Analyzing the geometrical errors of silicon nitride-titanium nitride on performing electric discharge machining using response surface methodology

Abstract

Ceramic materials that find their applications in die extrusion and the balls used in bearings have a longer service life compared to that of traditional materials. Since ceramic materials are having high hardness properties, they cannot be machined traditionally, because traditional machining processes rely on the relative hardness of the tool material to the workpiece material. However, electric discharge machining aids in the machining of ceramic composites with good surface integrity performed by the copper electrodes. As a result, Spark Erosion Machining was used to investigate the geometrical tolerance of Si₃N₄-TiN composites. Electric discharge machining parameters range over five levels, like current from 2 to 6 A, voltage from 30 to 50 V, dielectric pressure (kg/cm²) from 16 to 24 kg/cm², pulse on time (µs) from 15 to 19 μs, and pulse off time (µs) from 7 to 11 μs have been analyzed through an L₂₅ orthogonal array. Main effect plots and two-dimensional and three-dimensional interaction plots have been drawn to investigate the effect of the input parameter on the output parameters like circularity, cylindricity, perpendicularity, runout, top radial overcut, and bottom radial overcut. The grey relational analysis is employed in finding the significant parameters through analysis of variance, and for each model, the regression coefficient is found. The optimal input parameters for the desired output parameters are found to be a current of 5.855 A; pulse-on time of 16.55 µs; pulse-off time of 7.22 µs; dielectric pressure of 16.32 kg/cm²; and a voltage of 40.3729 V. This research will help to enhance the geometric accuracy and precision of machined holes in Si₃N₄-TiN composites. The results are finally estimated using a residual data analysis, which shows that spark erosion can be improved.