Optimization of Circular Conveyor Belt Systems with Multi-Commodity Network Flows

Abstract

Modern industrial production with alternative process plans and the use of complex machine equipment increases requirements for its intralogistics operations in terms of efficiency, resilience, and flexibility. One of the most common solutions for transporting workpieces between the manufacturing stations is a system of conveyor belts where each conveyor rotates in a fixed direction at a constant speed. The movement of the individual workpieces can be controlled only indirectly via a set of gates connecting different carousels. In this paper, we aim to increase the flexibility of conveyor belt systems by carefully scheduling the gates to route the workpieces efficiently along the production line according to their process plans. The key component of our solution is the discretization of both the time and positions on the belts to represent the system by a directed graph with circular components. To find the routing of workpieces that minimizes the total flow time, we have reduced the problem to the integer multi-commodity flow on the time-expanded network with an extension for the vertex precedences. Despite the simplicity of the formulation, the results suggest that off-the-shelf solvers can find optimized routing for instances with tens of workpieces and more than hundreds of belt positions within a few minutes.