Modeling the hybrid flow shop scheduling problem followed by an assembly stage considering aging effects and preventive maintenance activities.

Scheduling problem for the hybrid flow shop scheduling problem (HFSP) followed by an assembly stage considering aging effects and additional preventive and maintenance activities is studied in this paper. In this production system, a number of products of different kinds are produced. Each product is assembled with a set of several parts. The first stage is a hybrid flow shop to produce parts. All machines can process all kinds of parts in this stage but each machine can process only one part at a time). The second stage is a single assembly machine or a single assembly team of workers. The aim is to schedule the parts on the machines and assembly sequence and also determine when the preventive maintenance activities get done in order to minimize the completion time of all products (makespan). A mathematical modeling is presented and its validation is shown by solving a small scale example. This problem has been proved to be strongly NP-hard, then in order to solve the problem in medium and large scales, four heuristic algorithms is proposed based on the Johnson’s algorithm. The numerical experiments are used to run the mathematical model and evaluate the performance of the proposed algorithms. [ABSTRACT FROM AUTHOR]