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1 Introduction and problem background
"Minomi" is a concept that can be used in in-plant materials supply to assembly stations, either both for handling and presenting parts, or only for presenting them. The concept has never previously been clearly defined, but the basic feature of minomi is that no containers are used. Instead of being in containers, parts are resting on small fixtures, hanging from hooks, or simply stacked together. Research literature dealing with minomi is scarce, but [14] Liker and Meier (2006) state that the potential advantages of minomi include reduced motion waste, reduced damage to parts, reduced ergonomics problems, and a reduced number of process steps for materials handling. In addition to this, there are reports from Toyota's Kentucky plant of drastically reduced space requirements at the assembly stations as the previously used part bins are exchanged for smaller part racks ([5], [4] Chappell, 2006a, b). However, in spite of these stated advantages, very little knowledge of minomi actually exists. No research seems to have been conducted that focuses on more specifically identifying the effects of using minomi.
For mixed-model assembly of a large number of product variants, presenting parts at the assembly stations can be space consuming ([13] Johansson and Medbo, 2004) and available space is often scarce. Through the elimination of containers, minomi should enable parts to be presented at the assembly stations in a space efficient manner and in suitable picking positions. However, containers are generally an integral part of in-plant materials supply systems, and the efficiency of the materials handling is often closely linked to the design of the containers and to the interaction between the containers and the handling equipment ([7] de Souza et al. , 2008; [12] Harit et al. , 1997). Therefore, an in-plant materials supply system may not be able to operate in the same way when minomi is used as when containers are used, which, in turn, means that the performance of the system may be affected. Furthermore, a study by [11] Hanson and Johansson (2007), performed at four Swedish vehicle assembly companies, showed that the option of minomi is generally not even considered for transporting or presenting parts to assembly. Within industry, the lack of knowledge of minomi and the effects of...