## 4 Case Study
### The Method Employed in this Study Is Illustrated in Figure 7
#### 4.1.1 Phase 1: Plan  
In this phase, the problem definition was defined using the 5W + 2H approach. Table 1 presents the obtained information. Figure 7: Research method. Based on the information in Table 1, the problem of continuity between the winding and metal likely stems from a multifactorial issue. All factors ultimately converge on the presence of an undesirable direct connection, typically due to insulation failure. This failure can be attributed to various factors, notably the inadvertent insertion of the wire into the epoxy coating during the winding process, leading to contact with the laminate. The lamination itself features a sharp edge that damages the cable, further facilitating this contact. For visual reference, please see the magnified image of defective and non-defective parts in Figure 8.  
Table 2 outlines the application of the three-legged five-why analysis method, which facilitated a comprehensive investigation into the root causes of the error. This approach enabled the study to explore three distinct perspectives--specifics, detection, and systemic issues--in order to gain a thorough understanding of the underlying cause surrounding the error. \begin{table}
\begin{tabular}{l} \hline \hline \multicolumn{1}{c}{**PDCA Quick Response**} \\ \hline Problem description by customer/location of the problem: During hipot testing, armatures fail  due to cable contact with laminations when windings are introduced. This creates continuity  between the cable and metal part. \\ What is the problem? \(>\) Use 5W + 2H to determine the current situation (C/S). \\ Customer view \\ \hline \(\bullet\) & What happened? The hipot test armature fails due to cable contact with the lamination  during winding, likely caused by sharp lamination edges and damaging the cable. \\ \(\bullet\) & Why is it a problem? \\ \(\bullet\) & Customer impact: engine inoperative; \\ \(\bullet\) & Logistic impact: missed customer demand; \\ \(\bullet\) & Impact on part assembly: poor performance; \\ \(\bullet\) & Technical impact: armature non-compliance with hipot values; \\ \(\bullet\) & Reliability impact: armatures fail to meet standards; \\ \(\bullet\) & Severity: potential short circuit and motor burnout due to induced current. \\ \(\bullet\) & When did it start? The issue began in January 2022 and persisted to September 2022. \\ \(\bullet\) & Who detected it? The issue was detected by a certified hipot station operator. \\ \(\bullet\) & Where was it detected? The issue was detected at the hipot tester station. \\ \(\bullet\) & How was it detected? The issue was detected through a machine alarm indicating failure to  reach or exceed the test parameter values. \\ \(\bullet\) & How many defective parts? There were 1,173,538 defective pieces identified from January to  September 2022. \\ \hline \hline \multicolumn{1}{c}{Company View} \\ \hline \(\bullet\) & What is the difference between defective and non-defective parts? \\ \(\bullet\) & The difference between defective and non-defective parts is as follows: \\ \(\bullet\) & Non-defective part: Successfully completes the hipot test without triggering any alarms. The \\ \(\bullet\) & One more than one  
**Issue Description:**  
The production line for the armature subassembly came to a halt due to failures in the hi-pot tests. Details: During the specific process of checking armature resistance and varistor function and conducting a hipot test, the machine triggered the alarm due to a detected defective part, prompting a subsequent investigation. The high-potential tester's alarm blared, alerting operators of a part that failed the crucial insulation test. Why? The high-potential test detected unintended leakage current, indicating a direct electrical path between the armature cable and the laminated core. Why? The stress event compromised the epoxy coating, leading to a breach in cable insulation and contact with the lamination. Why? Non-uniform coating distribution during the manufacturing process resulted in a significant decrease in epoxy thickness on the lamination walls.