Scheduling a no-wait flowshop with separated setup and removal times

Consider the two-machine no-wait flowshop problem where the setup and removal times of a job at each machine are separated from the processing time. The scheduling objective is to minimize the sum of the total flowtime. Two optimization properties are first developed. In view of the NP-hard of this problem, optimal solutions seem unnecessary especially when the number of jobs is large. Then, combined the developed optimization properties with the greedy search a heuristic algorithm is developed. Computational experience demonstrates the effectiveness of the heuristic algorithm in finding near optimal schedules.