# Towards Self-Reinforced PLA Composites for Fused Filament Fabrication
## 4 Results and Discussion
### FFF 3D Printing  
One key issue during printing was layer adhesion and delamination. Often, the first or second layer detaches from the build plate while printing the layers above. The \(z\) offset of the printer needs to be calibrated accurately. For the Prusa printer, this offset is calibrated manually, following the instructions provided on their website. It should be noted that the offset for the tailor-made filament is different from the offset utilised for PLA from a commercial supplier. Apart from that, the following slicer settings were also found to improve the layer adhesion:  
1. The line width is increased to enlarge the surface area between different layers and so prevent delamination or peeling off. However, especially for the \(0^{\circ}\) orientation, the line width has to be chosen so that the sum of the lines converges precisely to the specified 8 mm specimen width;
2. The cooling is disabled on the first two layers to ensure an increased adhesion to the build plate. This choice prevents the layers from shrinking too fast and allows for a higher surface area with the build plate;
3. In order to give the filament more time to attach to the build plate and the surface below, the print speed was also reduced for the first two layers. The _equalize filament flow_ feature was used on the \(90^{\circ}\) and \(-45^{\circ}/45^{\circ}\) oriented specimens, considering the frequent change in print directions for these specimens. Tables 8-11 provides information on the optimised slicer settings used to 3D-print the specimens. We stress the importance of fine-tuning the process parameters [65]. Apart from the slicer settings, the placement of the specimens on the build plate is crucial. Not only does printing multiple specimens at once save time, but it is also more efficient and helps to prevent defects on the specimens. Figure 13: Three dimensional (3D) printed device to keep the filament coming from water bath on to the conveyor belt. **(a)** front-view of the 3D printed structure to keep the filament from slipping off of the conveyor belt, **(b)** top-view of the 3D printed structure. Figure 14 shows a frequent issue that was encountered during 3D printing. After finishing one layer, the print head would travel over the previously printed layer diagonally, leaving excess material in its path and potentially damaging the layer. For preventing such a failure, different measures were taken. In the case of the 90\({}^{\circ}\) and 0\({}^{\circ}\) specimens, it was sufficient to print two specimens next to each other, so that the longer sides align, as seen in Figure 15.  
However, the error correction on the \(-45^{\circ}/45^{\circ}\) specimens requires a different method. For these specimens, auxiliary STL-files were created. These auxiliary models are cuboids which have the same height as the specimen and a 4 mm \(\times\) 4 mm base area. They have to be placed with an \(x\) and \(y\) offset with respect to the actual specimen to prevent corrupted travel paths, as described in Figure 14. The optimised placement of the specimen with the auxiliary.stl files can be seen in Figure 16. \begin{table}
\begin{tabular}{l l} \hline Setting & Value \\ \hline Line width & 0.28 mm \\ Infill line distance & 0.28 mm \\ Infill line directions & [0] \\ Print speed & 60 mm s\({}^{-1}\) \\ Initial layer print speed & 20 mm s\({}^{-1}\) \\ Equalize Filament Flow & enabled \\ \hline \end{tabular}
\end{table} 
Table 10: Slicer settings 90\({}^{\circ}\) orientation. \begin{table}
\begin{tabular}{l l} \hline \hline
**Setting** & **Value** \\ \hline Layer height & 0.09 mm \\ Wall count & 0 \\ Top/bottom count & 0 \\ Infill density & 100 \% \\ Printing temperature Mat. A & 200 \({}^{\circ}\)C \\ Printing temperature Mat. B & 180 \({}^{\circ}\)C \\ Build plate temperature & 60 \({}^{\circ}\)C \\ Flow & 100 \% \\ Number of slower layers & 2 \\ Fan speed & 100 \% \\ Initial fan speed & 0 \% \\ Regular fan speed at layer & 3 \\ \hline \end{tabular}
\end{table} 
Table 8: Shared slicer settings.