Integrated flexible capacity and inventory management under flexible capacity uncertainty

Abstract

In a manufacturing environment with volatile demand, inventory management can be coupled with dynamic capacity adjustments for handling the fluctuations more effectively. In this study we consider the integrated management of inventory and flexible capacity management under seasonal stochastic demand and uncertain labor supply. The capacity planning problem is investigated from the workforce planning perspective. We consider a manufacturing firm that can temporarily increase its production capacity by utilizing contingent workers from an external labor supply agency. The uncertainty of contingent capacity arises from the (un)availability of contingent workers, the pool size and the behavior of the labor supply agency. Using a dynamic programming approach, we formulate an infinite horizon model determining the optimal levels of permanent and contracted capacity, in order to minimize the total cost of operations. Within the dynamic program, we determine the optimal operational capacity decisions, namely the size of contracted and contingent capacity to be utilized in each period. The characteristics of the optimal policies are analyzed under an infinite horizon setting. In addition we consider temporary labor contracts, that diminish the effects of supply uncertainty on the manufacturer, at a specific contracting cost. Our analysis shows that as the supply uncertainty and/or the expected cost of utilizing contingent workers increase, the value of temporary labor contracts also increase. In contrast increasing demand variability reduces the incentive of the manufacturer to own capacity and increases the utilization of contingent resources.