Introduction

The challenge of manufacturing management to introduce innovations in the manufacture of products entails not only the design and implementation of new methods but also organizational changes and the involvement of human resources (Thürer, Godinho Filho, Stevenson, & Fredendall, 2015). A key to innovation is the application of methodologies aimed at improving manufacturing, as well as processes such as lean manufacturing focusses on reduction of lead time and six sigma a well-established approach that looking for eliminate defects, which complement each other as Lean Six Sigma (LSS) (Godinho Filho & Utiyama, 2016). The combination of LSS is beneficial because it compensates for limitations in their components (Shokri, Shirley, & Nabhani, 2016). In addition, it is important for practitioners to be aware of LSS implementation processes, in view of limitations and impeding characteristics such as motivation (Albliwi, Antony, & Lim, 2015; Freitas & Costa, 2017).

The present study was motivated by the industry’s need for a framework that enables an organization to select project portfolios aligned with the manufacturing company’s strategic planning, and after implementation, monitor them for one year via financial indicators. Thus, the quest for competitiveness addressed by the study can be expressed in the following research question: Can Lean Six Sigma be proposed in a new way to achieve greater competitiveness? To answer this question, a new LSS framework and a case study was undertaken to develop a proposed guide that combines lean manufacturing (LM) and six sigma (SS). This combination, LM and SS, also highlights the lack of an LSS framework in the literature, which establishes application of a functional structure that simultaneously manages: the manufacturing and engineering area in the implementation of continuous improvement programs through lessons learned; elaborates risk and attractiveness analyses when selecting projects; uses process mapping combining with plan-do-check-act. The framework proposed in this paper aims at filling this gap.

Material and methods

Research methodology in this study can be divided into four stages (Table 1).

Basic theoretical aspects of literature

Lean manufacturing (LM) gained prominence in the 1980s as the result of a research project by the Massachusetts Institute of Technology, which studied practices adopted by leading companies in the automotive supply industry and found that the following LM practices significantly contributed to increased competitiveness (Bhamu & Sangwan, 2014). The Lean principles are (Womack & Jones, 2003; Snee, 2010): (i) identify value; (ii) measure the value; (iii) pull on customer demand; (iv) create value; (v) achieve perfection. For identify and measure the value, LM uses value stream mapping (VSM) to depict the entire process on a single page. VSM enables visualization of the transmission of information from the client to the plant and the flow of material in the process and thus facilitates to add value, and the discovery and eliminate of waste (Table 2).

By eliminating waste, the LM method has been found to reduce costs and the time between client request and delivery through identified via VSM. Tools have been described to reduce or eliminate waste (Table 3).

Six sigma (SS) initiated in the 1980s to increase manufacturing quality in the industry from 3σ to 6σ (zero defects), using statistical tools and process mapping. By understanding customer needs, the vision process, and project implementation, the SS method seeks to improve processes, reducing variation/s that generate defects, through a sequence Deming’s plan-do-check-act called Dmaic (Define, Measure, Analyze, Improve, Control) (Albliwi et al., 2015). Development management is receiving increasing attention in the manufacturing sector, from reactive design to predictive design quality. In this context, General Electric developed Dmadv (Define, Measure, Analyze, Design, Verify) cycle an extension of SS called design for six sigma (DFSS) for the development of new projects, wich reduces the number of design changes (projects that don’t break in the beginning) (Watson & Deyong, 2010).

Lean Six Sigma was defined: ‘a business strategy and methodology that increases process performance resulting in enhanced customer satisfaction and improved bottom line results’ (Snee, 2010). Lean manufacturing (LM) lacks a structured means to eliminate production variability, while six sigma (SS) does not focus on production time (Albliwi et al., 2015). Combining the best qualities of each method compensates for such shortcomings as follows. Accordingly, some enterprises that had adopted LM or SS-driven methodologies have elected to use both (Snee, 2010). Other adopters of LM or SS have sought to enhance their methodologies by incorporating elements of the other (Pacheco, Pergher, Vaccaro, & Jung, 2015). Such combination, LM and SS, known as LSS, may yield better results than the use of two parallel methods independently (Nicoletti, 2013).

Nowadays companies are paying increased attention to updating management processes. LSS approach has attracted perception from those who have yet to use LM and SS jointly (Assarlind & Aaboen, 2014). Applying the framework to projects serves to structure the research base according to the applicability of LSS.

Systematic literature review

In the systematic review of the literature performed in the present work we found papers that provide frameworks and characteristics for LSS. However, none of them, at the same time, presented a functional structure that manages projects in manufacturing and engineering, elaborates risk analysis, selects projects in line with manufacturing strategic planning, implements VSM combining Dmaic or Dmadv, monitors the return on investment for a year, disseminates lessons learned.

Today’s industries require minimum cost by reducing waste and variations, LSS strategies with a VSM and Dmaic cycle could meet this demand, while enhancing business competitiveness (Chaurasia et al., 2016). A decision support system that used portfolio selection to ensure that projects prioritized the required characteristics of the proposed LSS framework arising from research-elaborated alignment with the strategic planning is presented in (Hu, Wang, Fetch, & Bidanda, 2008).

The substantive processes of LSS are critical factors in its success (Jeyaraman & Teo, 2010) in guiding manufactures striving to attain competitiveness (Okhovat, Ariffin, Nehzati, & Hosseini, 2012). LSS provides an outline of how to combine LM and SS to gain valuable insights for CEOs who wish to structure their enterprises more efficiently (Assarlind, Gremyr, & Bäckman, 2013). Integrating VSM and DMAIC will reduce defects by eliminating manufacturing activities that do not add value (Swarnakar & Vinodh, 2016). LSS concepts can enhance the communications process and provide a problem-solving structure for improving ongoing projects (Barnes & Walker, 2010). LSS could integrate Dmaic and DFSS methodologies with lean concepts to better quality and increase productivity and Lean Six Sigma projects focus human behavior in changing processes to achieve excellence (Montgomery, 2010). Its lessons-learned process offers a perspective for organizational improvement efforts (Näslund, 2008). Dmaic and Dmadv methodologies are effective improvement tools, respectively (Sokovic, Pavletic, & Pipan, 2010). The LSS methodology concerns how to select black belt staff to motivate and direct teams (Hilton & Sohal, 2012). This is the LSS characteristics initially found through observations of the first authors studied.

One of the papers does not present a framework, but purposes to explore the most characteristics within LSS; and it describes that the issues that have emerged from this study include benefits, motivation, and limitations, factors providing opportunities for LSS researchers (Snee, 2010). Another paper presents the combination of LM and SS through a framework that describes the Dmaic cycle step by step, but does not emphasize VSM (Vinodh, Gauthan, & Anesh, 2011). There is a paper that describes deficiencies in overcoming lean anchorage within the Dmaic sequence, using training (Gnanaraj, Devadasan, Murugesh, & Sreenivasa, 2012). There is also a paper that establishes process information, and current and future VSM states to serve as a guide in developing an action plan (Chen, Li, & Shady, 2010).

The proposed Lean Six Sigma framework

The Lean Six Sigma framework was involved in four phases and ten steps (Figure 1). The framework was applied into project in a Brazilian manufacturing company.

Phase 1 (Establish organization): in the proposed LSS framework the initial phase is to select key personnel, including the black belt, who must be a leader with extensive experience in working on projects, capable of motivating staff to participate actively in changing organizational culture (Table 4).

Phase 2 (Select projects): This phase is composed by a sequence of: portfolio analysis (Table 5); select projects; define scope, time, and cost; maximize staff efficiency by multi-task assignments to LSS staff; analyze attractiveness versus risk (Table 6).

Phase 3 (Implement projects): the third phase is the first activity of the implementation that consists in assessing the current status of the process and determining whether it is the most critical one to meet the needs and expectations of the organization’s stakeholders. From this starting point, the priorities are set, and decisions are made about which areas of the business are to be addressed, and which techniques are the most suitable ones for this phase. In addition, to ensure that the resulting improvement is maintained, the process must be stabilized, confirming its financial result for an one-year period (Table 7).

Phase 4: Monitor projects: this phase monitors the indicators and disseminates the results to other business units (Table 8).

Case study

The manufacturing company at which the case study was conducted is located in southeast Brazil. The Brazilian site produces forged (450 employees, two shifts) for its multinational parent corporation, whose headquarters in the United States and which employs 90,000 staff in 190 sites in several countries. The case study provides evidence that the LSS methodology stimulates the incorporation of key elements from lean manufacturing and six sigma. The advent of new methodologies has substantially altered processes in the manufacturing company and has contributed to the success of companies whose CEOs recognize that further improvements are needed in today’s competitive markets.

Table 9 shows the application of the tools applied in the case study. In this table the tools are separated by their origin methodology, either LM or SS.

Hot forging cell automation (VSM/Dmadv) select personnel, risk and attractiveness analyses, project charter on the project in a forging business unit is about hot forging cell automation. It uses functional structure described in the framework and it defines: forging impact; goal, innovation, establish project charter (goal: reduce labor 35% by 04/15/2016; team: black belt (leader), engineer, operator; stakeholders: shareholders, customers, suppliers, employees, society; limitation of scope: robot application, and scheduling (Gantt: Define: 01-03/2015; Measure: 02-06/2015; Analyze: 04-07/2015; Design: 05-11/2015; Verify: 10/2015-04/2016). Table 10 shows Dmadv cycle.

Results and discussion

The new framework proposed in this paper emerged from a synthesis of successful practices described in the studies reviewed. This body of knowledge has revealed significant common points, such as added value mapping, which continue to help us identify opportunities for implementation in improvement.

As Table 11 shows, in the papers studied, people selection predominates (personnel) (Vinodh et al., 2011) while project selection (portfolio) is seldom used (Hu et al., 2008). On the other hand, the Dmaic cycle is prominent (Chaurasia et al., 2016). The consensus of the reviewed studies is that after implementing LSS projects, KPI should be applied (Drohomeretski, Costa, Lima, & Garbuio, 2014). The duration of this follow up, however, is not stipulated, although good practice recommends financial monitoring for a year. In the studies surveyed, only one paper briefly described this system. The application of VSM simultaneously with Dmaic was seen in diverse articles, but the application of Dmaic in conjunction with Dmadv was not often seen (Montgomery, 2010). There was a single study that simultaneously presented VSM, Dmaic, and Dmadv, but it did not demonstrate a practical case (Drohomeretski et al., 2014). Our study tries do bridge this gap. In the elaboration of the proposed framework, articles with focus on the manufacturing area were firstly considered. Also it was considered articles of general applications, as example Snee (2010) and service application (Chaurasia et al., 2016).

It was demonstrated that proposed LSS leads a company to competitiveness. It presents an organizational structure dedicated to the methodology (Shokri et al., 2016), which selects projects whose portfolios align with strategic planning (Hu et al., 2008). This selection is undergirded by risk assessment and stakeholder involvement. Although the reviewed studies applied LSS, their practical validity should be assessed in terms of lessons learned (Näslund, 2008). The results should be disseminated to the other business unit (Shokri et al., 2016).

Analysis of the relevant papers found in the study’s literature review confirms that any paper in the literature proposed an LSS framework like the one that proposed combining VSM at the same time with Dmaic or Dmadv. In addition, the framework proposed in this research also elaborates risk analysis through the personnel, adopts action plan: stage-gate control, stakeholder involvement, and it emphasizes that, on completing implementation, the ROI should be monitored for a year and the present study highlights the monitoring by KPI and lessons learned. These characteristics are not found together in any LSS framework previously published in the literature.

This article analyzes the organization, implementation, and lesson learned of projects based on the Lean Six Sigma approaches, and identifies the motivations that underpin these approaches and which may prevent users from obtaining the greatest possible benefit from their implementation of LSS. Nevertheless, organizational obstacles may hinder implementation of LSS. And even when well planned, there remain clear standards that serve as a reference for driving and sustaining performance improvement.

Conclusion

The present study proposed and implemented a Lean Six Sigma framework. The main findings of the case study highlight the gains in productivity and quality, the reduction of direct workforce in unhealthy area, the automation of the load-unloading providing a better quality of life and safety to the employees of the work cell.

The limitation of the research was to have carried out the case study in manufacturing, which limits the general applicability of the proposal. However, this study can serve as a reference model not only for the industry but also for others interested in adopting LSS approaches in their business, according to their specific needs. Further research should be undertaken to examine the applicability of LSS in a broad spectrum in different segments of companies.

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Author notes

ibs@sc.usp.br