Çelik profil üretimi yapan bir firmada yalın dönüşüm ve jidoka uygulamaları
Lean transformation and jidoka implemantation in a steel profile production company
Yazar: UĞUR AKYÜZ
Danışman: DR. ÖĞR. ÜYESİ MEHMET RIZA ADALI
Sakarya Üniversitesi / Fen Bilimleri Enstitüsü / Endüstri Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Endüstri ve Endüstri Mühendisliği = Industrial and Industrial Engineering

Özet:
Maliyetlerin artması halihazırda zorlu olan rekabet koşullarında işletmeleri daha da dezavantajlı hale gelmesine neden olmaktadır. İşletmeler, zorlu rekabet ortamında ayakta kalabilmek, fiyat avantajlarını ve kar marjlarını koruyabilmek için geleneksel üretim modellerinden ayrılmak, kısıtlı olan kaynakları en verimli şekilde kullanmak ve satış fiyatını artırmak yerine maliyetleri düşürmek işletmelerin öncelikli hedefi olmak zorundadır.
Değeri, müşteriye doğru zamanda, talep edilen miktarda, istenen kalitede ve en az maliyette ulaştırma isteği üretim sektöründe köklü bir değişime sebep olmuştur. Bu değişimin merkezinde de üretim süreçlerindeki israfları ortadan kaldırmayı amaçlayan bir yaklaşım olan Yalın Üretim yer almaktadır. Yalın üretim felsefesinin temel amacı süreçlerdeki israfların ortadan kaldırılması / en aza indirilmesidir. Süreçlerdeki 8 büyük israftan bir tanesi olan "Hatalı Üretim" israfı birçok şirketin karşılaştığı sorunlardan bir tanesidir. Çoğu firma yüksek fire veya hurda oranları ile üretimlerini devam ettirmektedir. İşletmeler farklı çözümler uygulayarak bu kayıpların ortadan kaldırılmasını / en aza indirilmesi amaçlamaktadır. Yalın üretim ve Toyota Üretim Sisteminin temel yapı taşlarından biri olan Jidoka, hatalı üretim israfının ortadan kaldırılması/en aza indirilmesi için kullanılabilecek en iyi tekniklerden bir tanesidir. Jidoka, makinelerde veya proseslerde meydana gelebilecek arıza, kalitesizlik vb. hataları tespit eden, süreci durdurarak hatanın sonraki süreçlere aktarılmasını engelleyen otomasyon sistemleridir. Jidoka, sadece tezgahlarla sınırlı olmayıp emek yoğun proseslerde de kullanılabilir. Bununla birlikte son yıllarda yazılım mimarilerinde de kullanılmaya başlanmıştır.
Bu çalışmada, çelik profil üretim sektöründe faaliyet gösteren işletmede, OEE sistemi kurulmuş ve ham madde, işgücü ve ekipman kapasitelerinin verimli kullanılabilmesi için Jidoka yöntemi uygulanmıştır. Mevcut durum analizinde 2022 yılına ait OEE ve duruş verileri kullanılmıştır. Bu veriler ışığında ilk olarak odak fabrika seçilmiştir. Seçim kararında hem duruş süreleri hem de yönetim tarafından alınan yatırım kararları etkili olmuştur. Fabrika seçiminden sonra uygulama yapılacak kayıp noktası belirlenmiş ve devreye alınmıştır. Çalışma sonucunda ilgili kayıp süresi 12,5% azalmıştır. Hurda miktarında da 19,5% iyileştirme sağlanmıştır.
Çalışmada elde edilen kazanımlar, yalın dönüşüm ile dijital dönüşüm entegrasyonunun işletmelere getireceği faydaları göstermiştir. Ayrıca Jidoka tekniğinin sadece kalite kayıplarına değil aynı zamanda kapasite kayıplarına da önlem olabileceği ortaya çıkmıştır. Elde edilen kazanımlar sonucunda uygulamanın firmanın diğer fabrikalarına da yaygınlaştırılmasına karar verilmiştir.

Abstract:
The increasing costs aggravate the already challenging competitive conditions, putting businesses at a further disadvantage. In order to survive in the tough competitive environment and maintain price advantages and profit margins, companies must prioritize departing from traditional production models, using limited resources most efficiently, and reducing costs rather than increasing selling prices.
The desire to deliver value to customers with timely, in the requested quantity, in customer-defined quality and at minimal cost has led to a profound transformation in the manufacturing sector. Lean production takes a place at the center of this change which aimed at eliminating wastes in production processes. The primary goal of the lean production philosophy is to eliminate or minimize waste in its processes. One of the 8 major wastes in processes is "Defective Production / Scrap" a problem encountered by many companies. Most companies continue their production with high scrap or defect rates. Companies aim to eliminate or minimize these losses by implementing various solutions. Jidoka, one of the fundamental pillar of Lean Production and the Toyota Production System, is One of the most effective techniques that can be employed to eliminate or minimize defective production waste. Jidoka is an automation system that detects faults, defects, etc., in machines or processes, stops the process, and prevents the error from being transferred to subsequent processes. Jidoka can be used not only with machines but also in labor-intensive processes. Moreover, it has begun to be implemented in software architectures recently.
In this study, an Overall Equipment Effectiveness (OEE) system has been implemented in the steel profile production industry. First of all, a downtime methodology suitable for the business processes was created. As part of study, a distinction was made between planned and unplanned downtime type. Planned downtimes were identified along with the underlying reasons inherent in the nature of the production processes, along with general definitions applicable to all companies. Next step, an unplanned downtime class was created, and 5 main categories were identified as the top reasons. While determining these main categories, both top reasons applicable to all production companies and sector-specific top reason titles were created. After defining the downtime classifications, the next step was to determine the point where the downtime signal would be received and to carry out the conceptual design for the MES system to calculate availability. For performance calculation, it is necessary to determine the target cycle time for the line. Within this scope, bottleneck points and target cycle times for each product were determined by analyzing the products produced on the line. In cases where multiple product types are produced within a shift, the target cycle time is proportionally weighted based on the net production times of the products and determined as a weighted average. Due to the nature of the hot rolling process, the amount of final product exiting the line will not be equal to the raw material input to the line. The difference in quantity between input and output will be deducted from the quality calculation as production losses (engineering scrap). In addition, if the final product exiting the line is out of tolerance (scrap) or requires reprocessing, it is also designed to be deducted from the quality calculation. After all formulas were determined, the workflow of the created OEE methodology was coded and implemented in the MES system based on the conceptual design.
With the establishment of a lean office, the company has embarked on a lean transformation process. In addition to integrating lean production practices (5S, autonomous maintenance, Kaizen, OEE, etc.) into the company, losses are also analyzed, and rapid precaution are taken. Within this scope, the downtime data for three factories within the company in 2022 were analyzed. After considering the analysis results and investment decisions, a pilot factory was selected. After selecting the target factory, downtime and scrap data for the factory were analyzed in detail. Despite the highest percentage of "Changeover" downtime in the downtime data, " Remaining Material on the Line" " downtime loss was chosen as the focal point. This is because there are already existing and ongoing improvement efforts related to the "Changeover" downtime, and the "Remaining Material on the Line" downtime not only creates capacity losses but also leads to quality losses (rolling scrap).
Remaining material on the line arises from instabilities that can occur during the rolling process. Main causes include voltage fluctuations in power lines, sudden increases in machine currents, or material passing through a machine at a speed higher than the recipe values for the next machine, preventing the material from entering the next machine. To restart production that has stopped due to remaining material on the line, the remaining material on the line needs to be cleared. During these operations, production cannot take place, leading to capacity losses. Additionally, since the remaining material on the line cannot be reworked or used, it is scrapped (rolling scrap). Andon systems have been installed to quickly respond to increases in current values and these abnormalities on the line. During changeover, the product recipe is called from the control panel of the SCADA system, and the number of rolling stand to be used in the product to be produced and which rolling stand will be used are marked on the recipe. In addition, the current tolerance values for the selected machines are entered as a percentage. If the machine current values exceed the tolerance value in the recipe during production, warning signals are displayed on the screens of the control room. The operator takes necessary actions based on this warning. High machine speeds sometimes do not allow the operator to make necessary interventions, leading to both capacity and quality losses due to material sticking to the line. At this point, the Jidoka system comes into play to minimize the losses experienced.
If, after passing through the intermediate shear point and entering the finishing group machines on the rolling line, the material cannot enter the rolling mill due to any reason and accumulates, the operator at the control tower detects this anomaly both through the production simulation screen and by monitoring the line live. The operator presses the button to trigger the intermediate shear. Upon the operator's press, the intermediate shear takes the "cutting" position, thus starting to cut the material coming from behind.
This prevents further accumulation of material on the machine. Additionally, with less remaining material on the line, the time required to clear it will be reduced.
As a result of the study, the relevant downtime decreased by 12.5%. There was also a 19.5% improvement in scrap quantity. The gains achieved in the study have demonstrated the benefits of integrating lean transformation with digital transformation for companies. Furthermore, the Jidoka technique has been shown to prevent not just quality losses, but also capacity losses. As a result of the gains achieved, it has been decided to extend the implementation to the company's other factories.