## 3 Results and Discussions
### Results for Ring-Only Configurations--Design Change Evaluation
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Configuration**} & \multirow{3}{*}{**Pre-Tension**} & \multirow{3}{*}{**Displacement**} & \multicolumn{2}{c}{**Von Mises**} & \multirow{3}{*}{**Normal**} & \multirow{3}{*}{**Normal**} & \multirow{3}{*}{**Normal**} \\  & & **[N]** & & **Max [mm]** & & **EF Ring** & **[MPa]** & **[MPa]** & **[MPa]** \\ \hline \multirow{3}{*}{
\begin{tabular}{c} New full ring \\ With wires 2 \\ and 3 \\ \end{tabular} } & EF metallic & 500 & 0.39 & 97.0 & 238 & 243 & 252 \\  & EF metallic & 1000 & 0.78 & 194.0 & 477 & 486 & 504 \\  & EF PLA & 500 & **37.77** & **192.3** & **994** & 713 & **856** \\  & EF PLA & 1000 & **74.41** & **368.6** & **1921** & **1388** & **1703** \\  & EF metallic & 500 & 0.24 & 78.3 & 237 & 244 & 250 \\  & EF metallic & 1000 & 0.48 & 156.5 & 474 & 488 & 501 \\  & EF PLA & 500 & **7.80** & 69.90 & 422 & 393 & 461 \\  & EF PLA & 1000 & **15.59** & **139.8** & **844** & 785 & **922** \\  & EF metallic & 500 & 0.08 & 34.8 & 236 & 244 & 247 \\  & EF metallic & 1000 & 0.16 & 69.7 & 472 & 488 & 494 \\  & EF PLA & 500 & 2.79 & 31.9 & 380 & 322 & 372 \\  & EF PLA & 1000 & **5.59** & **63.7** & 760 & 644 & 744 \\  & EF metallic & 500 & 0.05 & 29.1 & 236 & 244 & 248 \\  & 1000 & 0.10 & 58.2 & 472 & 487 & 496 \\  & EF PLA & 500 & 1.89 & 28.3 & 352 & 310 & 318 \\  & 1000 & **3.78** & **56.7** & 704 & 621 & 635 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Stress results for ring only configurations. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{**Configuration**} & \multirow{3}{*}{**Pre-Tension**} & \multirow{3}{*}{**Displacement**} & \multirow{3}{*}{**FM Stress**} & \multirow{3}{*}{**Normal**} & \multirow{3}{*}{**Normal**} & \multirow{3}{*}{**Normal**} \\  & & **[N]** & & **Max [mm]** & & **EF Ring** \\  & & & **[MPa]** & & **[MPa]** & & **[MPa]** \\ \hline \multirow{3}{*}{
\begin{tabular}{c} New full ring \\ With wires 2 \\ and 3 \\ \end{tabular} } & EF metallic & 500 & 0.04 & 27.6 & & 243 & 249 \\  & EF metallic & 1000 & 0.08 & 55.3 & & 487 & 498 \\  & EF PLA + CF & 500 & 1.17 & 27.1 & & 269 & 279 \\  & EF PLA & 1000 & 2.35 & **54.3** & & 538 & 559 \\  & EF metallic & 500 & 0.06 & 22.9 & 203 & & 249 \\  & EF metallic & 1000 & 0.10 & 37.6 & 203 & & 499 \\  & EF PLA & 500 & 2.05 & 20.9 & 309 & & 298 \\  & EF PLA + CF & 1000 & 3.50 & 34.9 & 306 & & 581 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Stress results for new full ring configuration with only two wires. wire preloads acting along the direction of the lowest transverse net section, leading to high stress concentrations. In the new ring design with only wire 1 and wire 3, the displacements increase significantly, and wire 3 experiences considerably higher stress than wire 1. However, the von Mises stress in the ring is reduced by up to 38% for the PLA + CF configuration at 1000 N wire pre-tension, meeting the strength criteria. Furthermore, it can be observed that wire 1, as is offset from the ring using some connection posts, is producing an out-of-plane load that adds additional bending to the EF ring. As reduced cost is seen as one of the advantages of 3D printing the EF rings, the cost of the new version presented in Figure 154 was estimated at approximately \(\xi\)10-\(\xi\)15 (depending on filament producer), including the PLA-CF filament cost, 3D printer amortization, and energy consumption. In comparison, a conventional steel ring used in external fixators typically costs around \(\xi\)50-\(\xi\)150, due to the added expenses of CNC machining and labor, despite a lower raw material cost. This highlights the economic potential of using AM for producing these rings, especially for decentralized and resource-constrained medical settings. Figure 15: Von Mises stress results of PLA-CF ring-only configurations with 500 N of wire pre-tension: (**a**) baseline PLA-CF ring; (**b**) new PLA-CF ring; (**c**) full PLA-CF ring; and (**d**) new full PLA-CF ring.