## 4 Conclusions  
For polyamide and polypropylene mesh weaving developed using the UPWM, the control factors (amplitude, weld pressure, hold time, and speed) of the UPWM were optimized via the Taguchi method. The influence levels of the factors of the two materials were somewhat different; this may be because of the difference in the structure of the fibers. The following are the findings of this study:  
* The knots made from PA filament after welding via the UPWM have stable strength at 75% compared to the original PA filament, with the following parameters after optimization: an amplitude of 32 \(\upmu\)m (34%), a welding pressure of 2.5 kg/cm\({}^{2}\) (41%), a hold time of 0.35 s (24%), and a speed of 5.5 mm/s (1%).
* The knots made of PP filament had relatively stable strength with the following parameters after optimization: an amplitude of 36 \(\upmu\)m (25%), a welding pressure of 2.0 kg/cm\({}^{2}\) (22%), a hold time of 0.25s (16%), and a speed of 6.0 mm/s (37%).
* In addition, the difference in the strength of the knots after optimization was significantly improved. However, the thickness of the knots after UW application was relatively small compared to that of the original rope, leading to the low strength of the knots. During the experiment, changing the speed increased the thickness, but reduced the adhesion of the weld. Therefore, it was necessary to reinforce typical materials such as thin films at the location of the knots.
* This research has important implications for the application of UPWM in the manufacture of trawl nets or similar polymer materials. It allows for the selection of welding parameters that are simpler, more cost-effective, systematic, and fast.  
Writing--original draft preparation, N.-D.N.; writing--review and editing, N.-D.N. and S.-C.H. All authors have read and agreed to the published version of the manuscript.  
The authors recognize and thank the National Science and Technology Council of the Republic of China for its partial financial support of this work under Contract Number NSTC 112-2221-E-992-040.  
Not applicable.  
Data Availability Statement: Data are contained within the article.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{**Specification**} & \multicolumn{4}{c}{**Factors**} & \multicolumn{4}{c}{**Tensile Strength (Mpa)**} \\ \cline{2-11}  & & **A** & **P** & **T** & **S** & **1** & **2** & **3** & **4** & **5** & **Mean** \\ \hline \multirow{4}{*}{PA} & Optimized & 80 & 2.5 & 0.35 & 5.5 & 80.7 & 88.6 & 82.4 & 90.1 & 85.8 & 85.5 \\ \cline{2-11}  & None optimized 1 & 85 & 3.0 & 0.3 & 5.0 & 41.6 & 36.5 & 44.2 & 90.8 & 30.9 & 48.8 \\ \cline{2-11}  & None optimized 2 & 80 & 2.0 & 0.3 & 5.0 & 44.4 & 30.12 & 36.8 & 41.0 & 43.2 & 39.1 \\ \cline{2-11}  & None optimized 3 & 80 & 3.0 & 0.3 & 6.0 & 76.3 & 45.0 & 66.9 & 54.9 & 60.1 & 60.6 \\ \hline \multirow{4}{*}{PP} & Optimized & 90 & 2.0 & 0.25 & 6.0 & 89.4 & 84.4 & 95.6 & 86.6 & 90.7 & 89.3 \\ \cline{2-11}  & None optimized 1 & 95 & 3.0 & 0.3 & 5.0 & 107.1 & 65.5 & 66.9 & 70.6 & 60.4 & 74.1 \\ \cline{2-11}  & None optimized 2 & 80 & 2.0 & 0.3 & 5.0 & 84.9 & 69.9 & 60.7 & 65.8 & 55.2 & 67.3 \\ \cline{2-11}  & None optimized 3 & 80 & 3.0 & 0.35 & 5.0 & 78.9 & 83.5 & 57.3 & 60.2 & 65.8 & 69.1 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The specification used to confirm the research experiment.