Simulasyon yardımıyla imalat sistemlerinin grup teknoloji esaslı yeniden yapılandırılması
Başlık çevirisi mevcut değil.
- Tez No: 46298
- Danışmanlar: DOÇ.DR. BÜLENT DURMUŞOĞLU
- Tez Türü: Yüksek Lisans
- Konular: Endüstri ve Endüstri Mühendisliği, Industrial and Industrial Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1995
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 72
Özet
ÖZET Son yıllarda imalat alanında gözlenen küreselleşme eğilimleri üretim işletmelerini derinden etkilemektedir. Bu süreç sonuçta küresel pazarların oluşmasına, dünya ölçeğinde bir rekabet ortamının doğmasına ve daha verimli ve hızlı üretim stratejilerinin geliştirilmesine yol açmıştır. Üçüncü endüstri devrimi olarak da adlandırılan bu geçiş dönemi üretim işletmelerine sunduğu birçok fırsatın yanında beraberinde bir çok zorlamaları da getirmektedir. Günümüz ortamı imalat işletmelerinin israf azaltıcı ve müşteri için değer oluşturan yeni işletim politika ve uygulamalarına yönelmesini zorunlu kılmaktadır. Yeni koşullara uyum sağlamak için gösterilen tüm çabalara genel bir kategori olarak“Dünya Ölçeğinde Üretim”ismi verilmektedir. Bu kavramın temel dayanaklarından biri de“Hücresel Üretim”dir. Hücresel imalat sistemleri, sistem içindeki benzer imalat karakteristiklerine sahip belirli bir parçalar grubunun (parça ailesi) baştan sona imalatına yönelik işlem, insan ve özellikle de tezgah gruplarının var olduğu veya oluşturulduğu sistemlerdir. Geleneksel olarak yapılandırılmış atelye tipi imalatın günümüz ihtiyaçlarını karşılayamaması hücresel üretime yönelen ilgiyi her geçen gün artırmaktadır. Bu tezde hücresel üretime geçişte, bir gerçek-yaşam problemine ait verilerden hareketle simulasyon önerilecektir. Çalışmada geleneksel imalat sistemlerinin grup teknolojisi esaslı olarak sürekli akış tipinde nasıl yeniden yapılandırılacakları üzerinde durulmuş, gerçek bir imalat sistemine ait verilerden yola çıkılarak oluşturulan bir hücrenin davranışları çeşitli koşullar da simulasyon yardımıyla modellenmiş ve değerlendirilmiştir. Daha önce atelye tipi olarak üretim yapan işletme bir grup teknolojisi çalışması ile parça ailelerini ve üretim hücrelerini belirlemiş bulunmaktadır. Hücresel üretim fiziki anlamda hayata geçirilmeden önce yeni sistemin performansının bilgisayar ortamında benzetiminin yapılması gerekmektedir. Seçilen çeşitli performans ölçütleri bazında eski ve önerilen sistemin verileri karşılaştınlmıştır. Bu amaçla PROMODEL simulasyon dilinden yararlanılmıştır, îş akış zamanı, tezgah kullanım oranlan, sipariş tamamlanma oranlan gibi performans ölçütleri üzerinde çeşitli değerlendirmeler yapılmış ve hücresel üretim sayesinde bu ölçütlerin iyileştirilebileceği gözlemlenmiştir. vıı
Özet (Çeviri)
SUMMARY GROUP TECHNOLOGY BASED RECONFIGURATION OF THE MANUFACTURING SYSTEMS THROUGH SIMULATION Facing the challenges of world-wide competition in manufacturing now requires operating policies, practices and systems that eliminate waste and create value for the customer. The market is now demanding that manufacturers provide high-quality products at substantially lower prices. Energy, materials labor costs and many other factors continue to increase pressures for the manufacturer. Competitiveness and profitability can only be maintained if manufacturers cut costs by becoming better at what they do and how they do it. This involves redesigning, remanufacturing, repackaging, and repricing to provide low-cost quality products and services, and yet, making profit. This movement today is called“World-Class Manufacturing”. The challenge brought about by this term is to be a mean, lean and competitive manufacturer. One of the basic components of world-class manufacturing is the standardization and simplification of design and manufacturing along with other components, total maintenance and total quality management. The systematic implementation of systems and procedures that standardize and simplify manufacturing operations is achieved through Group Technology (GT), a philosophy that exploits the underlying sameness that exists in the design and manufacture of high varieties of discrete parts. Reducing complexity in manufacturing is not only a desirable goal, but it is also a catalyst for achieving many other objectives that are related to adding value to the product by reducing waste and improving quality. Group Technology concepts and procedures provide a means for standardizing the parts that are designed and the methods of manufacture used to make these parts. Group Technology provides the basis to group thousands of part numbers into part families where each family contains similar parts that are processed along the same flow or routing of operations. Likewise, dissimilar machines can be grouped together into a unique production unit or workcell to produce each family of parts. Although each work cell produces many different part numbers, all parts are in the same part family and are processed in a repetitive manner. This standardized processing, possible through the grouping of similar parts, provides for simplified control and allows the workcell to be operated like a mini-production or flow line. Through standardization and simplification, group technologies provide the basis for cellular manufacturing and setup reduction. vimConversion of a factory from functional to cellular configuration is a major undertaking requiring the involvement and dedicated commitment of both management and shop floor personnel. Therefore, it is particularly important that everyone knows and believes in the advantages of cellular manufacturing and also understands how and why these advantages are possible. The following presents the major advantages of cellular manufacturing and the rational. 1. A high level reduction n production lead times and work-in-process inventories is possible. These reductions result primarily from changing from lot (batch) mode of processing to a continuous-flow mode of processing. Such reductions, however, are only possible with flow-line workcells that have reasonable balance and reliable system components. 2. A reduction in material handling is commonly achieved along with the reduction in the amount of factory floor space required to produce the same amount of products. Since material handling adds nothing to the product except cost, this reduction is an effective elimination of waste. Furthermore, by reducing both the amount of handling and the levels of in-process inventories, considerable floor space is gained for productive activities. 3. Considerable advantages related to direct labor are also achieved with workcells. By implementing cross-training programs, operators can learn to attend and run more than one machine at a time. Not only does this increase worker productivity but it also provides management with the flexibility to run the cell at different capacity levels by simply adjusting the number of operators and assignments in the cell. 4. The standardization that results from focusing on part families also helps decrease machine setup times. While part of this reduction is attributable to standardized tooling and fixturing, a significant reduction is also due to the improved organization and planning that comes from having a better understanding and focus of what is being manufactured. 5. Quality-related problems are expected to decrease in workcell environments. These reductions are attainable primarily from increased machine operator involvement in problem prevention. The combination of clustered operations, continuous material flow, and statistical tools provide both an awareness and a means to respond quickly to quality problems. Increased worker involvement in the quality of parts produced in the cells are also allows the supervisor to assume more of a role as coach controlling to ensure that production goals are met. 6. Cellular manufacturing simplifies shop-floor controls and decreases paperwork. 7. An indirect benefit that often results from the process of planning and implementing cellular manufacturing is better communication between product design and manufacturing engineering. This often occurs from the need to redesign or modify some parts in order to achieve the product ixconsistency necessary to produce all parts in the family in a flow-line workcell. The reorganization of manufacturing facilities from a functional (job-shop) layout to a cellular configuration is a major competitive strategy for manufacturing companies. Cellular manufacturing establishes concentrated miniprocessing and responsibility units which provide“point-of-manufacturing control, thus supporting the objectives of both just-in-time (JIT) manufacturing and Total Quality Management (TQM). Primary to cellular manufacturing is to identify or form suitable workcells. The cell formation problem can be stated quite simply. Given a set of parts (with known routings, batch sizes, machine setup and processing times, and estimated annual demands) and a set of machines, group the parts into ”families“ and organize the machines into ”machine groups", so that the families can be assigned to machine groups to form cells in a way that satisfies the constraints of the problem and minimizes the cost of the production. The process of cell formation identifies and exploits the linkages that exists among parts and machines. However, simply grouping machines into workcells on the shop floor does not guarantee that the advantages associated with cellular manufacturing will be achieved. Improperly designed workcells will not yield continuos flow processing and even greater losses in productivity than with the functional layout can result. In order to achieve effective an efficient manufacturing workcell five categories of design decisions must be considered. These five decision areas are : 1. Cell layout and capacity measures 2. Operator levels and assignments 3. Buffer levels and transfer batch sizes 4. System operating parameters 5. Just-in-time variables and effects After the machines and parts have been assigned to a workcell (through cell formation), the next issues to address are cell layout configuration and workstation capacities. Both of these issues concern the amount of machine capacity needed to provide some measure of workload balance between workstations and the specific configuration to use in placing the workstations on the shop floor. Together, cell layout and machine capacity provide the bridge between cell formation and cell design. In order to make decisions regarding the five areas above, simulation tools are widely used. These tools enable manufacturing systems behaviour to be analyzed under diverse conditions and can be used to predict the impact of variables such as demand, routing, setup times, and lot sizes on system performance. The analysis of the effects of these variables is critical to the success of design decisions. Simulation predicts the behaviour of complex systems by calculating the movement and interactions of system components. By evaluating the flow of parts through machines and workstations and by examining the conflicting demands for limited resources, we can evaluate physical layouts, equipment selections and operating procedures. Simulation gives us the ability to experiment on the model rather than thereal -world system, thereby allowing us to examine contemplated changes or new designs before actual purchase or installation. In simulating modem manufacturing systems, we are concerned with systems in which performance is principally affected by competition for resources (machines, workers, material handling devices, etc.). One faces several basic problems when trying to model these systems: determining the resources ( and their characteristics) that most affect performance, formulating a model or description representing these relationships, and determining the values of the performance measures of interest under given scenarios. When simulation is used as a design tool, the study is typically motivated by questions such as these: 1. What will be the throughput of this design? Will it meet the production goals? 2. Where are the bottlenecks? What can we change to increase throughput? 3. Which is the best among design alternatives? How does the system performance change as a function of the number and type of machines, number of workers, types of automation, in-process storage, etc.? (the typical criteria are throughput and cost, with additional concerns about delivery schedules, work-in-process, and resource utilization. Recent developments in simulation languages have enabled the modelling of large and complex systems. However, modelling is not an easy task since those languages are not designed for problem-specific purposes. Thus,, experimenting with simulation analysis can well be time consuming. The scope and objective of this thesis is to survey some of the design related topics in cellular manufacturing and group technology, and to develop suggestions for a real-world problem. The rest of this thesis is organized as follows: In the first chapter, an introduction to world-class manufacturing is presented. Chapter 2 covers the general manufacturing systems and provides comparison bed for traditional and cellular manufacturing systems. In Chapter 3, a detailed treatment of group technology and cellular manufacturing is made. Included in the chapter are the topics such as standardization and simplification processes via group technology, the role of group technology in discrete manufacturing, part families, focused shops and operations, layout considerations, advantages and disadvantages of workcells and cell formation. Simulation approach to system modelling is explained in Chapter 4. Further the role of simulation in manufacturing is discussed along with the advantages and disadvantages. X!Chapter 5 is a brief treatment of ProModel modelling approaches and commands is made. In addition, routing considerations and systems functions are described. In chapter 6, a real-world application of simulation on a pilot cell is performed. Under numerous experiments, a collection of scenarios are tested and evaluated. The performance measures interested are the manufacturing lead time, utilization rates, and job output-input rates. In the conclusions part, an argumentation on the difficulty and complexity of conversion process to the cellular manufacturing is made. In addition, a couple of suggestions are made toward future research and application. Xll
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