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# Sustaining the Effectiveness of Lean Six Sigma Implementation
in a Medical Device Company

Aaron McHugh¹ and Fionnuala Farrell¹

¹Department of Mechanical & Manufacturing Engineering, Atlantic Technical University-Sligo, Ireland
[arnmcu@gmail.com](mailto:arnmcu@gmail.com); [Fionnuala.farrell@atu.ie](mailto:Fionnuala.farrell@atu.ie)

**Abstract.** Lean Six Sigma (LSS) is a common methodology adopted by organizations to improve operational and financial performance by removing waste and reducing variation. While literature agrees LSS is beneficial, it is unclear whether the initial improved performance is sustained over time. Research has identified several critical success (CSFs) and failure (CFF's) factors which determine the effectiveness of LSS implementation along with its sustainability. Integral in sustaining the initial positive impact is recognizing these success factors during LSS implementation in conjunction with identifying and preventing critical failure factors.

This study aims to investigate whether the implementation of LSS has sustained a positive impact on the operational and financial performance of a Medical Device Company based in the West of Ireland. Using a mixed method approach; a case-study within one Medical Device organization was conducted. Key performance indicators (KPI's) such as defects and non-conformances were analyzed and trended. Additionally, survey data of critical success and failure factors in the areas of management, training, and culture was collated. The quantity of unit rejects, which ultimately leads to increased costs was used as the financial indicator in this study. The influence of Quality 4.0 and the global pandemic were also considered. A comparison was then made with two other similar sized companies in the region using semi-structured interviews.

Results indicated LSS has a sustained positive impact on the organization's operational and financial performance. Findings suggest Quality 4.0 was a significant contributing factor for sustaining this positive performance. The pandemic was shown to magnify the failure factors albeit offset somewhat by Quality 4.0. The comparison with the other two medical device organizations suggested that LSS alone could not sustain a positive impact highlighting the need to conduct further research into self-sustaining LSS methodologies along with the value to consider the new 'LSS 4.0' approach.

**Keywords:** LSS Implementation, LSS sustainability, critical success factors, critical failure factors, medical device.

# 1 Introduction

## 1.1 Introduction to Lean and Six Sigma Methodologies

Lean manufacturing, embedded in the Toyota Production System, is a technique which identifies opportunities to eliminate waste and non-value add activities [1, 2, 3]. Lean works as a cost-cutting strategy targeting an organization's competitiveness by improving process efficiency, optimizing human resources, and lowering costs by eliminating steps which provide no additional value [4, 5]. There are 5 core principles for lean manufacturing practices which comprise of defining the value, mapping the value stream, creating flow through the process, establishing pull, and seeking perfection [5, 6].

Six Sigma is a technique used for process improvements aiming to maximize profits and uses statistical measures such as Statistical Process control (SPC); Design of Experiments (DOE) and Failure Mode and Effects Analysis (FMEA) to determine the efficiency/quality of a product/service [7]. Studies by Costa et al.,[8], and Sim et al, [5], both suggest that six sigma focuses on business process improvements through minimizing process variation and conducting root cause analysis to reduce defects, therefore enhanced quality. The DMAIC process (Define, Measure, Analyze, Implement, Control) is Six Sigma's most utilized methodology aiming to improve existing business processes [7, 9, 10]. Six Sigma has progressed from solely using statistical tools and is currently used by organizations to improve their overall operational and financial performance, eliminate, or reduce defects, reduce process lead times and ultimately improve customer satisfaction [5, 11, 12].
## 1.2 Lean Six Sigma (LSS)

Combining both Lean and Six Sigma methodologies enhances an organization's ability to produce optimal results in terms of operational and financial efficiency, allowing for an overall greater performance than if each method was implemented separately [5, 6, 13, 14]. LSS has a two-pronged approach to minimizing waste and increasing value while also addressing quality issues that affect product and process performance and repeatability [7, 15, 16]. Alhuraish, et al., [17] theorized that an integrated LSS methodology improves a company's ability to achieve optimal results through waste reduction. LSS techniques are more efficient, resulting in a more prosperous manufacturing process with less waste and defects [18].

Despite the popularity of LSS, companies often revert to their old ways or let their standards falter after initially showing promising results, but which ultimately prove to be somewhat unsustainable due to various failure factors [19, 20]. While the research tends to agree that the implementation of LSS techniques is beneficial, the sustained impact that LSS has on operational and financial performances in the Medical Device Industry is not adequately measured [2, 8]. Prior research on LSS has tended to focus more on the key or critical success and failure factors of either lean, six sigma, or LSS but it is more focused on its implementation rather than sustaining LSS over time [19, 21, 22].

Many companies struggle to sustain LSS methodologies after implementation as they are unaware of the success or positive impact that these tools have [16]. The difficulty sustaining LSS initiatives may be due to failures in identifying new projects, a lack of support or focus from management or a failure to assign skilled personnel [14]. This research aims to bridge that gap for an Irish Medical Device company based in the West of Ireland through providing empirical evidence to prove if LSS can sustain a positive impact on the operational and financial performance. Specifically, the research questions considered in this study are two-fold:

1. Does the implementation of lean six sigma techniques have a sustained positive impact on the operational and financial performance in a Medical Device Company based in the West of Ireland?

2. Is there any indication that this impact is shared by similar Medical Device Companies in the West of Ireland?

Structured into five sections, this paper presents **Section 1** covering an introduction of Lean, Six Sigma, LSS and Sustainability of LSS and outlining the study's aim. **Section 2** covers a literature review, which includes a review of Lean Six Sigma in Industry, Operational and financial performance indicators, the critical success and failure factors, the influence of Quality4.0 and the global pandemic on LSS. **Section 3** explains the research methodology, details of the survey and limitations. **Section 4** covers results and analysis. **Section 5** provides a discussion and concluding comments specifying the implications of this research and directions for future research.

# 2. Literature Review

## 2.1 Lean Six Sigma in Industry

Lean Six Sigma (LSS) continues to grow in popularity and is considered one of the most effective methodologies used in the manufacturing industry for continuous improvement with larger manufacturing organizations more likely having LSS implemented than smaller ones typically due to resource constraints [13, 23, 24]. In contrast with most of the literature reviewed, Singh and Rathi, [2] found that LSS is implemented in the manufacturing sector to a lesser extent, albeit rapidly growing, than in the service and automobile sector. A study by Iyede, et al., [12], found that the extent of LSS implementation by manufacturing companies based in the West of Ireland was low in comparison to countries such as the UK, Belgium and Australia. This may be due to resource scarcity and lacking implementation know-how. Within the medical device industry, where strict regulatory standards by the US Food and Drug Administration (FDA), International Standards Organization (ISO) 13485, which outlines the requirements for Quality Management Systems for Medical Devices, and European Union Medical Device Regulation (EU MDR) need to be met, LSS has been shown to help with compliance [25, 26, 27].

The reasons why LSS is implemented tends to vary by industry and organizational strategic objectives, however the top reason given, according to research by Patel and Desai [23], was process improvement at 29%, followed by defect reduction, rework, and scrap at 16%. Continuous improvement
methodologies such as LSS are proving to be the key for organizations to achieve operational excellence. Interestingly, even despite being in a highly regulated industry, McDermott et al's study [28]; which assessed the readiness and maturity of continuous improvement (CI) deployment in the medical device industry; found there was an overall 'positive culture of acceptance and embracing of CI methods and initiatives'. It was suggested by Nour and Laux [27] that the Define-Measure-Analyze-Improve and Control (DMAIC) methodology has shown potential to improve the Corrective and Preventive Action (CAPA) process within medical device organizations which can help them to meet FDA regulations.

Organizations tend to implement different LSS tools and there is no set standard or set structure for the LSS tools that should be implemented – see Figure 1. Although not all companies possess the capabilities or resources to implement either LM or six sigma, Alhuraish, et al., [17] show that a sequential integration of both in the form of lean six sigma methodologies produce the optimal results for companies in terms of operational and financial performance.

<figure><img src="image_2.png" /><figcaption>Figure 1: Lean, Six Sigma and Lean Six Sigma Overview [3]</figcaption></figure>

Notwithstanding this, however, Cortes et al.,[30] highlight that it can be difficult to evaluate the success of lean six sigma due to the lack of relevant methods or indicators from which to evaluate them. Some of the most effective LSS tools used within organizations are 5S, Poka-Yoke, Kanban, Value Stream Mapping (VSM), Kaizen, DMAIC, and Plan-do-check-act (PDCA) [2, 29]. However, DMAIC is one of the least utilized tools with brainstorming, Standardized work and visual control most often deployed [16] as illustrated in Figure 2.

<table><caption>Figure 2: Status of Lean Manufacturing and Six Sigma Tools within industry [16]</caption><thead><tr><th>Tools</th><th>Used %</th><th>Tools</th><th>Used %</th></tr></thead><tbody><tr><td>Brainstorming</td><td>100</td><td>Poka-yoke</td><td>81.8</td></tr><tr><td>Standardized Work</td><td>97</td><td>VSM</td><td>81.8</td></tr><tr><td>Visual Control</td><td>97</td><td>Gemba</td><td>78.8</td></tr><tr><td>PDCA</td><td>97</td><td>Kanban</td><td>78.8</td></tr><tr><td>Cause and effect diagram</td><td>97</td><td>SMED</td><td>72.7</td></tr><tr><td>5S</td><td>93.9</td><td>Control chart</td><td>72.7</td></tr><tr><td>Pareto chart</td><td>93.9</td><td>Takt time</td><td>69.7</td></tr><tr><td>Flow chart</td><td>93.9</td><td>Design of Experiment</td><td>63.6</td></tr><tr><td>Check sheet</td><td>90.9</td><td>DPMO</td><td>60.6</td></tr><tr><td>TPM</td><td>84.8</td><td>Once piece Flow</td><td>57.6</td></tr><tr><td>VOC</td><td>84.8</td><td>DMAIC</td><td>57.6</td></tr><tr><td>FMEA</td><td>84.8</td><td>Cellular layout</td><td>48.5</td></tr><tr><td>Kaizen team</td><td>81.8</td><td>Regression analysis</td><td>39.4</td></tr></tbody></table>

## 2.2 Operational and Financial Performance Indicators

Organizations are continuously looking for ways to achieve optimal financial and operational performance. Literature indicates that companies that implement both Lean and Six Sigma have an enhanced operational, financial; customer satisfaction and innovation performance since certain tools
are more advantageous towards different metrics [5, 7, 8, 13, 16, 17, 31].

Most industries use annual savings or benefits as a performance measure after implementing LSS methodology, followed by the sigma index, defect reduction, and cost reduction but key performance indicators (KPIs) are more effective if they are tailored to the organization's own specific goals and values [23, 32]. KPIs tend to vary greatly between organizations or even internally in an organization and therefore it can be difficult to get a true sense of the success of LSS, but nevertheless they are invaluable if used in the right manner [23, 33]. Some of the most common operational KPIs include defects, lead time, down time, on-time delivery, and rework [13, 23, 34-36].

## 2.3 Critical Success and Critical Failure Factors

LSS implementation has not always been successful in the manufacturing and service industries and can be a result of various critical failure or success factors [37]. Summarized concisely, in a study by Yadav, et al., [3], were the factors responsible for the success of LSS implementation from multiple perspectives and the study focused primarily on the success factors for when LSS is implemented using Quality 4.0 technologies. Part of their literature review also identified the barriers of LSS implementation. These critical success factors were summarized by Jeyaraman, K. and Kee Teo, L. [38] and are presented in Figure 3.

Management's commitment, resources, training, and organizational culture were identified as areas of criticality in relation to the implementation and sustained success of LSS [10, 21, 22]. Management must be actively involved and support LSS for it to be a success while ensuring that sufficient resources are in place and any obstacles which may arise are dealt with [22, 37, 38]. An organization's top management's vision and strategies must be clearly communicated and aligned with LSS goals which the employees will work towards [40, 41, 42]. Creating this communication channel allows for information to be passed through management which is critical for employees to understand the objectives of the organization [20, 22, 43, 44].

As the LSS methodology becomes established within an organization, the employees should be sufficiently trained on all aspects of the LSS implementation to ensure that there is the necessary knowledge base which empowers the employees to take action when needed [21, 43, 44]. Training employees is a critical success factor for organizations which allows the employees to understand the tools and philosophy around LSS [38, 44]. Additionally, continuous improvement must be embedded within an organization's culture for successful LSS and if absent needs to be developed [22, 43, 45]. Significant organizational change is required for LSS implementation which may be initially daunting for employees, but they must be encouraged to embrace the change as part of the cultural shift [6, 17].

LSS should be set up for sustained success during the Control phase of the DMAIC methodology [5, 11, 12]. However, many companies have difficulty sustaining LSS and identifying critical success factors is crucial in allowing the company to sustain the benefits [14, 24, 46]. Introducing LSS into an organization is relatively straight forward and well understood however, sustaining the improvements gained can be more of a challenge [14, 42]. Knowledge and the ability to ensure the presence of the critical success factors, as summarized in Figure 3, is vital in attempting to sustain its positive influence on performance. Highlighted in this figure are the top three areas of Management commitment, organizational belief & culture, and effective training.
<figure><img src="image_3.png" /><figcaption>Figure 3: Critical Success Factors of Lean Six Sigma Implementation [38]</figcaption></figure>

## 2.4 Influence of Industry 4.0 and Quality 4.0 on Lean Six Sigma

Lean Six Sigma can be integrated with Industry 4.0 to optimize process efficiency. A systematic literature review on the integration of Industry 4.0 and Lean Six Sigma, conducted by Antony et al, [32] found that "there are benefits, motivations, critical success factors, and challenges to integrating Lean Six Sigma and Industry 4.0". Specifically, their literature review found that lean practices have a positive association with Industry 4.0 technologies and implementing them simultaneously leads to greater performance improvements [32]. Interestingly, it was found that Industry 4.0 provides little/no support for waste reduction via the softer lean principles of people and teamwork, one which was highlighted as a critical success factor through management and culture [32].

Quality 4.0 is the application of Industry 4.0 technologies such as the Internet-of-Things (IoT), Machine Learning, Artificial Intelligence (AI), Big-Data and Robotics to ensure quality improvement. Fundamentally it is the digitalization of total quality management, and the core concept is to align the practice of quality management with the emerging capabilities of Industry 4.0 to help organizations towards operational excellence [47]. Quality 4.0 has a positive impact on LSS and the combination of the two optimizes the service supply process while also reducing the waste of both human and material resources [48, 49]. The introduction of quality 4.0 is beneficial in overcoming some of the common barriers for LSS implementation and can help organizations to sustain LSS [3, 48].

## 2.5 Impact of Global Pandemic on Lean Six Sigma

Covid-19 has had a significant impact on the manufacturing industry in terms of workforce
reductions, worker health and safety, and other financial constraints resulting from production losses and site closures [50]. As a result, the importance of maintaining a competitive edge has expanded even more. LSS strategies can assist organizations' in meeting these shifting demands and achieving long-term, sustainable results [40]. There has been extensive research conducted on impact of COVID on healthcare operations. In a study conducted by Kuiper et al [51] on a Dutch healthcare institution, it was found that process improvement in healthcare has tended to cut capacity and flexibility which are needed to deal with excessive demand shocks, such as during a pandemic. The main reason for this failure seems to be an overly strong focus on cost reduction instigated by Lean Six Sigma during stable times. Other studies around the impact on teaching a practical based topic such as Lean Six Sigma at third level during the pandemic have been shared [52] and the effective use of a virtual 'Kaizen room', however limited research to date has been conducted in a manufacturing setting. In theory, it would be expected that the pandemic would have some level of a negative impact on the sustained impact of LSS for organizations operational and financial performance.

This study was carried out using a mixed methods approach which allows for greater data collection and achieves a greater overall perspective [53]. Similarly, Tashakkori and Creswell, [54] suggested that through mixed methods, where the data analyzed uses both a quantitative and qualitative approach, a better understanding with enhanced validity and reliability of results is achieved. Collis and Hussey, [55] advises that combining data collection methods such as interviews, questionnaires and archive searching can be best for collecting data.

**3.1 Survey**

A structured survey consisting of a mixture of 27 closed-ended and open-ended questions was used to collect the data (see Table 1 for the full list of questions). The closed-ended questions used a 5-point Likert scale (response options ranged from ‘greatly increased or much better’ to ‘greatly decreased or much worse’) with comment boxes added to allow for feedback for each question and a non-applicable ‘N/A’ option– this aligned to previous research conducted [16]. The questions constructed for the survey were primarily informed by literature findings in terms of the main key performance indicators [35, 36, 44, 51, 56, 57].

The final questionnaire was administered to 108 participants across three different business units within the company. The questionnaire was distributed electronically to participants through Survey Monkey, via email, and in printed format, distributed in person where Covid restrictions allowed. 76 responses were received giving a 70% response rate. This is in line with Yun GW and Trumbo CW [58], who carried out a study on response rate using a multi-mode approach where a 72% response rate was achieved; an improvement from an earlier study carried out by Schaefer DR and Dillman DA [59] which ascertained that a multimode approach to email administration of a survey will enhance response rates and obtaining rates close to 60% could be expected.

**3.2 Case Study**

An archival study of available data within the researcher's own company was carried out which analyzed some of the key metrics such as non-conformances, yield and number of rejects. Data for the number of non-conformances, yield and the number of reject units for each of the three business units from the fiscal years of 2016 to 2022 were collected.

From the results of the survey questionnaire, summarized in section 4 of this paper, a set of 8 general questions were developed [as presented in Table 2] which aimed to further develop the survey findings and to examine if these findings were common with two similar sized Medical Device companies based in the West of Ireland. The criteria to participate in this qualitative interview was that of being a Medical Device company based in the West of Ireland, have LSS techniques implemented and be of similar size in terms of employee numbers when compared to the researcher's company. The first company was represented by a Senior Quality Engineer while the second company was represented by a Process Improvement Program Manager. All semi-structured interviews were performed via individual Zoom calls and each interview was recorded through an electronic device after receiving the consent of the interviewee. The interview was replicated with a senior representative from the Lean department from the researcher's own company to validate the findings from the in-house survey.
<table><caption>Table 1: Survey Questions</caption><thead><tr><th>Question</th><th>Section</th></tr></thead><tbody><tr><td>1) Introduction</td><td></td></tr><tr><td>1) My role is:</td><td></td></tr><tr><td>2) How many years of experience do you have in the Medical Device sector?</td><td></td></tr><tr><td>3) What area or department do you work in?</td><td></td></tr><tr><td>4) Which of these most common Lean Six Sigma tools are in use in your area?</td><td></td></tr><tr><td>2) Key Performance Indicators</td><td></td></tr><tr><td>5) Over the last 3 years, the average number of defects in your work area has:</td><td></td></tr><tr><td>6) Over the last 3 years, the average number of man or method related NCMR's has:</td><td></td></tr><tr><td>7) Over the last 3 years, the process or work-step lead time has:(i.e. the time between the initiation and completion of a process/step)</td><td></td></tr><tr><td>8) Over the last 3 years, the number of A3's (DMAIC) being actively worked on has:</td><td></td></tr><tr><td>9) Over the last 3 years, the use of LSS tools in my working area has:</td><td></td></tr><tr><td>10) Over the last 3 years, the downtime of the workflow or process has (e.g. machine out of action or components unavailable):</td><td></td></tr><tr><td>11) Over the last 3 years, the on-time delivery of results being met has: (e.g. daily manufacturing targets met or product released on time)</td><td></td></tr><tr><td>12) Over the last 3 years, the number of escapes has: (e.g. product released without complete worksteps)</td><td></td></tr><tr><td>13) Please leave any comments in relation to KPFs (Questions 5-12) and Lean Six Sigma below:</td><td></td></tr><tr><td>3) Management</td><td></td></tr><tr><td>14) Over the last 3 years, encouragement from management to implement change or improvement ideas has:</td><td></td></tr><tr><td>15) Over the last 3 years, communication of successes or results from improvement projects has:</td><td></td></tr><tr><td>16) Over the last 3 years, resources allocated to continuous improvement initiatives has:(e.g. of resources are personnel, funding, time)</td><td></td></tr><tr><td>17) Please leave any comments that you may have in relation to management (questions 14-16) and Lean Six Sigma below.</td><td></td></tr><tr><td>4) Training</td><td></td></tr><tr><td>18) Over the last 3 years, the amount of training received for the use of continuous improvement tools (e.g. A3's) has:</td><td></td></tr><tr><td>19) Over the last 3 years, my teams understanding of how to use LSS tools has:</td><td></td></tr><tr><td>20) Please leave any comments that you may have in relation to training (questions 18-19) and Lean Six Sigma below.</td><td></td></tr><tr><td>5) Culture</td><td></td></tr><tr><td>21) Over the last 3 years, employee engagement in continuous improvement ideas or initiatives has:</td><td></td></tr><tr><td>22) Over the last 3 years, the company has maintained a strong emphasis on quality.</td><td></td></tr><tr><td>23) Over the last 3 years, I feel like I can voice my suggestions or improvement ideas:</td><td></td></tr><tr><td>24) When changes have been made to improve the work process, the improvement efforts are sustained over the long run</td><td></td></tr><tr><td>25) Please leave any comments in relation to culture (questions 21-24) and Lean Six Sigma below:</td><td></td></tr><tr><td>6) Closing Questions</td><td></td></tr><tr><td>26) In your own opinion, what impact do you believe the pandemic has had on operations, if any?</td><td></td></tr><tr><td>27) Any further Comments in relation to LSS?</td><td></td></tr></tbody></table>

<table><caption>Table 2: List of Semi-structured interview questions</caption><thead><tr><th></th><th>Question</th></tr></thead><tbody><tr><td>1</td><td>What is your role, how long are you working in company X and how does your role relate to LSS?</td></tr><tr><td>2</td><td>What are the most common LSS tools used in your company?</td></tr><tr><td>3</td><td>What LSS tools have you found to be the most effective?</td></tr><tr><td>4</td><td>LSS has been shown to have a positive impact on operational performance. Have you found that this is the case in your company?</td></tr><tr><td>5</td><td>Have you found that LSS has been capable of sustaining the impact over the last 3 years?</td></tr><tr><td>6</td><td>Have you found that LSS has been capable of sustaining a positive financial impact over the last 3 years?</td></tr><tr><td>7</td><td>What impact has the pandemic had on sustaining LSS in operations?</td></tr><tr><td>8</td><td>Has your company any plans to digitalise any of your processes through industry 4.0 or quality 4.0 methods which could benefit LSS?</td></tr></tbody></table>

## 4. Results

From the eligible responses there was an even split across job roles albeit a somewhat higher number of operators [44%] as captured in figure 4. Three Business units within the organization were represented equally as seen in figure 5 with approximately one third from each business unit – Peripheral, Aortic and Coronary.

<figure><img src="image_4.png" /><figcaption>Figure 4: Respondents Job Role</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Figure 5: Respondents Operating Unit</figcaption></figure>
## 4.1 Analysis of Results

The results of the survey were analyzed using Minitab software at a 95% confidence level. The answers to the survey's closed ended questions were gathered using a Likert Scale with N/A at a score of 1 and the corresponding scoring classified as per table 3 from very positive to very negative. One-tailed t-tests were carried out to test the statistical hypothesis and to show that the sample mean either accepts or rejects the null hypothesis [H0] which states that:

‘the implementation of Lean Six Sigma techniques does not have a sustained positive impact on the operational and financial performance of a Medical Device Company based in the West of Ireland’.

<table><caption>Table 3: Likert Scale Classification</caption><thead><tr><th>Very Positive</th><th>Positive</th><th>Unchanged</th><th>Negative</th><th>Very Negative</th></tr></thead><tbody><tr><td>2.0 -2.49</td><td>2.5-3.49</td><td>3.5-4.49</td><td>4.5-5.49</td><td>5.5--6.0</td></tr></tbody></table>

Additionally, ANOVA tests were performed to analyze the statistical significance of survey results from different job functions and different business units within the company. Since LSS is a methodology for continuous improvement, the performance measurements over time should improve or at least maintained at the initial positive performance results obtained once critical failure factors were mitigated [5, 11, 12, 62, 63]. Therefore, it was anticipated that the results for the key performance indicators should improve or maintain performance over the last 3 years. A result of $\leq 4.5$ was a positive or neutral result based on the Likert scale while a result of $>4.5$ was considered negative as per table 3. The only result which proved to be negative was the critical success factor of training.

## 4.2. Key Performance Indicators and Critical Success Factors

The overall company results can be seen in Figure 4 below. The Key Performance Indicators (KPIs) and Critical Success Factors (CSFs) were all less than 4.5 except for the CSF for training at 4.51 which marginally received a negative result. While the remaining CSF's and the KPI's did not improve over the last 3 years, they remained unchanged and therefore sustained their level of performance. 10 respondents claimed that the performance would have been lower over the last 3 years had it not been for 'SAP-ME' (SAP Manufacturing Execution) which is a Quality 4.0 enhancement tool which converted many manual or paper-based processes into automated and system-controlled processes. Absenteeism during the pandemic was shown to be the main obstacle for maintaining KPIs' performance. Not only was there a lack of resources in terms of personnel, but the survey responses (Figure 5) showed that supply chain was greatly impacted by the unavailability of components resulting in significant downtime in operations. The pandemic led to several personnel working from home and there were restrictions on movement in the workplace. The responses showed that this led to a reduction in the quality and level of training received over the previous 3 years. This was reflected in the 'training' CSF result showing a marginally negative response; further analysis of the results highlights this specifically in one business unit [see Table 4].

<figure><img src="image_6.png" /><figcaption>Figure 4: Mean Results of KPI's and the Perception of Existence of LSS Critical Success Factors</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Figure 5: Reasons for KPI/CSF being sustained at the Same Level of Performance</figcaption></figure>

## 4.3 Business Unit Comparison

The results shown in Table 4 below presents a comparison across the 3 business units - Peripheral, Aortic and Coronary. The difference in results found across the 3 business units were significant (p-value of 0.00 between each unit) with the Peripheral business unit returning the most negative results followed by Aortic and then the Coronary unit responses were most positive. Unlike the Aortic and Coronary units, the Peripheral unit did not implement Quality 4.0 enhancements, including the introduction of SAP-ME. Comments on the responses given highlighted that SAP-ME was accredited for maintaining several of the KPI's within the Aortic and Coronary units. The main LSS technique which was found to be in use within the company was the cell-operating-system (COS). The COS combines many of the LSS tools including standardized work, 5s, Heijunka, and Kaizen. During the pandemic, the Peripheral unit was unable to maintain its COS due to a lack of resources and knowledge of the COS technique. This stemmed from a lack of training, a high turnover of staff and a high absenteeism rate which all resulted in significantly worse results when compared to the Aortic and Coronary units. Through the COS disbanding and the lack of Quality 4.0 implementation, the Peripheral unit returned the most negative KPI and CSF results overall.

<table><caption>Table 4: Comparison of KPIs, Tools and CSF's between Business Units.</caption><thead><tr><th rowspan="2">Measurement:</th><th colspan="3">Mean Values</th></tr><tr><th>Peripheral</th><th>Aortic</th><th>Coronary</th></tr></thead><tbody><tr><td>Key Performance Indicators</td><td>4.47</td><td>4.00</td><td>3.73</td></tr><tr><td>Tools/DMAICs</td><td>4.65</td><td>3.63</td><td>3.42</td></tr><tr><td>CSF: Culture</td><td>4.01</td><td>3.46</td><td>3.27</td></tr><tr><td>CSF: Training</td><td>5.08</td><td>4.06</td><td>3.87</td></tr><tr><td>CSF: Management</td><td>4.74</td><td>3.75</td><td>3.49</td></tr></tbody></table>

## 4.4 Non-conformances, Yield and Rejects

The non-conformance data seen in Figure 6 shows the 'man and method' related non-conformance data. The number of man or method Non-conformance Material Reports (NCMRs) generated within the Peripheral and Coronary units reduced by almost 50% after COS implementation which shows the benefits of this LSS technique. Quality 4.0 was introduced via SAP-ME in May 2019 to the Coronary and Aortic units. There was a slight reduction in the number of NCMR's after this introduction which further enhanced the COS LSS implementation. More crucially however, it shows that the number of NCMR's opened remained relatively consistent since its introduction. To the contrary, the Peripheral unit began to show an increase in the number of NCMR's since September 2020. The Peripheral unit did not implement SAP-ME, so it was solely relying on COS LSS. Additionally, the COS implemented was unable to sustain itself within the Peripheral group resulting in the COS disbanding. The effects can be seen in Figure 6 where the number of NCMR's directly started to increase and have remained increased since the COS was removed. It must be noted that the
production volumes vary between the 3 units, therefore each line in figure 6 is analyzed individually
and they are not proportional to each other.

<figure><img src="image_8.png" /><figcaption>Figure 6: Man and Method Quantity of non-conformances raised per Business unit</figcaption></figure>

Similar patterns were seen in the yield and reject data. Like the NCMR data, the implementation of COS had a positive impact and the manufacturing yield increased by as much as 20%. Quality 4.0 enhancements maintained the high yield and low reject rates which remained constant within the 2 units which implemented it. The major change over the last 3 years however was the reduction in yield and increase in rejects within the Peripheral group by almost 15% since one of its COS lines reverted to a non-cell manufacturing line. This shows that the loss of the COS in the manufacturing line has had a negative impact on the operational performance, leading to financial losses.

**5.0 Discussion and Conclusion**

As stated in the literature review section of this paper, organizations are continuously looking for ways
to achieve optimal financial and operational performance. Those companies that implement both
Lean and Six Sigma have an enhanced performance [5, 7, 8, 13, 16, 17, 31]. Introducing LSS into an
organization is relatively straight forward and well understood however, sustaining the improvements
gained can be more of a challenge [14, 42]. The primary research question of this study was to
determine if the implementation of lean six sigma (LSS) techniques had a *sustained* positive impact
on the operational and financial performance in a medical device company based in the West of
Ireland. From an operational performance perspective the company's KPI's showed that the
performance remained unchanged over the last 3 years and therefore indicating that LSS implemented
was capable of sustaining the positive impact. This aligns with the literature which showed that LSS
improves the overall efficiency, effectiveness and performance of an organisation in addition to
sustaining the level of success over time through the use of the control phase in the DMAIC process
[5, 11, 12, 60].

However, it must be stated that Quality 4.0 likely had a significant positive role in sustaining this
impact over the last 3 years aligning with previous studies [3, 49]. This was particularly evident
amongst the Peripheral Unit, who did not have Quality 4.0 implemented, whereby a borderline
negative result was seen for the operational key performance indicators. Further study would need to
be carried out to assess the sustained impact of LSS as a standalone methodology, however it is worth
noting Arcidiacono and Pieroni's [48] work where they suggested a new methodology called lean six
sigma 4.0 due to the success of the LSS and quality 4.0 working in tandem.

In line with Antony et al., [57]; who claimed that the key performance indicators can be more effective
for determining financial performance if they are tailored to the organizations own specific goals and
values rather than Lamine's [61] typical return on investment, return on equity or return on total assets;
and consistent with Ikumapayi et al., [7]; Lal Bhaskar,[6]; Sim et al.,[5]; this study analyzed the
financial performance based on the number of unit rejects, which are essentially due to defects, and
non-conformances leading to increased inventory, transport and waiting resulting in increased costs
to the company. Findings for this study show the number of units rejected has remained consistent
over the last 3 years within the Coronary and Aortic business units thus indicating a positive sustained
performance whilst the Peripheral business unit did see an increase in reject units after the disbanding
of the COS even though some LSS techniques were still in place.

The semi-structured interviews conducted with two other medical device industries highlighted many of the critical failure factors within management, culture and training consistent with literature [38] and from the output of this data it was found these CFF's were likely to be a contributor to the negative trends in operational performance within these companies. Factoring in that they did not have any Quality 4.0 enhancements, it could further suggest that the main researched company may have experienced similar results had it not been for some Quality 4.0 techniques being implemented. The other companies aligned more with the findings of the Peripheral business unit's performance.

While we cannot conclude if LSS was the only factor for sustaining operational and financial performance, we can certainly conclude that together with quality 4.0 there are signs that both methodologies work symbiotically for improved performance. Therefore, it should be considered by companies to introduce quality 4.0 along with LSS, as per the LSS 4.0 methodology suggested by Arcidiacono and Pieroni [48] to make their processes more robust, particularly in times of adversity. Similar to the findings of Kumar et al; [50] the pandemic had presented unprecedented challenges to the company from a resource and training perspective which greatly changed the landscape and the day-to-day operations.

Overall the results indicated LSS has a sustained positive impact on the organization's operational and financial performance. Findings suggest Quality 4.0 was a significant contributing factor for sustaining this positive performance. The pandemic was shown to magnify the failure factors albeit offset somewhat by Quality 4.0. The comparison with the other two medical device organizations suggested that LSS alone could not sustain a positive impact highlighting the need to conduct further research into self-sustaining LSS methodologies and value of considering the new Lean Six Sigma 4.0 methodology discussed by Arcidiacono and Pieroni [48].

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