Analysing Warehouse Material Flow using a Lean Framework A Case Study of an Engineer-to-Order Company

Abstract

Warehouse operations in Engineer-to-Order (ETO) manufacturing environments face dis- tinctive challenges due to high product variability, project-based production, and complex material flows. Despite this, limited research has addressed warehouse operations in ETO settings. This study examines how Lean principles can be used to analyse warehouse ma- terial flow and identify inefficiencies contributing to lead time in an ETO context. A qualitative single-case study was conducted at a European defence manufacturer op- erating under an ETO production strategy. Data were collected through semi-structured interviews and analysed using thematic analysis. In addition, a process flowchart was developed to visualise and support the analysis of the warehouse material flow. Womack and Jones (1997) five core Lean principles – value, value stream, flow, pull, and perfection – were applied together with the ETO context as an analytical framework. The findings reveal a range of inefficiencies, including batch-based material reservations, consolidation delays, fluctuating workloads, limited system support, and normalised re- liance on an express flow mechanism. These inefficiencies are explained as the result of disrupted material and information flow, the absence of effective pull mechanisms, and the interaction between waste (muda), unevenness (mura), and overburden (muri). The ETO context amplifies these challenges through high variability, late engineering changes, and siloed working practices. The study concludes that Lean principles provide a productive diagnostic framework for ETO warehouse environments, though their applicability is differentiated. The seven wastes transfer directly, while the principles of flow, pull, and perfection require contex- tual adaptation given the structural variability inherent to ETO production. The findings contribute to the empirical understanding of Lean application in non-repetitive manufac- turing environments and offer guidance for improving warehouse performance based on Lean theories under conditions of high customisation and growth.