Multi-job production (MJP) is a class of flexible manufacturing systems intended to produce different products (job-types) according to a given product-mix and build-schedule. In MJP systems, all job-types are processed by the same sequence of manufacturing operations, but with different processing times at some or all machines. To characterize MJP, we introduce the work-based (rather than the traditional part-based) model of production systems, which is "insensitive" to whether a single- or multi-job manufacturing takes place. Using this model, we develop a method for performance analysis of MJP serial lines with the emphasis on their throughput and bottlenecks as functions of the product-mix. We show, in particular, that for the so-called conflicting job-types, there exists a range of product-mix, where the throughput of MJP is larger than that of any individual job-type involved. To characterize the global behavior of MJP systems, we introduce the notion of Product-Mix Performance Portrait, which represents the system throughput and bottlenecks for all feasible product-mixes. Finally, we apply the results obtained to a section of the underbody assembly system at an automotive assembly plant, calculate its performance portrait, and evaluate the efficacy of potential continuous improvement projects.
International Journal of Production Research
Multi-product manufacturing, Flexible production systems, Product-mix, Serial lines, Exponential machines, Finite buffers, Work-based model, Throughput, Bottleneck, Performance portrait, Automotive assembly.