## 4 Results  
From September 2021 to January 2022, three Delphi structured questionnaire interviews were performed. The statistical results of the third Delphi questionnaire revealed that (1) the high fitness selection criteria was employed with the mean of \(\geq\)4.2, (2) the consistency selection standard deviation was \(\leq\)0.5, (3) the consensus of the K-S test has reached consistency, and (4) the subitems of progressive significance have reached the significance level of **_p_ < 0.01. The subitems would be kept only when the above four requirements were met. Based on the final statistical analysis result of the third Delphi research questionnaire, the subitems of ten key control factors in production quality were obtained, as shown in Table 7.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Item** & **Mo** & **M** & **SD** &
\begin{tabular}{c} **K-S** \\ **Z-Test** \\ \end{tabular} & **Choice** \\ \hline
**2. Key Factors of the Extrusion Line Design** & & & & & \\ \hline
2–3 & Extruder main screw geometric design & 4 & 4.23 & 0.421 & 2.774 ** & Keep \\ \hline
2–4 &
\begin{tabular}{c} The relationship between the metering pump \\ and main screw output \\ \end{tabular} & 4 & 4.23 & 0.576 & 1.525 * & Delete \\ \hline
2–9 &
\begin{tabular}{c} The maximum output of the screw and the \\ cooling design of the cooling rolls \\ \end{tabular} & 4 & 4.08 & 0.474 & 1.525 * & Delete \\ \hline
3. Key Factors of Polypropylene Forming and Mold Manufacturing & & & & \\ \hline
3-4 & Core/cavity and product modeling design & 4 & 4.23 & 0.576 & 1.525 * & Delete \\ \hline
3-5 & Forming heating controller element stability & 4 & 4.46 & 0.499 & 1.941 ** & Keep \\ \hline
3-6 &
\begin{tabular}{c} The deviation of forming heating constant \\ temperature control area \\ \end{tabular} & 4 & 4.23 & 0.421 & 2.774 ** & Keep \\ \hline
3-7 & Near to scenic sport or night markets & 4 & 4.46 & 0.499 & 1.941 ** & Keep \\ \hline
**4. Key Factors of Mold and Thermoforming Line Equipment Design** & & & & \\ \hline
4-5 &
\begin{tabular}{c} The maximum clamping force of the \\ thermoformer and mold forming area design \\ \end{tabular} & 4 & 4.23 & 0.421 & 2.774 ** & Keep \\ \hline
4-9 & Maximum product depth and trimmer opening & 4 & 4.15 & 0.533 & 1.525 * & Delete \\ \hline \multicolumn{4}{c}{*_p_ < 0.05, **_p_ < 0.01.} & & & \\ \end{tabular}
\end{table}
Table 6: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **Item** & **Mo** & **M** & **SD** &
\begin{tabular}{c} **K-S** \\ **Z-Test** \\ \end{tabular} & **Choice** \\ \hline
**1. Key Factors of Polypropylene Extrusion Sheet Production** & & & & \\ \hline
1–2 & PP extruder main screw output pressure control & 5 & 4.54 & 0.499 & 1.941 ** & Keep \\ \hline
1–3 & PP extruder polymer temperature control & 4 & 4.46 & 0.499 & 1.941 ** & Keep \\ \hline
1–4 & T-die lips adjustment depends on sheet thickness & 4 & 4.38 & 0.487 & 2.219 ** & Keep \\ \hline
1–5 & Cooling rolls pressing stability & 4 & 4.38 & 0.487 & 2.219 ** & Keep \\ \hline
1–7 & Cooling rolls temperature stability & 4 & 4.31 & 0.462 & 2.496 ** & Keep \\ \hline
**2. Key Factors of the Extrusion Line Design** & & & & & \\ \hline
2–3 & Extruder main screw geometric design & 4 & 4.23 & 0.421 & 2.774 ** & Keep \\ \hline \hline \end{tabular}
\end{table}
Table 7: Statistical analysis of the final Delphi technique.