Optimal skill assignment with modular architecture in spare parts supply systems

We study a single location supply system for repairable spare parts. The system consists of a multi-server repairshop and inventory of ready-to-use spare parts. When a failed part is received, a new (or as-good-as-new) replacement (if on stock) is sent back, and the failed part is queued for repair. In the case of unavailability, the failure requests are fulfilled when a ready-for-use part is received from the repairshop. The repairshop has several multi-skilled parallel servers (technicians). Each server has a limited set of skills, i.e. is capable of repairing only certain types of parts. Typically it is considered that the skill sets of each server partially overlap with the skill sets of other servers. In this paper, on the contrary, we study grouping (pooling) of skills and servers such that there is a full overlap of the skill sets of the servers from same groups while there is no overlap of the skill sets of the servers from different groups.