Kısıtlar teorisi yaklaşımı ile darboğaz kaynak yönetimi
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Date
2001-10-23
Authors
Tezcan, Murat Özgür
Journal Title
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Publisher
Uludağ Üniversitesi
Abstract
1970'li yıllarla beraber Japonya ve diğer doğu ülkelerinden gelen rekabet baskısıyla krize giren Amerika ve Avrupa'daki işletmeler bu durumu aşmak için çeşitli arayışlara girmişlerdir. Bunlardan bazıları tam zamanında üretim ve toplam kalite yönetimi gibi Japonya kökenli yaklaşımları benimserken bazıları da özgün yöntemlere yönelmişlerdir. Dr. Eliyahu Goldratt tarafından geliştirilen Kısıtlar Teorisi' de bu yönelimin bir sonucudur. Kısıtlar Teorisi genel anlamda bir yönetim felsefesi olarak ele alınabilir. Hedefi olabilecek yüksek performansın önünde bir engel olan kısıtları bulup onları etkin hale getirerek sistem çıktısını dolayısıyla satışlar yoluyla kazanılan parayı artırmaktır. Kısıtlar teorisi üç ana daldan oluşmaktadır. Bunlar lojistik, performans yönetimi ve problem çözme/düşünme süreçleridir. Kısıtlar Teorisi'nin lojistik yaklaşımında önemli olan darboğaz kaynakların tespit edilmesi ve verilecek diğer tüm kararların darboğazı etkin kılmak amacına bağlanmasıdır. Çünkü darboğaz olmayan kaynakların darboğaz kaynağa göre yüksek bir kapasite kullanım oranı ile çalışmasının sistem çıktısına olumlu bir katkısı yoktur aksine süreç içi envanterlerin artması gibi olumsuz bir sonucu vardır. Bir imalat ortamında darboğaz makinayı etkin kullanmanın yolu önüne bir zaman tamponu koyarak onu istatistiksel dalgalanmalar ve bağımlı olayların etkisinden korumaktır. Zaman tamponu aslında darboğaz makinenin malzeme bulamamaktan dolayı aylak kalmasını engelleyen bir envanter biriktirme mekanizmasıdır. Ama Kısıtlar Teorisi lojistik yaklaşımında zaman tamponu büyüklüğünün belirlenmesi özellikle birden fazla kısıt makinanın olduğu durumlarda önemli bir sorun halini almaktadır çünkü bu büyüklük sistem performansını önemli ölçüde etkilemektedir. Bu çalışmada ilk olarak Kısıtlar Teorisi tarihsel gelişimi ve alt dallan ile birlikte ayrıntılı biçimde incelenmektedir. Ardından bir imalat ortamında tespit edilen kısıt makinalar için çeşitli yaklaşımlarla zaman tamponu büyüklükleri bulunmaktadır. Bunun ardından yaklaşımların performansları kısıt makine işlem yüzdeleri, parça çıktı miktarları ve ortalama toplam envanter miktarları kriterleri çerçevesinde istatistiki olarak karşılaştırılarak değerlendirilmekte ve sonuç olarak en uygun tampon büyüklüğü tespit edilmektedir.
By the 1970s, after the American and European companies experienced exhaustive competition coming from the far-eastern countries, they initiated several projects to overhaul their competitiveness. While some of these were about to adopt the approaches such as Just In Time (JIT) and Total Quality Management (TQM) which were originated by the Japanese, others involved inventing their own methodology to boost the competitiveness. Theory of Constraints (TOC), which was developed by Dr. Eliyahu Goldratt, is an end product of such an approach. Basically, Theory of Constraints can be considered as a management philosophy. It's goal is to find the obstacles preventing an organization from achieving its highest potential performance, then remove those obstacles and install the management measures to increase to the output of the system, which is the money coming through sales. Theory of Constraints have three foundations which are logistics, performance management and problem solving / thinking process. The logistics node of the Theory of Constraints locates the bottleneck resources and then constructs all other decisions on the efficient utilization of the bottleneck. Running the non-bottleneck resources higher than the bottlenecks does not contribute to increase the output of the system; it also results in increased work in process (WIP) inventory levels. In a manufacturing environment, the best way to efficiently utilize a bottleneck machine is to protect the throughput from the statistical fluctuations and the intervention of the dependent events is to insert a time buffer in front of it. In fact, the time buffer is a mechanism to hold inventory to protect the bottleneck machine from being idle when it cannot receive the materials to process from upstream machines. However, determination of the size of the time buffer becomes an important issue especially when multiple constraint machines exist in the manufacturing environment. Size of the inventory hold in the system as the time buffer has an important effect on the performance of the system. In this study, the Theory of Constraints and its three foundations are examined firstly. Afterwards, some competing techniques to determine the size of the time buffers are introduced and their performance is compared statistically in terms of the criteria, such as the percentage use of the constraint machines, the number of the parts that are produced in a standard period and the average total inventory. In light of these comparisons, a proper buffer size is proposed.
By the 1970s, after the American and European companies experienced exhaustive competition coming from the far-eastern countries, they initiated several projects to overhaul their competitiveness. While some of these were about to adopt the approaches such as Just In Time (JIT) and Total Quality Management (TQM) which were originated by the Japanese, others involved inventing their own methodology to boost the competitiveness. Theory of Constraints (TOC), which was developed by Dr. Eliyahu Goldratt, is an end product of such an approach. Basically, Theory of Constraints can be considered as a management philosophy. It's goal is to find the obstacles preventing an organization from achieving its highest potential performance, then remove those obstacles and install the management measures to increase to the output of the system, which is the money coming through sales. Theory of Constraints have three foundations which are logistics, performance management and problem solving / thinking process. The logistics node of the Theory of Constraints locates the bottleneck resources and then constructs all other decisions on the efficient utilization of the bottleneck. Running the non-bottleneck resources higher than the bottlenecks does not contribute to increase the output of the system; it also results in increased work in process (WIP) inventory levels. In a manufacturing environment, the best way to efficiently utilize a bottleneck machine is to protect the throughput from the statistical fluctuations and the intervention of the dependent events is to insert a time buffer in front of it. In fact, the time buffer is a mechanism to hold inventory to protect the bottleneck machine from being idle when it cannot receive the materials to process from upstream machines. However, determination of the size of the time buffer becomes an important issue especially when multiple constraint machines exist in the manufacturing environment. Size of the inventory hold in the system as the time buffer has an important effect on the performance of the system. In this study, the Theory of Constraints and its three foundations are examined firstly. Afterwards, some competing techniques to determine the size of the time buffers are introduced and their performance is compared statistically in terms of the criteria, such as the percentage use of the constraint machines, the number of the parts that are produced in a standard period and the average total inventory. In light of these comparisons, a proper buffer size is proposed.
Description
Keywords
Kısıtlar teorisi, Darboğaz kaynak yönetimi, Zaman tamponu, Theory of constraints, Management of bottleneck resources, Time buffer
Citation
Tezcan, M. Ö. (2001). Kısıtlar teorisi yaklaşımı ile darboğaz kaynak yönetimi. Yayınlanmamış yüksek lisans tezi. Uludağ Üniversitesi Fen Bilimleri Enstitüsü.