European Journal of Operational Research 66 (1993) 135-147 135 North-Holland Theory and Methodology Batching policies for a repair shop with limited spares and finite capacity Richard C.H. Chua Andersen Consulting, 45 South Seventh Street, Minneapolis, MN 55402, USA Gary D. Scudder Vanderbilt Uniuersity, Owen Graduate School of Management, 401 Twenty-First Auenue South, Nashville, TN 37203, USA Arthur V. Hill Curtis L. Carlson School of Management, 271 19-th Auenue South, University of Minnesota, Minneapolis, MN 55455, USA Received January 1990; revised April 1991 Abstract: Efficient batching for repair is essential to minimizing the 'equipment downtime' experienced by end-users when a repairable product fails. In this paper, the batching problem for a repair shop with limited spares and finite capacity is formulated and batching policies are developed. The performance of these policies is examined in a simulation model of a hypothetical repair shop. A policy called 'SP-WBPT' performed very well in all the environments tested. In this policy, the size of the batch is the number of failed parts of that part type waiting to be repaired. Batch selection is based on the shortest batch processing time per part, weighted by the number of available spares. Keywords: Batching; Repairables; Scheduling; Simulation 1. Introduction For expensive products such as aircraft en- gines and military equipment, repair is often more economical than disposal in the event of break- down. Equipment set-up for repair work can ac- count for a major portion of the repair time. In many repair shops, batching of parts for repair is Correspondence to: Gary D. Scudder, Vanderbilt University, Owen Graduate School of Management, 401 Twenty-First Avenue South, Nashville, TN 37203, USA. essential to minimize the 'downtime' experienced by the end-user. We illustrate the repair process with batching in Figure 1. When a failed unit (such as an aircraft engine) arrives, the failure is diagnosed and the unit is disassembled in the diagnosis/dis- assembly station. Assuming the failure of the unit (engine) is caused by the failure of a single part, the failed part is identified, removed from the rest of the unit, and routed through the repair center according to the repair requirements. In the meantime, the incomplete unit awaits re- 0377-2217/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved