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1. Introduction
The Lean manufacturing system is often referred to as a systematic methodology that aims at consistent elimination of wastes (Muda) that prevails within a manufacturing environment (Liker, 1997; Wan and Chen, 2008; Tortorella et al., 2017). It also eliminates the wastes that occur because of overburden (Muri) and unevenness in workloads (Mura) (Womack and Jones, 2010). Lean wastes are often classified into seven categories, namely, defects, over-processing, waiting, transportation, inventory, overproduction and motion (Pavnaskar et al., 2003; Abdulmalek and Rajgopal, 2007; Stone, 2012). Underutilization of human talent and environmental wastes are considered as the eighth and ninth lean wastes, respectively (Kuriger and Chen, 2010; Vinodh et al., 2011; Ruben et al., 2017). Six Sigma is a disciplined and data-driven methodology which focuses on reducing defects and variability of any process output (Harry, 1998; Antony and Banuelas, 2002). It also aims at improving the quality level of the process by using a set of statistical and empirical tools and techniques (Linderman et al., 2003; Thawani, 2004; Reosekar and Pohekar, 2014). Processes that operate with “Six Sigma quality” in the short term are assumed to develop long-term defect levels below 3.4 defects per million opportunities (Henderson and Evans, 2000; Salah et al., 2010; Grima et al., 2014).
The benefits of Lean and Six Sigma methodologies are combined to derive an integrated strategy named Lean Six Sigma (LSS) to increase process performance and enhance customer satisfaction (Shah et al., 2008; Vinodh et al., 2011; Laureani and Antony, 2015). LSS is a systematic approach that improves performance of a system which is measured based on quality, cost, delivery and customer satisfaction (Arnheiter and Maleyeff, 2005; Hu et al., 2008; Pepper and Spedding, 2010). Triple bottom line (TBL) approach focuses on providing greater business value by creating balance between the components of environment, economy and society which are called as the sustainability components (Elkington, 1994). By aligning LSS principles with the TBL approach, a combined benefit of defect reduction with removal of variation is experienced (Muralidharan, 2015). This also helps in minimizing the overall resource consumption that comprises raw materials, energy and scrap. Environmental considerations are commonly referred to as the activities or operations that focuses on environmental compliance,...