Proposing a lean-optimized scheduling model of mixed-flow prefabricated component production in off-site construction

The scheduling of prefabricated component production is crucial for production efficiency and timely delivery in off-site construction (OSC). However, the prevalence of mixed-flow production in prefabrication renders conventional scheduling methods inadequate, leading to cost overruns and waiting issues. This study introduces a lean-based mixed-flow production scheduling approach to address the scheduling challenges in mixed-flow prefabrication. Guided by lean principles, this research analyzes the mixed-flow production process and process wastes, resolving issues of group production, pull production, and overall scheduling enhancement through multiobjective optimization modeling. A nondominated sorting genetic algorithm II (NSGA-II) based solution algorithm was established to minimize completion times, tardiness/earliness penalty, and type changes, thereby eliminating waste and ensuring continuous production. The effectiveness of the proposed approach was validated through a real case study, showing an average 1.84% reduction in makespan, 24.19% cost savings, and 36.03% reduction in waiting times compared to conventional nonlean optimization methods, while demonstrating good stability and reliability. This study innovates in engineering scheduling management and contributes to the development of lean construction theory, providing concrete support for component suppliers' successful delivery and promoting further development in OSC.