Hazır giyim endüstrisi için bir yalın performans kıyaslama aracı önerisi
A lean performance comparison tool proposal for apparel industry
Yazar: BURAK COŞKUN
Danışman: DOÇ. DR. CANAN SARIÇAM
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Tekstil Mühendisliği Ana Bilim Dalı / Tekstil Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2021
Konu: Tekstil ve Tekstil Mühendisliği = Textile and Textile Engineering

Özet:
Bu çalışmada hazır giyim işletmelerinin yalın üretime geçişinde bir yol haritası sunulmuş, yalın üretime geçiş sonrasında işletme içi ve işletmeler arası yalınlık performans kıyaslamalarını kolaylaştıran bir kıyaslama aracı geliştirilmiştir.
Çalışmada öncelikle yalın üretimin temel ilkeleri aktarılmış; hazır giyim endüstrisinde yalın üretim uygulamaları ve yalınlık performans skor ölçümü üzerine literatür özeti paylaşılmıştır. 
Metot bölümünde, bulanık sayılar ile yalın performans indeksinin geliştirilmesi aktarılmıştır. Yalın performans indeksini oluşturan birincil performans skoru, bağıl performans skoru, ortalama performans skoru ve genel performans skoru kavramları anlatılmış; geliştirilen yalın performans değerlendirme aracının uygulama aşaması için seçilen bir hazır giyim üreticisinde gerçekleştirilen ölçüm ve geliştirme yöntemlerine değinilmiştir.
Genel yalınlık performans skorunun elde edilmesi için öncelikle her bir performans metriği için performans metriğinin oransal ve numerik ifadeleri işletmeden elde edilen veriler kullanılarak hesaplanmıştır. Elde edilen skorlara birincil performans skoru adı verilmiştir. Ardından her bir performans metriğinde işletmenin elde ettiği skorlar sektör standartlarına göre değerlendirilerek performans skorları güncellenmiştir. Güncellenmiş performans skorlarına bağıl performans skoru adı verilmiş, bağıl performans skorlarının eldesinde, bağıl performans değerlendirmeye izin veren bulanık sayılar temelli bir yöntem benimsenmiştir. Performans metriklerindeki bağıl performans skorlarının elde edilmesinin ardından her bir performans göstergesi için ortalama performans skorları performans göstergesinin ilişkili olduğu performans metrikleri bağıl performans skorları aritmetik ortalaması alınarak hesaplanmıştır. Ortalama performans skorlarının da aritmetik ortalaması alınarak geliştirilen yalınlık indeksine ilişkin tüm değerlendirmeleri içeren genel yalınlık performans skoru elde edilmiştir. 
Mevcut durum performans skoru belirlendikten sonra pilot olarak seçilen bir işletmede yalın üretim uygulamaları gerçekleştirilmiştir. Değer akış haritalama (DAH), spagetti diyagramları, değer analizi, iş zaman etüdü, hat dengeleme gibi yalın yöntemler kullanılarak üretim sürecindeki israflar tespit edilmiş; sektördeki iyi yapılmış yalın uygulamalar araştırılarak gelecek durum üretim hattı tasarlanmıştır.  
Tasarlanan üretim hattından hareketle gelecek durum performans metrikleri kullanılarak bağıl performans skorları, performans göstergesi bazında ortalama performans skorları ve genel yalınlık performans skoru yeniden hesaplanmıştır. İlk durum performans skoru ve iyileştirilmiş performans skoru karşılaştırılarak değerlendirmelerde bulunulmuş, geliştirilen performans skorunun etkinliği kanıtlanmıştır.

Abstract:
In today's global competitive environment, the apparel producer companies as well as the apparel retailers have to respond the frequently changing consumers' demands and maintain their positions by adapting the changes in the doing business such as providing large style variety in lower quantities due to shorter life cycles of the products. Moreover, they have to achieve all their activities in much more sustainable manner. The only way for success requires to adapt the dynamic structure of the era and to be open for new ideas. In this respect, the enterprises should optimize their own infrastructure with the well-established systems, novel techniques and advanced technologies. 
Lean production is a system that provides increases the profitability by decreasing the costs by eliminating all the factors and activities such as the redundant labour force, excessive material, high levels of stock, non-value adding transportation. In other words, the companies employing lean practices can produce at lower costs, higher quality and in more timely manner by using only the necessary resources.
Having been employed firstly in automotive industry in 1950's, the lean production and the relevant lean principles were adapted by the other industries in time. The textile and apparel industry became one of those industries. Plenty of fabric mills, trim suppliers, apparel producers and retailers modified their systems, processes and production plants according to lean methods. Nonetheless, it was understood that benefiting the lean production and practices at most required an establishment of carefully made plan, which facilitated both the implementation and assessment of performance evaluation in an efficient and effective manner. 
In this respect, the aim of this study was determined as suggesting a road map for the implementation of lean applications and proposing a comparison tool for lean performance evaluation in the apparel industry. Toward this aim, the road map was suggested to help the companies in determination of which processes should be accomplished. Moreover, a comparison tool was developed, which enabled the companies to assess their current and future position within the lean production implementation in comparison to their previous performances or the other counterparts. In this way, the needs of both the apparel companies dealing with their own performances and the apparel retailers working with many suppliers after a burdensome supplier selection and assessment procedures was tried to be satisfied. Considering these points, the comparison tool was developed in modular structure enabling to make a detailed assessment in terms of many performance indicators and relevant performance metrics generally used in apparel production. Moreover, in case that it facilitated the positioning of the companies, the performance evaluations were made in comparison to the industry standards for the attainable performance levels with the usage of fuzzy logic and fuzzy numbers. The modular structure revealed four different performance evaluation by calculating primary performance score, relative performance score, average performance score and the overall performance score. Thus, the comparison tool allowed to make one general evaluation based on overall performance scores on one hand and it allowed to go into detail in absolute and relative performance evaluation in terms of performance metrics, performance indicators on the other hand. The verification and the validation of the comparison tool was shown with an application in real case. In parallel with this, the road map planned was executed for the selected apparel retail company. The current and future position of the company evaluated with the employment of value stream mapping, spaghetti diagrams and value analysis. Moreover, line balancing technique and the other lean practices were employed to decrease the wastes in production processes was established. The findings showed that the improvement in the lean performance can be obtained with the implementation of the carefully planned road map. The initial performance and the future performance scores were calculated using the data from the real case and the lean comparison tool. In parallel with the study accomplished, the thesis was arranged as follows. 
In the introduction part of thesis, a brief information about lean production principles was introduced and the need for an instrument for lean performance evaluation was explained. It was put forward that a comprehensive tool was needed for the industry having the capabilities of determining an overall performance score and making detailed analysis in different performance levels. 
In the second part, history of mass production systems and the emergence of lean production was explained. Besides, the five principles of lean production which are value, value stream, flow, pull systems and perfection were defined and the general lean practices such as just in time, kanban, poke-yoke, jidoka, total productive maintenance, single piece flow, single minute exchange of dies, heijunka, 5S and kaizen were explained.          
In the third part, the implementation of lean production in the apparel industry with many different examples from literature were given. It was realized that mainly value stream mapping, kaizen, 5S, process analysis and line balancing techniques were mostly used in the transformation of the production into lean production. Besides, the researches about the development of lean index were reviewed, their capabilities and discrepancies were listed. It was found that similar methods and systematics were used in building of lean indices, but the selected performance metrics differed according to the industry. For this reason, it has been revealed that specific parameters must be determined to evaluate the lean performance in a particular industry. Moreover, it was observed that the performance evaluations were either made on single scores or made by using more than one performance scores. These studies emphasized the need for a modular type of lean performance comparison tool.     
In the fourth part, the methodology executed in the study and the application procedure were identified. In this way the road map was outlined. Specifically, the modular structure with the different performance scores were detailed and the usage of fuzzy numbers in obtaining relative performance scores were introduced. Moreover, the inherent techniques and practices in the lean transformation, which were employed in the application were specified. 
In the fifth part, the application of the lean transformation in a selected apparel manufacturer was accomplished and the findings were given. In parallel with this, the development of the comparison tool was explained. In this respect, the structure of the comparison tool consisting of thirty-five unit-less performance metrics under five performance indicators, which are the management of time, quality, efficiency, cost and stock levels. The validation and verification of the tool was made with the usage of the real data for the current and future position of the real manufacturer. Relative performance scores of determined metrics, average performance scores and overall lean performance score were re-calculated on the production line for the initial and future situation in order to show the effectiveness of the developed performance index. 
In the final part, the study was summarized with the suggestions for further researches. It was underlined that; the comparison tool had a widely uses for both the apparel producers and the apparel retailers. It was pointed out that the dynamic and flexible nature of the comparison tool allowed to be easily be modified by eliminating some of the current metrics or improving the tool with the additional performance metrics. Even, some suggestions of improvements were made in terms of performance metrics such as production line efficiency, inventory cost to sales ratio, total equipment efficiency, production area efficiency, profitability, number of products per employee, employee absenteeism rate, and performance indicators like human resources, customer satisfaction, visual management, planning, production area. Moreover, it was pointed out that even though the comparison tool was developed for the general use of the apparel industry, the performance indicators were stated to involve some type of weights in order to calculate the performance scores for different type of production in which either the design or the quality parameters might be much more important as in the case of the production of fast fashion products or basic type of products.