PLM driven digital twin manufacturing through EBOM to MBOM transformation in railway industry

The railway industry value chain, including locomotive manufacturing, maintenance-of-way equipment, and railcar production, operates under intense product complexity, high customization demands, and continuous pressure to reduce delivery timelines. This paper examines how Product Lifecycle Management (PLM)-driven digital thread capabilities support Engineering Bill of Materials (EBOM) to Manufacturing Bill of Materials (MBOM) transformation and closed loop manufacturing (CLM) in railway contexts. A qualitative multiple-case study was conducted across three rail manufacturing organizations through purposive theoretical sampling to represent variation in product type (locomotive, maintenance-of-way, railcar), digital maturity, and geographic location while sharing a common PLM platform foundation. Evidence was drawn from published case documentation, internal system specifications, PLM configuration records, workflow documents, and practitioner knowledge from implementation roles. Within-case analysis was followed by cross-case pattern comparison to identify recurring governance mechanisms, data structures, and deployment patterns. The findings show that governed BOM transformation, manufacturing-specific item types, visualization data pipelines, and phased PLM deployment are key prerequisites for digital thread integrity. The study contributes a five-layer reference architecture derived from cross-case evidence, offering a transferable framework for digital manufacturing transformation in complex discrete manufacturing environments, including rail manufacturing.