## 4 Results
### Optimal Parameter Settings for the Individual Performance Measurements
#### 4.1.3 Material Cost
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**(b) Regression Model** & **Prediction Model** & **R-sq.** \\ \hline
**Sample** & & \\ \hline ASTM & y = 0.65 \(-\) 0.16L1 \(+\) 0.16L2 \(-\) 0.31 OI \(+\) 0.31O2 \(+\) 0.07P1 \(-\) 0.12P2 \(+\) 0.05P3 \(+\) 0.12L1\(-\) 0.12L1\(-\) 0.12L2\(-\) 0.12L3\(+\) & 81.99\% \\ D638 & 0.12L2\(-\)O2 \(-\) 0.05 OI\(-\)P1 \(+\) 0.13 OI\(-\)P2 \(-\) 0.08 OI\(-\)P3 \(+\) 0.05O2\(-\)P1 \(-\) 0.13O2\(-\)P2 \(+\) 0.08O2\(-\)P3 & 81.99\% \\ \hline ASTM & y = 0.34 \(-\) 0.11L1 \(+\) 0.11L2 & 59.13\% \\ D3039 & y = 0.32 \(-\) 0.09L1 \(+\) 0.09L2 & 53.92\% \\ \hline \hline \end{tabular}  
*: optimal value.  
\end{table} 
Table 9: _Cont._layer thickness level can precisely deposit the filament to build the thin part. Similarly, the change in the build orientation from 0\({}^{\circ}\) to 90\({}^{\circ}\) increases the average amount of the filament consumption from 20.77 cm\({}^{3}\) to 21.12 cm\({}^{3}\) for ASTM D638, from 66.21 cm\({}^{3}\) to 68.48 cm\({}^{3}\) for ASTM D695, and from 41.65 cm\({}^{3}\) to 44.00 cm\({}^{3}\) for ASTM D3039, respectively. The greater impact of build orientation on material cost observed in the ASTM D695 and ASTM D3039 designs (see Figure 10b,c) seems to be caused by a brim generated for each design during the additive manufacturing process. Simplify3D automatically generates wider brim areas of the experiments for these design types to properly fix the fabricated parts than the ASTM D638 at the 90\({}^{\circ}\) build orientation, and thereby the experimental outputs consume a larger amount of the CFR-PEEK filament. This may result in the greater impact of build orientation on the material cost as seen in Figure 10b,c. The predicted material cost obtained from the regression model, only including statistically significant factors for each design, is shown in Table 11. It is noted that there are multiple parameter combinations that minimize the material cost of each design since layer thickness and build orientation only critically impact the material cost of each design. Thus, the 0.2 mm layer thickness and the 0\({}^{\circ}\) build orientation form the optimal parameter settings to minimize the material cost of each design regardless of its printing speed for the fabrication. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c} \hline \hline \multicolumn{13}{c}{**(a) Estimated Material Cost (\(\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{ \mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{\mathbf{  }}}}}}}}}}}}}}\))**} \\ \hline \hline
**Sample** & **L101P1** & **L101P2** & **L101P3** & **L102P1** & **L102P2** & **L102P3** & **L201P1** & **L201P2** & **L201P3** & **L202P1** & **L202P2** & **L202P3** \\ \hline ASTM & & & & & & & & & & & & \\ D638 & 2.47 \({}^{\ast}\) & 2.47 \({}^{\ast}\) & 2.52 & 2.52 & 2.52 & 2.71 & 2.71 & 2.75 & 2.75 & 2.75 \\ ASTM & & & & & & & & & & & & \\ D695 & 8.22 \({}^{\ast}\) & 8.22 \({}^{\ast}\) & 8.50 & 8.50 & 8.50 & 8.30 & 8.30 & 8.30 & 8.58 & 8.58 & 8.58 \\ ASTM & & & & & & & & & & & & \\ D3039 & & 5.05 \({}^{\ast}\) & 5.05 \({}^{\ast}\) & 5.34 & 5.34 & 5.34 & 5.34 & 5.34 & 5.64 & 5.64 & 5.64 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Estimated material cost of each parameter combination and the fitted regression models. Figure 10: Main effect plots of the significant factors for material cost. **(a)** ASTM D638; **(b)** ASTM D695; **(c)** ASTM D3039.