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Research paper : Toward the integrated optimization of steel plate production process (K. Nishioka et al.)−107−Synthesiology - English edition Vol.5 No.2 (2012) management at the level of plants, that the basic environmental setting for inducing the emergent phenomena on the shop floor was implemented.[26]-[27] Furthermore, from the viewpoint of how the production control system was made possible, it is important that core persons capable of taking charge of the bottom-up type synthesis were fostered systematically, and such persons played the role of promoting emergent activities on the shop floor.To introduce the roles of the “technical group” to which the engineers that contributed to the development of the proposed models belong, the group is positioned at the relay point that links the manufacturing site and the staff departments. It has a broad coordination function not limited simply to manufacturing technology for the operation of the plant, and plays the core role in the operation and innovation of the production system (see NOTE 4). It is general practice to assign technical staff to the “technical group” at the time of new recruitment to the company, and as new recruits, they experience on-site work in three shifts. After this period, technical staff gain experience in various job positions but exceptional engineers and leaders of steelworks including the superintendent tend to remain in the “technical group.” Such career path suggests that the company has had the intention of fostering the staff in the “technical group” as principal enablers[29] (persons who help others to realize objectives in emergent activities) in the emergent processes by having them physically embed in the staff the knowledge on coordination and means of problem solution acquired through OJT in many fields (corresponding to the habitus of P. BourdieuTerm 5 [28]).Engineers working as system integrators are responsible for achieving both technical superiority by the sophistication of equipment/ operational technologies and economic rationality. The costs and risks that arise when introducing the lean production system to the steel industry at the meticulous level of the automobile industry are imagined to far surpass the authorized scope of decision-making by the on-site plant management. The integrated optimization of the production processes needs to be evaluated from the viewpoint of overall optimization in plant management and the proposed models provide a quantitative guideline for examining in concrete terms how the shop floor management balances the conflicting needs of technologies and management. For example, for the promotion of the lean production system, it becomes necessary to eliminate bottleneck processes, and when studying the optimal equipment investment, it was not possible in the past to evaluate quantitatively the increment of integrated efficiency that the reinforcement of equipment in the finishing processes will incur, making it difficult to make a proper decision in investment in the finishing process equipment. The proposed model opened the possibility of effectively presenting to the management of Kimitsu Works and sales departments of the Headquarters, not to mention within the Plate Mill, the advantages and the necessity of integrated optimization. We also developed in succession the production control systems for the improvement of on-site operation, the optimization of material design aiming to improve production control activities conducted by the staff in charge, the optimization of the tapping schedule and the development of the infrastructure for supply chain management and others. And during such development work, the efficacy of the quantitative analyses made using the multi-scale models was verified.As explained above, the history of the formation of the multi-scale models proposed in this research has the following bilateral characteristics. Firstly, if the models are considered in terms of their formation process, it is recognized that the structure of the models was determined by the know-how gained in the research method used by the engineers who were in charge of the development, more specifically, by the hierarchical structure approach to complex phenomena. Contrastively, when we saw a series of models that we introduced be developed and emerged in the form of a production control system, we recognized that it is worthwhile to widely propagate the system in the industrial society, and we recognized anew, while working on the formalization of the system, the merits obtainable by systematizing the model as a multi-scale model. 7 Summary and future considerationsIf the essence of the manufacturing industry is “transcribing information into materials,” the lean production system that creates material flows synchronized with the flow of information is one of the “aspects to be targeted” in the pursuit of the essence of the manufacturing industry.[30] The quest for economies of scale by the mass production system initiated by Ford created the time-wise multi-scale hierarchical structure of production control, represented by the second time scale manufacturing lines, production plan on the monthly time scale and very prolonged lead time / large stock. Ohno who took the lead in the lean production system, under the slogan of “Overcome economy of scale,” however, succeeded in this by controlling manufacturing lot sizes and pursuing the synchronization of manufacturing with the production line.[4] When the lean production system is considered within the framework of time-wise multi-scales, it can be understood as the result of the convergence of the manufacturing time scales on that of the mainline. In contrast, because the steel industry is a process industry, and due to the fact that the influence of manufacturing lot size on productivity and quality is larger compared with the automobile industry, an assembly industry, it is fundamentally difficult to realize the similarly high level of manufacturing synchronization and compression of time scales as that of the automobile industry. However, the case example analyzed in this paper shows that the integrated optimization may even be realized in industries other than

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