چکیده:
Scheduling problem for the hybrid flow shop scheduling problem (HFSP) followed by an assembly stage considering aging effects 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 the same 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 an example in small scale. Since this problem has been proved strongly NP-hard, in order to solve the problem in medium and large scale, 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.
خلاصه ماشینی:
"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).
According to literature review, no study has been done on HFS problem followed by an assembly stage considering the aging effects on the process time and also preventive maintenance activities.
The aim is to determine sequence of products to be assembled and also scheduling the parts and assigning them to machines in each stage of hybrid flow shop to be fabricated in order to minimize the completion time of all products.
We define index I as below to identify type of the problems: / Because the range for number of parts and their processing times and also the assembly time of products are uniform it is clear that: If Then The hybrid flow shop stage will be bottleneck If Then The assembly stage will be bottleneck Else(I ) Then There will be balance condition between two stages Hence we have generated three types of problems as shown in table 1.
The aim is to determine sequence of products to be assembled, scheduling the parts and assigning them to machines in each stage of hybrid flow shop to be fabricated, and also determine when the preventive maintenance activities get done."