## 3 Results and Discussion
The feed rates examined were 0.025 mm/rev, 0.050 mm/rev, 0.075 mm/rev, and 0.1 mm/rev, corresponding to 238.85 mm/min, 477.7 mm/min, 716.55 mm/min, and 955.4 mm/min, respectively. Once the CNC code was generated and specimens milled, the arithmetic mean roughness (Ra) values were measured on every milled surface at every defined feed rate, as is presented in Table 4. The measurements were conducted considering the direction of the deposited filament, as shown in Figure 5. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Conventional Milling**} & \multicolumn{2}{c}{**Climbing Milling**} \\ \hline
**Feed Rate (mm/min)** & **Parallel** & **Perpendicular** & **Parallel** & **Perpendicular** \\ \hline
238.85 & 0.475 μm & 0.495 μm & 0.550 μm & 0.540 μm \\ \hline
477.7 & 0.540 μm & 18.300 μm & 0.967 μm & 0.790 μm \\ \hline
716.55 & 1.460 μm & 1.060 μm & 2.133 μm & 2.467 μm \\ \hline
955.4 & 2.433 μm & 2.689 μm & 2.830 μm & 3.520 μm \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Arithmetic mean roughness (Ra) values of feed rates. Figure 5: ASA 20 wt.% CF specimens before and after milling. This table of values shows an atypical value at a feed rate of 477.7 with conventional machining on the face perpendicular to the beads. This is because the specimen presented a crack on this surface, generating an excessively high roughness value, that should not be considered. An ANOVA was conducted to assess the influence of milling strategy and feed rate on surface roughness. The results revealed \(p\)-values of 0.0128 for milling strategy and 0.000 for feed rate. This indicates that feed rate has a significantly greater impact on surface roughness than milling strategy, with a 95% confidence level. Figure 6 presents two potential regression models that predict average roughness as a function of feed rate, stratified by milling strategy. The blue line represents the fitted regression line, the green lines illustrate data dispersion, and the gray lines indicate the model error. Both regression models were validated by calculating the percentage error, with a maximum acceptable error of 10%. All accepted values were within this limit. Based on these models and the values presented in Table 4, a feed rate of 238.85 mm/min resulted in excessively low roughness levels, falling below the desired range. Conversely, feed rates of 716.55 mm/min and 955.4 mm/min produced arithmetic mean roughness (Ra) values exceeding the established range. A feed rate of 477.7 mm/min yielded Ra values within the required range, excluding the outlier attributed to an internal crack. Notably, both models demonstrated an increasing trend in Ra with an increasing feed rate, consistent with the findings in the reviewed literature [28; 29]. This phenomenon occurs because a lower feed rate results in a greater volume of material removal per unit surface area, leading to a reduced milling footprint. To illustrate the practical application of these findings, a case study involving the design of a composite material mold for a car engine carrier is briefly presented. The carter, a critical engine component, stores lubricating oil. Through extensive research, the carter's model specifications and the mold requirements for manufacturing it with an epoxy resin and 70% carbon fiber fabrics were determined. While detailed product specifications are beyond the scope of this study, the surface roughness requirement was established at 0.762-1.524 um, as specified in Original Equipment Manufacturer (OEM) manuals [34; 35]. Considering these requirements, a mold was designed, printed in two parts, and subsequently assembled. The mold's dimensions were adjusted to account for the differential  
Figure 6: On the (**left**) is the arithmetic mean roughness as a function of milling speed for conventional milling. On the (**right**) is the arithmetic mean roughness as a function of milling speed for climbing milling. contraction coefficients of the composite materials used for the part and the mold.