INTEGRATING PRODUCTION SCHEDULING, DELIVERY, AND 3D LOADING PROBLEMS IN A TWO-STAGE SUPPLY CHAIN

In this study, a two-echelon supply chain with one distribution center and several retailers is investigated. In the distribution center, handling retailer's orders are considered an operation that should be completed on a single workstation. This study combines production scheduling and delivery problems with three-dimensional (3D) loading problems. In the integration of production scheduling and delivery problems, production, inventory, and transportation decisions are considered simultaneously to minimize the total production setup, inventory, and routing costs. The purpose of this problem is to determine the sequence and quantity of production, type of vehicles, the visiting sequence of each vehicle, and the inventory level at the distribution center and retailers in such a way that the total cost is minimized The total cost includes the production setup costs, holding cost in the distribution center, transportation cost, vehicle arrangement cost, and penalty costs. Then, the vehicles and batches are considered 3D components with length, width, and height, and the 3D loading problem is investigated. The purpose of the 3D loading problem is to provide practical loading. A mathematical model is presented to solve the loading problem. The problem under study is NP-hard, so medium and large-sized instances cannot be solved optimally in a reasonable time. Hence, a meta-heuristic algorithm based on a genetic algorithm is proposed to solve the problem. The computational results show that the proposed algorithm decreases the computational times by 92.36% on average and only leads to a 3.624% increase in the total cost compared to the optimal solution.