Tam zamanında üretim sistemleri
Just in time production systems
- Tez No: 39857
- Danışmanlar: PROF.DR. GÖNÜL YENERSOY
- Tez Türü: Yüksek Lisans
- Konular: Endüstri ve Endüstri Mühendisliği, Industrial and Industrial Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1993
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 184
Özet
ÖZET Geçtiğimiz an yıl süresince İmalat Kaynakları Planlaması, Tam Zamanında üretim -felsefesi ve Esnek îmalat gibi yöntemlerin kullanılması ile imalat planlama ve kontrolunda önemli değişimler gerçekleşmiştir. Dünya pazarlarında gittikçe yoğunlaşan rekabet ortamında, kendilerine bir pay yaratmaya veya mevcut pay oranlarını kotumaya çalışan firmalar, artık minumum maliyetle ve rekabet edebilir bir -Fiyatla üretim yapmak zorundadırlar. Bu rekabet avantajını yakalamanın tek yolu üretim ortamını, istenen kalitede ve miktarda üretim yapacak şekilde iyileştirmedir. Bu tezde incelenen JIT (Just-In-Time Production - Tam Zamanında üretim) sistemi şirketlere mükemmel derecede iyileştirme imkanları sunmaktadır. Son yıllarda dünya ekonomisine damgasını vuran Japonların dünyaya hediye ettiği bu -Felsefe, gerçek anlamda uygulandığı takdirde şirket karlılığında oldukça büyük etki yapabilmektedir. Bu tez kapsamında genelde, JIT üretim sistemini başarılı bir şekilde yerleştirmek için, gerekli ortamın yaratılması ve bu ortamın sürdürülebilmesi için uygulanması gereken adımlar tanıtılmış ve konu ayrıntısıyla incelenmiştir. ikinci bölümde, üretim sistemlerinin temel kavramları açıklanmıştır, üçüncü bölümde, son yıllarda gelişen modern üretim -Felsefeleri genelde temel nitelikleriyle tanıtılmıştır. Bu bölümde JIT sistemi çok kısa olarak açıklanmıştır. Dördüncü bölümde, Tam Zamanında üretim Sistemlerinin temel kavramları giriş niteliğinde açıklanmıştır. Bu bölümde özellikle kanban hareketleri üzerinde durulmuştur. Beşinci bölümde, Tam Zamanında üretim Sistemini yerleştirmek için üç adimi ı bir proses açıklanmıştır. Altıncı bölümde, tamir bakım politikalarının etkinliğinin JIT üzerindeki etkileri ve çeşitli tamir bakım politikalarının simülasyon yoluyla denendiği bir model ve sonuçları açıklanmıştır. Yedinci bölümde, iş tatminin JIT ortamı üzerindeki etkileri daha evvel bir firmada yapılmış anket sonuçlarıyla incelenmiştir. Bu bölümde ilginç sonuçlar elde edilmiştir. Sekizinci bölümde, kalite ile JIT arasındaki var olması gereken karşılıklı etkileşimlerden bahsedilmiştir. Dokuzuncu ve onuncu bölümlerde, JIT' in başarılı yerleştirilmesi için bazı engeller ve yanlış anlaşılmış kavramlardan söz edilmiştir. On birinci bölümde, MRP (Malzeme ihtiyaç Planlama) sistemi içine JIT' i yerleştirmek için üç adımlı bir proses tanıtılmış ve bir firmada uygulanan sonuçları gösterilmiştir. Son bölümde, kanban ve MRP II sistemleri çeşitli yönleriyle karşılaştırılmış ve avantajları ve dezavantajları açıklanmıştır. Sonuç olarak; bence JIT kendine has kurallarına göre uygulandığında bir firmayı şimdi bulunduğu yerden çok ileriye götürmeyi başaracaktır. ix
Özet (Çeviri)
SUMMARY JUST IN TIME PRODUCTION SYSTEMS Just in time (JIT) techniques are becoming ever more papular as a method -For managing industrial systems more efficiently. Many organizations are, for good reason, interested in finding out benefits of JIT before installing such systems. The oil crisis of 1773 created a severe decline in profitability for Japanese manufacturers, who sought to offset this threat with a new method for improving labor productivity without excessive capital investments. The JIT system was developed by Toyota to respond to this need. The concept of JIT manufacturing has evolved into an organizational philosophy by which“muda”(Japanese for waste) and“mura”(Japanese for unevenness) are to be eliminated in all facets of the organization. One of the basic reason for JIT receiving its wide international acclaim is due to its focus on eliminating all wastes existing in the system, whether it is waste of materials, capacity, labour or time. JIT or Toyota production system, in action is often called a kanban system. Kanban is the Japanese word for the piece of paper wrapped in a clear plastic that accompanies each bin of parts for assembly. Kanbans are only one aspects of the broader system of JIT, which can be viewed as a management philosophy focused on execution. The concept is simple : To strive for the goals of zero inventory (ZI) and total quality control (TG&Ü) by eliminating all waste of time and material. JIT is a philosophy covering all aspects of a manufacturing operation with the aim of producing only as required with perfect quality and no waste. It uses a collection of techniques and relies heavily on thoughtful and disiplined shop floor practice. The main concepts underlying JIT are : 1. System re-design and simplification, 2. Continual improvement, 3. Visibility, 4. People involvement, 5. Total quality management, 6. Standardization of operations, x7. Waste removal. The objectives are that -Finished goods are manu-Facturing just-in-time to be delivered : sub-assemblies are manu-Factured just- in-time to be assembled into -Finished goods : parts are -Fabricated just-in-time to go into sub-assemblies : materials are purchased just-in-time to be trans-formed into -finished products. Thus, -Fbrmal materials requirements planing is alsa reqired ta some extent. The assumption made in JIT are that demand is stable; thus, it is more likely to be used -For repetitîve manu-Facture. Other assumptions are that the manu-Facturing system will be re-design to create a JIT manu-Facturing enviroment : there is a -Focused plant, appropriate control system, involvement af ali necessary people : availablity of ccoperative material suppliers and long term business planing decide the market, make and define product -Families. Some o-F the JIT tecnniques are : 1.Pull method of production, 2.Statistical process control (SPC), 3.Preventive maintanence, 4.Multiskilled workers, 5.Level scheduling, 6.Set-up time reduction, 7.Revised plant layout, 8.Reduced lot sizes, 9.Supplier involvement, 10.Workplace organization, 11.Small group improvement activities, 12.Management commîtment. The main organızational implications o-F JIT are : 1.The business will be re-organised on JIT principles, 2.Product.Families and associated manufacturing/assembly çelIs will be -Formulated, 3.Departmantel barriers will be broken down, 4.A -Flatter organizational structure, 5.A cellular layout will be used, xi6.A continous improvement programme will be implemnted, 7.There will be operatör responsibility -far product quality, 8.Multi-functional working practices will result, 9.There will be multi-process responsibility, 10.There will be delegation of responsibility to the lowest level and hence decentralisation of the business, 11.There will be a wilingness for the required çultüre change, To ensure successful implementation of JIT, it is incumbent on management to understand the philosophy, characteristics and mindset of JIT and recognize that impact of change on ali organizational functions must be considered. Management must support the teams' efforts by the sharing of business information and goals, by allocating time for the team to meet to solve problems, by recognizing the accomplishments of the employee teams, and by providing resources and technical support. Today the technologies associated with JIT, many developed in Japan, have become more complex than kanbans and bins. They range from group tec±ınologies and focused factories to automation, robot i es and integrated information systems like MRP II and CAD/CAM. Key features in successful JIT implementation are : 1.Company wide and top management led planing, 2.An attidute of employee involvement, 3.Continous improvement of products, process and people, 4.Comprehensive education and training, 5.A realistle production schedule, 6.A JIT supplier champion steering committee, 7.Supplier development. After JIT is implemented successfully, JIT leads to : 1.Clear visibility of problems, sets targets and achievements, 2.A clear statement of responsibility and ownership of problems, 3.A plant configuration ta facilitate smooth continous flow, 4.Minimal set-up and change över times, 5.Standardised operations and process, 6.Batch quantities reduced to values ideally approaching öne, 7.Less than full machine utilisation, xii8.Smooth, levelled production schedule, 9.Effective production and inventory control system, 10.Preventive maintenance programmes, 11.Flexible multi-Functional working practices, 12.A prevealing attidute of total quality management, 13.The production process that have been prepared to automation by eliminating ali existing wastes before automation is introduced. There are -four basic elements of JIT. These are suppliers, quality, quantity and logistics. Suppliers must be part o-f team. There must be signi-Ficant relationship between suppliers and manu-facturer. JIT requires a trusting and sharing partnership such that vendors become part of a team and can deliver zero de-fect parts, -Frequently on time, to eliminate sa-fety stock and rein-force the JIT objectives of TED and 21. While the advantages o-f JIT have been widely discussed, some of the weakness of JIT have received less attention. These weaknesses are barriers to the succes-full JIT implementation. Japanese companies have been dealing with these barriers -for many years. Unless these barriers have been overcomed, these barriers may have led un-foreseen results. These barriers include the lack use of Theory Z, lack of total employee commitment, attempting to produce at capacity, excessive emphasis on short run and outdated cost accounting systems. These barriers are less imposing in Japan and the Japanese government helps Japanese companies overcome these barriers. in order to overcome these barriers, it is necessary to understand the scope and meaining of JIT philosophy very well. E-Ffective implementation of JIT will result in lower production costs, higher rates of productivity, better quality products and on time delivery of finished goods. Production costs are reduced thrcugh low inventory levels (ideally zero) achieved through frequent vendor deliveries directly to WIP and prompt delivery o-f finished goods, which significantly reduces holding cost of inventory. Increased productivity is reached by decreased in thrcughput times achieved by setup -flexibility, group technology, roboties, automation and in-process QC. JIT manu-facturing is a popular buzzword in world industry today. However, many misconceptions exist regarding JIT manu-facturing and few truly understand the meaning and scope of this manu-facturing philosophy. JIT refers to a collection of disciplines that manufacturers adhere to in seeking ör striving -far excellences. The basic JIT philosophy is -formed on two tenets : Continuous improvement and elimination wastes. Öne o-f the misconception is JIT commonly thought o-f as an inventory and delivery program in which small quantities of material are delivered in the correct amount of exactly when and where they are needed. Another misconception is that JIT isa purchasing ör material management project. These are öne of the benefit of working xiiiJIT system not entire JIT system. JIT manu-facturing has become an organizational philisophy which transcends -Factory -Floor applications. in a manu-facturing -Firm, eacb functional area has an important to play in the support o-f JIT thraugh the cantinual elimination o-F departmantal waste and unevenness. Even in non-manufacturing organızations, these same concepts can be applied to achieve competitive advantages. Given the breadth o-f JIT's application to industry, it is essential that the techniques comprising it be selected carefully based upon organızational characteristics. As a consequence, JIT is ideal solution -For the manu-facturer who are striving to attain perfect production system. JIT in concert with total quality control (TOC) and employee involvement (El) provides production process -flexible enough to meet daily demand with per-fect quality with minimum cost and competitive price. When JIT is implemented in accordance with its rules, JIT could reduce rework 66%, cycle time to produce a unit 90%, work-in-process 80%, unit hours %20, serap costs 60%, inventories by more than 75%, break even points by more than %30 and improve productivity o-F direct, indirect and salaried employees by more than 30% and quality 50%. Final impact to the production system of JIT, ali this with a 20% improvement total capacity, with no additional -Floor space required. I-F JIT is so wonder-Ful, Why isn't everyone doing it? The answer is basically that people do not like change.
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