Minimizing and Balancing Ergonomic Risk of Workers of an Assembly Line by Job Rotation: a MINLP Model

Abstract

In today's economic context the workforce is a crucial asset in manufacturing industries. The employee performance and productivity are affected by many factors related on one hand to the line efficiency and, on the other hand, to the well-being of the workers. On the basis of new technologies and driven by Industry 4.0 paradigms, the need of a high production rate cannot neglect the safeguarding of the workers. In case of repetitive manual tasks, workers are exposed to the risk of musculoskeletal disorders (MSDs), that can be reduced by applying ergonomics principles both in design (e.g. workstation design, equipment tools identification, etc.) and in operative phases (e.g. workload balance, tasks assignment, etc.). In the operative phase, job rotation is one of the most widespread methods for alleviating physical fatigue and reducing the stress due to repetitive tasks. However, often, job rotation strategies fail due to the lack of systematic approach or effective management of rotation schedules, being very difficult to identify an effective job rotation schedule allowing maintaining the same productivity rate. The problem is of particular interest under the perspective 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 proposed a model for minimizing the exposure risk of workers involved in repetitive manual tasks, by balancing the human workloads and reducing the ergonomic risk within acceptable limits, for a given production target. Risk and its acceptability are evaluated using the RULA method, according to a mixed integer programming approach. Results shown the effectiveness of the model to identify the optimal job rotation schedules jointly achieving productivity and ergonomic risk goals.

Designing Cyclic Job Rotations to Reduce the Exposure to Ergonomics Risk Factors

“…Implementing a complex rotation schedule, like that shown in Figure 1a, supposes some organizational problems [39]. Each worker must follow a different and complex path, and the workers must memorize the sequence of workstations.…”

A job rotation‐scheduling model for blue‐collar employees' hand–arm vibration levels in manufacturing firms

“…Thus, we did not have a chance to directly compare the results of this paper with any related literature. However, there are studies that investigate other ergonomic attributes of workplaces (such as noise exposure or physical workload of employees) in a job rotation environment (Aryanezhad et al, 2009; Digiesi et al, 2018; Yoon et al, 2016; etc. ).…”

“…There are some studies which focus on ergonomic issues in arranging manufacturing operations in the literature. In previous studies on this topic, some researchers have taken into account repetitive actions in assembly‐line balancing by employing the Occupational Repetitive Actions index (Baykasoglu et al, 2017; Moussavi et al, 2016; Sana et al, 2019), whereas others considered the working position in assigning workers to jobs by adopting rapid upper limb assessment (RULA) or rapid entire body assessment (REBA) (Digiesi et al, 2018; Yoon et al, 2016). To the best of our knowledge, there is no published paper that integrates HAV into job rotation schedules in manufacturing companies.…”

“…Hochdörffer et al (2018) developed the job rotation schedules in their short‐term planning studies according to the ergonomic feature of the workstation decided upon whether the whole body would operate for the duty or hand–finger system mostly. Further, Digiesi et al (2018) developed a nonlinear mathematical model to minimize the ergonomic risk exposure of the workers which were caused by repetitive manual tasks. They integrated their mathematical model with RULA, which is one of the ergonomic risk assessment approaches.…”

Impact of work-sharing on the performance of production line with heterogeneous workers

“…The objectives of their proposed model minimize the production cost, labor cost, and production waste. A recent work of Digiesi [12] proposed a job-rotation workforce scheduling model, to minimize the exposure risk of workers occurring from repetitive manual tasks. They implemented the Rapid Upper Limb Assessment (RULA) method to consider the exposure risk.…”