Gestion conjointe de production et qualité appliquée aux lignes de production non fiables

RÉSUMÉ Cette recherche s'intéresse aux lignes de production non fiables formées de plusieurs machines satisfaisant une demande fixe de produits finis de type unique et comprenant des stocks d'encours à capacité fixe. Deux types de machines sont considérés ici: un type de machine dont une partie de la production est non conforme aux normes de la qualité et un autre type de machine dont la production est 100 % conforme. La thèse est organisée selon trois contributions principales. L'objectif visé dans la première partie est de développer des modèles d'analyse de performance et des techniques d'optimisation efficaces pour le réglage des paramètres de conception suivant une approche de contrôle de type CONWIP (Constant Work-In-Process). Notre recherche s'inscrit dans le courant des approches de décomposition des ateliers de fabrication. L'analyse de la performance de ces systèmes aléatoires discrets/continus repose essentiellement sur les équations de Kolmogorov et le principe de la demande moyenne. De plus, nous introduisons des blocs de construction formés de paires de stock local-machine globale. La machine globale commune à toutes ces paires permet alors d'introduire une mesure de corrélation importante entre tous les blocs de construction quelle que soit la distance des stocks qui entrent dans leur composition. Ceci permet de créer des liens entre blocs de construction de la décomposition qui se situent au-delà de leurs voisinages respectifs, comme c'est le cas dans d'autres méthodes de décomposition. Cet aspect de corrélation des machines est caractéristique de la stratégie de production CONWIP. De plus, dans notre modélisation globale, la dynamique totale du stock dans la boucle CONWIP est considérée comme étant essentiellement affectée par les statistiques de fiabilité de la machine M1, et la probabilité de disponibilité des pièces dans le stock (n-1), reflétant ainsi l'opinion que le CONWIP est une forme de Kanban imposée à une collection de machines.----------ABSTRACT This research is concerned with unreliable production lines. Two types of machines are considered here: a machine for which part of the production is part substandard in quality and a machine whose production is 100% in conformity. The thesis is organized according to three principal contributions. In the first part of our research and for a given choice of the maximum allowable total storage parameter, the performance of constant work-in-process (CONWIP) disciplines in unreliable transfer lines subjected to a constant rate of demand for parts is characterized via a tractable approximate mathematical model. For a (n-1) machines CONWIP loop, the model consists of n multi-state machine single buffer building blocks, separately solvable once a total of (n-1)2 unknown constants shared by the building blocks are initialized. The multi-state machine is common to all building blocks, and its n discrete states approximate the joint operating state of the machines within the CONWIP loop; each of the first (n-1) blocks maps into a single internal buffer dynamics, while the nth building block characterizes total work-in-process (wip) dynamics. The blocks correspond to linear n component state equations with boundary conditions. The unknown (shared) constants in the block dynamics are initialized and calculated by means of successive iterations. The performance estimates of interest, mean total wip, and probability of parts availability at the end buffer in the loop are obtained from the model and validated against the results of Monte-Carlo simulations. In the second part of our research, we address the optimal production control problems for an unreliable manufacturing system that produces items that can be regarded as conforming or non conforming. A new stochastic hybrid state Markovian model with three discrete states, also called modes is introduced. The first two, operational sound and operational defective are not directly observable, while the third mode, failure, is observable. Production of defective parts is respectively initiated and stopped at the random entrance times to and departure times from the defective operational mode. The intricate piecewise-deterministic dynamics of the model are studied, and the associated Kolmogorov equations are developed under the suboptimal class of hedging policies

The ConWip Production Control System: a Literature Review

International audienceA growing body of literature dealing with ConWip has been observedduring the past decade. Considering the current industrial challengescharacterized by adaptability, product customization, shortened lead times andcustomer satisfaction, ConWip appears to be an effective and adaptedproduction control system for manufacturers. Given this context, this paper aimsto update the previous literature review about ConWip that was made in 2003and to provide an understanding key through an original classification method.This method allows the reader to distinguish papers that concentrate on ConWipsizing, ConWip performance, ConWip environment or on the comparison ofConWip with other PCS. It also provides a reading key about the researchapproach. Taking these criteria into account, this paper helps to answer thefollowing questions: how can ConWip be implemented? How can ConWip beoptimized? Why and when should ConWip be used? The paper then concludeswith some research avenues

Une approche de décomposition pour le dimensionnement optimal des aires de stockage dans une ligne de production à fiabilité limitée

Abstract We consider a production line composed of m unreliable machines in a tandem configuration. Each machine is represented by a two state Markov chain in continuous time in which states it can respectively process materials up to a specified maximum rate or its production is stopped. Furthermore, buffers are introduced between each machine of the line in order to limit the impact of machines' breakdown on the productivity of the line.Disruption of material throughout the system may become an economical issue.For instance, the customer demand could be satisfied inconsistently, leading to supplementary inventory costs, unprofitable sales and customer dissatisfaction. Then, work-in-process produce by and available to machines play a major role in this system, making it possible for machines to continue to produce materials when one or several of them are being repaired thus maintaining up to a point a continuous flow of production through the line. The level of reliability of work stations must be taken into account in order to calculate a more efficient production plan and better schedule delivery of materials.The objective of this study is to size storage areas of the production line so that disruptions of machines do not affect a continuous flow of parts throughout the system and at a minimum cost of holding inventories in the line. A solution has been proposed by Sadr and Malhamé (2004a). They have developed a decomposition and aggregation methodology for the approximate performance analysis of the line when upstream to downstream machine capacities are monotone decreasing.In this case, a constant average production rate is imposed via a pull mechanism. The main advantage of this scheme is that causality propagates unidirectionally (upstream to downstream), thus making it possible to use dynamic programming as an optimization tool for storage areas sizing and cost optimization of holding inventories in the line. A dual method has long been thought possible. Increasing production rates would represent a push mechanism policy and causality would propagate in this formulation from downstream to upstream. In this study, we examine the possibility of using this methodology for the dual case.----------Résumé Le sujet de cette étude est un système de production composé de m machines en série, que l'on nomme ligne de production. La fiabilité des machines est représentée par un état de bon fonctionnement pour lequel la machine produit à un rythme donné et par un état de mauvais fonctionnement pour lequel la production de cette machine est arrêtée. Le temps passé dans chacun des états est représenté par une loi exponentielle. Ainsi, chaque machine peut être modélisée par une chaîne de Markov en temps continu à deux états. Finalement, des aires de stockage sont introduites dans toute la ligne en prévention des pannes aléatoires des machines de production.Définir la taille optimale de ces aires de stockage est délicat. La fiabilité du système n'étant pas parfaite, une décision de redimensionnement des aires de stockage peut avoir des conséquences sur la production globale du système difficilement prévisibles. On est tenté de réduire les inventaires pour minimiser le coût de stockage mais le risque de rupture de la production est alors augmenté en conséquence. La production globale peut être fortement diminuée et ne plus satisfaire la demande du client ainsi que l'approvisionnement du fournisseur. L'objectif de cette recherche est de développer un modèle mathématique de cette ligne afin de déterminer quelle politique de gestion des aires de stockage permet d'assurer une production moyenne déterminée, à un coût minimal de stockage des biens en cours de production. Une première solution a déjà été proposée par Sadr et Malhamé (2004a) et aboutit sur une méthode de décomposition et agrégation de cette ligne de production. En considérant une demande constante et des taux de production décroissants dans la ligne de production, Sadr et Malhamé (2004a) mettent en évidence une propagation unidirectionnelle, de l'amont vers l'aval, des phénomènes d'arrêt de production qui se manifestent quand les aires de stockage se vident. Ils proposent une modélisation mathématique de la ligne et minimisent le coût de stockage des inventaires par programmation dynamique. La possibilité d'une méthode duale de leurs travaux a longtemps été soupçonnée. Elle considérerait un approvisionnement constant et des taux de production croissants dans la ligne. La production serait alors considérée en flux poussé et les phénomènes de blocage de la production se réaliseraient quand les aires de stockage se remplissent. Dans cette étude, on examine la possibilité d'exploiter une telle méthode duale en suivant les étapes établies dans leurs travaux

Efficient buffer design algorithms for production line profit maximization

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 447-465).A production line is a manufacturing system where machines are connected in series and separated by buffers. The inclusion of buffers increases the average production rate of the line by limiting the propagation of disruptions, but at the cost of additional capital investment, floor space of the line, and inventory. Production lines are also a special case of assembly/disassembly systems as well as closed-loop systems. This thesis makes contributions to production system profit maximization. The profit of a production line is the revenue associated with the production rate minus the buffer space cost and average inventory holding cost. We assume that machines have already been chosen and therefore our only decision variables are the buffer sizes and the loop population. The difficulties of the research come from evaluation and optimization. We improve evaluation of loop systems. The optimization problem is hard since both the objective function and the constraints are nonlinear. Our optimization problem, where we consider the nonlinear production rate constraint and average inventory cost, is new. We present an accurate, fast, and reliable algorithm for maximizing profits through buffer space optimization for production lines, and extend the algorithm to closed-loop systems and production lines with an additional maximum part waiting time constraint. A nonlinear programming approach is adopted to solve the optimization problem. Two necessary modifications are proposed to improve the accuracy of the existing loop evaluation method before optimization of loops is studied. An analytical formulation of the part waiting time distribution is developed for two-machine one-buffer lines. It is used in the profit maximization for production lines with both the production rate constraint and the maximum part waiting time constraint. Numerical experiments are provided to show the accuracy and efficiency of the proposed algorithms. Finally, a segmentation method and an additive property of production line optimization are studied. They enable us to optimize very long lines rapidly and accurately.by Chuan Shi.Ph.D

Design and Management of Manufacturing Systems

Although the design and management of manufacturing systems have been explored in the literature for many years now, they still remain topical problems in the current scientific research. The changing market trends, globalization, the constant pressure to reduce production costs, and technical and technological progress make it necessary to search for new manufacturing methods and ways of organizing them, and to modify manufacturing system design paradigms. This book presents current research in different areas connected with the design and management of manufacturing systems and covers such subject areas as: methods supporting the design of manufacturing systems, methods of improving maintenance processes in companies, the design and improvement of manufacturing processes, the control of production processes in modern manufacturing systems production methods and techniques used in modern manufacturing systems and environmental aspects of production and their impact on the design and management of manufacturing systems. The wide range of research findings reported in this book confirms that the design of manufacturing systems is a complex problem and that the achievement of goals set for modern manufacturing systems requires interdisciplinary knowledge and the simultaneous design of the product, process and system, as well as the knowledge of modern manufacturing and organizational methods and techniques