## 4 Case Study
### The Method Employed in this Study Is Illustrated in Figure 7
#### 4.1.2 Phases 2 and 3: Do and Check  
In phases 2 and 3, the focus is on implementing improvements and verifying their effectiveness. Key improvement opportunities to address the identified insulation breakdown between the cable and lamination include the following:  
* Conducting peel strength analysis to assess the adhesive strength of the epoxy coating;
* Validating the epoxy coating addition process;
* Adjusting the voltage at the epoxy coating curing station to optimize curing conditions for better insulation;
* Testing different thicknesses of the epoxy coating to determine the optimal balance between insulation effectiveness and production efficiency;
* Evaluating the impact of rotating the lamination faces 180\({}^{\circ}\) on the compatibility of the armature body with the epoxy coating. Additionally, a Differential Scanning Calorimetry (DSC) test was conducted to analyze the thermal behavior and curing properties of the epoxy coating, aiming to provide further process optimization efforts. The epoxy coating peel test serves as a crucial element of process validation, assessing the additive strength of the epoxy coating to the laminated shell. It simulates the forces exerted by the cable during the winding process, offering insights into the coating's ability to resist detachment under real-world conditions. The test involves applying controlled tensile force to detach the epoxy coating from the laminations. This procedure is conducted using a specialized machine similar to the one depicted in Figure 9.  
The peel test specification stipulates a detachment force of 58.8399 N (6 kgf). However, conducting the test with the armature in a vertical position (Figure 10a) resulted in a significantly higher force of 416.78 N (42.5 kgf). Upon consulting with the company's headquarters in China, it was revealed that this vertical orientation was incorrect. They advised that the armature should be positioned at an angle between 80\({}^{\circ}\) and 90\({}^{\circ}\) during the  
Figure 9: Machine for epoxy coating peel test. test. This ensures the pushing tip contacts the most sensitive area, where the cable exerts the maximum force. Re-running the test with the armature tilted, as recommended, led to a dramatic decrease in detachment force for the same sample--from 416.78 N to 51.9752 N (42.5 kgf, to 5.3 kgf). This result clearly falls below the specified threshold (Figure 10b). The previously employed incorrect testing procedure likely explains why the epoxy coating exhibited increased susceptibility to cracking and chipping. Validation of the Epoxy Coating Addition Process  
To comprehensively validate the production process and ensure consistent output quality, a process parameter matrix was documented, encompassing all critical parameters for each phase (laminating and degreasing, cooling, epoxy addition, and cleaning). Table 3 details the specific parameters, as well as their maximum, minimum, and average values. Figure 11 illustrates the epoxy coating curing process for armatures, highlighting the critical temperature points through each phase. To identify potential areas for process improvements, an initial assessment was conducted. The assessment aimed to determine if the parameters listed in Table 3 exhibited statistical control over critical output characteristics at different process phases. Control charts were generated for individual measurements. Figures 12-15 demonstrate stable and predictable processor behavior for the laminating and degreasing and epoxy curing temperatures. Lines and dots in Figures 12-15 represent the following: central line (\(\overline{X}\)) represents the mean of the process data; each dot represents and individual data point collected from the process. Control limits (UCL--Upper Control Limit and LCL--Lower Control Limit) represent the statistically expected range of variation in the process. The absence of data points outside the control limits, trends or other patterns of statistical instability indicates consistent process performance.