Minimization of Machine Idle Time in Flow shop Scheduling Using anEfficient Heuristic Algorithm

Abstract

Machine idle time is a critical determinant of productivity in flowshop manufacturing systems. While most scheduling studies minimize makespan, machine idle time is often reduced only indirectly. This paper addresses this gap by explicitly minimizing Total Intermittent Machine Idle Time (TIIT_M), which represents avoidable idle gaps between consecutive job operations that are directly influenced by sequencing decisions. A single-objective constructive heuristic is proposed to minimize TIIT_M in permutation flowshop scheduling. Makespan (C_max) is treated strictly as a secondary performance indicator, not an optimization objective. The effectiveness of the proposed heuristic is evaluated using two industrial case studies representing small- and large-scale problem instances. For the small instance and larger instances, comparative experiments are conducted against well-known heuristic and metaheuristic algorithms. Results demonstrate that the proposed heuristic achieves superior or competitive TIIT_M with minimal computational effort, making it suitable for practical scheduling environments where machine utilization continuity is critical.