Reducing physical ergonomic risks at assembly lines by line balancing and job rotation: A survey

Factors such as repetitiveness of work, required application of forces, handling of heavy loads, and awkward, static postures expose assembly line workers to risks of musculoskeletal disorders. As a rule, companies perform a post hoc analysis of ergonomic risks and examine ways to modify workplaces with high ergonomic risks. However, it is possible to lower ergonomic risks by taking ergonomics aspects into account right from the planning stage. In this survey, we provide an overview of the existing optimization approaches to assembly line balancing and job rotation scheduling that consider physical ergonomic risks. We summarize major findings to provide helpful insights for practitioners and identify research directions

Stability measure for a generalized assembly line balancing problem

AbstractA generalized formulation for assembly line balancing problem (GALBP) is considered, where several workplaces are associated with each workstation. Thus, all tasks assigned to the same workstation have to be partitioned into blocks: each block regroups all tasks to be performed at the same workplace. The product items visit all workplaces sequentially, therefore, all blocks are proceeded in a sequential way. However, the tasks grouped into the same block are executed simultaneously. As a consequence, the execution of a block takes only the time of its longest task. This parallel execution modifies the manner to take into account the cycle time constraint. Precedence and exclusion constraints also exist for workstations and their workplaces. The objective is to assign all given tasks to workstations and workplaces while minimizing the line cost estimated as a weighted sum of the number of workstations and workplaces. The goal of this article is to propose a stability measure for feasible and optimal solutions of this problem with regard to possible variations of the processing time of certain tasks. A heuristic procedure providing a compromise between the objective function and the suggested stability measure is developed and evaluated on benchmark data sets

Reverse supply chains: A source of opportunities and challenges

Reverse supply chains: A source of opportunities and challenges

Reconfiguration des lignes d'usinage de transfert

International audienceUne ligne de transfert est composée d'une séquence de machines où des blocs d'opérations sont exécutés de façon séquentielle par des têtes d'usinage [1]. Le but de la reconfiguration d'une ligne est de minimiser le coût de passage d'un produit à un autre. Pour ce problème, nous proposons un modèle mathématique qui tient compte des contraintes liées à la réutilisabilité des équipements existants

Design, simulation and experimental investigation of a novel reconfigurable assembly fixture for press brakes

A reconfigurable assembly fixture is a major and important component of a reconfigurable assembly system. It isrequired for the assembly of a variety of press brake models inorder to reduce the assembly time and overall production time.The stages and requirements for the design of an assembly fixtureand understanding of the assembly process for press brakemodels were used to design a reconfigurable assembly fixture.A detailed design analysis of parts of the fixture and the hydraulicsystem is considered and presented in this article. The stress anddisplacement analysis of the parts is executed using Solidworksexpress simulation. The parameters of the hydraulic componentswere determined from force requirements, and the hydraulic system was modelled physically using Matlab Simscape hydraulics.The response of the hydraulic system was obtained for eachactuator in the system in order to depict the output of the actuators from the spool displacement of the valves. Stress analysisconducted on parts of the fixture showed that it can withstandmaximum stresses that are lesser than the yield strength of thematerial used for the part. It was also established that synchronization of hydraulic actuators can best be achieved by the use of asine input to the electrohydraulic valve. An experimental investigation was done using FESTO hydraulic test bench in order toobserve the synchronized extension and retraction of the hydraulic actuators. The simulation of the hydraulic system, electricsystem and the programmable logic controller was prepared using automation studio. The design is envisaged to provide the industries with relevant information on accurate location and gripping of press brake frames rather than turning and repositioning of the frame in order to fit other parts during assembly. The article provides relevant information on the design analysis of a reconfigurable assembly fixture for press brakes which is novel because articles on reconfigurable assembly fixtures have not considered its application to press brake assembly

Decision support for design of reconfigurable rotary machining systems for family part production

To remain competitive in currently unpredictable markets, the enterprises must adapt their manufacturing systems to frequent market changes and high product variety. Reconfigurable manufacturing systems (RMSs) promise to offer a rapid and cost-effective response to production fluctuations under the condition that their configuration is attentively studied and optimised. This paper presents a decision support tool for designing reconfigurable machining systems to be used for family part production. The objective is to elaborate a cost-effective solution for production of several part families. This design issue is modelled as a combinatorial optimisation problem. An illustrative example and computational experiments are discussed to reveal the application of the proposed methodology. Insight gained would be useful to the decision-makers managing the configuration of manufacturing systems for diversified products

Workforce management in manual assembly lines of large products: a case study

Assembly lines are used for a large variety of products in different industrial sectors. In this paper the focus is placed on complex assembly systems and workstations used for the final assembly of large and bulk products, such as trucks, aircrafts, buses, tool machines. An high number of tasks to be performed at a single assembly station, several workers involved in parallel in the assembly process and long Takt times make such systems different from the models intensively studied in the literature (e.g. the traditional Simple Assembly Line Balancing Problem). This study firstly presents a new balancing model to address the problem of the total cost minimization when different operator skills are involved at the same time and then it applies the model to a real industrial case

Résolution d’un programme linéaire sous incertitude avec l’Uninorme R ∗

Lors de la résolution d’un problème de décision, il est souvent nécessaire de tenir compte de l’incertitude des paramètres, par exemple sur les valeurs des coûts. Plusieurs critères ont été proposés dans la littérature pour prendre en compte l’optimisme du décideur dans le cas des scénarios discrets. Les plus classiques sont Hurwicz [1] et OWA [3]. Dans le critère OWA, on classe les coûts des différents scénarios du meilleur au moins bon, puis on calcule une moyenne pondérée sur les coûts classés (les poids dépendent du classement). Le critère d’Hurwicz est un cas particulier de l’OWA quand le meilleur scénario a un poids de α, le pire scénario a un poids de 1 − α et tous les autres scénarios ont un poids de 0. Ces deux critères sont compensatoires, c’est à dire qu’un bon scénario va atténuer l’effet d’un mauvais scénario et inversement. Dans cet article, on se place dans le cas où l’ensemble des scénarios est fini et équiprobable et on s’intéresse à prendre en compte l’optimisme du décideur avec un critère qui ne soit pas compensatoire, distinguant ainsi des zones de risques et d’opportunités. On va utiliser pour cela un critère d’agrégation R ∗ appartenant à la famille des Uninormes. D’abord on définit ce critère et ses propriétés pour l’utiliser ensuite pour résoudre un programme linéaire (PL)

A bibliographic review of production line design and balancing under uncertainty

This bibliography reviews the solution methods developed for the design and balancing problems of production lines such as assembly and disassembly lines. The line design problem aims in determining the number of workstations along with the corresponding assignment of tasks to each workstation, while the line balancing problem seeks an assignment of tasks, to the existing workstations of the line, which ensures that the workloads are as equal as possible among the workstations. These two optimisation problems can be also integrated and treated as a multi-objective optimisation problem. This review considers both deterministic and stochastic formulations for disassembly lines and is limited to assembly line design and balancing under uncertainty. This bibliography covers more than 90 publications since 1976 for assembly and 1999 for disassembly

Équilibrage des lignes de désassemblage sous incertitude en présence de composants polluants

International audienceLe problème d'équilibrage d'une ligne de désassemblage consiste en l'affectation des tâches de désassemblage, I = { 1 , 2 ,..., N } , N ∈ N ∗ , à une séquence de postes de travail, J = { 1 , 2 ,..., M } , M ∈ N ∗ , sous les contraintes de précédence et du temps de cycle, C t . Cer- taines tâches impliquent le désassemblage des composants polluants. Les durées des tâches, ζ i , i ∈ I sont des variables aléatoires indépendantes normalement distribuées avec des paramètres connus i.e. ζ i ∼ N ( μ i ,σ i ) , t i > 0 , i ∈ I . Les contraintes de précédence sont modélisées par un graphe AND/OR, [1]. L'objectif est de minimiser le coût total de la ligne, en minimisant le nombre de postes de travail, ainsi que le nombre de postes sur lesquels le désassemblage des composants polluants est effectué. En même temps, il est nécessaire d'assurer que la probabilité d'arrêt de la ligne à cause d'un dépassement du temps de cycle sur un poste de travail soit inférieur à 1 − α , où α représente un seuil fixé par le décideur (de l'ordre de 5% )