## 2 Materials and Methods
### Additive Manufacturing  
Printing was performed using an Attat Saturn printer (Atmant Sp. z o.o., Cracow, Poland), modified for the extrusion of paste materials. The printer has a build volume of 1100 mm in width and 1000 mm in depth, and it can print objects that are up to 750 mm high. Instead of the nozzle used for filament extrusion, a print head was installed, consisting of a material container, a belt-driven mixer, and an extrusion screw powered in the same way (Figure 3a). Figure 2: Complete workflow and order of the practical tests. The print head can be filled with up to 15 kg of material or, alternatively, fed via a hose (Figure 3b). A belt is used to drive an axle, which is responsible for mixing the material in the container and drives the extrusion screw in the lower section. The mixing of the material is therefore always linked to extrusion and vice versa. To guarantee precise positioning of the material, a 3D-printed nozzle was attached after the extruder screw using a clamp. The printer can be controlled via a display, and printing parameters can be adjusted in addition to manual control of coordinates and calibrations. For example, the material flow, printing speed, and temperature can be modified during printing, and the build chamber can heat up to 60 \({}^{\circ}\)C if required. The print head was attached to the holder, as shown in Figure 3a. A detailed image of the individual parts of the print head, including the nozzle, can be found in Appendix A. The main task was the extrusion of blocks, from which the test specimens were cut out. These blocks were designed with a slight oversize to compensate for any shrinkage or geometric deviations (Table 5 and Figure 4). The models were created with the software Fusion360 version 2.0.16009x86_64, and Cura version 5.5 was used to slice the STL data. To test the specimens in the directions described in Figure 4, the printed geometries were cut into 9 cuboids and 9 cubes. Blocks A, C, and D each consisted of 5 layers of 10 mm and were intended to produce the cuboids (oversize of 10 mm instead of the actual height of 40 mm). The cubes were cut out of block B after it had hardened. It consisted of 6 layers of 10 mm each so that the 50 mm high cubes could be safely produced. To optimize printing, the settings in the slicer were adjusted, so that the print head followed a continuous path during generation. Table 6 shows an overview of the most important process parameters. The layer height is the amount by which the print head rises in the z-direction after each layer has been applied. It was set to 10 mm. As the nozzle had a diameter of 20 mm, the Line Width was also 20 mm. To achieve as few extrusion interruptions as possible, the entire body was printed as infill. This meant that breaks between the wall and infill could be avoided, and the machine path simplified by the zig-zag pattern. Since the main purpose of the underwater extrusion experiment was to collect observations on behavior, the same slicer settings and paste composition were used. In a standard stacking box measuring 600 \(\times\) 400 \(\times\) 200 mm, 10 L of tap water at ambient temperature was added. As the print head had to be moved into the box from above, it was positioned in the installation space in such a way that its walls did not touch the print head at any time (Figure 5). \begin{table}
\begin{tabular}{c c c} \hline
**No** & **Parameter** & **Value** \\ \hline
1 & Layer Height & 10 mm \\
2 & Line Width & 20 mm \\
3 & Infill Line Width & 20 mm \\
4 & Wall line Count & 0 \\
5 & Top/Bottom Thickness & 10 mm \\
6 & Top/Bottom Layers & 0 \\
7 & Infill Density & 100\% \\
8 & Infill Pattern & Zig Zag [90,90] \\
9 & Infill Layer Thickness & 10 mm \\
10 & Print Speed & 60 mm/s \\
11 & Build Plate Adhesion & none \\ \hline \end{tabular}
\end{table} 
Table 6: Slicing parameters and their values. Figure 4: Visualized sliced volumes. The prints (apart from the UW3 DP) were generated on 10 mm high tiles, which could easily be removed from the build chamber.