Additive manufacturing of spare parts in military maintenance systems: a review of technological advances and logistical implications

Military maintenance organizations hold some of the largest and least liquid spare parts inventories in existence, and they operate them under conditions that commercial after-sales networks rarely face: intermittent demand, aging platforms, vanished suppliers, and supply lines that an adversary actively tries to sever. This review examines what additive manufacturing (AM) can realistically contribute to such systems. Drawing on 49 verified sources published between 2019 and 2025, of which 46 are peer-reviewed journal articles, the analysis is organized along three axes: the technological maturity of AM processes relevant to spare parts production and repair; the logistical and economic evidence on when printing outperforms stocking; and the qualification, certification, and digital-security constraints that currently govern adoption. The evidence supports a consistent conclusion. AM already delivers documented value at the margins of military supply chains. Audit data record procurement lead times cut from two years to roughly one week, and unit costs reduced by several orders of magnitude for selected parts. Yet operations research modeling shows that printing complements rather than replaces inventory, with dualsourcing savings of 8-30% concentrated among low-demand, long-lead-time items. The binding constraints are no longer primarily technical: qualification pathways, fatigue-critical defect populations, and the cybersecurity of the digital thread now set the adoption frontier. The review contributes a three-axis readiness framing that connects engineering, logistics, and assurance literatures which have largely developed in isolation, and identifies the research gaps that matter most for defense maintenance planners.