Optimizing Machining Inspection Processes in the Automotive Industry Using Yamazumi Analysis and Karakuri-Based Lean Improvements

The cylinder machining process at PT TACI is carried out to cut aluminum workpieces into body components of automotive AC compressors. A total of nine-cylinder machining lines are operated at the facility. Several challenges have been encountered, including low labor efficiency and the existence of non-productive activities (muda). In this study, labor efficiency in the cylinder machining inspection process was analyzed using the Standard Working Chart and the Yamazumi Chart. The Standard Working Chart was utilized to document standardized worker activities, while the Yamazumi Chart was employed to evaluate workload distribution and to support optimized task allocation through job loading combination. Furthermore, a Karakuri system was implemented as a mechanical aid aimed at eliminating waste (muda). The findings indicated that the integration of these methods led to a significant reduction in non-productive time, improvement in process efficiency, and support for the implementation of lean manufacturing principles. Waste time identified prior to improvement included 13.2 minutes spent on cleaning activities and 40.5 minutes on waiting times. These non-productive activities were eliminated after the proposed improvements were applied. It is concluded that the proposed approach is effective in enhancing labor optimization using a mechanically simple and energy-efficient system. It is concluded that the proposed approach is effective in enhancing labor optimization using a mechanically simple and energy-efficient system. This study contributes to the development of lean manufacturing strategies in machining inspection processes and suggests that future research could explore the integration of digital monitoring tools to further enhance real-time efficiency and adaptability.