# Surface Quality of Staggered PCD End Mill in Milling of Carbon Fiber Reinforced Plastics
## 3 Machined Surface Roughness
### Influence of Milling Parameters on Surface Roughness  
According to the range analysis of surface roughness and the experimental results, the influence of the cutting parameters on the surface roughness is shown in Figure 3.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**No.**} & **Cutting Speed \(\mathbf{v}\)** & **Milling Width \(a_{\mathrm{e}}\)** & **Feed Per Tooth \(f_{\mathrm{z}}\)** & **Surface Roughness** \\  & **(m/min)** & **(mm)** & **(mm/tooth)** & **\(R_{\mathrm{a}}\) (\(\mu\)m)** \\ \hline
1 & 50 & 0.5 & 0.01 & 2.97 \\
2 & 50 & 1 & 0.02 & 3.77 \\
3 & 50 & 1.5 & 0.03 & 4.21 \\
4 & 50 & 2 & 0.04 & 4.83 \\
5 & 100 & 0.5 & 0.02 & 3.26 \\
6 & 100 & 1 & 0.01 & 3.12 \\
7 & 100 & 1.5 & 0.04 & 4.21 \\
8 & 100 & 2 & 0.03 & 3.60 \\
9 & 150 & 0.5 & 0.03 & 3.00 \\
10 & 150 & 1 & 0.04 & 3.73 \\
11 & 150 & 1.5 & 0.01 & 2.27 \\
12 & 150 & 2 & 0.02 & 3.20 \\
13 & 200 & 0.5 & 0.04 & 3.01 \\
14 & 200 & 1 & 0.03 & 2.93 \\
15 & 200 & 1.5 & 0.02 & 2.90 \\
16 & 200 & 2 & 0.01 & 2.67 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Orthogonal experimental results of surface roughness.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**No.**} & **A—Cutting Speed \(\mathbf{v}\)** & **B—Milling Width \(a_{\mathrm{e}}\)** & **C—Feed Per Tooth \(f_{\mathrm{z}}\)** \\  & **(m/min)** & **(mm)** & **(mm/tooth)** \\ \hline
1 & 3.942 & 3.058 & 2.755 \\
2 & 3.547 & 3.388 & 3.282 \\
3 & 3.050 & 3.395 & 3.435 \\
4 & 2.877 & 3.573 & 3.943 \\ R(Max. – Min.) & 1.065 & 0.515 & 1.188 \\ \hline Rank of primary-secondary & & C, A, B & \\ \hline \hline \end{tabular}
\end{table}
Table 5: Range table of surface roughness.  
As shown in Figure 3a, the surface roughness decreases with increasing milling speed. Because the high temperature resistance of carbon fiber is higher than that of resin material, and because the temperature will rise during high speed milling, the resin material is heated and softened. The resin coating on the machined surface increases due to the heating effect of the tool. In addition, during high speed milling, the cutting time of carbon fiber is shortened, and the fiber deformation is reduced, so the surface roughness is low.  
In Figure 3b, the surface roughness increases a little with increasing milling width. In Figure 3c, with the increase in feed per tooth, the surface roughness increases. When the feed per tooth increases, the amount of fiber cut by the mill in each tooth increases, resulting in more machining defects. Meanwhile, with an increase in the feed per tooth, the springback effect of carbon fiber is enhanced, the resin coating is reduced, and the fracture of carbon fiber is increased, which result in an increase in the surface roughness.  
When 0.02 mm/tooth \(<\)\(f_{\mathrm{z}}\)\(<\) 0.03 mm/tooth and 1 mm \(<\)\(a_{\mathrm{e}}\)\(<\) 1.5 mm, the surface roughness changes slightly. In this range of \(f_{\mathrm{z}}\) and \(a_{\mathrm{e}}\), cutting speed \(v\) has the greatest influence on the surface roughness, and influences of \(f_{\mathrm{z}}\) and \(a_{\mathrm{e}}\) are relatively small. When the variations of \(f_{\mathrm{z}}\) and \(a_{\mathrm{e}}\) are small and \(f_{\mathrm{z}}\) is small, the surface roughness changes slightly. However, when cutting speed \(v_{\mathrm{c}}\) changes, the cutting temperature will change, resulting in complex surface topography.