Comparing fixed and walking worker strategies: design implications of individual worker efficiency on assembly line performance

Human workers are essential in modern assembly systems, enabling flexibility, reconfigurability, and efficient resource utilisation while minimising costs. However, high workforce turnover and heterogeneity in individual skills and efficiency make it challenging to meet production targets effectively. Fixed Worker Assembly Line (FWAL) and Walking Worker Assembly Line (WWAL) represent two alternative workforce strategies to handle variations in production volume and mix. Current literature mainly proposes comparison analyses focusing on productivity assets, whereas workforce different efficiency levels have been rarely integrated in comparative models. This study investigates the suitability of these strategies based both on production characteristics and worker efficiency through the simulation of multiple scenarios, considering factors such as productivity rate, workstation layout, assembly time unbalancing, moving times, buffer capacity, and worker efficiency. Results show that mixed-model assembly lines with parallel stations and walking workers (MMAL-PSWW) perform best in environments with high worker heterogeneity, low ideal productivity rates, and significant system unbalancing. The key outcome of this research is a decision tree model that serves as a practical decision-support tool, offering clear guidelines to help managers select the most effective assembly line design under varying operational conditions. Highlights Exploring the comparison between fixed worker and walking worker strategies in assembly system, considering real-world constraints. Introducing a simulation approach that incorporates multiple factors influencing system performance, with particular emphasis on variables related to individual worker efficiency. Providing decision-makers with a graphical decision support tool to evaluate the impact of worker efficiency on assembly line strategy optimisation.