Journal of Industrial Engineering and Management Studies

Abstract Flow shop scheduling has traditionally focused on minimizing completion time; however, growing energy costs and sustainability concerns necessitate the simultaneous consideration of energy consumption as an optimization objective. In addition, in many real-world manufacturing systems, such as chemical, food, and continuous production industries, jobs must be processed without waiting between successive operations, a constraint that significantly increases problem complexity. Despite its practical relevance, the combined consideration of no-wait flow shop scheduling and energy-aware optimization has received limited attention in the literature. This study develops a bi-objective no-wait flow shop scheduling model that simultaneously minimizes makespan and total energy consumption, accounting for both active and idle energy usage of machines. A mathematical formulation is proposed, and due to the NP-hard nature of the problem, the NSGA II metaheuristic algorithm is employed to obtain high-quality Pareto-optimal solutions. Model validity is verified using small-scale instances solved optimally, followed by large-scale computational experiments. Furthermore, a comprehensive parametric sensitivity analysis is conducted to examine the influence of key factors, including processing time, number of tasks, and machine energy consumption in active and idle states, on both objectives. The results reveal that idle energy consumption has a disproportionately high impact on total energy usage and completion time, underscoring its critical role in sustainable scheduling decisions. The findings provide both theoretical insights and practical guidelines for designing energy-efficient schedules in no-wait production environments.