Mathematical Model and Optimization of Surface Roughness During Electrical Discharge Machining of Ti-5Al-2.5Sn with Graphite Electrode

摘要

The phenomena occurring between the electrodes in electrical discharge machining (EDM) are still not fully understood. It is impossible to use one existing model for new materials. This paper aims to develop a comprehensive mathematical model for surface roughness (SR) in EDM on Ti-5Al-2.5Sn alloy, which is not presented so far. The process parameters, including the peak current, pulse on time, pulse off time and servo voltage are selected in this study. Optimum values of the chosen parameters related to surface roughness is ascertained by obtained mathematical model using response surface methodology. Experiments based on design of experiment (DOE) for both positive and negative polarity of the graphite electrode are conducted. Some experiment is also conducted to confirm the validity and the correctness of the established mathematical model as well as the optimal combination. The obtained result from verification yields an average error of 4.94% for the polarity is positive while 5.21% for negative polarity. Besides that, scanning electron microscopy (SEM) is performed to investigate the surface topography of the machined workpiece. Therefore, the positive polarity having the superior surface finishes.