OBRABOTKAMETALLOV Vol. 27 No. 2 2025 technology Ta b l e 8 Optimal setting parameter for S/N data Sl.No Parameter Description 1 WEC Level 4219 for optimal machining. 2 Ig Level 16, as higher current improves material removal and reduces machining time. 3 Vg Level 40, as lower gap voltage enhances spark stability. 4 Ton Level 38, indicating that longer pulse-ON times are favorable. 5 Toff Level 5, where shorter pulse-OFF times maximize machining efficiency. Ta b l e 9 ANOVA for utility function (UMRR, SR, TWR) for SN data Source DoF Seq SS Adj SS Adj MS F-ratio P-values % contribution Ig 2 3.141 3.141 1.5707 3.94 0.051 5.344 Vg 2 49.435 49.435 24.7174 61.96 0.000 84.102 Toff 2 1.816 1.816 0.9082 2.28 0.149 3.089 Residual error 11 4.388 4.388 0.3989 – – 7.465 Total 17 58.780 – – – – 100 S = 0.6316 R-Sq = 92.5% R-Sq(adj) = 88.5% Table 9 presents the pooled ANOVA results for the utility function that combines multiple performance measures (MRR, TWR, SR) derived from S/N data. The analysis evaluates the contribution and significance of process variables on overall performance. Below is a detailed breakdown. Each process variable (Ig, Vg, and Toff) has two degrees of freedom (DoF), corresponding to the levels tested for each parameter. The residual error has eleven degrees of freedom, representing variability unexplained by the factors. The total DoF is 17, which is the sum of all DoF. The sequential sum of squares indicates the contribution of each factor to the total variability in the utility function. Vg (49.435) contributes the largest share of variability, indicating it has the most significant effect on performance. Ig (3.141) has a moderate impact, while Toff (1.816) has the least contribution among the three factors. Adjusted sum of squares reflects the portion of variability accounted for by each factor after adjusting for other factors. The adjusted mean squares is obtained by dividing the adjusted sum of squares (Adj SS) by the degrees of freedom (DoF), representing the mean contribution of each factor to variability. The F-ratio is the ratio of adjusted mean square (Adj MS) to the mean square of residual error and determines the significance of each factor. P-values test the null hypothesis that a factor has no effect. Significant factors include Vg (P = 0.000), which is highly significant (P < 0.05) and strongly influences the utility function. Ig (P = 0.051) is marginally significant, showing some influence on performance. Toff (P = 0.149) is not significant (P > 0.05), indicating minimal impact. Gap voltage (Vg) dominates the utility function with an 84.102 % contribution, confirming its critical role in determining performance. Ig contributes moderately with 5.344 %, and Toff contributes minimally with 3.089 %. Residual error of 7.465% accounts for of unexplained variability. S (0.6316) is the standard deviation of residuals, representing the goodness-of-fit; lower values indicate a better fit. R-Sq (92.5 %) is the proportion of total variability explained by the model, indicating that the
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