Transforming the traditional assembly line production system into a Seru production system and an implementation

Advanced manufacturing environments have emerged as an ideal solution to address modern market challenges that demand a wide product range and reduced time-to-market. Among cellular systems consisting of independent, modular, and flexible workspaces adapted to similar product families, Seru is increasingly being adopted for both production and assembly tasks. The Seru production system, which first emerged in Japan, has been adopted by technology giants such as Sony, Fujitsu, and Canon, and has been characterized by beyond-lean concepts. Seru, meaning "cell" in Japanese, is spreading worldwide with its three modes, particularly for companies engaged in assembly production. Although Seru has been adopted by major companies in Japan, it has not yet gained widespread recognition in international literature. The modes of Seru include Divisional Seru, Rotating Seru, and Yatai. The essence of Seru lies in the organization of various types of products by multi-skilled workers with cross-training capabilities. Seru production is an innovative system where traditional production lines are dismantled and replaced with flexible, easily installable and removable, low-cost lines. In production environments where this system is implemented, it is possible to optimize critical factors such as total completion time minimization, worker efficiency, cost, and worker assignment. This study aims to adapt the Seru production model to the production system of a bicycle manufacturing company in Turkey. The primary objective of the research is to minimize the total production time by replacing the traditional assembly production line with flexible conveyor belts through the adoption of the Seru production model. Rotating Seru, one of the Seru modes, formed the foundation of the implementation. The bicycle manufacturing company assembles two different product types - children's and adult bicycles - on two separate traditional linear lines. Consequently, Line-Seru scheduling was performed to keep the processes for each product type within the same production line. A two-Seru model was designed, with one Seru dedicated to children's bicycle assembly and the other to adult bicycle assembly. The modeled Seru production line aimed to minimize total completion time. Additionally, the study focused on reassigning workers to Serus and tasks based on their skills. Regarding worker assignment, workers were first evaluated for their multi-skill capabilities to determine their suitability for Seru assignments. After determining worker competency levels, a compatibility matrix was created for the study model. The traditional model and the proposed Seru model were compared based on total completion time. Furthermore, the optimization problem focused on assigning workers to processes based on their capabilities and redesigning the production process, with workers pre-designated for specific Serus. A mixed-integer mathematical model was established to adapt the optimization model. Lingo 18.0 software was used to perform the analysis. The optimization study conducted with the developed Line-Seru transformation model achieved significant improvements in production system performance. The minimization of total completion time, optimal worker assignments, and production system restructuring were successfully accomplished. Comparative analysis between the traditional production system and the Seru-based system revealed approximately 42% improvement in total completion time. This improvement was concretely observed in terms of working days, with the completion time reducing from 11.5 days in the traditional system to 6.5 days in the Seru system. The obtained results clearly demonstrate the potential of the Seru production system to increase efficiency, and this study serves as a valuable reference for future Seru-based optimization research.