In-Plant Milk-Run Distribution for Material Provision Optimization in Lean Production

Under the circumstance of advanced globalization, it is increasingly difficult for production companies to remain competitiveness. Many of them are forced to restrict budget and reduce production costs. In addition, the customization of product increases continuously. This results in extension of product variation and reduction of product life cycle. Therefore, the companies need a high flexibility to respond quickly to changes in the market and to customer requirements. Lean thinking, as a powerful tool, has been implemented by many companies in production and manufacturing. In order to avoid waste in lean manufacturing, it is necessary to manage efficiently the material flow. In this study, for a lean material handling system in the lean manufacturing of a company, an in-plant milk-run distribution system is taken into consideration. The system consistsof vehicles, which move periodically in certain routes. The materials are delivered in short intervals from a central storage area to several points of use in the production. By using milk-run in plant, the material handling processes can be standardized and therefore the waste can be eliminated. One additional aim of the study with milk-run distribution for the material provision is to minimize the handling time, which determines directly the personal costs. In order to realize the aim, the work has beendivided into several steps. At first, the production processes, especially the material provision for the production have been analyzed. Secondly, the technological solutions have been analyzed in order to handle different loading units required by different machines in the production. Thirdly, the milk-run distribution for lean production is formulated as an optimization problem with the object of minimizing the number of vehicles and the distance traveled under the constraints of specific time periods, capacity of vehicle and related stations etc. Fourthly, two optimization methods are developed in order to find the optimal solution for the milk-run problem and the performance of different methods is also compared.