A mini-line approach for pull production

In high volume manufacturing, the just-in-time system using pull production is often successfully applied to achieve good performance in cost, time, and quality. However, its recent application to printed circuit board manufacturing is hampered by three conditions: Product variety proliferation, short product life cycle, and significant machine setup time. The mini-line approach (MLA) proposed in this paper is designed to implement pull production in such manufacturing environments without losing its benefits. MLA is hierarchical in addressing the production planning and control problem, consisting of multiple layers of optimization problems. These problems involve questions such as how many mini-lines should be formed, which product families should be grouped into mini-lines, how many machines should be allocated to each mini-line at each production stage, how much and when each product family should be produced, and how loading and flow of materials should be controlled. We first present the hierarchical framework of MLA, and introduce the static mini-line problem (SMP) that is valid under the condition that the product volume mix does not change. Then, from the SMP, we derive a set of optimization problems that constitute MLA: Similarity index problem, product grouping problem (PGP), and modified line segmentation problem. Next, we develop solution procedures for these three problems. The overall approach is evaluated by computational experiments where the characteristics of data sets were obtained from a large-scale manufacturer. We demonstrate that MLA performs well under both stable and gradually shifting product volume mix.