Modeling of workflow congestion and optimization of flow routing in a manufacturing/warehouse facility

This paper discusses the notion of workflow congestion in the context of material handling equipment interruptions in a manufacturing or warehousing facility. Development of a combination of probabilistic and physics-based models for workflow interruptions permits evaluation of the expected link travel time. The problem is then of routing in a way that minimizes total expected travel time. The rerouting problem is modeled as a multicommodity flow problem with link capacity design. A greedy upper bounding and Lagrangean relaxation algorithm are developed to solve this efficiently. To calibrate our modeling process we develop an object-oriented simulation model that explicitly considers various workflow interruptions. Our major finding is that rerouting traffic in a congested facility can significantly alleviate congestion delays and improve the efficiency of material movement. A managerial insight derived from this work is that rerouting is most effective in medium traffic-intensity situations.