Including rest allowance in mixed-model assembly lines

Abstract

Ergonomics has a significant impact on productivity and human safety in manual assembly lines. For this reason, several studies in recent years have proposed including ergonomics in assembly lines. However, most works are focused on simple assembly lines, while only a few studies exist for mixed-model assembly lines (MMALs). Thus, in this paper, we propose a new methodological approach to include physical fatigue and rest allowance (RA) as ergonomic parameters in MMAL problems. For the balancing problem, we propose a linear mathematical model that minimises the cycle time by including RA. For the sequencing decision, we develop a heuristic approach that assigns workers to workstations according to the workers’ age and their related maximum physical capacity. Then, we propose a linear sequencing model that minimises the work-overload by also evaluating RA to assign each worker according to her or his features. Finally, to complete the study, we test the mathematical models in a real case application and provide a detailed discussion of the results to highlight the benefits we can achieve with this approach.

KEYWORDS:

• Mixed-model assembly line
• human factor
• recovery time
• ageing
• mathematical model
• case study

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Serena Finco

Serena Finco is a Post-doctoral Researcher at the University of Padova. She holds a PhD in Industrial Engineering and she graduated at the University of Padova in Innovation Product Engineering. Her researches are mainly related on industrial and logistic system design and modelling with a particular focus on the integration of ergonomics principles in assembly systems design and balancing techniques. She is also involved in European and Italian projects.

Martina Calzavara

Martina Calzavara is an Assistant Professor in the Department of Management and Engineering at the University of Padua. She is currently teaching in courses, lectures and workshops, at the University of Padua and in other Italian institutes. Her researches are mainly related to industrial and logistics systems design, management and modelling. In particular, she is often focuses on the design and on the improvement of warehousing and assembly systems, through the mathematical modelling of both economic and ergonomics aspects. She is usually also involved in various practical interdisciplinary research projects with important Italian companies.

Fabio Sgarbossa

Fabio Sgarbossa is Full Professor of Industrial Logistics at the Department of Mechanical and Industrial Engineering (MTP) at NTNU (Norway) from October 2018. He was Associate Professor at University of Padova (Italy) where he also received his PhD in Industrial Engineering in 2010. He is leader of the Production Management Group at MTP and he is responsible of the Logistics 4.0 Lab at NTNU. He has been and he is involved in several European and National Projects. He is author and co-author of about 100 publications in relevant international journals, about industrial logistics, material handling, materials management, supply chain. He is member of Organizing and Scientific Committees of several International Conferences, and he is member of editorial boards in relevant International Journals.

Ilenia Zennaro

Ilenia Zennaro is an Assistant Professor and researcher in the Department of Management and Engineering at the University of Padua. Her research interest includes industrial and logistics systems design, management and modelling, and sustainability of industrial plants. In particular, on the design and on the improvement of warehousing and assembly systems, considering both economic and ergonomics aspects, and on maintenance management and on transportation, considering sustainability aspects. She is usually also involved in various practical interdisciplinary research projects with Italian and European companies.