Optimal dynamic assignment of a flexible worker on an open production line with specialists

This paper models and analyzes serial production lines with specialists at each station and a single, cross-trained floating worker who can work at any station. We formulate Markov decision process models of K-station production lines in which (1) workers do not collaborate on the same job, and (2) two workers can work at the same task/workstation on different jobs at the same time. Our model includes holding costs, set-up costs, and set-up times at each station. We rigorously compute finite state regions of an optimal policy that are valid with an infinite state space, as well as an optimal average cost and the worker utilizations. We also perform a numerical study for lines with two and three station. Computations and bounds insightfully expose the performance opportunity gained through capacity balancing and variability buffering.