A new value stream mapping approach for complex production systems

In this paper, an innovative framework to apply Value Stream Mapping to products with complex Bill of Materials is presented. Value Stream Mapping is one of the best tools to map a process and to identify its main criticalities. Unfortunately, it can be effectively applied to linear systems only. When the manufacturing process is complex with flows merging together, Value Stream Mapping cannot be used straightforwardly. Thus, the main objective of this work is to solve this limitation so that lean production can be enhanced in complex systems too. The proposed approach is based on seven iterative steps and integrates Value Stream Mapping with other tools typical of industrial engineering. The basic idea is to execute a preliminary analysis to identify the 'critical production path' using the Temporized Bill of Material. Then, improvements are made considering all possible sharing with other secondary paths as possible constraints. Once the critical path has been optimized, a new path may become critical. Thus, the analysis proceeds iteratively until the optimum is reached and the Work In Process level has decreased under a desired value. A case study taken from a real setting environment is finally presented to assess the validity of the methodology proposed here.