# Design Study for a New Spanner
## 3 Design Experiment  
Based on the above design concept, we use computer-aided engineering (CAE) techniques to analyze spanner operations with different valve wheel sizes. The Taguchi method [2] is a crucial part of engineering design, especially for product development and improvement. To reduce the weight of the finished product, the spanner handle was designed based on four design factors (Figure 5): A: outer diameter, B: bend radius, C: angle, and D: connected fillet.  
Table 1 shows the maximum and minimum boundaries of the new spanner size. The other constants are as follows:  
1. Material: Aluminum Alloy;
2. Allowed Tensile strength: 280 (MPa);
3. Capability stress of bend torque (M): 100 (N-m);  
Before the analysis, the value of the force moment must be defined. Assuming an ordinary person can output 300 N and the force arm is 30 cm, then  
\[\text{M}=r\times F=0.3(\text{m})\times 300\text{ N}=90\text{ (N }-\text{ m}) \tag{1}\]  
We set torque at 100 (N-m).  
1. ANSYS [3] numerical analysis setting: 1. Element type: SOLID187;
2. Node No:45885; and
3. Meshing method: Free mesh (tetrahedron).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Factor** & **Factor Code** & **Level 1** & **Level 2** & **Level 3** \\ \hline Outer diameter & A & 20 mm & 22 mm & 24 mm \\ \hline Bend radius & B & 33 mm & 35 mm & 37 mm \\ \hline Angle & C & 45\({}^{\circ}\) & 50\({}^{\circ}\) & 55\({}^{\circ}\) \\ \hline Connected fillet & D & 0.25 mm & 0.5 mm & 0.75 mm \\ \hline \hline \end{tabular}
\end{table}
Table 1: Design parameters and limitations.  
Figure 5: Size parameters of the new spanner.  
The orthogonal Array (L9) is used to assign the design parameters and interactions to various columns of the orthogonal array. The design parameter combination for each numerical analysis using ANSYS software [3] is shown in Table 2 and Figure 6.  
From the response diagrams of each factor, it can be seen that the best level combination should be A3B2C3D3 and the optimal design size shown in Table 3.  
According to the above analysis result, the maximum von Mises stress is concentrated on the connection between handle and the trapezoid in 138.5 MPa, as shown in Figure 7.  
Figure 8a shows the resulting prototype, while Figure 8b shows a 3D schematic model. The experiment results show the proposed design to improve operator safety.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Factor** & **A** & **B** & **C** & **D** & **Von Mises** & **S/N Ratio** \\
**No.** & **(mm)** & **(mm)** & **(Degree)** & **(mm)** & **Stress (MPa)** & **S/N Ratio** \\ \hline
1 & 20 & 30 & 45 & 0.25 & 430.54 & \(-\)52.6803 \\ \hline
2 & 20 & 35 & 50 & 0.50 & 307.57 & \(-\)49.7589 \\ \hline
3 & 20 & 40 & 55 & 0.75 & 230.68 & \(-\)47.2602 \\ \hline
4 & 22 & 30 & 50 & 0.75 & 199.93 & \(-\)46.0176 \\ \hline
5 & 22 & 35 & 55 & 0.25 & 286.21 & \(-\)49.1337 \\ \hline
6 & 22 & 40 & 45 & 0.50 & 253.23 & \(-\)48.0703 \\ \hline
7 & 24 & 30 & 55 & 0.50 & 194.20 & \(-\)45.7650 \\ \hline
8 & 24 & 35 & 45 & 0.75 & 146.87 & \(-\)43.3387 \\ \hline
9 & 24 & 40 & 50 & 0.25 & 285.98 & \(-\)49.1267 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Design parameters values per L9 orthogonal array.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Factor** & **Factor Code** & **Best Results** \\ \hline Outer diameter & A & 24 mm \\ \hline Bend radius & B & 35 mm \\ \hline Angle & C & 55\({}^{\circ}\) \\ \hline Connected fillet & D & 0.75 mm \\ \hline \hline \end{tabular}
\end{table}
Table 3: Optimal design size combination.  
Figure 6: Factor S/N ratio of the new spanner.