The validity of the multi-objective optimization can be further verified by evaluating the performance index 𝐶𝐶 𝑖𝑖 * in Table and Table . The top ranking solutions correlate to the highest 𝐶𝐶 𝑖𝑖 * value (closest to 1) from the experiment verification, confirming the validity of the parameter ranking. To demonstrate the advantage of multi-objective optimal solutions over single-objective-best solutions, 𝐶𝐶 𝑖𝑖 * values were also compared for both scenarios, see Table . It can be seen that compared to single-objective-best solutions, 𝐶𝐶 𝑖𝑖 * for the multiobjective optimal solutions can achieve 13.4% -67.6% performance improvement for CF/PEKK and 29.6% -83.3% improvement for CF/epoxy. Some previous studies dealt with the optimization problem by converting multi-objective problem into a single-objective one. Feito et al. optimized the cutting speed, feed rate and tool geometry in drilling of CF/epoxy by giving different weighting factors to each objective. The optimal cutting speed can vary from 25.56 m/min to 100 m/min with the change of weighting factors. Large variation of optimal drilling parameters were also reported by previous studies with the same approach adopted. The limitation of the above mentioned methodology also lies in that the optimal results are significantly affected by expert knowledge and/or personal preferences. In comparison, the approach we proposed here shows better robustness and reliability. The complex trade-off relationship between multiple objectives can be effectively visualized and the best closeness to the ideal solution (with optimal values of all objectives) can be achieved.