## 2 Materials and Methods
### Principle of Continuous Fibre Integration
#### 2.1.2 Target Variables  
The target variables for successfully integrating rovings within the developed LS machine are illustrated in Figure 2.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Symbol** & **Description** & **Unit** & **Setting** & **Setting Range** \\ \hline \(\mathrm{h}_{\mathrm{D}}\) & Distance between fibre nozzle and powder bed & mm & PLC & 0–2 \\  & surface & & & \\ \hline \(\mathrm{v}_{\mathrm{D}}\) & Feed rate of the fibre nozzle & mm/min & PLC & 0–1000 \\ \hline \(\mathrm{v}_{\mathrm{R}}\) & Feed rate of the roving = feed rate of fibre nozzle & mm/min & PLC & 0–1000 \\ \hline \(\mathrm{d}_{\mathrm{D,o}}\mid\mathrm{d}_{\mathrm{D,i}}\) & Outer \(\mathrm{d}_{\mathrm{D,o}}\) and inner diameter \(\mathrm{d}_{\mathrm{D,i}}\) of the fibre nozzle & mm & Lathe & \(\mathrm{d}_{\mathrm{D,o}}\geq 2\) \\ \(\mathrm{d}_{\mathrm{D,i}}\geq 0.6\) & & & & \(\mathrm{d}_{\mathrm{D,i}}\geq 0.6\) \\ \(\mathrm{A}_{\mathrm{HM3}}\) & Area of the heat source (metal sheet) & mm\({}^{2}\) & Laser cutting & \(\approx\)22,500 \\ \hline \(\mathrm{h}_{\mathrm{HM3}}\) & Distance of heat source (metal sheet) to powder & mm & Feeler gauge tape & 0–2 \\  & surface = air gap width & & & \\ \hline \(\kappa\) & Curvature of fibre nozzle & - & Lathe & Planar/concave \\ \hline \(\mathrm{\epsilon}_{\mathrm{D}}\) & Emissivity of fibre nozzle (black oxidised) & - & Varnish & 0–1 \\ \hline \(\mathrm{\epsilon}_{\mathrm{P}}\) & Emissivity of the powder (Sintratec PA12) & - & State of delivery & \(\approx\)0.9 \\ \hline \(\mathrm{\epsilon}_{\mathrm{HM3}}\) & Emissivity of the matt black painted metal sheet & - & Varnish & 0–1 \\ \hline \(\mathrm{T}_{\mathrm{D}}\) & Fibre nozzle temperature & \({}^{\circ}\mathrm{C}\) & PLC & \(\ldots\)400 \\ \hline \(\mathrm{T}_{\mathrm{O}}\) & Powder bed surface temperature & \({}^{\circ}\mathrm{C}\) & PLC & \(\ldots\)200 \\ \hline \(\mathrm{T}_{\mathrm{HM3}}\) & Heat source temperature (metal sheet) & \({}^{\circ}\mathrm{C}\) & PLC & \(\ldots\)200 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Influencing variables due to the integration concept with the setting range.  
For successful roving integration, the HAZ must be created so that the roving is below the level of movement of the recoater at \(\mathrm{h_{S}}\) (=set layer thickness in the printing process). In other words, the depth of the HAZ \(\mathrm{t_{HAZ}}\) must be set so that the roving sinks deep enough into the melt, i.e., with \(\mathrm{h_{R}}\) < \(\mathrm{h_{S}}\), and thus does not create a disturbing contour for the recoater (process reliability). The result of the FE model is, therefore, a value for \(\mathrm{t_{HAZ}}\) corresponding to a roving thickness of 0.4 mm. If the roving extends too far out of the part (\(\mathrm{h_{R}}\geq\mathrm{h_{S}}\)), a collision between the recoater and the roving can occur during the subsequent recoating process. This will cause the part to be dragged by the recoater, and the printing process will have to be stopped. In addition, the width of the HAZ \(\mathrm{b_{HAZ}}\) must be set as narrow as possible to place rovings as close to the edges of the part as possible without melting unsintered and loose powder outside the part edges. In addition, the HAZ's width and depth are expected to influence the achievable FVC in part strongly and, thus, on the attainable mechanical properties. To maximise the FVC in future considerations, the smallest possible values for \(\mathrm{b_{HAZ}}\) and \(\mathrm{t_{HAZ}}\) are targeted. For economical production, the processing time of the roving integration is also highly relevant. The processing time is given by the feed rate \(\mathrm{v_{D}}\) of the fibre nozzle. The target values for successful fibre integration are summarised in Table 2.