Leveraging Lean-Six Sigma and Ergonomics in Production

Optimizing Safety and Operational Benefits

Master's Thesis, 2009

85 Pages







1.1 Motivation: Costs of work-related injuries
1.2 Benefits of Lean-Six Sigma

2.1 Estimated costs and Statistics
2.2 Risk factors work-related musculoskeletal disorders
2.3 Work-related musculoskeletal injuries

3.1 DMAIC Process
3.1.1 Process Mapping and Flowcharts

5.1 Short-term and Long-term benefits
5.1.1 Examples in Manufacturing
5.1.2 Research data systematic review

6.1 Implementation Challenges and Limitations of Lean-Six Sigma
6.2 Effectiveness of leveraging Lean-Six Sigma
6.3 Effectiveness of leveraging Participatory Ergonomics
6.4 Impact of Lean-Six Sigma on musculoskeletal disorders / injuries




I would like to express my sincere gratitude and heartfelt thanks to my Project Advisor Dr. Michael Jorgensen for his encouragement, support, and guidance throughout my project. My appreciation is more than I can truly express in words, as he has accorded me unwavering support and offered me the kindest help.

I would also like to express my thanks and appreciation to Dr. Krishna K. Krishnan and Dr. Lawrence E. Whitman for their time, effort, and support throughout my time here at Wichita State University. You are the reason I have made it this far.

I thank all my colleagues and friends at Wichita State University for their support and encouragement.

Dr. Jorgensen, Dr. Krishnan, and Dr. Whitman, thank you again for your time, encouragement, and agreeing to review my project. God bless you so much.


1. Sample PDCA Cycle with examples for ergonomics

2. Participatory ergonomics framework (PEF) dimensions

3. Key principles for successful implementation of continuous improvement

4. Critical factors for a potential Six Sigma

5. Behavior phases participatory ergonomics

6. Reactive process in the participatory ergonomics “Blueprint”

7. Common challenges and limitations of Six Sigma today


1. Top 10 causes of work-related injuries in 2007

2. 1998-2007 direct costs from work- related injuries

3. Cumulative effects of physical risk factors

4. 1998-2007 workplace injuries by category

5. Sample Six Sigma DMAIC Process

6. Sample Ishikawa diagram

7. Sample Pareto chart for number of injuries

8. Sample FMEA Worksheet

9. Workplace design template / Standardization

10. Examples of waste “muda” in Lean terms

11. Square D Plant: An example of a Lean system

12. Sample holistic Lean-Six Sigma model

13. Participatory ergonomics pathways and evaluations

14. Lean Process and Safety flowchart

15. High capacity lift module

16. Overhead crane

17. “Blueprint” for implementing participatory ergonomics

18. Dow Chemical injury / illness rate (1994 - 2008)

19. Conceptual framework: Linking Lean with work characteristics and /or injury



Simon Peters Mungecho

Wichita State University, 2009

This paper argues that implementing Lean-Six Sigma and ergonomics concurrently presents great opportuniti es for manufacturing companies. It focuses on how these compani es could profit from addressing ergonomics- related injuries by leveraging Lean- Six Sigma with their ergonomics / safety programs. The paper also looks at how such a strategy could transform an organization, lower workers compensation claims’ costs, increase productivity, safety, efficiency, and improve the bottom-line. It is fundamental and critical for manufacturing companies with limited resources today, to harness the mutual benefits of investing on health and safety issues using methodology such as Lean- Six Sigma. The research concluded that manufacturing businesses that leveraged Lean- Six Sigma and ergonomics made significant improvements. There is no doubt from the study that work-related injuries are very expensive and can negatively affect an organization’s competitive advantage. They can also affect the quality of work and the workers. The paper concludes by outlining some successive models and recommendations.

Keywords: Lean, Six Sigma, ergonomics, injuries, safety, WMSDs, systems, processes



1.1 Motivation: Costs of Work-related Injuries

Manufacturing companies are losing millions of dollars each year from work related injuries. According to Liberty Mutual Workplace Safety Index (LMWSI) (2009), the estimated direct costs from work-related injuries and illnesses in United States in 2007 were $53 billion. According to Anderson & Budnick (2009), the estimated true costs to United States businesses in 2006 including indirect costs were between $61.8 and $154.5 billion. On average, indirect injury costs are between 3 to 5 times of direct costs (Anderson & Budnick, 2009; Maudalya et.al, 2008). Unfortunately, companies have to absorb all indirect costs, hence decreasing their bottom line (Maudalya et.al, 2008). Indirect costs include slowed or loss in productivity, costs of overtime, temporary replacements, rescheduling, increase in insurance premiums, affect on employee morale, liability fines, and time for injured workers to adjust (Maudalya et.al, 2008). According to Centers for Disease Control (CDC) (2001), American businesses lost an estimated $122.6 billion from fatal and nonfatal work-related injuries in 1999; an amount exceeding profits reported by top fifteen Fortune 500 companies (Maudalya et.al, 2008).

Maudgalya et.al (2008) did an empirical analysis of 17 previously published case studies to determine the relationship between safety initiatives and increased levels of productivity, cost efficiency, and quality. The National Safety Council Press (2001)

published the 17 case studies. The objective was to compare all 17 case studies using the Workplace Safety Intervention Appraisal Instrument (WSIAI) framework to establish validity and consistency and scored relative to key variable (workplace safety). WSIAI is applicable and modifiable for evaluating published workplace safety interventions case studies to determine their effectiveness, can be used to review / measure analysis of different safety case studies, and can help determine the validity of exposure relevant to research questions. Maudgalya et.al (2008) used 51 questions from WSIAI to conclude: (1) Not Applicable, (2) Yes, (3) Partial, (4) No, and (5) Unable to Determine. The study then rated the answers from the assessment on a scale (a) 0-0.25: poor (b) 0.26-0.75: marginal (c) 0.76-1.25: average, and (d) 1.26-2.00: good (Maudgalya et.al, 2008). Results from the 17 previously published case studies indicated that, when manufacturing compani es (in the study) prioritized workplace safety as a business objective, there was an average increase of 66% in productivity, 82% in safety, 44% in quality, and 71% in cost efficiencies. Further analysis by Maudgalya et.al (2008) to determine the relationship between quality, safety, productivity, and cost savings, concluded there is enough evidence to support that safety initiatives are compatible with Lean manufacturing and pursuing safety as a business goal yields both safety and operation sustainability.

1.2 Benefits of Lean-Six Sigma

Toyota production systems (TPS), masterminded by Taiichi Ohno of Japan, was the pioneer of Lean production systems (Genaidy & Karwowski, 2003). Toyota Motor Company, according to Genaidy & Karwowski (2003), later promoted TPS. Although costs from work-related injuries are signifi cant, the Institute of Management and Administration (IOMA) (2004) argues that advocating for solutions solely based on costs savings from health and injuries actually limits the effectiveness of safety initiatives. A case study at WE Energies using a cost-benefit analysis based on ergonomic solutions alone yielded a 16-month payback period. In contrast, when the same company did the same analysis based on ergonomics and productivity gains, they observed an 8 -month payback thus convincing management to strongly-support safety interventions (Institute of Management and Administration, 2004). One of the key performance indicators (KPIs) in manufacturing during the industrial age was productivity. In the 1960s and 1970s, quality also became one of the KPIs (Maudgalya et.al, 2008).

Womack et.al (1991) argued that Lean manufacturing today is a living example, a widely accepted approach that encompasses both quality and productivity. Antony (2008) and Furst (2007) argued that Lean manufacturing focuses on processes and functions that eliminate waste and enhance efficiency and productivity. Lean manufacturing also focuses on preventing waste on human resources by creating worker friendly environments through an adherence to safety and health principles; eliminating operational procedures that endanger worker health and safety and increase nonprofit generating costs related to liability, medical insurance, and workers compensation claims (Maudgalya et.al, 2008).

The concept of Six Sigma originated with Motorola engineers in the 1980s (Williamsen, 2005). According to Williamsen (2005), the Six Sigma approach encompasses effectiveness and efficiency in its pursuit of perfection. According to Antony (2008), Six Sigma is a methodology that identifies and eliminates variations in processes and systems by targeting and focusing on critical business components (Critical-to-X). It is a data-driven approach widely used in quality improvement processes (Furst, 2007). The practice of Six Sigma is in the form of phased proj ects: Define, Measure, Analyze, Improve, and Control. It is also applicable as a quality improvement framework (Goh, 2002).

Furst (2007) defined Lean-Six Sigma as an approach that combines the best in Six Sigma and Lean to optimize intended outcomes. It combines the use of data to drive metrics and Kaizen elements to streamline internal processes, procedures, and to maximize efficiency. According to Furst (2007), many organizations have successfully implemented Lean-Six Sigma to improve both their safety and operational outcomes. Maudgalya et.al (2008) argued that quality, safety, and productivity utilize components of process control such as root cause analysis, include variability reduction, and require corrective action, all of which are Lean-Six Sigma techniques. By eliminating process variability, companies can reduce the probability of quality and safety failures.

A quality study by J.D Power and Associates (Powers, 1996) in the Automobile industry concluded that 15 out of the 31 brands analyzed improved their quality after implementing Lean systems with Toyota having the best quality; less than 50 problems reported per 100 Toyota vehicles. According to Koning et.al (2006), Six Sigma has fewer standard solutions, but it provides a powerful analytical problem-solving framework for an organization. Lean, on the other hand, is not very analytical and structurally detailed, but its total systems approach is quite effective. Therefore, Koning et.al (2006) argued that Lean-Six Sigma is the ideal solution that combines both approaches. Maudgalya et.al (2008) stated that some of the 17 case studies published by National Safety Council Press (2001) are good examples of how a process control and variability reduction can result in improved quality, safety, and productivity. Companies can derive maximum benefits from Lean manufacturing by considering productivity, safety, and quality initiatives in the matrix before embarking on implementation (Maudgalya et.al, 2008). Main et.al (2008) argued that manufacturing companies should address Lean and safety concurrently to create an optimal work environment that yields the best throughput with minimal risks and waste. Creating worker friendly environments that adhere to safety and health is an extension of Lean manufacturing focus on human resources, includes eliminating hazard operational processes that may harm the health and safety of the worker, add to liability costs, increase worker compensation, and medical costs (Maudgalya et.al, 2008).

The ANSI B11 Technical Report 7: Designing for Safety and Lean Manufacturing released by The Association for Manufacturing Technology (AMT) (2007) concluded that manufacturing companies implementing Lean systems to avoid risk or reduce the cost of risks, should understand the net effect of the change, whether it is positive or negative. Main et.al (2008) noted that if Lean programs do not adequately address safety, they could lead to sub-optimal results and increased risk to workers. Main et.al (2008) argued that ignoring safety initiatives might derail efforts of becoming Lean. Resnick (2007), commenting on the impact of Lean process improvement, concluded that when ergonomics tools are integrated in the job design processes and leveraged with Lean and Six Sigma approaches they result in job processes that optimize productivity, quality, and safety. Optimization of these benefits would in essence contribute to an enhanced bottom line and enable a manufacturing business to become more competitive. The objective of this paper is to demonstrate how and why manufacturing companies should leverage Lean-Six Sigma and ergonomics to harness optimal safety and operational benefits.



2.1 Estimated Costs and Statistics

Studies suggest that work-related injuries not only affect a company’s competitiveness but can also be very costly. The Liberty Mutual Workplace Safety Index (2008 & 2009) estimated direct workers’ compensation costs in United States related to workplace injuries and illnesses in 2006 and 2007 at $48.3 and $53 billion, respectively. However, by adding indirect costs, the true cost estimate to American businesses was between $61.8 and $154.5 billion considering indirect costs are usually two to five times of direct costs (Anderson & Budnick, 2009). Work-related musculoskeletal disorders (WMSDs) account for about 33.3% of all workplace injuries and about 75% of the costs of injuries in manufacturing (Kerk et.al, 2007). According to MacLeod (2006), surgery­requiring WMSDs can cost about $15K for a wrist disorder, $20K for a shoulder injury, and $40K for a back injury. Estimated annual costs of lost workdays in 2001 from WMSDs (e.g. lost earnings and workers’ compensation) were between $13 and $20 billion and as high as $50 billion when indirect costs were included (National Research Council (NRC) (2001). In 2002, the average cost of a back injury in California was $47,938, $37,552 for carpal tunnel syndrome, $53,576 for slip and fall, and $38,494 for other musculoskeletal disorders (Workers' Compensation Insurance Rating Bureau of California (WCIRB). A study done by Duke University Medical Center (2004) found out that the cost associated with low back pain averaged more than $90 billion annually in health care expenses, with the cost of treating the back pain averaging about $26 billion of those costs. In 2000, the European Agency for Safety and Health at Work (EASHW, 2000) reported that averages of 600 million days of work were lost in Europe each year due to work related illness. In addition, estimated economic costs of occupational illness in Europe were up to 3.8% of European GDP, 40-50% of those costs attributed to WMSDs (EASHW, 2000). Liberty Mutual (2009) research, found that costs from WMSDs continued to be extremely high in the United States. Estimated direct costs from overexertion were $12.7 billion (24%), $ 7.7 billion for falls on the same (14.5%), and $6.2 billion for falls on the lower floor (11.7%) (figure 1). Overexertion, repetitive motions, and falls still remain major causes of work-related injuries and associated costs (LMWSI, 2009).

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Figure 1 Top 10 causes of work-related injuries in 2007 (Liberty Mutual, 2009).

A study by Silverstein et.al (1998) examined the impact of upper extremities’ claims in Washington State between 1987 and 1995, and found that the average direct worker’ compensation claims were $15,790, $12,794, and $6,593 for rotator cuff syndrome, carpal tunnel syndrome, and epicondylitis, respectively. Over the 10-year period (1998-2007), direct costs from work-related injuries grew about 42.8% (figure 2) (Liberty Mutual, 2009). From (figure 2), costs from work-related injuries continued to rise from 1998 to 2002, and then decreased for a period of three years until 2005. However, there has been a steady increase between 2006 and 2007 of 8.9%. There was no available data to explain why costs decreased during the period indicated on (figure 2). It is clear however, that work-related injury costs are an ongoing challenge; businesses should take necessary actions to prevent, eliminate, or reduce work-related injuries.

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Figure 2 1998 - 2007 direct costs from work- related injuries (Liberty Mutual, 2009).

2.2 Risk Factors for Work-related Disorders

Risk factors are job characteristics and attributes that are likely to contribute to the onset of work-related musculoskeletal disorders (OSHA, 2000). Kerk et.al (2007) classified potential risk factors likely to cause work-related injuries into three major types: (1) Physical risk factors such as forceful exertions, awkward posture, vibration, muscle stress, fatigue, and excessive repetitiveness; (2) Personal factors such as age of the worker, gender, past health history, and individual level of fitness; and (3) Social factors such as organizational climate, personal problems, and job attitudes. According to research by Liberty Mutual (2009), the top 10 causes of workplace injuries were overexertion: injuries caused from lifting, pushing, pulling, carrying, holding, and throwing; slipping or tripping; twisting, hit by or struck by an object; and repetitive motions (figure 1). Force exertion is a combination of increased body demand plus more than the muscles and other physiological changes can sustain (NIOSH, 1997). According to Putz-Anderson (1988), body posture is the primary determinant of how much force or stress the body can generate and tolerate plus which joints and muscles the body needs to use to complete a task. Resnick (2008) described the cumulative effects of exposure to physical risk factors (figure 3) which eventually leads to injuries, low productivity, poor quality, increased error rates, rework, and low profits.

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Figure 3 Cumulative effects of physical risk factors adapted from (Resnick, 2008).

Other injuries may occur due to the risk of continuous contact with hard or sharp objects such as work surface edges or pinch grips. This creates increased localized pressure (Kerst et.al, 2003), which can affect normal blood flow and nerve functions. Resnick (2007) argued that overexertion can lead to recordable injuries that increases workers’ compensation and human resources costs, increases error rates, lowers productivity and employee morale.

2.3 Work-related Musculoskeletal Injuries / Disorders

Kerst et.al (2003) defined work-related musculoskeletal disorders (WMSDs) as illnesses that occur due to prolonged overuse of human joints, muscles, and body tissues eventually making them sore or unusable. Work-related musculoskeletal disorders, according to OSHA (2000), are injuries and disorders of soft body tissues and the nervous system. Body tissues include the tendons, cartilages, ligaments, joints, and cartilages. WMSDs occur gradually over a long period of exposure to risk factors such as force, posture, duration, and frequency (Kerst et.al, 2003).

Normally, the onset of wear and tear is a function of frequency, duration, and force. Vibration, localized body contact stress, extreme temperature, and duration of exposure, also speed up the onset of WMSDs (Kerst et.al, 2003). Carpal tunnel syndrome, tendonitis, epicondylitis, and rotator cuff syndrome affect the hand / wrist, elbows and shoulders (Silverstein et.al, 1998). Repetitive force, awkward wrist postures, and segmental vibration can lead to carpal tunnel syndrome, a compression of the median nerve. Epicondylitis is an inflammation of the elbow tendons caused by forceful repetitive rotations of the forearm (Silverstein et.al, 1998). Rotator cuff syndrome is inflammation or degeneration and tear of the tendons around the shoulder caused by high muscle loads, shoulder abduction and adduction, and frequent shoulder rotations (Silverstein et.al, 1998). During physical exertions, the body recruits muscles proportional to complete the task but when the body is fatigued after a prolonged use, muscle coordination becomes a challenge (Resnick, 2007). This is a recipe for increased error rates, lower productivity, and increased risk for WMSDs such as chronic low back pain, carpal tunnel syndrome, tendonitis, and suboptimal work methods (Resnick, 2007). As shown in figure 4, injuries from overexertion and repetitive motions decreased between 1998 and 2007, while falls, bodily reactions, and struck by or against an object increased during the same period (LMWSI, 2009). However, as shown in figure 1, indicates, overexertion, and falls are still the leading causes of workplace injuries and associated costs.

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Figure 4 1998 - 2007 workplace injuries by category (Liberty Mutual, 2009).

Silverstein et.al (1998) performed a study on upper extremities in Washington State between 1987 and 1995, and concluded that high-risk activities and exposures for shoulder and elbow disorders were prevalent in construction industries. This was associated to frequent segmental vibration, repetitive motions, and awkward postures in those industries. Disorders associated with manual material handling including low back pain were high in logging, garbage collection, nursing homes, and foundries. Manufacturing and food processing were the riskiest for gradual onset of carpal tunnel syndrome. A study by Brenner et.al (2004) observed that (WMSDs) caused by factors such as repeated pressure, vibration, and motion and contributes to carpal tunnel syndrome, tendonitis, and rotator cuff syndrome rose dramatically. Strains attributed to prolonged durations of repetitive tasks also increased. WMSDs per 10,000 workers rose by 20.2% between 1982 and 2001. Of all new cases of illness during the same period, WMSDs rose from 21.4% to 64.8% (Brenner et.al, 2004).

Occupational injuries are a major and ongoing challenge for manufacturing companies. Several studies (e.g. Liberty Mutual, 2009; Anderson & Budnick, 2009; and Kerk et.al, 2007; and MacLeod, 2006) drive a strong business case why manufacturing compani es should address risk exposures for work-related injuries at all costs in order to remain competitive and profitable in today’s global business; direct and indirect costs are immense and overwhelming as observed. In addition, available statistics also indicated that overexertions (e.g. lifting, carrying, pushing, pulling, and throwing), falls, and repetitive motions are highly prevalent in the workplace today resulting in high numbers of WMSDs. All this strengthens the need to integrate methodologies such as Lean-Six Sigma with ergonomics not just for safety reasons, but also for operational benefits.



3.1 DMAIC Process

The Six Sigma DMAIC process (figure 5) is a five-step process: Define, Measure, Analyze, Improve, and Control (DMAIC).

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Figure 5 Sample Six Sigma DMAIC Process adapted from (Gilkinson et.al, 2007).

3.1.1 Process Mapping and Flowcharts

Process maps, also referred to as process flow diagrams, are graphical illustrations on how to complete a process or a task effectively within the constraints such as resources and time (Williamsen, 2005). It also allows teams in charge of continuous improvement to break down complex sequences of events into simpler steps resulting in “spaghetti diagrams ’ which are easier for the team to analyze for errors, inefficiencies, complexities, and safety hazards to be eliminated (Williamsen, 2005).

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The Ishikawa diagram is a method also referred to as cause and effect or fishbone diagram. It was founded by Kaoru Ishikawa in the early 1960s to graphically-represent all factors influencing a problem (Battino, 2006; Williamsen, 2005). It systematically helps find an idea and allows a clear problem representation structure. According to Battino (2006), the goal of using the Ishikawa diagram is to help identify risks associated with a challenging problem during a risk analysis, to formulate alternative preventive solutions. Williamsen (2005) reported on a Fortune 500 company experiencing injuries in multiple locations, indicating that the company’s safety team used an Ishikawa diagram to identify multiple potential causes for soft tissue injuries. An example of an Ishikawa diagram (figure 6) consists of a straight horizontal line pointing to the problem at the end, diagonal adjacent line representing the main influential aspects (e.g. man, methods, machine, and materials), and smaller line representing potential causes (Battino, 2006).

The five “Why’s” is a problem solving technique developed by Sakichi Toyoda that involves asking the question “Why” five times. The method explores three key elements: (a) statements of the problem(s) at hand (b) honest assessments and answers regarding the problem(s) and, (c) commitment to get to the bottom of the problem(s) and solve them (Serrat, 2009). General steps in this process are team formations, developing a problem statement, asking the “Why” questions multiple times, settling on likely root causes, developing a logical analysis of the problem, and finally developing corrective actions (Serrat, 2009). Drawbacks associated with the five “Whys” technique include probability of stopping at symptomatic problems instead of digging deeper into the actual problems and root causes, asking the wrong questions to the problem, and sometimes different teams generating different root causes for similar problems (Serrat, 2009).

3.1.3 The Multi-Phase Process

The Define phase of the DMAIC process involves setting goals, selecting safety teams, assigning tasks, and identifying ergonomic problems at hand (Ferreras & White, 2005) . It also involves selecting a job or a task to review, understanding the scope of the problem and establishing measures, targets, and other goals (Silva, 2006). To decide on the job to review, safety teams can use past injury data from trend charts, employee surveys, Pareto charts (figure 7), and ergonomic checklist (Silva, 2006). Understanding the scope of the problem involves evaluation of injuries and illness claims data, bottleneck in the production, and absenteeism (Silva, 2006) and OSHA 300 logs. A Pareto chart (figure 7) helps identify areas with unacceptable failures that warrant serious actions that need highest priority (e.g. assembly, packaging, and FGI according to Pareto chart in figure 7). The basis for measures and targets includes reduction of WMSDs risk, worker discomfort, costs of injuries and illnesses, and rework (Silva, 2006). Process maps and flowcharts are other techniques used to identify ergonomic problems for improvement (Ferreras & White, 2005).

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Figure 7 Sample Pareto chart for number of injuries adapted from (Silva, 2006).

The measure phase of the DMAIC process involves measuring and quantifying performance and WMSDs risk factors, performing ergonomic task and job evaluations, and identifying measurable problem areas (Balci et.al, 2005; Ferreras & White, 2005). In addition, teams also need to collect job / task information such as name, schedule, time of exposure, current process, medical data, and determine risk scores using tools such as the Baseline Risk Identification of Ergonomic Factors survey (BRIEF) (Silva, 2006). BRIEF is a structured and formalized rating system that uses a screening process to identify risky postures and associated risk factors (Humantech, 1995). Pareto charts for strains and medical visits, Critical to Quality assessments, ergonomics checklist, and frequency histograms are valuable tools. The “current state” and the “to-be-state of the new ergonomic program” are established at this stage of the process (Balci et.al, 2005; Ferreras & White, 2005).

The Analyze phase of the DMAIC process is a critical step to the success of an ergonomics program. It entails analyzing job and tasks performances, finding root causes of risk factors, validating the root causes, and assessing improvement opportunities before the team can embark on intervention strategies (Balci et.al, 2005; Ferreras & White, 2005). It also involves brainstorming ideas and prioritizing improvements (Silva, 2006) . According to Balci et.al (2005) and Ferreras & White (2005), an analysis of potential ergonomic failures such as awkward posture, excessive force, repetitive tasks, reaching, bending, twisting, and mechanical stress forces is critical at this phase. To identify root causes of risk factors, companies can use the Ishikawa diagram (figure 6). Once the identification of the root causes (from the Ishikawa diagram) is completed, the safety team can then use ergonomics tools to analyze the severity, frequency, exposure, durations of exposure, and the impact of the problem (s). To do this, companies can use a variety of ergonomics tools (Silva, 2006): NIOSH Lifting Equation (for lowering and lifting tasks), Liberty Mutual Manual Materials Handling Tables (for carrying, pushing, and pulling tasks), and Ergonomics questionnaire (discomfort levels). Useful tools and techniques for upper extremities’ exposures include Rapid Upper Limb Assessment (RULA), Rapid Entire Body Assessment (REBA) (Marras & Karwowski, 2006), and the Moore-Garg Strain Index (Moore and Garg, 1995). Moore and Garg Strain Index divides jobs into tasks and then assesses risks on distal upper extremities (hand, elbow, and wrist) using six factors for each task and each hand. Finally, companies can utilize the American Conference for Governmental Industrial Hygienists -Threshold Limit Values (ACGIH-TLV) tables to analyze exposure to back injuries. Liberty Mutual Manual Materials Handling Tables are psychophysical tables, developed by Liberty Mutual that companies can use to perform “what if’ scenarios for ergonomic interventions that provides best degree of control and most cost effective.

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Figure 8 Sample FMEA Worksheet adapted from (Silva, 2006).

Failure Modes and Effects Analysis (FMEA) (figure 8), can be used to brainstorm ideas and for prioritizing improvements (Silva, 2006). Identifying failure modes / risks inherent in the process helps determine their impact and causes. Safety teams can then prioritize them for improvements; a process that involves multiplying the probability of occurrence, level of severity, and ability to find the problem before initiating corrective action plans to eliminate or reduce the risks (Jones, 2004). For example, the more often (frequent) a worker (s) moves materials manually between floors manually, the higher the probability that an injury will occur. The heavier the material and the longer the duration of this exposure means the more likely the severity of injury will be high.

The Improve phase of the DMAIC process is where solutions to risk factors are identified, ergonomic intervention plans are designed, practical corrective methods are selected, and target improvement scores are set (Balci et.al, 2005; Ferreras & White, 2005; Silva, 2006). The Improve phase is also where a safety team ensures that improvements for root causes identified in the Analyze phase are adequately addressed and implemented without allowing additional hazards or bottlenecks (Silva, 2006) by developing control mechanisms, process scorecard, controlling frequencies and variations, and designing engineering and administrative controls (Balci et.al, 2005; Ferreras & White, 2005). Engineering controls includes work modification, equipment design modification, and set up reductions. Administrative controls include job rotations, training, and safety teams (Smith, 2002).

Finally, the Control phase of the DMAIC processes involves ensuring a continued use of the new safety initiatives through worker training, supervision, and up -to-date documentation. Monitoring and standardizing the improvements are also critical to ensure that initial gains are sustainable. Standardizing also involves designing a template for use in other areas with similar tasks / jobs (figure 9) and developing action plans to identify other jobs that may benefit from the improvements made (Silva, 2006). Risk safety management can utilize the Six Sigma tools to identify ergonomic issues, evaluate job / tasks related to those issues, and to control risk exposures where tasks and job requirements exceed operator capability (Smith, 2002). A data-driven approach such as Six Sigma can help develop reliable and repeatable results from ergonomics risk factor surveys. Reliability in this regard means the ability for different workers to achieve the same risk score for a job or task. Repeatability is the ability to achieve the same risk score looking at the same job or task several times (Smith, 2002; Humantech, 2002).

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3.2 Lean Process

Lean processes strive to banish or minimize waste and excesses, “muda or mura”, many of which can lead to ergonomic problems (figure 10). For example, excessive manual transportation of materials can result in high-sustained carrying, push, and pull forces (figure 10). Too much inventory means workers may have to carry, move, transport, pack, push, or pull large amounts of material. This could lead to frequent bending and twisting, reaching, and lifting (Gilkinson et.al, 2007). Excess motions contribute to risk factors such as repetitive lifting, repetitive bending and twisting, reaching, and frequent shoulder abduction and adduction (figure 10) (Gilkinson et.al, 2007) . From an ergonomics perspective, employees should have adequate rest break times. Gilkinson et.al (2007) observed that overproduction, overprocessing, rework, and overtime could all lead to muscle fatigue, repetitiveness, and frequent reaching and carrying. A Lean systems approach is applicable in quantification and reduction of unnecessary tasks and routines or excesses (Smith, 2002). In addition, the ability to quantify present risk factors before and after Lean implementation is a critical process because Lean teams need to understand, validate, and quantify positive and negative effects on the levels of WMSDs and risks factors (Wilson, 2005).

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Figure 10 Examples of waste “muda” in Lean terms adapted from (Galante, 2009).

3.2.1 Kaizen

Kaizen improvement methods originated during the World War II through an internal component of the US manpower commission called Training Within Industry (TWI) (Bogdanoiu, 2008; Huntzinger, 2002). The Japanese later developed the Kaizen philosophy, a continuous improvement approach in safety, quality, technology, productivity, and processes after World War II (Bogdanoiu, 2008; NIOSH, 2008). “Kai ” means school and "Zen ” means wisdom in Japanese (Bogdanoiu, 2008). According to Chapman (2006), Kaizens are short-term projects or activities, intensely driven, and aimed at solving a specific problem or a goal in the company. Kaizen can help eliminate waste by improving and standardizing processes. It is a great philosophy for manufacturing companies to use in their safety aspects because it engages all operators in the risk identification process (NIOSH, 2008). Vassie (1998) defined Kaizen as a Japanese approach that emphasizes on continuous improvement.

Bessant et.al (1994) proposed six key elements for effective implementation of continuous improvement programs; clear strategy, enabling infrastructure, supportive culture, a clear process management, strategic planning, and availability of problem solving techniques. A case study by Vassie (1998) at a UK chemical company with 1300 employees, demonstrated that Bessant et.al (1994) proposals for continuous improvements are applicable in managing health and safety. Kaizens focuses on identifying problems, solving them at the source (e.g. risks factors, poor work designs, and poor equipment designs), and developing standards to ensure continued solutions (Bogdanoiu, 2008). Bogdanoiu (2008) also argued that continued improvements results in improved quality and productivity, safer workplace, lower costs, faster deliveries, and higher customer satisfaction.

Chapman (2006) described steps that a Kaizen event should follow in order to effectively implement and have positive impacts on ergonomics. First, safety teams, generally six to eight people, must identify problem areas or target areas by using OSHA injury logs, injury trend charts, and injury reports from targeted areas. Then teams can use safety audits, interviews, questionnaires, videos, and observations (gemba walk) to understand fully the magnitude of the current WMSDs risks factors. Gemba is an area where workers are actually doing the work (e.g. a workstation, a work cell, and loading dock) (Chapman, 2006). The team leader or a consultant with broad understanding of safety provides guidance and knowledge required in executing the Kaizen event. Second, the safety team then sets goals, objectives, and benchmarks based on the company goals such as the level of injury reduction required, performance metrics to use, and the type of injuries to reduce (Chapman, 2006). Finally, the team leader and the management outline a Kaizen newspaper / checklist to assign responsibilities to team members and process owners. This includes problems identified, desired countermeasures, start and completion dates, percentage complete, and company EHS engineer (Chapman, 2006). Once solutions are established, Lean managers or ergonomic coordinators from the company must ensure their sustainability.


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Leveraging Lean-Six Sigma and Ergonomics in Production
Optimizing Safety and Operational Benefits
Wichita State University  (Engineering)
Industrial Engineering
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ISBN (eBook)
ISBN (Book)
leveraging, ergonomics, production, optimizing, safety, operational, benefits, lean, six sigma, business, improve
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Simon Mungecho (Author), 2009, Leveraging Lean-Six Sigma and Ergonomics in Production, Munich, GRIN Verlag, https://www.grin.com/document/917735


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