Tam zamanında üretim sistemi ve bir simülasyon uygulaması /
Yazar: MÜMTAZ İPEK
Danışman: PROF.DR. GÖNÜL YENERSOY
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Endüstri Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 1995
Konu: Endüstri ve Endüstri Mühendisliği = Industrial and Industrial Engineering
Dizin: Benzetim = Simulation ; Tam zamanında üretim = Just in time production

Özet:
Anahtar Kelimeler: Tam Zamanında Üretim Sistemi, Kanban Sistemi ve Çekme Sistemi Bir ülke ekonomisi için hücre niteliğinde olan işletmelerin varlıklarını sürdürebilmeleri ancak üretimle mümkündür. Üretim sistemlerinin etkinliğini düşüren başlıca sorunlar talep tahminlerinin isabetsiz, hazırlık süreleri ile toplam imalat süresinin uzun, stokların büyük miktarlarda, taşıma ve ıskarta maliyetinin yüksek olmasıdır. Stok maliyetinin azaltılması için iki farklı sistem uygulanmaktadır. Bunlardan birincisi Malzeme İhtiyaç Planlaması (MİP), ikincisi ise Toyota Motor Fabrikası tararından geliştirilen Tam Zamanında Üretim Sistemi (TZÜS)'dir. Tam Zamanında Üretim; gerekli parçaların, gerekli miktarlarda, gerekli zamanda ve gerekli kalite seviyesinde üretilmesidir. Bu sistemin yaklaşımı yüksek düzeyde stok tutarak sorunları gizlemek veya olumsuz etkilerini azaltmaya çalışmak değil, sorunların temeline inerek kalıcı çözümler aramaktır. Bu nedenle TZÜS'de hammadde, yan mamul ve ürün stoklan mümkün olduğunca azaltılmaktadır. Tam Zamanında Üretim Sisteminin amaçlan şunlardır: Sıfir hata, sıfir hazırlık zamanı, sıfir envanter, sıfir taşıma, sıfir arızalanma, sıfir temin süresi, bir birimlik parti büyüklüğü. Yukarıdaki amaçlan gerçekleştirmek için, TZÜS'nin uygulanması gerekli elemanları şunlardır: İsrafi ortadan kaldırmak, toplam kalite kontrol, çalışanların katılımı ve ayrıca kanban, grup teknoloji, hazırlık zamanının azaltılması, toplam üretken bakım. Bu çalışmada üç istasyonlu bir üretim hatunda mevcut sistem ile TZÜS'ni karşılaştırmak amacıyla SIMAN ile simülasyon yapılmış, akış zamanı, çıkan parça sayısı, kuyruk uzunlukları ve makina kullanımları ölçüt olarak alınmış, TZÜS'nin daha iyi sonuçlar verdiği görülmüştür. vu

Abstract:
Keywords: Just-In-Time Production System, Kanban System and Pull System. The firms are like the cells of the economy. The vitality of these cells is up to their ability of having their existence continued according to changing social, political and economic conditions - by having clean blood in their veins -~ that is by production. The firms during their activity have to keep the production factors at the level which provides the highest productivity. The use of these sources productively is up to the effectivity of the production system. The most important problems which decrease the productivity of the production systems of the firms in our country are insufficiency of the control and planning of the production, unpredictability the demands, the excess quantity of work-in-process; the longness of set-up times, the longness of total operation periods, the highness of transportation and scrap costs. There is two different system to decrease the inventory which constitute an importante percentage of the costs: One of them is MRP or MRP II, a more developed form of MRP. The second is Just-In-Time Production System (JIT) which has been developed by the Japans. Japan, too, has been affected by the Second World War crisis; it has lost a great deal of its sources as capital, land, labour beside its natural resources. Japan firms were desiring to build up themselves and take their part in world markets. One of these firms, Toyota Motor Company, started to produces traks by having licence from USA. But, it wasn't in a position to compete with the western companies, because of the stuation it was in. then Ford Company in USA was having mass production low price. The Japans ahve believed in the necessity of improving their methods in order to maintain their industrial life, they started to search for new methods by trying-error. Meanwhile Taiichi Ohno, the premier vice-president of Toyota, has stated that everything which is not used in the system is a waste, especially the stocks kept for the continuity of the production, and in case of transporting the parts in time, the stocks would be abolished from the system and the material would be minimized. Thus, concept of just-in-time has been coined. That Toyota has over-come the petrol crisis in 1973 by this method have been remarked by other Japanese firms. Later, American firms have struggled to adapt the JIT to themselves. vmToyota Production System is called to the JIT developed by Toyota which has a distinguished place today, in the world car market. İn addition, the name as Zero Inventory Production (ZIP), Material As Needed (MAN) and Kanban System, because of the cards in the structure of the system, are being used. Just-In-Time Production is the production of the necessary parts in the neccassary quantity, quality and time. The approach of this system is unsteady of keeping inventory and buffer stock at a high level, and working with long lead times to find permanent solutions to the problems. The most important target of JIT is to keep out everything seen as waste from the system. Waste is the activities as handling, storage, counting, ordering, scheduling which do not increase the value of the product, but rather increase the cost, and everything which is above the required level. JIT can be succefully applied in batch production. The speaciality of this production is to-apply a repetitive manufacturing system and to have a simple work flow. In order to increase the output quantity in repetitive manufacturing system, standart parts are being processed in small parties and to simplify the work flow, cellular layout is being preferred instead of process-oriented layout. JIT avoids the accumulation existence of stocks and recognize it as river bed. If the amount of the materials in the production is taken as water in the river, as the level of the water - that is the stocks - decreases the rocks in the bottom of the river - that is the problems - will be seen easier and it will be possible to overcome them. Therefore in the JIT System row material, work-in-process product stocks are being as much as possible. The decreasing of the stocks are also related to the decreasing of lead and total processing time. Feed-back speed increases as the same amount as the decrease in time. Manufacturing line is stopped when needed to solve the problems which came out at once and at place. The JIT approach involves a continuous commitment to the pursuit of excellence in all phases of manufacturing systems design and operation. JIT seeks to design a manufacturing system for efficient production of 100 % good units. It seeks to produce only the required items, at the required time and in the required quantities. This is probably the simplest statement of the JIT approach to manufacturing. To be more specific, JIT seeks to achieve the following goals:. Zero defects. Zero set-up time. Zero inventories. Zero handling. Zero breakdowns IX. Zero lead time. Lot size of one There are two aspects of the set of goals listed above which are worth nothing: (1) In the minds of many manufacturing or industrial engineers trained in the Western approach to manufacturing systems design and operation, these goals seem very ambitious, if not unattainable. (2) The attempt to consider all of these goals simultaneously is unusual in the context of the traditional approach to manufacturing systems. The traditional approach to manufacturing has been reductionist, which involves consideration of well defined aspects of the overall manufacturing problem - in fact, separate sub-problems - which are tackled and solved a separate problems. This approach has lead to the proliferation of specialists in the various manufacturing functions, with a resulting absence of any generalist to consider the whole of the manufacturing system. The JIT approach can clearly be characterized as holistic, at least in terms of the range of goals it sets for itself. In order to achieve the goals mentioned above, it is necessary to apply the elements of JIT below:. Total Quality. People Involment. Elimination of Waste The other elements of JIT are:. Kanban system. Grup technology. Reducing set-up time. Total Productive Maintenance In this study, a serial line consisting of three stations has been simulated as a push system and a pull system (JIT system). SIMAN simulation language has been chosen to simulate the models. Simulation anlysis is a natural and logical extension to the analytical and mathematical models inherent in operations research. Formulating decision models not only closely approximate the real-world environment but also produce answers through standard numerical and/or mathematical manipulations of the resulting equations. It is evident that there are many situations that cannot be represented mathematically because of the stohastic nature of the problem, the complexity of problem formulation, or the interactions needed to adequately describe the problem under study. For many stiuations defyning mathematical formulation, simulation is the only tool that might be used to obtain relevant answers.The definition of simulation is below: Simulation is a numerical technique for conducting experiments on a digital computer, which invelves logical and mathematical relationships that interact to describe to the behavior and structure of a complex real-world system over extended periods of time. SIMAN simulation language has been used in this study. SIMAN is a powerful, general-purpose simulation language for modeling discrete, continuous, and/or combined systems. Discrete-change systems can be modeled by using either a process-interaction or event-scheduling orientation. Continuous-change systems are modeled with algebraic, difference, or differential equations. A combination of these orientations can be used to model combined discrete-continuous models. SIMAN is designed around a logical modeling framework in which the simulation problem is segmented into a "model" component and an "experiment" component. This framework is based on_ the theoritical concepts about systems developed by Zeigler (1976). The model describes the physical elements of the system (machines, workers, storage points, transporters, information, parts flow, etc.) and their logical interrelationships. The experiment specifies the experimental conditions under which the model is to run, including elements such as initial conditions, resource availability, type of statistics gathered, and length of run. The experiment frame also includes the analyst's specifications for such things as the schedules for resource availability, the routing of entities, etc. Because experimental conditions are specified external to the model description, they are easily changed without modifying the basic model definition. Once a model and experiment have been defined, they are linked and executed by SIMAN to generate the simulated response of the system. As the simulation executed, SIMAN automatically saves the responses specified in the experiment. The SIMAN Output Processor can then be used to generate plots, tables, bar cards, histograms, and confidence intervals from the saved data. The data can also be displayed by using commercially available mainframe, minicomputer, or microcomputer presentation-quality graphics packages. The following list describes some of the features of SIMAN.. A set of special-purpose constructs to simplify and enhance the modeling of manufacturing systems.. Compatibility of mainframe, minicomputer, and microcomputer versions to permit movement between computer systems without modification.. Interactive graphics capability for building models, defining experiments, and displaying model outputs.. An interactive debugger for interactive monitoring and control of simulation execution. XI. The Cinema system, which generates a real-time, high resolution, color graphics animation of the modeled system.. A modular structure that encourages integration with other analysis technologies (Suri and Tomsicek 1988) and intelligent interfaces (Brazier and Shannon 1987, Murray and Sheppard 1987, Ford and Schroer 1987). The actual production system and the new JIT production system have been simulated by SJMAN. The following results have been gained. To compare the actual production system with JIT production system four difFerente performance criterias have been determined. These are the flow time, the number of parts which leave the system, queue length and machine utilization. When SIMAN results have been evoluated, it has appeared that the values of JIT production system are better then the actual production system. xn