## 3 Experimental
### Experimental Set-Up
#### 3.1.1 Test Specimens, Methods and Design of Experiments
Electrfi Conductive Filament (M3D) [28] (see Table 2). Thus, three different fillers were investigated to determine their process parameter specific influence on resistivity. Both PPC and 3 dk use as filler CB and, therefore, have a significant higher resistance than the CNT (FFE) and copper filled material (M3D). Thus, by utilizing these materials, various design opportunities were possible, e.g., electrical conductors, heat radiation surfaces, or flexible sensor (cf. Table 1). Besides information about feedstock material's resistivity, Table 2 also shows the processing conditions of the individual materials. Table 3 presents the design of experiments for determining material- and process-specific dependencies of resistivity. The variation parameters were selected based on the literature review and the ranges of the individual process parameters in accordance with the processing conditions shown in Table 2. Even though other parameters such as line width or overlap also influence the compaction between layers and thus resistivity, these parameters were not considered in this contribution due to the increased scope of the experimental investigations. The maximal extrusion temperature was chosen as 10 \({}^{\circ}\)C above the recommended temperature. It has to be noted that the materials FFE and M3D are not processable below an extrusion temperature of 220 \({}^{\circ}\)C or 170 \({}^{\circ}\)C caused by a low flowability (see Figure 3). Therefore, the minimal extrusion temperature was set to 220 \({}^{\circ}\)C for FFE and 170 \({}^{\circ}\)C for M3D. Besides the extrusion temperature, high speed may also result in defects and, thus, in a damaged specimen, thus the maximum speed was set to 60 mm/s. It is worth noting that the range of process parameters can be increased by changes in manufacturing conditions, for example, varying build platform temperature or using additional types of adhesives. A full fractional parameter variation was chosen for each material. Thus, 351 batches each with three specimens were manufactured. Consequently, in total, 1053 specimens were additively manufactured in the selected design of experiments. The conditions of manufacturing are described in detail in Section 3.1.2. The design of experiments was limited to the determination of resistivity (cf. specimen shown in Figure 1). The measurement of the heat resistivity was solely conducted with selected process parameter sets that exhibit low electrical resistance. These specimens were defined based on the experimental investigations regarding resistivity. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Name**} & **Filler/Matrix Material** & \multicolumn{2}{c}{**Temperature (\({}^{\circ}\)C)**} & \multicolumn{2}{c}{**Resistivity \({}^{1}\) (\(\Omega\)m)**} \\ \cline{2-6}  & **Build Platform** & **Nozzle** & \
\begin{tabular}{c} **Feedstock Material** \\ \end{tabular} &
\begin{tabular}{c} **Processed** \\ **(x/y and z)** \\ \end{tabular} \\ \hline PPC [25] & CB/PLA & \textless{}50 & 215–230 & 0.15 & 0.3/1.15 \\
3 dk [26] & CB/PLA & 60–70 & 200–230 & 0.24 & 0.23/n/a \\ FFE [27] & CNT/PLA & \textless{}70 & 215–230 & \(75\times 10^{-4}\) & n/a \\ M3D [28] & Copper & Room & 130–160 & \(6\times 10^{-5}\) & n/a \\  & Nanowires/PCL & temperature & & & \\ \hline \hline \end{tabular}  
\({}^{1}\) information according to manufacturer.  
\end{table} 
Table 2: Overview of the composite materials used in the experimental investigations with their recommended processing conditions.