## 4 Case Study
### The Method Employed in this Study Is Illustrated in Figure 7
#### 4.1.2 Phases 2 and 3: Do and Check
However, it is important to consider the following crucial clarification: prior to these experiments, peel strength measurements (see Section Epoxy Coating Peel Test) were conducted incorrectly, potentially inflating the observed capacities. Therefore, while the current data show reduced capability compared to those earlier measurements (Table 5), they provide a more accurate picture of the process performance. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**(a)**} & \multicolumn{3}{c}{**(b)**} \\ \hline  & **N** & **Mean** & **StDev** &
\begin{tabular}{c} **SE** \\ **Mean** \\ \end{tabular} & **N** & **Mean** & **StDev** & **SE** \\ \hline C9 & 35 & 96.0 & 33.4 & 5.6 & C10 & 35 & 134.4 & 23.6 & 4.0 \\ \hline C11 & 30 & 58.5 & 28.0 & 5.1 & C12 & 30 & 141.3 & 58.4 & 11 \\ \hline \multicolumn{8}{c}{C9 = Data before 1 st experiment} & \multicolumn{8}{c}{C10 = Data before 1 st experiment} \\ \hline \multicolumn{8}{c}{C11 = Data after 1 st experiment} & \multicolumn{8}{c}{C12 = Data after 1 st experiment} \\ \hline \multicolumn{8}{c}{Difference = \(\mu\) (C9)—\(\mu\) (C11)} & Difference = \(\mu\) (C10)—\(\mu\) (C12) \\ \hline \multicolumn{8}{c}{Estimate for difference: 37.54} & Estimate for difference: \(-6.9\) \\ \hline \multicolumn{8}{c}{95\% CI for difference: (22.31, 52.76)} & 95\% CI for difference: (\(-30.0\), 16.2)} \\ \hline \multicolumn{8}{c}{T-Test of difference = 0 (vs \(\
eq\))} & T-Test of difference = 0 (vs \(\
eq\)) \\ \hline T-Value = 4.93 & T-Value = \(-0.61\) \\ \hline \multicolumn{8}{c}{\(p\)-Value = 0.000 DF = 62} & \multicolumn{8}{c}{\(p\)-Value = 0.548 DF = 37} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Mean difference test results for breaking force before and after increasing voltage in the curing station: (a) short-side armature; (b) long-side armature. Testing Different Thicknesses of the Epoxy Coating to Find the Optimal Balance between Insulation and Production Efficiency  
To potentially address the low detachment force observed earlier, a second test increased the epoxy coating thickness. The thickness was raised from its original 0.250 mm to 0.350 mm while maintaining the previously tested curing voltage of 3.1 kV. Table 8 shows the results of a mean difference test for breaking force before and after changing the epoxy layer thickness. The aim is to statistically evaluate whether there was a change after this modification, taking the initial data obtained in the previous adjustment (the voltage change) as reference. The significance level and type of test were the same as those used to evaluate the previous change. As a result of the test and according to the \(p\)-value in Table 8a, it can be concluded that there is statistical evidence to accept the null hypothesis, since the \(p\)-value is not below \(\alpha\). Therefore, there was not a change in the mean breaking force of the short side of the armature after the epoxy coating adjustment. However, a slight increase was observed based on mean values (Table 8a). The \(p\)-value in Table 8b suggests that there was a change in the breaking force of the long side of the armature after adjustment of the epoxy coating. Increasing the epoxy thickness proved promising, resulting in boosted Ppk values on both