Production Ergonomics: Identifying and managing risk in the design of high performance work systems

Sammanfattning: Poor ergonomics in production systems can compromise performance and cause musculoskeletal disorders (MSDs), which pose a huge cost to society, companies, and afflicted individuals. This thesis presents a research trajectory through the problem space by: 1) Identifying and quantifying workplace risk factors for MSDs, 2) Identifying how these risks may relate to production strategies, and 3) Developing an approach to integrating ergonomics into a companies’ regular development work. A video analysis tool for quantifying postures while working was developed. The tools’ reliability, accuracy, and ability to identify risks for MSD were evaluated. The tool had generally good accuracy and good to moderate reliability. Low back MSDs were strongly associated with working trunk postures. Operators with high exposure to peak flexion level had 4.2 times higher MSD risk than unexposed operators. Similarly high peak extension velocity increased risk by 2.9 times. (Paper 1) Two pre-post case studies using multiple mixed methods were conducted to examine how production strategies can affect productivity and ergonomics outcomes. The case of electronics assembly, showed how automation can increase output while eliminating repetitive monotonous work. Automation to serial flow, however, resulted in increased repetitiveness at remaining assembly stations. Despite ergonomic workstation design efforts, shoulder loading increased 14%. (Paper 2) The case of engine assembly compared cellular and line production strategies. The line demonstrated system, balance, and disturbance related losses resulting in forced operator waiting. Nevertheless, the line overcame productivity barriers in the operation of the cellular system. The line system showed increased repetitiveness with cycle times that were 6% of previous, uneven distributions of physical tasks such as nut running, and reductions in influence over work scales all implying increased risk. Teamwork in the line system contributed to significantly increased co-worker support – an ergonomic benefit. (Paper 3) An action research project was initiated, with the same engine manufacturer, to integrate ergonomics into regular development work. The change process was slow and marked by setbacks, caused by both individual factors (e.g. disinterest, changing jobs, illness), and organisational factors such as inter-group communication barriers and short project timelines that limited uptake of new approaches. Despite these setbacks the resolute production manager, acting as a “political reflective navigator”, was able to establish credibility, overcome resistance, and begin to integrate ergonomics into regular developmental processes. The process remains slow and is vulnerable so long as the manager is navigating alone. (Paper 4) Workplace risk factors could be precisely and accurately quantified. These risks are embedded in strategic choices in the design process. Load amplitudes were determined by workstation layout and the material supply sub-system. Risk related to the pattern and duration of loading were determined more by flow and work organisation elements. Psychosocial risk factors appear to be affected by a combination of system design elements. Managing the emergence of these risks proactively requires attention to ergonomics throughout the design process, especially in strategic choices. Integrating ergonomics into early development stages implies changing roles for groups and individuals in the organisation. This approach appears feasible but is difficult and remains an under-utilised strategy for sustainable competitive advantage.