DescriptionIn today’s customer driven economy, moving products quickly, efficiently, and cost effectively offers crucial advantages to companies. To achieve these goals, more and more companies are finding that cross-docking can play an integral part in their distribution model by partially replacing or complementing existing warehousing facilities. Crossdocking is a material handling and distribution operation, which moves products quickly and directly from inbound trucks (ITs) to outbound trucks (OTs) through the crossdock facility where products are being resorted or consolidated, without being stored or only with a short-term storage, usually within 24 hours or sometimes only within one hour.
This research deals with the scheduling of both ITs and OTs at a crossdocking facility where three objectives are considered: The first objective is to minimize the starting and handling time of all ITs; the second objective is to minimize the total weighted distance of pallets traveled inside the crossdock facility; and the third objective is to minimize the total departure time of all OTs. Multi-objective mixed-integer program formulations are built in order to address the problem. Justification for the use of these objectives in optimizing cross-dock operations is given. Different models are built for three different door layouts at crossdocking facility.
Since the problems are NP-hard, we consider the problem size limitations to obtain an exact solution. In addition, a restriction-approximation approach to solve the models is proposed and the efficiency of our approximation method is proved based on generated data. Finally, numerical examples are provided using the mathematical models built and the approximation approaches. Results for different layouts and scenarios are compared to evaluate the characteristics of different crossdock layouts.