## 2 Materials and Methods
### Experimental Factors and Strategies  
The repeatability of AM experiments is a challenge because the experiments are not only affected by the processing parameters, but studies also indicate that there are major differences between machine types and even between machines of the same make [30,31]. Furthermore, the variations may occur between builds in the same machine and even different positions in the same build [21,32]. It is, therefore, of paramount importance to design rigid experiments by utilizing blocking strategies, or at the very least enable some characterization of such variations. The current experiment applies both blocking and randomizing strategies and replicates all specimens of the main study three times to enable the characterization of variation. The main purpose of the experiment is to investigate the effect of part build orientation on dimensional and geometric accuracy. In order to obtain data points of adequate density, part build orientations from 0 to 180 degrees are investigated at five-degree intervals around a single axis. To minimize unwanted variations (noise) in the experiment, all variables are kept constant or handled with blocking and randomization strategies, as displayed in Table 1.  
In addition to the experimental variable (part build orientation), four variables from Table 1 stand out: (i) placement in build, (ii) build ID, (iii) feature type, and (iv) feature size. It is necessary to produce several specimens simultaneously to complete the experiment within a reasonable time and keep the cost at an acceptable level. A blocking strategy is implemented with regards to the part location in the build to enable linear comparison along the axes of the machine by defining fixed positions in the build space where specimens may be fabricated. The details of the build layout are presented in Section 2.3. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Variable** & **Strategy/Type** & **Levels** & **Values** \\ \hline Part build orientation (\(\varphi\)) & Experimental & 37 & \(\varphi\,\in\{0,\,5,\ldots,180\}\) \\ \hline Placement in build (P) & Blocking/randomization & 45 & \(\text{P}(i,j,k)\) where \(i\in\{1,\,2,\,3\}\), \(j\in\{1,\,2,\,3\}\), _and_ \(k\in\{1,2,\ldots,5\}\) \\ \hline Build ID (B) & Blocking/randomization & 3 & \(\text{B}\in\{1,\,2,\,3\}\) \\ \hline Feature type (F) & Experimental & 4 & \(\text{F}\in\{\text{plane, cylinder, cone, sphere}\}\) \\ \hline Feature size (S) & Experimental & 1–4 &
\begin{tabular}{c} \(S_{cylinder}\,\in\{4,\,8,\,16,\,24\}\) \\ \(S_{cone}\in\{12,\,24\}\) \\ \(S_{sphere}\in\{24\}\) \\ \end{tabular} \\ \hline Laser power & Constant & 1 & \(\ast\) \\ \hline Scan speed & Constant & 1 & \(\ast\) \\ \hline Raster pattern & Constant & 1 & \(\ast\) \\ \hline Layer thickness & Constant & 1 & 120 \(\mu\)m \(\ast\) \\ \hline Build chamber temperature & Constant & 1 & 180 \({}^{\circ}\)C \\ \hline Room temperature & Regulated & 1 & 20–21 \({}^{\circ}\)C \({}^{\dagger}\) \\ \hline Humidity & Regulated & 1 & 40–50\({}^{\circ}\)\({}^{\ddagger}\) \\ \hline Material & Constant & 1 & PA2200 (PA12) \\ \hline Postprocessing & Constant & 1 & Air blasting \\ \hline STL file resolution & Constant & 1 & Tolerances 0.01 mm and 2\({}^{\circ}\) \\ \hline \hline \end{tabular}  
* given by EOS parameter profile “Balanced”; \({}^{\dagger}\) approximate range with natural variation. Supplementary data are available in the online repository at GitHub: [[https://github.com/TheThorb/Leirmo](https://github.com/TheThorb/Leirmo)]([https://github.com/TheThorb/Leirmo](https://github.com/TheThorb/Leirmo))\_Exp1_Publication1, accessed on 29 January 2021.  
\end{table} 
Table 1: Experiment variables with their designated type/strategy and number of levels. Because the build space is too small to fit three replications of all 37 levels of the experimental variable \"part build orientation\" in a single build, the experiment must be completed through three separate builds.