## 6 Conclusions  
This study focuses on the experiment of grinding parameters that uses two performance measures, including surface roughness and workpiece MRR. The influences of abrasive size, contact force, belt linear speed as well as feed speed were investigated for achieving 45 steel grinding with high surface quality and high MRR. The two objectives including minimization of the surface roughness and maximization of the MRR are converted to one comprehensive goal by using the weighting objective method. The CCD and RSM were used to facilitate the understanding of the deep influence of grinding  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Result**} & \multirow{2}{*}{\(\mathbf{\lambda_{a}}\)} & \multirow{2}{*}{\(\mathbf{IP},\mathbf{F},\mathbf{V_{\mathrm{S}}},\mathbf{V_{\mathrm{W}}}\)} & \multirow{2}{*}{\(\mathbf{R_{a}}\)} & \multirow{2}{*}{Error of \(\mathbf{R_{a}}\)} & \multirow{2}{*}{\(\mathbf{Z_{w}}\)} & \multirow{2}{*}{Error of \(\mathbf{Z_{w}}\)} & \multirow{2}{*}{\(\mathbf{R_{a}}\)} & \multirow{2}{*}{\(\mathbf{Z_{w}}\)} \\ \cline{5-8}  & & & & & & & & & \(\mathbf{R_{a}}\) \\ \hline \multirow{4}{*}{Reference group} & / & [400\%, 20.00 N, 7.00 m/s, 3.00 mm/s] & 0.390 & \(\pm\)0.050 & 0.018 & \(\pm\)0.001 & / & / \\  & 0.6 & [400\%, 21.38 N, 7.13 m/s, 2.00 mm/s] & 0.382 & \(\pm\)0.050 & 0.020 & \(\pm\)0.001 & \(-\)2.05 & 11.11 \\  & 0.7 & [400\%, 20.53 N, 7.09 m/s, 2.00 mm/s] & 0.372 & \(\pm\)0.050 & 0.020 & \(\pm\)0.001 & \(-\)4.62 & 11.11 \\ Optimized group & 0.8 & [400\%, 20.50 N, 7.02 m/s, 2.00 mm/s] & 0.341 & \(\pm\)0.050 & 0.019 & \(\pm\)0.001 & \(-\)10.51 & 5.55 \\  & 0.9 & [400\%, 20.38 N, 6.97 m/s, 2.00 mm/s] & 0.332 & \(\pm\)0.050 & 0.019 & \(\pm\)0.001 & \(-\)14.87 & 5.55 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Comparison of optimization results by using weighting objectives method and response surface methodology (RSM).  
Figure 10: 2D profiles of the workpiece surfaces from optimized and unoptimized group. Optimized group: (a) \(R_{a}=0.332\pm 0.050\)\(\mu\)m, (b) \(R_{a}=0.382\pm 0.050\)\(\mu\)m; Unoptimized group: (c) \(R_{a}=0.550\pm 0.050\)\(\mu\)m, (d) \(R_{a}=0.750\pm 0.050\)\(\mu\)m, (e) \(R_{a}=0.850\pm 0.050\)\(\mu\)m.  
parameters. The optimum grinding conditions were obtained under different grinding goals. Based on the results and comparisons, it is observed that the approach proposed in this work has enhanced the surface grinding performance and optimized the grinding parameters in the surface grinding process. The knowledge derived from this study would be useful for expanding practical use of grinding parameters optimization technology.  
[PERSON] devised the research plan. [PERSON] and [PERSON] performed the research and wrote the initial manuscript. [PERSON] helped [PERSON] do the research. [PERSON] edited the manuscript and made the final figures. [PERSON] and [PERSON] provided technical help over the course of the research. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Laser Manufacturing and Additive Manufacturing Project of National Key Research and Development Program of China (Grant No. 2018 YFB1108000), National Natural Science Foundation of China (Grant No. U1609209), and Wenzhou Municipal Key Science and Research Program (Grant No. ZG2017003).  
The authors declare no conflict of interest.