XVII International Scientific Conference on Industrial Systems (IS'17) Novi Sad, Serbia, October 4. – 6. 2017. University of Novi Sad, Faculty of Technical Sciences, Department for Industrial Engineering and Management Available online at http://www.iim.ftn.uns.ac.rs/is17 IS'17 A RULA-Based Optimization Model for Workers’ Assignment to an Assembly Line Salvatore Digiesi Department of Mechanics, Mathematics and Management (Polytechnic University of Bari, V.le Japigia 182, Italy, salvatore.digiesi@poliba.it) Francesco Facchini Department of Mechanics, Mathematics and Management (Polytechnic University of Bari, V.le Japigia 182, Italy, francesco.facchini@poliba.it) Giorgio Mossa Department of Mechanics, Mathematics and Management (Polytechnic University of Bari, V.le Japigia 182, Italy, giorgio.mossa@poliba.it) Giovanni Mummolo Department of Mechanics, Mathematics and Management (Polytechnic University of Bari, V.le Japigia 182, Italy, giovanni.mummolo@poliba.it) Abstract Performance of assembly lines require meeting conflictual goals: a high production rate and a high level of flexibility. Flexibility is often provided by human dexterity and the cognitive capabilities of the workforce. In the case of repetitive manual tasks, workers are exposed to the risk of musculoskeletal disorders (MSDs). In these contexts, a high production rate leads to high physical workload, and job rotation is adopted in order to reduce the ergonomic risk. The problem is of particular interest in the view of the workforce aging, a social European phenomenon which is also affecting production systems performance. Designing and scheduling of human-based assembly systems require a joint evaluation of production system performance and a good balancing of MSDs risk among workers. The authors propose a mixed integer non linear programming model allowing for the balancing of MSDs risk while meeting production rate of an assembly line. Risk and its acceptability are evaluated using the RULA method (Rapid Upper Limb Assessment), widely recognized as an effective tool for the risk assessment of Upper Limb Work related MSDs (UL-WMSDs). Different workers' performance due to their respective training levels / skills and age is considered in the problem formulation. Results show the model's capacity to identify optimal job rotation schedules jointly achieving productivity and ergonomic risk goals. Performances of the solutions obtained improve as workforce flexibility increases. Key words: Human Workload Balancing; Mathematical Programming; RULA; UL-WMSDs 1. INTRODUCTION In a context where the market paradigms radically change in order to meet competition on global markets and to ensure long-term success, the companies need to adapt to shorter delivery times, increasing product variability and high market volatility. One of the major cornerstones to meet these challenges is the implementation of models based on the digital information and the communication technologies in order to introduce a dynamic production environment allowing to ensure competitiveness and overall well being of workers. Currently there is a digital transformation in progress that covers crosscutting aspects of the industrial activities under economical, technological, social, and well being perspective. A technological development to fit into the so-called Fourth Industrial Revolution finalized to improving the performance of the process and of the product ensuring the psychophysical wellbeing of worker. The main goal of Industry 4.0 is to “rethink” f actories through the use of digital, to reconsider the design approach and to monitor the production process in real time. In particular in assembly system, the application of Digital Manufacturing leads to a series of steps forward, 8