Modeling and solving assembly line design problems by considering human factors with a real‐life application

Ergonomics has been playing an important role in assembly system design (ASD) that contains not only the main assembly line balancing problem but also the subassembly line balancing and assembly layout problem. The ergonomics in ASD has an impact both on productivity and on workers’ health, especially when frequent changes in the product mix occur. In this study, we propose a systematic approach in order to handle ASD, which consists of three subproblems, while considering ergonomic risk factors. The first two subproblems are solved simultaneously using the proposed rule‐based constructive search algorithm, where ergonomic risks are evaluated by OCRA method. Later, layout problem is solved under transportation constraints using local search methods with various neighborhood structures. To provide the applicability and evaluate the performance of the proposed systematic approach, a real‐life case study in a harness manufacturing company is solved and prototype productions are performed.     

Effect of Job Rotation Types on Productivity,Accident Rate,and Satisfaction in the Automotive Assembly Line Workers

This study investigates different autonomous job rotation types to analyze their impacts on productivity, accident rate, and worker's satisfaction. The subjects of research were 422 assembly‐line units in 3 production plants from an automobile company. The preferred rotation types and workers’ satisfaction scores in the 422 units were surveyed by the average worker's experience and work productivity, quality and accident rate scores were traced over a 5‐year period. Results showed that workers with little work experience preferred to work in shorter cycles composed of a small variety of tasks, whereas workers with more experience preferred longer cycles composed of a larger variety of tasks. In addition, autonomously chosen rotation systems proved to boost productivity and work satisfaction when compared to units that did not implement job rotation. In contrast, only 4 out of 10 rotation types showed improvements in decreased number of accidents. Of the 10 rotation types, ones with daily cycles with a small range of tasks and weekly cycles with a wide range of tasks displayed the most promising results for productivity, work satisfaction, and accident prevention. This study implies that the preferred types of rotation do not necessarily lead to higher productivity, safety, and satisfaction. The results of this study are expected to serve as a basic guideline for job design.     

Influence of shift work in process industry on workers' occupational health,productivity, and family and social life: An ergonomic approach

Shift work is a major feature of modern work practices. It involves working at times considered unconventional for most workers, such as at night. Although the community often benefits from such work practices, shift work can be hazardous for both the workers and the community. There are increased risks for accidents and errors, increased sleepiness and fatigue due to difficulties sleeping, increased health problems, and disruptions to family and social life. More shift workers complained of sleep disturbance, poor sleep quality, tiredness at awakening, and sleepiness in work than did non‐shift workers. More shift workers also complained of gastrointestinal disturbances than did non‐shift workers. The aim of this article is to provide general information on shift work, work schedules, and the effects of work schedules on sleep, fatigue, performance, the health of the human operator, and productivity. © 2010 Wiley Periodicals, Inc.     

The impact of absenteeism on the quality of assembly line production: The importance of a specialization requirement

Absenteeism among manual workers is without doubt one of the most significant factors that affect the functioning of assembly lines. It is a widely held view that high levels of absenteeism have negative repercussions on the quality and costs of operations. According to the scientific theory of work, workers who temporarily stand in for their absent colleagues affect production quality levels because of a lack of work specialization and experience. However, new and sophisticated automation can eliminate the effect of absenteeism on assembly line production. This article gathered more than 960,000 products produced by different levels of absenteeism. The effects of absenteeism on the quality of products in assembly lines over the course of one year were analyzed. In contrast to established thinking, the empirical evidence presented here confirms that absenteeism does not always produce problems in the quality of products. This evidence can be explained by the need for specialization among manual workers has been reduced by the invention of more sophisticated and specialized machinery. © 2007 Wiley Periodicals, Inc.     

Manufacturing assembly serial and cells layouts impact on rest breaks and workers’ health

Rest breaks are necessary for workers to avoid and/or recover from overall fatigue and to preserve their health. The type of assembly layout, either in lines or in cells, is a determining factor for organizing work at manufacturing companies, and it could also influence workers' work break and microbreak times. This study aimed at evaluating rest breaks in serial and cell assembly layout configurations as well as the layout's influence on workers' health. One hundred and twenty workers from a large automobile industry, divided into two groups (series and cells), were measured for their cycle-times and break times through biomechanical exposure analysis and questionnaires to evaluate the behaviors, physical, cognitive, and mental health. The Kolmogorov-Smirnov test was used to verify the distribution of the data with a significance level of p < 0.05. The cell assembly-line layouts had the greatest cycle-time and break time, and the workers had a higher level of physical activity (p < 0.05). The serial assembly-line layouts did not generate major occupational risk, need for rest, reduced capacity for work, or higher levels of stress for the workers. The production layouts differed in relation to the cycle-times for just-in-time manufacturing, but there was no difference in relation to the production demands and to the workers' health.Relevance to industryWhen taken at appropriate times, rest breaks in the workplace can improve workers’ overall health and productive performance, which reduces healthcare costs and improves industrial productivity.     

Role of ergonomics in the transfer of technology to industrially developing countries

Technological development has contributed to economic growth and social progress as well as a reduction of many sources of occupational accidents, injuries and stresses. However, advanced technology has also brought new sources of work stress and injuries. Industrially developing countries (IDC) have tended to try to achieve economic growth and development by importing technology designed for IDC. However, because of several complex technical, cultural and socio-economic factors, this policy has not been always successful. Inappropriate technology transfer has led to many work environment and productivity problems. Consideration of ergonomics in the choice and utilization of the transferred technology can help to create a good fit between technology, technology users and the operating environment. Application of ergonomics is, however, not widely spread in most IDC. Ergonomics input will create the appropriate working environment in which people are safe and motivated to participate and can better utilize company resources for increasing system productivity, reliability and availability.     

Role of ergonomics in the transfer of technology to industrially developing countries

Technological development has contributed to economic growth and social progress as well as a reduction of many sources of occupational accidents, injuries and stresses. However, advanced technology has also brought new sources of work stress and injuries. Industrially developing countries (IDC) have tended to try to achieve economic growth and development by importing technology designed for IDC. However, because of several complex technical, cultural and socio-economic factors, this policy has not been always successful. Inappropriate technology transfer has led to many work environment and productivity problems. Consideration of ergonomics in the choice and utilization of the transferred technology can help to create a good fit between technology, technology users and the operating environment. Application of ergonomics is, however, not widely spread in most IDC. Ergonomics input will create the appropriate working environment in which people are safe and motivated to participate and can better utilize company resources for increasing system productivity, reliability and availability.     

Corporate ergonomics programme at Volvo Car Corporation

One of Volvo Car Corporation's core values is "Environmental Care". Volvo Cars has a tradition of attention to the work environment and has over the years developed a working environment management system, an organisational strategy for the participation of everyone, a working environment policy, standards/specifications and methods for efficient practical performance. The Production Ergonomics Project is an example of this. In order to achieve results in ergonomics one has to work comprehensively, which means working with the product, the process, the workplace, the individuals and the work organisation. The key to success is to train all categories concerned in load ergonomics and to perform methodical ergonomic work through the whole chain from design to production.     

Psychophysical Demands and Perceived Workload—An Ergonomics Standpoint for Lean Production in Assembly Cells

The adoption of a lean production model means a systematic implementation of various management methods and practices. Such a model presents the human element as a key factor in continuous improvement efforts, influencing workers’ job content and the quality of work. However, there are few evidences regarding research on quantitative assessment of the work demand, either psychological or physical, in a lean production environment. Therefore, this study aims to analyze from an ergonomics perspective the psychophysical demand and workers’ perceived workload within assembly cells undergoing a lean production implementation. The proposed method integrates complementary concepts of widely known techniques, enabling the consolidation of several assessment criteria into one particular index for both psychological and physical demands. Such a diagnostic method is illustrated in a case study from the automotive parts manufacturing sector, whose application is performed in three critical assembly cells selected by senior management. Our findings show systemic gaps between work demand and employees’ profile, indicating improvement opportunities in order to provide a better work environment.     

The effect of improved workplace design on the development of work-related musculo-skeletal illnesses

An earlier paper (Westgaard and Aaras, 1984) described the work environment and the health situation of production workers at a small Norwegian factory, prior to an extensive ergonomics effort which primarily aimed to reduce static muscle strain by constructing new workplaces. It was concluded that the old work situation significantly contributed to a high level it musculo-skeletal disorders, most likely because the old work situation made it necessary to work with high level of muscle load for long periods of the working day. This second paper concerns the other important query which initiated Have the extensive ergonomics and environmental efforts at this factory had any effect in terms of improved health of the workers? The factory, the old workplaces and the ergonomics adaptations were described in the preceding paper, and are therefore not included here.     

Rest break interventions in stoop labor tasks

Hand cultivation and harvest of agricultural products constitute strenuous physical tasks. Working with labor-management ergonomics committees in agricultural settings, the UC Agricultural Ergonomics Research Center (AERC) tested an experimental rest and recovery protocol for its impact on symptoms and productivity during two types of work tasks. The experimental condition consisted of adding a 5 min rest break to every working hour in which there was no other scheduled break (e.g., lunchtime). This resulted in an additional 20 min of rest per workday. We tested the intervention in two trials: Trial one compared workers (n=66) randomly assigned to an experimental or a control group during the harvest of commercial strawberries. Trial two utilized a cross-over design (n=16 pairs of workers) to compare experimental and control conditions while workers inserted bud grafts into young 18' high citrus trees. For both trials, workers under the experimental condition reported significantly less severe symptoms than workers under control conditions. The order in which the intervention was given, however, appeared to result in variations in productivity. We conclude that the introduction of frequent, brief rest breaks may improve symptoms for workers engaged in strenuous work tasks.     

Determinants of business sustainability: An ergonomics perspective

There is a need to integrate both macro- and micro-ergonomic approaches for the effective implementation of interventions designed to improve the root causes of problems such as work safety, quality and productivity in the enterprise system. The objective of this study was to explore from an ergonomics perspective the concept of business sustainability through optimising the worker–work environment interface. The specific aims were: (a) to assess the working conditions of a production department work process with the goal to jointly optimise work safety, quality and quantity; (b) to evaluate the enterprise-wide work process at the system level as a social entity in an attempt to trace the root causes of ergonomic issues impacting employees throughout the work process. The Work Compatibility Model was deployed to examine the experiences of workers (that is, effort, perceived risk/benefit, performance and satisfaction/dissatisfaction or psychological impact) and their associations with the complex domains of the work environment (task content, physical and non-physical work environment and conditions for learning/growth/development). This was followed by assessment of the enterprise system through detailed interviews with department managers and lead workers. A system diagnostic instrument was also constructed from information derived from the published literature to evaluate the enterprise system performance. The investigation of the production department indicated that the stress and musculoskeletal pain experienced by workers (particularly on the day shift) were derived from sources elsewhere in the work process. The enterprise system evaluation and detailed interviews allowed the research team to chart the feed-forward and feedback stress propagation loops in the work system. System improvement strategies were extracted on the basis of tacit/explicit knowledge obtained from department managers and lead workers. In certain situations concerning workplace human performance issues, a combined macro–micro ergonomic methodology is essential to solve the productivity, quality and safety issues impacting employees along the trajectory or path of the enterprise-wide work process. In this study, the symptoms associated with human performance issues in one production department work process had root causes originating in the customer service department work process. In fact, the issues found in the customer service department caused performance problems elsewhere in the enterprise-wide work process such as the traffic department. Sustainable enterprise solutions for workplace human performance require the integration of macro- and micro-ergonomic approaches.     

Determinants of business sustainability: an ergonomics perspective

There is a need to integrate both macro- and micro-ergonomic approaches for the effective implementation of interventions designed to improve the root causes of problems such as work safety, quality and productivity in the enterprise system. The objective of this study was to explore from an ergonomics perspective the concept of business sustainability through optimising the worker-work environment interface. The specific aims were: (a) to assess the working conditions of a production department work process with the goal to jointly optimise work safety, quality and quantity; (b) to evaluate the enterprise-wide work process at the system level as a social entity in an attempt to trace the root causes of ergonomic issues impacting employees throughout the work process. The Work Compatibility Model was deployed to examine the experiences of workers (that is, effort, perceived risk/benefit, performance and satisfaction/dissatisfaction or psychological impact) and their associations with the complex domains of the work environment (task content, physical and non-physical work environment and conditions for learning/growth/development). This was followed by assessment of the enterprise system through detailed interviews with department managers and lead workers. A system diagnostic instrument was also constructed from information derived from the published literature to evaluate the enterprise system performance. The investigation of the production department indicated that the stress and musculoskeletal pain experienced by workers (particularly on the day shift) were derived from sources elsewhere in the work process. The enterprise system evaluation and detailed interviews allowed the research team to chart the feed-forward and feedback stress propagation loops in the work system. System improvement strategies were extracted on the basis of tacit/explicit knowledge obtained from department managers and lead workers. In certain situations concerning workplace human performance issues, a combined macro-micro ergonomic methodology is essential to solve the productivity, quality and safety issues impacting employees along the trajectory or path of the enterprise-wide work process. In this study, the symptoms associated with human performance issues in one production department work process had root causes originating in the customer service department work process. In fact, the issues found in the customer service department caused performance problems elsewhere in the enterprise-wide work process such as the traffic department. Sustainable enterprise solutions for workplace human performance require the integration of macro- and micro-ergonomic approaches.     

Field Studies of Shift Work at an Austrian Oil Refinery I: Health and Psychosocial Wellbeing of Workers who Drop Out of Shiftwork

Most of the problems that arise in shift workers prove to be social or family-bound rather than strictly medical, though health may in fact be affected seriously by these problems. The present study was concerned with the question whether, and in what way, men giving up shift work (‘ drop-outs ’) differ from those who stay on shift work, and from those on permanent day work. A questionnaire containing items about personal, family, and social life, and health, working conditions, and sleep was given to 270 workers in an oil refinery. All respondents were subsequently interviewed.

Taking all the results together it is concluded that shift and night work leads, in a proportion of cases, to difficulties with regard to work and family life, as well as in social and health matters. The results from the ‘drop-outs’ group indicate that in certain individuals very long lasting ‘ psychosomatic’, ‘pseudoneurotic’ or ‘sensitisation’ reactions may develop.     

Multi-position ergonomic computer workstation design to increase comfort of computer work

This paper presents a new design of computer workstation that is aimed at increasing the comfort of a user working for long periods at a computer. As we have become a society that spends a lot of time working on computers, the computer workstation needs to provide comfort to users. Discomfort and an improper position can negatively affect overall health and productivity. A new type of ergonomic computer workstation, which allows users to sit in multiple working positions, is proposed in order to provide better comfort to people who spend a long time sitting at their workstations. We have designed and developed a new multi-position ergonomic computer workstation which has 19 degrees of freedom and which can accommodate from 5th to 95th percentile human size. Four types of working position (upright, lean-back, zero-gravity and lean-forward) are preset by choosing different angular positions of the workstation parts. Positions of the workstation parts can be changed by controlling the actuators. These four positions were used to evaluate the comfort of the workstation. Subjective and objective evaluations, including comparison of the prototype and standard computer setup, were carried out using human subjects and ergonomic principles. Results showed that the new workstation is much more comfortable, supporting the body in a balanced way. Users have the freedom to stretch and relax in different working positions before they feel any noticeable discomfort; as a result, it lets users work for a longer period without strain, thus resulting in higher productivity.     

Mapping workers’ performance to analyse workers heterogeneity under different workflow policies

Manual work in assembly lines allows one to benefit from human reasoning capabilities and to assure the flexibility to adapt to fluctuations in production volume, products mix and reduced product lifecycles. With the objective of quantifying and systematizing the knowledge about the heterogeneity of workers’ performance, data was collected in an industrial setting. The results demonstrate a significant variation in workers’ performance in terms of speed and variability of the task completion time. A mapping approach is proposed aiming to quantify the workers’ performance and visualize performance patterns. Since the human performance is influenced by the setting where the workers perform their job, two real assembly line pacing mechanisms were set and studied: pacing derived from the manual assembly system rhythm and pacing imposed by a fixed time constraint. The type of pacing clearly influences workers’ performance (i.e., speed and variability) and revealed a significant influence in the assembly line output. In particular, imposing a fixed and equal time constraint for every worker reduces the heterogeneity of workers’ performance and improves the assembly line output.     

Ergonomics and international standards: history, organizational structure and method of development

Egonomics international standards were formally considered in 1973 by a symposium of the International Ergonomics Association (IEA) held at Loughborough University in the UK. Recommendations led to the establishment of ISO TC 159 'Ergonomics', with Germany (DIN) holding the secretariat. Six subcommittees (SC) were established and have worked towards standards. These have been rationalized to the present four subcommittees: SC1, Ergonomics guiding principles; SC3, Anthropometry and biomechanics; SC4, Ergonomics and human system interaction; and SC5, Ergonomics of the physical environment. The subcommittees have over 15 working groups (WG) covering over 50 work items that will lead to ergonomics ISO standards. Over 20 ISO standards have already been produced and a number have been reconfirmed at automatic five-yearly reviews. The organizational structure is presented as well as methods of standards production from proposed work item to international standard. European standards (EN) are produced under CEN TC 122 'Ergonomics', which has 11 working groups. How European Standards are produced and organizational links with ISO TC 159 are described.