RESEARCH ARTICLE Istanbul Business Research Istanbul Business Research, 51(1), 123-147 DOI: 10.26650/ibr.2022.51.938481 htp://ibr.istanbul.edu.tr/ htp://dergipark.org.tr/ibr Submited: 17.05.2021 Revision Requested: 26.09.2021 Last Revision Received: 29.09.2021 Accepted: 08.10.2021 Published Online: 18.01.2022 Integratng the Theory of Constraints and Six Sigma: Process Improvement Implementaton Erhan Ekleş 1 , Mevhibe Ay Türkmen 2 Abstract Businesses apply many management philosophies aiming to manage processes efectvely, eliminate botlenecks and improve their process performance. The most important of these philosophies are the Theory of Constraints and the Six Sigma. These are used separately in process improvement and performance enhancement in many businesses. Recently, an integraton model approach of two philosophies has been examined in the literature in an efort to reduce their weaknesses and increase their strong efects. In the literature, three diferent approaches are identfed for the integraton model of Theory of Constraints and Six Sigma. In this study, the integraton model of Jin, Abdul-Razzak, Elkassabgi, Zhou, & Herrera, (2009) was applied in an industrial enterprise in order to identfy and eliminate the root causes of the decline in sales fgures. It has been revealed that the integraton model can help to identfy and eliminate these root causes and how it benefts the business. As a result of the applicaton, an improvement in producton cost by 1.56% and 3.55% and an increase in σ value from 1.4 to 2.3 were determined. With this model, constraints in the producton process were determined, managed and eliminated. Keywords Theory of Constraints, Six Sigma, Integraton Model, Power Cable Producton 1 Corresponding Author: Erhan Ekleş (Master), Pamukkale University, Insttute of Social Sciences, Producton Management and Marketng MSc Program, Denizli, Turkiye. E-mail: eekles18@posta.pau.edu.tr ORCID: 0000-0002-3853-6981 2 Mevhibe Ay Türkmen (Assoc. Prof. Dr.), Pamukkale University, Faculty of Economics and Administratve Sciences, Department of Business Administraton, Denizli, Turkiye. E-mail: mturkmen@pau.edu.tr ORCID: 0000-0003-2365-6726 To cite this artcle: Ekles, E., & Ay Turkmen, M. (2022). Integratng the Theory of Constraints and Six Sigma: Process Improvement Implementaton? Istanbul Business Research, 51(1), 123-147. htp://doi.org/10.26650/ibr.2022.51.938481 This work is licensed under Creatve Commons Atributon-NonCommercial 4.0 Internatonal License Introduction On the basis of protecting their assets and to ensure continuity, companies should manage their processes efectively, eliminate bottlenecks and improve their process performance. In order to perform those actions, they apply many management philosophies. One of them is the Theory of Constraints (TOC), which Goldratt mentioned in his book “Goal” written in 1984, and another is the Six Sigma (6σ) philosophy developed by Motorola in the 1980s. The popularity of these concepts continues in today’s business world and literature. The purpose of the TOC is to increase the capacity of the whole system with the purpose of reaching businesses’ goals and targets now and in the future. It has been seen that studies