# Precision Manufacturing of Patterned Beryllium Bronze Leaf Springs via Chemical Etching
## 4 Experimental Results
### Quality Measurements of Leaf Springs  
Using the optimal process parameters obtained through the Taguchi method, the four V-shaped leaf spring Figure 1 shows was fabricated five times using an etching method. As a comparison, the same leaf spring was also fabricated five times using the wire-EDM method [21]. The images of a ring and line from the leaf springs fabricated using these two methods are shown in Figure 9. Their roundness, straightness and offset were measured using a MUMA 200 (2011, 3 DFamily, Inc., Nanjing China), the results of which are provided in Tables 9-11, respectively.  
Figure 8: Leaf springs with a complex pattern.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Etching (\(\mu\)m)** & **Wire-EDM (\(\mu\)m)** & **Difference (\(\mu\)m)** \\ \hline
1 & 27 & 45 & 18 \\
2 & 36 & 76 & 40 \\
3 & 20 & 49 & 29 \\
4 & 16 & 88 & 72 \\
5 & 35 & 76 & 41 \\ mean value & 26.8 & 66.8 & 40.0 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Results of error in straightness.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Etching (\(\mu\)m)** & **Wire-EDM (\(\mu\)m)** & **Difference (\(\mu\)m)** \\ \hline
1 & 7 & 17 & 10 \\
2 & 6 & 15 & 9 \\
3 & 4 & 19 & 15 \\
4 & 4 & 23 & 19 \\
5 & 7 & 20 & 13 \\ mean value & 5.6 & 18.8 & 13.2 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Results of error in roundness.  
Figure 9: A ring of a leaf spring using (**a**) wire-EDM, (**b**) etching and a line of a leaf spring using, (**c**) wire-EDM and (**d**) etching.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Etching (\(\mu\)m)** & **Wire-EDM (\(\mu\)m)** & **Difference (\(\mu\)m)** \\ \hline
1 & 4 & 31 & 27 \\
2 & 43 & 63 & 20 \\
3 & 37 & 40 & 3 \\
4 & 25 & 63 & 38 \\
5 & 21 & 78 & 57 \\ mean value & 26.0 & 55.0 & 29.0 \\ \hline \hline \end{tabular}
\end{table}
Table 9: Results of error in roundness.  
We can see from Figure 9 that the edge of the leaf spring developed using an etching process is much smoother than that using wire-EDM. From the measured data in Tables 9-11, we can conclude that the roundness, straightness and offset of the leaf springs achieved through etching are much better than those achieved using wire-EDM.  
The measurement uncertainty for the leaf springs is mainly composed of five parts. The first one is the measurement repeatability which reflecting the contributions from random errors. The second one is the indication error which reflecting the contributions from resolution, evaluation algorithm and so on. The third one is the attitude error which reflecting the contributions from the different attitudes of the leaf springs. The forth one is the alignment error. The fifth one is the contributions from temperature and humidity which can be ignored when evaluating the form errors. One of the holes, and a rectangle leaf from the manufactured leaf spring, shown in Figure 1 were measured 10 times, using the proposed method, in a standard measurement environment (\(u_{5}=0\)). Table 12 shows the measurement results and standard uncertainties (\(u_{1}\)). From Table 12, we can also