Bir tekstil firmasında kanban sisteminin uygulanması
An Application of kanban system in a textile company
- Tez No: 46520
- Danışmanlar: DOÇ.DR. SEMRA DURMUŞOĞLU
- Tez Türü: Yüksek Lisans
- Konular: Mühendislik Bilimleri, İşletme, Engineering Sciences, Business Administration
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1995
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 124
Özet
Hedef olarak küresel rekabetin artış gösterdiği günümüzde, geleneksel üretim tekniklerinde değişiklikler yapılması zorunlu haline gelmiş ve bu amaç doğrultusunda, son yıllarda pek çok teknik ortaya çıkmıştır. Bu teknikler arasında, en çok üzerinde durulan, en gözde tekniklerden birisi de, Japonların TAM ZAMANINDA ÜRETİM (TZÜ) felsefesidir. Tam Zamanında Üretim felsefesi üzerinde odaklasan bu çalışma genel olarak beş bölümden oluşmaktadır: Birinci bölüm giriş niteliğindedir. Bu bölümde, çalışmanın amacı ve neden bu konunun seçildiği ortaya konulmuştur. Türk Sanayinin durumu ve Tam Zamanında Üretim sisteminin getirebileceği faydalar kısaca özetlenmiştir. İkinci, üçüncü ve dördüncü bölümler gelişme niteliğindedir. İkinci bölümde, Tam Zamanında Üretim felsefesi tanımlanmış ve ortaya çıkışı kısaca anlatılmıştır. Yine bu bölümde, Tam Zamanında Ürerimin prensipleri, uygulama stratejileri, performans ölçümleri ve Kanban sistemi üzerinde durulmuştur. Üçüncü bölümde, konuya ilişkin yapılan literatür araştırması, endüstriyel uygulama alanları ve uygulama örneklerinden bahsedilmiştir. Dördüncü bölümde, Türk Tekstil Sanayiinin yapısı ve sorunlarından; ayrıca, Türk tekstil ürünleri dış ticareti ve AET'nin bu sektöre etkileri üzerinde durulmuştur. Beşinci bölümde, verilerin toplanıp çalışmanın yapıldığı tekstil firması tanıtılmış ve bu firmanın mevcut koşulları altında iki farklı simülasyon çalışması yapılmıştır. Mevcut sistemin modellendiği ilk simülasyon çalışmasından elde edilen veriler ışığında, mevcut sistemde oluşan darboğazları ve ara stokları elimine etmek için, Kanbanlı bir TZÜ modeli kurulmuş ve bu model üzerinde ikinci bir simülasyon çalışması yapılmıştır. Sonuç bölümünde ise, mevcut sistem koşullan altında yapılan iki farklı simülasyon çalışmasının sonuçlan birbirleriyle karşılaştırılmıştır. TZÜ sisteminin getirdiği avantaj ve dezavantajlar ortaya konulmuştur. Bu bulgular doğrultusunda, TZÜ sisteminin başarılı olabilmesi için gerekli önerilere de yer verilmiştir.
Özet (Çeviri)
SUMMARY AN APPLICATION OF KANBAN SYSTEM IN A TEXTILE COMPANY Under intensive global competitive pressure, most companies around the world have applied innovative thinking to management and begun to examine technology that can lead to improved manufacturing flexibility, product quality, and production costs. It is particularly challenging today to find ways to improve manufacturing performans because of shortened product life cycles, diverse customer needs, and rapidly advancing manufacturing technology. Among the available technology, Japanese production management has thus far received high praise. The success of Japanese industrial and manufacturing has been attribute to several factors, including government co-operation with and support for industry, Japanese management style, and the cultural and social structure of Japanese society (Huang et al. 1983). Recently, much attention has been focused on Japanese production management techniques. Especially on the disign of just-in-time (JIT) systems and related implementation issues. Several research methodologies have been used for JIT manufacturing techniques. Some researchers used an analytical approach to model JIT production (Bitran and Chang 1987, Davis and Stubitz 1987, Deleersnyder et al. 1989, Jordan 1988, Rees et al. 1987). Some used field- or empirical-based methodologies to address the behaviour impact (Brown and Mitchell 1989, Crawford et al. 1988, Finch and Cox 1986, Schonberger 1987). Others used computre simulation to study related design and adaptability problems (Huang etal. 1983). The subject of just-in time (JIT) is an approach, methodology, philosophy, concept or strategy. JIT is all these things and more. JTTs origins in Japan during the 1960s caused it to be initially considered as an approach to inventory management. Others viewed JIT as an approach to quality control. The nature of JIT, though, cannot be considered a limited inventory or quality control approach, but a multitude of approaches with applications throughout the business organization. JIT is not just for a couple JOof departments in an organization, it is for all departments in all types of organizations. The term of JIT has been traditionally referred to as a concept or approach to producing only the right items, in just amount needed, at the right time. However, it has since evolved as a philosophy of continuous improvement. Problems with which it has typically dealt are: waste elimination, quality assurance, cost reduction, meeting production quotas, meeting delivery schedules, safty, new product development, productivity improvement, and supplier management. Some innovative concepts and technologies, rooting at waste elimination, JIT automation, and trouble free, have been invented or enhanced in Japan to manage production systems. A framework for JIT production is shown as follows: Objective Ideas Techniques Waste elimination JIT- Automation-.Trouble tree - Pull systems with kanbans - Single minutexchangeof die (SMED) - Level (smoothing) production - Cellular (flow) manufacturing - Standard operations - Multi-process (skill) handling Industrial engineering Jidoka (autonomation) - Visual control - Five S movement - Total productive maintenance(TPM) - Poka-Yoke systems Quality inspection at source - Total quality control (TQC) Figure 1. Framework of JIT production system. JITs integrative nature started expanding from inventory and quality control into other areas of operations, like production scheduling. One commonly used JIT scheduling methodology is the kanban card system. As industry and academic researchers explored the ramifications of JTT in the 1970s in Japan and during the 1980s in the United States and throughout the world, it became clear that the dynamic nature of JTT is not a limited methodology, is made up in part of many methodologies. No longer just a Japanese method of inventory management, JIT is now an internationally known approach to excellence in production and operations management. xuJITs pursuit of perfection can philosophically and strategically be seen to embrace all aspects of business operations, in all countries. A simple definition for JIT is the successful completion of a product or service at each stage of production activity from vendor to customer just- in-time for its use and at a minimum cost. JIT can also be generally defined as a strategy or guiding philosophy whose goal it is to seek manufacturing excellence. JIT is based on eight key principles: 1. A produceto-order production schedule, 2. Unitary production, 3. Eliminated waste, 4. Continous product flow improvement, 5. Product quality perfection, 6. Respect people, 7. Eliminated contingencies, 8. Maintain long-term emphasis. All organizations can use these principles. They have application to both manufacturing and service organizations. They can be used to improve the production of custom products, in job shop operations as well as homogeneous products in repetitive manufacturing. In the first principle, the manufacturer in a produce-to-order system waits to produce products until the customer places the order. The goal of the system is to produced the finished goods just-in-time for consumption. In the second principle, each unit of finished product is viewed as a separate order. The goal of the JIT system is a production lot size of one. This principle allows production flexibility and reduces inventory costs. XlllIn the third principle, waste, referred to by the Japanese as muda, should be eliminated in every area of the operation. The goal is to use no more than the rninimum amount of equipment, materials and human resources necessary to achieve production objectives. In the forth principle, improving product flow is the same as improving productivity. In a JIT system the product flow goal is to eliminate bottlenecked processes and all problems that decrease the production flow. In the fifth principle, the goal in a JIT system is me habitual seeking of zero defects. Under the JTT concept called total quality control(TQC) quality is an ongoing and never-ending pursuit of perfection in the product In the sixth principle, people produce goods, systems do not People are the most important asset a company has. In a JTT operation that importance is made clear to everyone. IN a JIT system people are given greater responsibility to control work flow and greater authority to insist on product quality improvements than non-JIT operations. In the seventh principle, when management is concerned about having enough inventory to cover a surge in customer demand, they acquire contingency inventory that represents a waste if it is not used. In the eighth principle, since most of the other principles of JTT are continual, an investment in JTT should be viewed as a long term commitment. The benefits of a JIT system do not always reveal themselves in the short term. To implement the seven prior principles takes time. In the short term, some production costs may actually go up because of the learning that must take place. In this thesis, after the explanation of JIT manufacturing system and the kanban system, a simulation study concerning the applicability of JTT system in a Turkish company is developed. This thesis consists of five chapters as following; In the first chapter, it is expressed why this subject is choosen, what the goal of this study is, what sort of studies are done. Moreover, the textile industry in Turkey and the benefits which can be provided by JIT production management are explained. jrivJIT production management principles are discussed in the second chapter. The related production planning and scheduling principles include: 1. Uniform daily production scheduling, 2. Production scheduling flexibility, 3. A synchronized pull system, 4. Using automation where practical, 5. A focused factory, 6. Improved flexibility in workers, 7. Cutting production lot size and setup costs, 8. Allowing workers to determine production flow, 9. Improving communication and visual control. A uniform daily production schedule is a day-to-day schedule of production where there is little or no variation in production quantities between days. To accomplish a uniform daily production schedule requires the planning activity called load leveling. Load leveling is a production plan established to allow unitary levels of each product to have flexibility to change from month-to-month, but remain the same each day during a monthly planning period. The second specification of these principles is to seek production scheduling flexibility. Production capacity can be defined as the output capability of a work center. A production schedule is set to meet known customer demand. Seeking a synchronized pull system is the third specification. A pull system operates only in production environments where known customer orders drive the production effort. The schedule of production is pulled by the actual customer demand. Using automation where practical is very useful in a JIT production operation. Automation usually involves robots, electronic sensors and automated handling systems. As a general principle, JIT production managers automate only those jobs that automation can perform better than humans. XVThe fifth specifications is to seeking a focused factory. A focused factory is one that is dedicated to producing a limited number of different products with a limited number of production processes. A focused factory is only justified where there is a sufficient and continous demand for a single product or a product family. Furthermore, in that group technology(GT) is expressed. Improved flexibility in workers is very important in a JTT operation. Several tactics are employed in JIT operations to overcome the problems of rapid turnover and improving worker flexibility. Two of these tactics include cross- training and the use of part-time workers. Production lot size and setup costs can create some problems such as production scheduling problems. There are several tactics that can be used to reduce setup costs. One of these, the five 5's of proper arrangement(seiri), orderliness (seiton), cleanliness (seiso), cleanup (seiketsu) and discipline(shitsuke) can help reduce setup times at work centers. Another simple tactic to reduce setup time is the practice of planning and staging production activities at the work centers. Each work center along a GT cell or assembly line should be design to permit the worker to decide the flow of production. The last specification emphasizes the importance of improved communication is very necessary for JIT success. Furthermore, Kanban systems, what kind of Kanbans there are, what the differences between any kind of Kanbans are, Kanban rules, determining the Kanban numbers, an application strategy for JIT manufacturing systems and performance measurement of JIT management are discussed in the second chapter, too. In the third chapter, some literature searches, related with JIT, simulation and textile, are given. In addition to this, performance measurements in simulation studies and industrial areas applied for JIT are discussed with examples. In the forth chapter, the development of Turkish Textile Industry and its situation in world trade are expressed. Under that headline, the structure and problems of Turkish Textile Industry, its situation in world trade and the impact of EEC (European Economic Community) on the Turkish Textile Industry are discussed in this chapter. In the fifth and last chapter, simulation studies, which have done in a textile company for the applicability of JIT system, are given. The assumptions, parameters and variables that belong to models are discussed and simulation results are compared each other. XVIOne of the most important steps in simulation studies is to interpret and implement the results. Ar pointed out previously, because each study used a different model with different assumptions, experimental factors, and measures of performance, it is very difficult to compare and verify individual results. Some major conclusions that are consistent across previous studies are summarized as below:. Several environmental (process) factors, such as setup time, lot size, and variability in processing time and demand rate, have been found to be crucial to the success of JIT implementations (Huang et al. 1983, Kimura and Terada 1981, Krajewski et al. 1987). This suggest that these factors should be paid special attention when one designs and implement a JIT system.. Some studies (Changchit and Kung 1988, Huang et al. 1983, Lu et al. 1989) have found that simply increasing the number of kanbans (inventory level) cannot resolve bottleneck problems. A bottleneck must be dealed with by reducing the bottleneck itself; that is, special effort should be put into reducing the processing time (including set up and operating time) at the bottleneck station. To approaches have been applied in the past: one is to increase the transferability of skilled workers; the other is to use automated machinery at the bottleneck station.. It was also shown that an increase in variability of processing times leads to a decrease in production rate and increase in shortages (Gupta and Gupta 1989, Huang et al. 1983). Therefore, in order to meet the required demands, management must consider the trade-off between increasing inventories and using overtime.. Some studies (Gupta and Gupta 1989, Huang et al. 1983, Lu et al. 1989, Schroer et al. 1984, 1985) have confirmed that higher production rate can only be realized when the amount of buffers (number of kanbans) is optimal. Therefore, merely increasing the number of buffers may not increase production rate.. Several studies (Huang et al. 1983, Kimura and Terada 1981, Villeda et al. 1988) have also shown that pull systems with a certain degree of variability in the final assembly stage will transmit amplify the effect of variability to the entire system. Because the final assembly stage is the key to trigger the whole pull system, it is imperative that one attempts to reduce the variability at this stage. It was also shown by Schroer et al.(1984, 1985) that there is no major difference in utilization between systems with one kanban card or two xviikanban cards if the time between parts arrival is the same. This result rules out the concern over which type of kanban should be used.. It is also interesting that if processing time was increased due to machine breakdown, the use of buffers will increase the line efficiency of a pull- type system (Gupta and Gupta 1989, Krajewski et al. 1987, Sarker and Fitzimmons 1989). The buffering strategy, however, is in conflict with JIT philisophy, which tries to reduce inventory.. Several studies (Changchit and Kung 1988, Gupta and Gupta 1989, Huang et al. 1983, Krajewski et al. 1987, Sarker and Harris 1988) Have also shown that balanced and smoothed operations at each stage are essential for successful JIT implementation. In addition, if the variation in processing time is significant, the output rates with unbalanced stations are always superior to those with perfectly balanced design (Villeda et al. 1988).. Finally it was shown by Sarker and Fitzimmons (1989) that high variation in processing times at individual stations will lower the production rate of a pull- type system much faster man a push-type system. Therefore, although a pull-type system will always have a small WIP, it is less efficient than a push-type system, especially if the variability of processing time is high. In summary, computer simulation is recognized as an excellent facility for studying JIT practice. With a reasonable amount of time and investment, a computer simulation can be used to compare alternative manufacturing settins under a JIT production philosophy; to study the impact of internal and external factors on JIT implementations; and to compare the performance of a JIT approach with other planning and control techniques. However, these types of study should be undertaken with care; in particular, researchers should pay more attention to such issues as model verification, experimental design, and statistical output analysis and interpretation, otherwise results from the study may be suspect and hard to explain. xvm
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