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Research paper−96−Synthesiology - English edition Vol.5 No.2 pp.96-113 (Sep. 2012) concept or methodology of the lean production system originally derived from pull-type production control is made applicable to the manufacturing processes of the steel industry that has a process structure suited to push-type production control. In the Plate Mill of Kimitsu Works, the production control system was remodeled to realize integrated optimization in a process industry resulting, in the early 2000s when demand rose sharply due to the rapid expansion of the Chinese economy, in a substantial shortening of manufacturing lead time thanks to the reduction of in-process stock (Fig. 1) and in the faster expansion of production compared with other plate mills in Japan (Fig. 2). How could optimization at the level of the entire plate mill be achieved, where the manufacturing flow is complex and the constraint hurdles are quite high? This paper explains how the innovation of the production control system on the shop floor was realized, and what the steel industry, a process industry, can learn from the lean production system, by identifying and modeling the realized production control system as a multi-scale hierarchical structure. 2 Manufacturing of steel plates The manufacturing processes in a steelworksTerm 2 consist of producing pig iron at the blast furnace that consumes raw materials of iron ore, coal, etc., then producing steel by refining iron at the converter. Steel thus produced is molded into slabs (oblong sheets of steel) on the continuous casting 1 IntroductionIntegrated optimization in production control for manufacturing an unlimited variety of products with zero defect, using minimum resources, in the minimum manufacturing lead timeTerm 1 and with zero stock, is the ultimate goal of monozukuri (manufacturing). Generally, production control is classified largely into pull- and push-types.[1][2] The pull-type production control is used for the type of manufacturing for which in upstream processes optimal parts and intermediate goods are provided sequentially to the requirement of downstream processes or customers and is applicable to assembly industries. One such industry is the automobile industry, which gave birth to the lean manufacturing system, one of the major successes of the 20th century. In contrast, in push-type production control, instructions for production are given to feed parts and intermediate goods starting from the entrance of processes and to channel them from the upstream processes to those of downstream. It is applicable to many industries including process industries such as steelmaking and chemical. The issue here, where push-type production control is concerned, is how the integrated optimization of production can be achieved, while simultaneously realizing the minimization of manufacturing lead time and the improvement of efficiency (productivity).This paper analyzes examples of relevant cases of Kimitsu Works of Nippon Steel Corporation, and studies how the - A proposal for production control by multi-scale hierarchical modeling-Integrated optimization of production in the steel industry to simultaneously minimize lead time and improve productivity is a real challenge. Lean manufacturing, recognized as a leading successful example of such optimization, is characterized by synchronization of time scale of production with that of the mainline. However, in the steel industry, it is inherently difficult to implement synchronization and reduction of production time to the same degree as in the automobile industry. This difficulty motivated our method for integrated optimization of production at the plant level in the steel industry, by modeling the production control as a multi-scale hierarchical structure in time. This paper describes an attempt to systematize production knowledge in industry by a synthesis of practical knowledge (of shop-floor engineers) and company experiences.Toward the integrated optimization of steel plate production processKeywords : Steel industry, integrated optimization, production control system, multi-scale hierarchically structured model, lean production system[Translation from Synthesiology, Vol.5, No.2, p.98-112 (2012)]Kiyoshi Nishioka1,4*, Yasushi Mizutani2, Hironori Ueno3, Hirofumi Kawasaki1 and Yasunori Baba41. Nippon Steel Corporation 2-6-1 Marunouchi, Chiyoda-ku 100-8071, Japan *E-mail: 2. Nippon Steel Corporation Kimitsu Works 1 Kimitsu, Kimitsu 299-1141, Japan 3. Nippon Steel Corporation Nagoya Works 5-3 Toukai, Toukai 476-8686, Japan 4. Research Center for Advanced Science and Technology (RCAST), The University of Tokyo 4-6-1 Komaba, Meguro-ku 153-8904, JapanOriginal manuscript received November 11, 2011, Revisions received January 27, 2012, Accepted January 31, 2012

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