## 3 Results  
### Heating  
Figures 3 and 4 depict the tensile strengths of the heated samples in the longitudinal (x) and transverse (z) directions as a gradient map. Since for each part and thus each layer time, the heated and unheated substrate temperatures were determined, this gradient map, in contrast to two-dimensional representations, enables the comparison of the obtained values with the tensile strength of unheated specimens at the original unheated substrate temperature and the final heated substrate temperature. Furthermore, it visualizes the trends of different traversing velocities and increasing substrate temperatures on the tensile strength obtained for both heated and unheated specimens. The colored gradient map represents the main results achieved by the heated specimen. The red surface illustrates the tensile test results obtained from unheated parts at the base unheated substrate temperature recorded at the identical layer time. In contrast, the gray surface represents the tensile strengths of unheated specimens directly manufactured at the final heated substrate temperature. According to the hypothesis that the substrate temperature is the most decisive factor in the bond strength formation, the gray surfaces should correlate closely with the heated results. The heated samples exhibit slightly higher longitudinal tensile strengths than the unheated specimens at the target temperature. As expected, this represents a significant increase in tensile strength compared to the results of the base temperature samples. This is even more evident in the transverse tensile strength, where the additional heat almost doubled the tensile strength around the target temperature of 160 \({}^{\circ}\)C compared to the tensile strength at the base temperature of 130 \({}^{\circ}\)C.  
Figure 2: Tensile test setup with a tactile strain gauge and a fractured x-specimen with additional representation of fractured specimens for both the x- and z- direction of testing. The tensile modulus, \(E_{t}\), was calculated by the secant slope [23] between the strain values \(\epsilon_{1}=0.0005=0.05\%\) and \(\epsilon_{2}=0.0025=0.25\%\) and the respective stresses \(\sigma_{1}\) and \(\sigma_{2}\) in megapascal:  
\[E_{t}=\frac{\sigma_{2}-\sigma_{1}}{\epsilon_{2}-\epsilon_{1}} \tag{1}\]  
The results of the tensile modulus, as shown in Figure 5, support the above findings; however, the tensile modulus in the transverse direction yielded slightly lower results than the original test at the target temperature. Nevertheless, the increase over the base temperature is significant. Figure 4: Tensile strength of the heated specimens in the transverse direction with the reference tensile strength for unheated specimens at the same base temperature (red) and the achieved heated temperature (gray). Figure 5: Tensile modulus of the heated specimens in the transverse direction with the reference tensile strength for unheated specimens at the same base temperature (red) and the achieved heated temperature (gray). Figure 3: Tensile strength of the heated specimens in the longitudinal direction with the reference tensile strength for unheated specimens at the same base temperature (red) and the achieved heated temperature (gray). Figure 6 depicts an overview of the standard and nominal results of the tensile strength for the heated samples in both the longitudinal and transverse direction. The plots in the z-direction show slightly higher values for setups manufactured at 0.080 m/s. In previous investigations, the tensile strength in the longitudinal direction varied only minimally even with decreasing temperatures, since the strength is mainly dependent on the strength of the bulk of the strand. The heated results showed the same effect compared to the transverse results, which mainly depend on temperature-driven fusion bonding mechanisms across the interface [7; 10; 15].