Bottleneck identification and productivity improvement using BasicMOST and Yamazumi diagrams: An automotive assembly line case study

The case study was carried out at the plant of a company that is one of the world's largest automotive suppliers and addresses the application of the BasicMOST method for production process optimization. Work measurement and time study methods represent core competencies of Lean specialists and provide a simple and effective approach to identifying waste, unnecessary overproduction, and inefficiencies in production processes. This study uses the BasicMOST method, one of the predetermined time methods used for indirect labor measurement, in combination with Yamazumi diagrams to visualize the value-adding and non-value-adding activities. The current real-life state of the tail light assembly line was analyzed to locate the bottlenecks in the production process. An analysis employing the BasicMOST method, Yamazumi diagram, and chronometric measurements identified critical bottlenecks on the assembly line. Their elimination through targeted investments in pallets and manual pressing equipment led to an increase in productivity from 6.84 to 10 pcs/h/operator, a reduction in standard minute consumption, the elimination of overtime, greater flexibility in responding to customer requirements, and a significant reduction in personnel costs. As a result, production efficiency and overall competitiveness were substantially improved. The optimization of the production process was carried out in several iterative steps, each subsequently verified by video analysis and updated using the BasicMOST method. The results of this study demonstrate that the combined application of the BasicMOST method and graphical visualization using the Yamazumi diagram represents an effective tool for optimizing work processes, reducing costs, enhancing competitiveness, and ensuring production profitability.