The value of the shortest loop covering all work centers in a manufacturing facility layout

Abstract

In this study we develop mathematical models to design circular material flow systems. We first develop a tight formulation to find the shortest loop covering all work centers within a manufacturing facility layout. The shortest loop is an attractive solution for most types of conveyors and power-and-free systems, where the length of the flow path is the major driver of the total cost. We develop a primal as well as a dual graph formulation and discuss their one-to-one correspondence in node-edge as well as in connectivity constraints. Our solution times outperform other optimization models available for the facility layout shortest loop design problem. We then approach trip-based material handling, such as automated guided vehicle systems, where the total loaded and empty trip distance is the major driver of the total cost. The problem in these systems evolves into concurrent design of the loop, pickup and dropoff station, and the empty vehicle dispatching policies. On the foundation of the shortest loop model, we propose a decomposition heuristic for design of trip-based flow systems. Computational results indicate that the heuristic provides high quality and robust solutions.

Keywords:

• Materials handling
• Facility planning
• AGV
• Generalized traveling salesman problem

Acknowledgements

This work was partially supported by Research, Scholarship, and Creative Activity Award, California State University, Northridge. This support is gratefully acknowledged. Thanks are due to the anonymous referees for their valuable comments.