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

Research Article Balancing the Production Line by the Simulation and Statistics Techniques: A Case Study

Abstract: A wide range of the real world problems in industries are related to misbalances of the production line and excessive Work in Process parts (WIP). Simulation is an effective method to recognize these problems with consuming least cost and time. Moreover, total system efficiency of a production line can be extremely improved by examining different solution scenario via the simulation techniques. In this research, we utilize the simulation technique founded upon the software Enterprise Dynamics (ED) for evaluating the cause of these problems and trying to find the improvement solutions in Sadid Pipe and Equipment Company (SPECO). Two parameters of diameter and thickness are important factors affecting the time of workstations. The effects of these factors on process time are evaluated by hypothesis tests. Two improvement scenarios have been presented. In the first scenario, the layout design of the factory has been improved with regard to production process and bottleneck station. In the second one, an essential improvement has been carried out by reduction in wastages. Regarding the accomplished simulations, it is concluded that it is possible to eliminate the existing bottleneck by implementing changes in the locations of production stations or reducing the waste in some stations. The improvements eventually result in balancing the production line

PROBLÈMES COMBINATOIRES EN CONFIGURATION DES LIGNES DE FABRICATION (ANALYSE DE COMPLEXITÉ ET OPTIMISATION)

L'objectif de la thèse est de créer et développer de nouvelles méthodes de résolution efficaces des problèmes combinatoires en configuration des lignes de fabrication. Deux problèmes ont été particulièrement étudiés: le problème d'équilibrage et de choix d'équipement pour des lignes dédiées et le problème de minimisation des coûts de changements de séries pour des lignes multi-produits. Une solution du premier problème consiste en une affectation admissible des ressources à un nombre de stations à déterminer de sorte que le coût total soit minimal. Afin de résoudre ce problème, nous l'avons réduit au problème de partition d'ensemble et l'avons résolu par des heuristiques gloutonnes et une méthode exacte de génération de contraintes. Les expérimentations sur différentes instances ont montré que la nouvelle approche de résolution surclasse les approches antérieures de la littérature en termes de qualité de solution et de temps de calcul. Pour le second problème deux critères sont considérés lexicographiquement : la minimisation du nombre de stations et la minimisation du coût de changement de séries. Nous avons examiné successivement les cas d'exécution parallèle et séquentielle des opérations. Des solutions approchées ont été trouvées par des heuristiques gloutonnes. Ensuite, nous avons proposé deux modèles de programmation linéaire en nombres entiers (PLNE) afin de trouver le nombre de stations minimal et ensuite d'obtenir le coût de changement de séries minimal. Les résultats des expérimentations sur ces nouveaux problèmes se sont avérés prometteurs à la fois en termes de qualité de solution et de temps de calcul.The objective of this thesis is to create and develop new effective solution methods for production line configuration problems. Two problems were studied: the equipment selection and balancing problem for dedicated lines and the setup cost minimization problem for multi-product lines. A solution for the first problem consists in a feasible assignment of the resources to an unknown number of stations so that the total cost is minimized. In order to solve this problem, we reduced it to the set partitioning problem and solved it by greedy heuristics and an exact method of constraint generation. The computer experiments on different problem instances showed that the new solution approach outperforms the previous methods from the literature both in terms of solution quality and computational time. For the second problem two criteria were considered lexicographically: the minimization of the number of stations and the minimization of the total setup cost. We examined successively the cases with parallel and sequential execution of operations. Approximate solutions were found by greedy heuristics. Then, we proposed two integer programming models in order to obtain the minimal number of stations and then the minimal setup cost. The experimental results for this new problem proved to be promising both in terms of solution quality and computational time.ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

Reduction approaches for a generalized line balancing problem

International audienceAn NP-hard optimization problem dealing with the assignment of operations to the workstations and spindle heads of a machining transfer line is studied. Precedence, inclusion and exclusion constraints among the operations, capacity and cycle time constraints exist. The objective is to minimize the cost of the line being designed. This problem has been referred to as the Transfer Line Balancing Problem (TLBP) and is a generalized case of well-known simple assembly line balancing problem. In literature, few exact methods have been proposed to solve it. Since the problem is NP-hard, those that do are too time-consuming for solving real life industrial cases. This paper presents effective pre-processing methods which can reduce the size of the initial problem in order to shorten the solution time required. These methods are evaluated on three datasets of new generated problem instances and known benchmarks. The results obtained show that for certain cases the solution time can be significantly reduced when these pre-processing methods are applied