<![CDATA[The electric motor of the Geminis-GE 5-650 S lathe machine experienced excessive vibration that persisted despite two bearing replacement attempts. This study aimed to identify the root cause of the excessive vibration using the 5 Whys method. Data were collected through visual inspection, vibration measurement, technician interviews, and a review of the equipment manual. The collected data were then systematically analyzed using the 5 Whys method to trace the cause-and-effect relationship until the root cause was identified. The analysis revealed that the excessive vibration was not caused by bearing failure but by wear on the shaft bearing seat resulting from a previous repair. The wear reduced the shaft dimensions, increased the radial clearance, disrupted rotor rotational stability, and ultimately generated excessive vibration. These findings explain why previous bearing replacements failed to eliminate the vibration, as they did not address the actual root cause of the problem. Based on these findings, shaft restoration or replacement is recommended, together with the implementation of standardized repair procedures, post-repair inspections, and also strengthening preventive maintenance program to minimize the risk of similar failures in the future.]]>
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