## 3 Results and Discussion
### Optimisation of Target Variables
For this reason, additional specimens were used to analyse the nozzle feed rate limits. A nozzle temperature of 345 \({}^{\circ}\)C was set for these specimens, and the nozzle feed rate was varied. The additional feed rates were 160, 180, 200, 220, 240 and 300 mm/min. Each setting was repeated twice. In addition, to obtain comparability between the specimens, only the specimens from the CCD using a nozzle temperature of 345 \({}^{\circ}\)C were used. The results for the measured roving overlaps, the level of movement of the recoater (red) and a linear trend line (black) for the measured measuring points are shown in Figure 13(a). Figure 13(b) also indicates the rovings' orientation in the selected specimens' component. The level of movement of the recoater in Figure 13(a) was 100 \(\upmu\)m and corresponded to the set layer thickness during printing. Figure 13(a) also shows the variation of the  
Figure 14: Influence of nozzle feed rate on roving overlap (**a**) and uncontrolled roving orientation within the specimen (**b**). The red line in (**a**) indicates the layer thickness during printing. Figure 13: Comparison of the response surface plots with (CCD) and without (FE model) roving influence on HAZ depth (**a**). Comparison of the experimental results for the HAZ at the central point with and without roving integration (**b**). measured values. However, an increasing nozzle feed rate leads to the roving sinking less into the HAZ, resulting in an increased risk of the recoater hitting the roving or possibly entangling it. Although there were fewer measured values for the specimens with feed rates above 140 mm/min, three values (i.e., 25% of these specimens) exceed the 100 um limit. Looking at Figure 14b, it is noticeable that the shape and orientation of the rovings varied significantly among the specimens. While in some specimens, the fibre was flat and wide, in others, it was high and narrow. Orientation is, therefore, a strong scattering factor that significantly influences successful fibre integration. In particular, the random orientation of the rovings significantly influences the roving overlap and, thus, the process reliability. For this reason, process limits are defined, which result from the tests and the relationships previously described. On the one hand, it can be noted that as the nozzle feed rate increased and the nozzle temperature decreased, the roving sink less deep into the part. This increases the risk of the recoater getting stuck on and entraining the roving. In addition, it was observed that this also increased the risk of powder adhering to the nozzle, leading to an abortion of the printing process. Powder sticking to the nozzle occurred at 335 \({}^{\circ}\)C at 160 mm/min and 345 \({}^{\circ}\)C at 200 mm/min. In the CCD study, the range between 335 \({}^{\circ}\)C and 355 \({}^{\circ}\)C for the nozzle temperature and between 92 mm/min and 140 mm/min for the nozzle feed rate were examined in more detail. No disturbances occurred during the production of 52 specimens, which is the reason to assume that a process-reliable fibre integration takes place in this range. Possible reasons for the lower coefficients of determination, as well as the uncontrolled roving orientation, are listed below:  
* The entire structure of the fibre integration unit remains in the process chamber of the developed LS machine during the printing time, which also causes it to heat up. Due to the thermal expansion of the fibre integration unit, the manually set values (e.g., nozzle distance) can change compared to the cold state of the system and thus contribute to scatter in the results. In addition, the feed spindles for positioning the fibre integration unit also expand thermally.