## 3 Results and Discussion
The results presented in Table 2 indicate a reduction in porosity with increasing flow rate, from 0.172% to 0.184% at 245 C. At 260 C, the benefit of carbon fiber reinforcement, specifically its enhanced heat dissipation, minimizes inclusions resulting from material degradation and gas emissions [33]. Figure 1: Marked positions for warping measurement procedure of ASA 20 wt.% CF specimens. To quantify porosity and assess the influence of various parameters on pore formation, an ANOVA was performed. This analysis examined the effects of perimeter distance, flow rate, and temperature. The results indicated that flow rate, or the extrusion multiplier, was the most significant factor determining internal pore content, yielding a \(p\)-value of 0.000. This is consistent with the expectation that increasing the flow rate results in higher internal material density, effectively filling the internal pores formed during inter- and intralayer material deposition. Similarly, an analysis was conducted to quantify the crack length and porosity observed during milling in the direction aligned with the deposited beads, using ImageJ(tm) v1.38. Table 3 presents the measured defect area values at different layers and perimeter distances. These results were subsequently used in an ANOVA to determine the influence of perimeter distance, material flow rate, distance to the perimeter, and temperature on crack formation. The analysis revealed that all parameters, except the milling distance to the borders, significantly affected crack formation, with temperature exhibiting the strongest influence (\(p\)-value = 0.0037). Figure 3 illustrates the types of defects quantified in Tables 2 and 3. Figure 3a depicts the defects observed during milling perpendicular to the deposition direction, representing an inherent characteristic of this process. Figure 3b shows cracks resulting from interlayer cohesion failures. \begin{table}
\begin{tabular}{c c c c c} \hline
**Temp/Multiplier** & **245 °C/0.172\%** & **245 °C/0.184\%** & **260 °C/0.172\%** & **260 °C/0.184\%** \\ \hline Porosity (\%) & 0.86\% & 0.92\% & 0.86\% & 0.92\% \\ \hline Pore areas at layer 4 (mm\({}^{2}\)) & 0.0148 & 0.0047 & 0.0102 & 0.0023 \\ \hline Pore areas at layer 8 (mm\({}^{2}\)) & 0.0163 & 0.0053 & 0.0119 & 0.0031 \\ \hline Pore areas at layer 12 (mm\({}^{2}\)) & 0.0112 & 0.0066 & 0.0092 & 0.0046 \\ \hline \end{tabular}
\end{table} 
Table 2: Porosity values in mm\({}^{2}\) of ASA 20 wt.% CF specimens. Figure 2: Staircase milled specimen shape. To validate the developed models, the percentage error between experimental values and model-predicted values was calculated. A maximum acceptable error threshold of 10% was established. Applying this criterion, specimens printed at 245 \({}^{\circ}\)C with an extrusion multiplier of 0.175% were excluded from further analysis. Based on the remaining results, the optimal printing parameters were determined to be an extrusion temperature of 260 \({}^{\circ}\)C and an extrusion multiplier of 0.172%. While this combination resulted in slightly higher internal porosity compared to the 0.184% multiplier, it yielded greater material stability and printing regularity, with reduced warping and cracking and improved dimensional stability. Additionally, milling at a distance of 4 mm from the perimeter effectively reduced crack formation across all configurations. Utilizing these optimized printing parameters, a subsequent experiment was conducted to determine the optimal milling conditions. The specimens for the second experiment (Figure 5) were printed and milled according to the parameters outlined in the Materials and Methods Section. The objective was to identify the milling conditions that yield the lowest arithmetic mean roughness values on the milled surfaces. Consequently, the variables studied in this stage were feed rate and milling strategy (conventional milling/up milling or climbing milling/down milling). Consistent with the literature findings [25; 26; 27; 28], feed rate was considered the most influential parameter in polymer milling.