## 3 Optimization and Analysis
### Verify Printing Effect
#### 3.2.2 Print Reliability Test  
In addition to the print fit, printing reliability is also necessary after corner optimization. A typical print specimen was designed, as shown in Figure 10a, with a thickness of 10 mm and a large volume to ensure that the fiber laid length was large enough. The g-code generated by corner slicing software before and after corner optimization was used for the printing test, and the number of faults, such as blocked nozzles occurring in the printing process, was counted and analyzed. The fiber laying design of the sample is shown in Figure 10b, where the red line indicates the fiber track. In combination with the shape of the specimen, the single-layer fiber laying amount per turn was about 530 mm, and 40 corner layings were completed. Each specimen used one layer of pure PLA substrate at every interval to lay one layer of fiber-reinforcing layer. There were 50 layers in total, of which 24 were fiber-reinforced layers, and the sample size was large enough.  
Figure 10: Reliability assessment of typical printing specimens. (**a**) Schematic diagram of typical specimens. (**b**) Fiber laying Trajectory.  
Figure 9: Fit evaluation of typical printing specimens. The fitting degree is used to evaluate the effect on printing specimens.  
Three groups of controlled experiments were designed. Each layer was offset and printed 3, 6, and 10 times, respectively, and cleaned up after failure, with printing continued from the fault until all the g-codes of the sample were printed. The failures that occurred during printing are shown in Figure 11a. A comparison of laying effects between the two algorithms when the number of fiber-laying turns was 10 is shown in Figure 11b. The optimized laying was more accurate, and the fiber laying before optimization partially overlapped with the external wall.  
In this paper, the printing reliability of CFRF is reflected in the number of printing failures. Table 4 shows the statistical data for printing failures. It can be seen that when the number of laying turns of CFRF was 3 in the same layer, there was no blockage of the nozzle before or after the operation of the corner optimization algorithm. As the number of laying turns increased, the g-code before optimization began to fail in the printing process, leading to printing failure. When the number of printing turns was 6 for each fiber layer, two failures occurred in the printing process of CFRF. The total length of CFRF for the 24 layers was 127,200 mm, and there were 960 printing corners when the number of laying turns was 10, with 8 occurrences of nozzle blockage failure. It can be seen that printing length of CFRF is an important parameter affecting the probability of printing failure. With the increase in fiber printing length, the probability of blockage per unit distance increases continuously. However, the g-code generated by the corner optimization algorithm had no nozzle blockage problem under different printing turns of CFRF. So, the printing reliability was greatly improved.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Number**} & **Laying Turns of** & **Laying Length of** & **Total Length of** & **Number of** & **Number of** \\  & **CFRF for Each** & **CFRF for Each** & **CFRF (mm)** & **Failures after** & **Failures before** \\  & **Layer** & **Layer (mm)** & **Optimization** & **Optimization** \\ \hline
1 & 3 & 1590 & 38,160 & 0 & 0 \\
2 & 6 & 3180 & 76,320 & 0 & 2 \\
3 & 10 & 5300 & 127,200 & 0 & 8 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Printing failure statistics for CFRF.  
Figure 11: (**a**) Printing failure. (**b**) Corner optimization algorithm before and after the printing effect.