Production Scheduling

Generally speaking, scheduling is the procedure of mapping a set of tasks or jobs (studied objects) to a set of target resources efficiently. More specifically, as a part of a larger planning and scheduling process, production scheduling is essential for the proper functioning of a manufacturing enterprise. This book presents ten chapters divided into five sections. Section 1 discusses rescheduling strategies, policies, and methods for production scheduling. Section 2 presents two chapters about flow shop scheduling. Section 3 describes heuristic and metaheuristic methods for treating the scheduling problem in an efficient manner. In addition, two test cases are presented in Section 4. The first uses simulation, while the second shows a real implementation of a production scheduling system. Finally, Section 5 presents some modeling strategies for building production scheduling systems. This book will be of interest to those working in the decision-making branches of production, in various operational research areas, as well as computational methods design. People from a diverse background ranging from academia and research to those working in industry, can take advantage of this volume

A MODEL BASED APPROACH TO THE DESIGN AND IMPLEMENTATION OF COMPUTER AIDED PRODUCTION MANAGEMENT SYSTEMS

This work investigated the use of generic models in the early stages of the design and implementation of computer aided production management (CAPM) systems. A set of issues that affect the success of such CAPM systems was identified, using information obtained from literature and observations made by the author during an in-depth case study of the design and implementation of a CAPM system. The set of issues included the failure of many manufacturing companies to take a systemic perspective of CAPM and the importance of developing a thorough understanding of existing systems and how these systems are currently integrated. Requirements were proposed for an improved approach to the design and implementation of CAPM systems. Taking the requirements into consideration the concepts underlying the use of and types of models were explored. In particular, the use of generic models and how generic models could help manufacturing companies were considered. The work also investigated the use of soft systems thinking and the concept of a business process to encourage a systemic perspective to be taken. A genetic process model was proposed as a means of meeting the requirements of an improved approach. A generic model of an "order fulfilment" process in a manufacturing company was developed and a way of using it which embodies soft systems principles was proposed. The model and its use was validated using five key needs of practitioners. The validation involved a review of the model by practitioners and the use of the model in a local company as part of a project to design and implement a CAPM system. The originality of this work lies in the development by the author of a generic model which can be used as part of an improved model based approach to the design and implementation of CAPM systems. This should provide clear advantages over existing approaches

Lead-time reduction and improving the operating efficiency

For a successful manufacturing company to consistently realise success invariably requires the organisation to find new methods of achieving competitive advantages. Today time is on the cutting edge and represents one of the most determinants of leading companies. This project is a part of an ongoing effort to sustain a competitive position and thus maintain company prosperity especially with new competitors entering the European Community (EU). Additionally reduced lead-time at Hephaestus S.A., will lead to reduced operating costs, which will enhance the profitability of this company. The aim of this project is to develop a generic tool based on the knowledge gained from a literature research into formal methodologies for reducing leadtime. This generic tool was tested by its application to the activities of Hephaestus S.A., and investigated how problems areas can be addressed. Finally recommendations have been made to Heaphaestus S.A. for reducing its lead-time and improving its operating efficiencyMS

Diffusion of agile supply chains attributes: a study of the UK upstream oil and gas industry cluster

This study examines agile supply chain capabilities in oil and gas clusters, in the light of cluster and industrial district theory. The aim is to provide evidence of their potential impact on competitiveness and business performance within the UK upstream oil and gas cluster. Agility is the ability of organisations to operate and prosper in market conditions characterised by dynamism and constantly changing customer tastes. Clusters and industrial districts refer to the geographic concentration of firms in an industry that enables the firms to benefit from competition and cooperation as well as enhanced productivity within the cluster.A review of past theoretical and empirical studies on supply chain management, agility and clusters identifies four dimensions of agility: customer enrichment, cooperating to compete, mastering change and uncertainty, and leveraging the impact of people and information. The cluster theory points to the competitive advantage of being in geographic proximity to the members of a supply chain, including enhanced productivity, easy access to enriched and high quality factors of production, reduction of transaction and transportation costs as well as increased innovativeness. These all contribute to improving the competitive capability of a firm as well as having impact on the business performance of organisations. A survey of 880 firms in the UK upstream oil and gas cluster was conducted to determine the specific impact of cluster location attributes on the agility of supply chains. Six case studies involving the three tiers of the supply chain and supporting organisation were carried out.Structural equation modelling revealed strong impact of clusters on competitive objectives but weak impact on business performance. Results from the survey show that cluster agility has strong impact on both competitive objectives and business performance. The case study revealed that agility is a strategic tool adopted by the smaller organisations within the supply chain to mitigate the scale of large organisations. Equally, SMEs consider that being in UK oil and gas cluster enhances their responsiveness

MRP IV: Planificación de requerimientos de materiales cuarta generación. Integración de la planificación de la producción y del transporte de aprovisionamiento

Tesis por compendioEl sistema de planificación de requerimientos de materiales o MRP (Material Requirement Planning), desarrollado por Orlicky en 1975, sigue siendo en nuestros días y, a pesar de sus deficiencias identificadas, el sistema de planificación de la producción más utilizado por las empresas industriales. Las evoluciones del MRP se vieron reflejadas en el sistema MRPII (Manufacturing Resource Planning), que considera restricciones de capacidad productiva, MRPIII (Money Resource Planning), que introduce la función de finanzas; y la evolución comercial del mismo en el ERP (Enterprise Resource Planning), que incorpora modularmente todas las funciones de la empresa en un único sistema de decisión, cuyo núcleo central es el MRP. Los desarrollos posteriores de los sistemas ERP han incorporado las nuevas tecnologías de la información y comunicaciones. Asimismo, éstos se han adaptado al contexto económico actual caracterizado por la globalización de los negocios y la deslocalización de los proveedores desarrollando otras funciones como la gestión de la cadena de suministro o del transporte, entre otros. Por otro lado, existen muchos trabajos en la literatura académica que han intentado resolver algunas de las debilidades del MRP tales como la optimización de los resultados, la consideración de la incertidumbre en determinados parámetros, el inflado de los tiempos de entrega, etc. Sin embargo, tanto en el ámbito comercial como en el científico, el MRP y sus variantes se centran en el requerimiento de los materiales y en la planificación de las capacidades de producción, lo que es su desventaja principal en aquellas cadenas de suministro donde existe una gran deslocalización de los proveedores de materias primas y componentes. En estos entornos, la planificación del transporte adquiere un protagonismo fundamental, puesto que los elevados costes y las restricciones logísticas suelen hacer subóptimos e incluso infactibles los planes de producción propuestos, siendo la re-planificación manual una práctica habitual en las empresas. Esta tesis doctoral propone un modelo denominado MRPIV, que considera de forma integrada las decisiones de la planificación de materiales, capacidades de recursos de producción y el transporte, con las restricciones propias de este último, tales como diferentes modos de recogida (milk-run, camión completo, rutas) en la cadena de suministro con el objetivo de evitar la suboptimización de estos planes que en la actualidad se generan usualmente de forma secuencial e independiente. El modelo propuesto se ha validado en una cadena de suministro del sector del automóvil confirmando la reducción de costes totales y una planificación más eficiente del transporte de los camiones necesarios para efectuar el aprovisionamiento.Díaz-Madroñero Boluda, FM. (2015). MRP IV: Planificación de requerimientos de materiales cuarta generación. Integración de la planificación de la producción y del transporte de aprovisionamiento [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48524TESISCompendi

Metodología de implantación de modelos de gestión de la información dentro de los sistemas de planificación de recursos empresariales. Aplicación en la pequeña y mediana empresa

La Siguiente Generación de Sistemas de Fabricación (SGSF) trata de dar respuesta a los requerimientos de los nuevos modelos de empresas, en contextos de inteligencia, agilidad y adaptabilidad en un entono global y virtual. La Planificación de Recursos Empresariales (ERP) con soportes de gestión del producto (PDM) y el ciclo de vida del producto (PLM) proporciona soluciones de gestión empresarial sobre la base de un uso coherente de tecnologías de la información para la implantación en sistemas CIM (Computer-Integrated Manufacturing), con un alto grado de adaptabilidad a la estnictura organizativa deseada. En general, esta implementación se lleva desarrollando hace tiempo en grandes empresas, siendo menor (casi nula) su extensión a PYMEs. La presente Tesis Doctoral, define y desarrolla una nueva metodología de implementación pan la generación automática de la información en los procesos de negocio que se verifican en empresas con requerimientos adaptados a las necesidades de la SGSF, dentro de los sistemas de gestión de los recursos empresariales (ERP), atendiendo a la influencia del factor humano. La validez del modelo teórico de la metodología mencionada se ha comprobado al implementarlo en una empresa del tipo PYME, del sector de Ingeniería. Para el establecimiento del Estado del Arte de este tema se ha diseñado y aplicado una metodología específica basada en el ciclo de mejora continua de Shewhart/Deming, aplicando las herramientas de búsqueda y análisis bibliográfico disponibles en la red con acceso a las correspondientes bases de datos

Sistemas distribuídos de produção em ambiente de produção simultânea

Novos paradigmas de produção emergem na economia global, aparentemente baseados em três tendências principais. Estas tendências são: aumento da dinâmica de reconfiguração dos sistemas de produção, distribuição dos recursos do sistema de produção, e virtualidade dos sistemas, i.e. sistemas que são configurados em termos organizacionais, sem alteração da implantação física dos equipamentos. A primeira tendência deve-se ao aumento de requisitos do produto, nomeadamente ao nível da qualidade, variedade e entrega. A segunda tendência resulta de uma necessidade de melhoria do desempenho do sistema de produção, e a terceira, deve-se à impossibilidade de agrupamento físico de recursos de produção distribuídos globalmente e às possibilidades oferecidas pelos sistemas de comunicação existentes. Com base nas referidas tendências surgem novos requisitos de projecto e operação de sistemas de produção. Podem-se seleccionar alguns destes requisitos, resumidos da seguinte forma: aumento da reconfigurabilidade do sistema baseada em recursos de produção distribuídos e na entrega rápida dos produtos encomendados. Com base nestes requisitos, apresenta-se uma definição e desenvolve-se um modelo de Sistema Distribuído de Produção (SDP), denominado MSDP. Neste modelo existe uma relação estreita entre a estrutura genérica do sistema distribuído de produção e a estrutura de transformações de estado do produto encomendado. Desenvolve-se ainda um modelo conceptual baseado em agentes de software do MSDP, e uma representação formal do modelo com base em Redes de Petri e em mecanismos de modelação apresentados por Lecompte, Deschamps and Bourrières (2000). O modelo formal desenvolvido é aplicado a várias configurações de sistemas, relacionadas com a estrutura de algum produto encomendado. Esta aplicação permite verificar a possibilidade de utilização do modelo para representar diferentes SDPs e para estudar o comportamento de SDPs de acordo com a filosofia de Produção Simultânea. Esta filosofia tem como principal objectivo a redução do prazo de entrega de encomendas através da redução do tempo de percurso de fabrico de cada encomenda. O estudo realizado neste trabalho permite concluir que o modelo pode ser utilizado para projecto e avaliação de sistemas distribuídos de produção dedicados a cada encomenda. Além disso, verificou-se que se obtêm ganhos importantes de tempo de percurso de fabrico e de qualidade de serviço de produção para pequenos graus de simultaneidade. Isto foi avaliado para algumas estruturas, por aplicação de estratégias de Produção Simultânea baseada na utilização de recursos de produção alternativos e na partição de encomendas. Como esperado, o melhor desempenho obtém-se para a partição máxima, i.e. partições em lotes de processamento de uma unidade. No entanto, na maioria dos casos testados, a maior parte do ganho verifica-se para pequenos graus de partição. Estes resultados foram obtidos num enquadramento de experimentação que não considerou nem custos de transporte e preparação nem de posse. Baseado nos resultados obtidos e no facto dos dois primeiros custos aumentarem com o aumento da partição e os custos de posse tenderem a diminuir com esse aumento, para tirar vantagem efectiva da Produção Simultânea, devem adoptar-se graus de partição moderados.Apparently, a new paradigm of production is emerging in the new and global economy based on three main tendencies. Such tendencies are: increasing dynamics of manufacturing systems reconfiguration, distribution of the manufacturing resources of a production system, and virtuality of systems, i.e. systems that are configured only on organizational and control terms, not on physical rearrangement of facilities. The first tendency is due to increasing product demand requirements, namely quality, variety and delivery. The second, resulting from a need for enhancement of production performance and, the third, is due to the unfeasibility of physically grouping and rearranging world wide distributed production facilities and due to capabilities offered by world wide communication and logistic systems. Based on the referred tendencies new requirements arise for production systems design and operation. Some can be selected and synthesized as: increased ability for system reconfiguration based on distributed resources and fast delivery of each product ordered. Based on such requirements a definition of Distributed Production Systems (SDP) is put forward together with a model, the MSDP model, of such systems. Such model is closely related with the processing structure of an ordered product to be manufactured. Based on the MSDP model, a formal representation is developed using Petri Nets and modelling mechanisms put forward by Lecompte, Deschamps and Bourrières (2000), and an agent based conceptual model is presented. The formal representation of the model is applied to a variety of systems configuration instances according with the product ordered. The application aim is twofold: first, testing the model suitability for representing and reconfiguring different SDP and, second, for studying the behaviour of SDP, under the Simultaneous Manufacturing philosophy. This philosophy aims at minimizing time delivery of orders through maximum reduction of production flow time of each production order. The study carried out in this work lead to the conclusion that the model is suitable for representation, design and evaluation of distributed production systems dedicated to each product order. Further, a small degree of simultaneous manufacturing was proved enough to achieve important gains in order flow time reduction and quality of the manufacturing service. This was evaluated, for a few system configurations with strategies to simultaneous manufacturing based on simultaneous allocation of order manufacturing requirements to replicated machines, i.e. manufacturing resources, and also based on order splitting at a few different levels. As expected, the best values of performance were obtained under maximum order splitting, i.e. under split batches of size one. However, in most cases tested, the lion share of benefits from splitting was obtained for small degrees of it. These results were obtained under a framework for experiments that did not take into account neither handling and set-up costs nor holding costs. Based on the findings reported and onto the fact that the first two costs increase with order splitting and that holding costs tend to decrease with it, then, it was concluded that, to take effective advantageous of simultaneous manufacturing, moderate degrees of order splitting should be adopted

Reproductive Health Hazards in the Workplace

A report by the Office of Technology Assessment (OTA) that "reviews current knowledge of hazards and suspected hazards to the reproductive health of American's working men and women and to the health and well-being of their children" (Foreword)

Smoking and Second Hand Smoking in Adolescents with Chronic Kidney Disease: A Report from the Chronic Kidney Disease in Children (CKiD) Cohort Study

The goal of this study was to determine the prevalence of smoking and second hand smoking [SHS] in adolescents with CKD and their relationship to baseline parameters at enrollment in the CKiD, observational cohort study of 600 children (aged 1-16 yrs) with Schwartz estimated GFR of 30-90 ml/min/1.73m2. 239 adolescents had self-report survey data on smoking and SHS exposure: 21 [9%] subjects had “ever” smoked a cigarette. Among them, 4 were current and 17 were former smokers. Hypertension was more prevalent in those that had “ever” smoked a cigarette (42%) compared to non-smokers (9%), p\u3c0.01. Among 218 non-smokers, 130 (59%) were male, 142 (65%) were Caucasian; 60 (28%) reported SHS exposure compared to 158 (72%) with no exposure. Non-smoker adolescents with SHS exposure were compared to those without SHS exposure. There was no racial, age, or gender differences between both groups. Baseline creatinine, diastolic hypertension, C reactive protein, lipid profile, GFR and hemoglobin were not statistically different. Significantly higher protein to creatinine ratio (0.90 vs. 0.53, p\u3c0.01) was observed in those exposed to SHS compared to those not exposed. Exposed adolescents were heavier than non-exposed adolescents (85th percentile vs. 55th percentile for BMI, p\u3c 0.01). Uncontrolled casual systolic hypertension was twice as prevalent among those exposed to SHS (16%) compared to those not exposed to SHS (7%), though the difference was not statistically significant (p= 0.07). Adjusted multivariate regression analysis [OR (95% CI)] showed that increased protein to creatinine ratio [1.34 (1.03, 1.75)] and higher BMI [1.14 (1.02, 1.29)] were independently associated with exposure to SHS among non-smoker adolescents. These results reveal that among adolescents with CKD, cigarette use is low and SHS is highly prevalent. The association of smoking with hypertension and SHS with increased proteinuria suggests a possible role of these factors in CKD progression and cardiovascular outcomes