value in pulse-on time and then decreases with further increase in pulse-on time, while it increases with increase in peak current in both pure and diatomite powder-mixed dielectric fluids. Electrode wear ratio decreases to a minimum value with increase in peak current in pure dielectric, but remains fairly constant with further increase in peak current, while increase of peak current in diatomite powder-mixed dielectric has minimal effect on EWR throughout the range. Electrode wear ratio also decreases to minimum and then increases with further increase in pulse-on time. Future research based on these findings has been outlined.