The results at optimum cutting condition were predicted using the estimated signal to noise ratio equation
discussed by Yang and Tang [30]. For surface roughness,
according to Fig. 2(a–d), the optimal cutting parameters
are A3B1 C2D3 where A is cutting speed, B is feed rate, C
is depth of cut, and D is cutting fluid condition. Therefore,
the prediction of the S/N ratio is calculated as 11.9, as
shown in Table 7. The conformation experimental result
at A3B1 C2D3 level shows the S/N value as 13.4 which is
close to the predicted value.
For tool wear, according to Fig. 3(a–d), the optimal cutting parameters are A3B1 C2D3 where A, B, C, and D have
the same meaning as in the paragraph above. Therefore,
the prediction of the S/N ratio is calculated as 31.3, as
shown in Table 8. The conformation experimental result
at A3B1 C2D3 level shows the S/N value as 31.8 which is
also close to the predicted value.