A major challenge in designing and controlling flow lines is to achieve high customer service level while stay lean. Just-In-Time (JIT) manufacturing approach has triggered various 'pull production system', such as CONWIP or Kanban controls, which emphasizes on response to demand rather than forecasts. We identified and documented the anatomy of various pull type control policies. Based on the analysis, we designed a new class of control policy called Extended CONWIP Kanban control (ECK). We conducted comprehensive simulation comparison studies. Simulation results showed that the new control policy can achieve higher service levels with lower inventories than other policies including hybrid ones. We developed a state space comparison methodology to compare various policies with that of optimum solution. Our analysis reveals that our ECK policy provides the most adjustment flexibility toward the optimum. We also proposed a parameter design procedure and an adaptive parameter adjusting system. A case study verifies the advantages and utilities of the ECK policy. Beside the cost savings, another major advantage of the ECK policy is its robustness. That is, the total cost of the ECK policy is less sensitive to demand or system variations.

Kanban and Constant Work-In-Process (CONWIP) control methods are designed to impose tight controls over inventory, while providing a satisfactory production rate. This paper generalizes systems with kanban or CONWIP control as assembly/disassembly networks with multiple-loop structures. We present a stochastic mathematical model which integrates the information control flows into material flows. Graph theory is used to analyze the multiple-loop structures. An efficient analytical algorithm is developed for evaluating the expected production rate and inventory levels. The performance of the algorithm is reported in terms of accuracy, reliability and speed. / Singapore-MIT Alliance (SMA)

Submitted by admin tede (tede@pucgoias.edu.br) on 2017-10-09T12:07:31Z No. of bitstreams: 1 Bianca Marcelo Mamede.pdf: 2670645 bytes, checksum: da945ec531f92927e420ca490396ffed (MD5) / Made available in DSpace on 2017-10-09T12:07:31Z (GMT). No. of bitstreams: 1 Bianca Marcelo Mamede.pdf: 2670645 bytes, checksum: da945ec531f92927e420ca490396ffed (MD5) Previous issue date: 2017-05-18 / The CONWIP production management method overcomes in productive systems because it eliminates waste and enhances the productive process’ performance. Maketo- stock production systems need to reduce stocks in order to enhance the performance of their productive processes. However, the application of CONWIP is sparse in MTS systems industrial reality. Hence a research has been done, through computational simulations and modelling methodology, with the aim to compare the operational results of a real productive MTS system with the results that a CONWIP method managed system would generate. The CONWIP hás held the demand by reducing the excess production presented by MTS, using 71% less inputs and reducing the processing stocks (WIP) by 85%. Considering the Factory Physics laws, the CONWIP performance was better when compared to MTS for enhancing the resources usage, reducing the processing time variability and eliminating the waste. This work hás contributed to reduce CONWIP performance analysis through computational simulation and modelling studies absence in literature. / O método de gerenciamento da produção CONWIP sobresai em sistemas produtivos jobbing por eliminar desperdícios e aprimorar o desempenho do processo produtivo. Sistemas de produção make-to-stock (MTS) necessitam reduzir estoques de modo a aprimorar o desempenho de seus processos produtivos. Entretanto a aplicação do CONWIP é escassa na realidade industrial de sistemas MTS. Nesse contexto foi realizada uma pesquisa, através da metodologia de modelagem e simulação computacional, com o objetivo de comparar os resultados operacionais de um sistema produtivo MTS real com os resultados que geraria ao ser gerenciado pelo método CONWIP. O CONWIP atendeu a demanda reduzindo a produção em excesso apresentada pelo MTS, utilizando 71% menos insumos e reduzindo o nível de estoques em processo (WIP) em 85%. Considerando as leis da Ciência da Fábrica o desempenho do CONWIP foi melhor, comparado ao MTS por ter aprimorado a utilização dos recursos, reduzido a variabilidade dos tempos de processamento e eliminado desperdícios. Este trabalho contribuiu para diminuir a ausência de estudos na literatura com análises do desempenho do CONWIP através da modelagem e simulação computacional.

Au cours de la dernière décennie, le système de contrôle de production (PCS) Constant Work InProgress (CONWIP) a été étudié par un nombre croissant de publications. Compte tenu des défis industrielsactuels, tels que la nécessité de s’adapter, la personnalisation croissante des produits, la réduction des délaiset l’importance grandissante du service rendu aux clients, le ConWip semble être un PCS efficace et agilepour les industriels. Cette thèse débute par une revue systématique des travaux sur le ConWip remontant à2003 basée sur une méthode de classification originale. Cette méthode permet de catégoriser les papiers quise concentrent sur le dimensionnement, la performance, le contexte d’implémentation et la comparaison avecd'autres PCS. En plus de proposer une clé de lecture pour interpréter les approches de recherche, les critèresconsidérés répondent à des questions sur la façon de mettre en oeuvre, la façon d’optimiser et les raisonspour lesquelles utiliser le ConWip. Une étude sur les pistes de recherche proposées ou applicables au ConWipa ensuite permis de mettre en évidence les plus prometteuses et d’en extraire les principales tendances.L'objectif consiste ici à mettre à jour les lacunes de la recherche existante sur le ConWip. L'une d'entre ellesamène à des questions clés liées à la mise en oeuvre du ConWip dans un environnement caractérisé par unmix produit élevé et/ou par un mix gamme opératoire élevé. Dans ce contexte, quatre algorithmes qui génèrentdifférentes gammes génériques sont ensuite présentés. Ces gammes, appelées « gammes enveloppes » sontimplémentées dans Wipsim, un outil d'ingénierie utilisé dans les projets de conception et d'amélioration deslignes d'assemblage ConWip, qui permet de calculer les paramètres ConWip optimisés pour chacune desgammes. Un échantillon de données, dérivé d'un cas industriel, est utilisé pour tester les quatre algorithmes.Nous les comparons à travers leur sensibilité au mix produit et selon l'impact induit par l'introduction dedifférents produits atypiques dans le mix. Nos expériences montrent que nos algorithmes génèrent desgammes enveloppes pertinentes et aident les praticiens à choisir le plus adapté à leur contexte spécifique. / In the past decade, a growing body of literature has investigated the CONstant Work InProgress (ConWip) production control system (PCS). In view of the current industrial challengesentailing adaptability, product customisation, decreas- ing leadtimes and customer satisfaction, ConWipseems to be an effective and adaptive PCS for manufacturers. A ConWip systematic review datingback to 2003 and provides a guide for understanding through an original classification method. Thismethod enables the differentiation of papers that concentrate on Con- Wip sizing, performance andcontext as well as a comparison with other PCSs. In addition to providing a key to interpreting theresearch approaches, the criteria considered answers questions on how to implement, how to optimiseand why and when to use ConWip. The survey of research avenues proposed or applicable to CONWIPclassify them, highlight the most promising and extract the main trends. The final aim is to provide somegaps. One of the them deals with key questions related to the implementation of ConWip in a highproduct mix and/or high routing mix environment. Four algorithms that generate different genericroutings are presented. These routings are implemented into Wipsim, an engineering tool used inprojects to design and improve ConWip assembly lines, which allows the optimized ConWip parametersfor each routing to be calculated. A sample of data, derived from an industrial case, is used to test thefour models. We compare them via their sensitivity to the mix product and through the impact of theintroduction of different, atypical products. Our experiments show that our algorithms generatedworthwhile generic routings and help practitioners choose among them, depending on a specificcontext.

The increasing competition between the companies forces them to develop the production in a continuous manner in order to maintain the competitiveness in the global market, and became as efficient and effective as possible. This master thesis is conducted at Getrag All Wheel Drive Company which is one of the largest suppliers for transmissions and powertrain systems .This Company has worked actively for long time to improve the production flow at the manufacturing departments by using usual methods. Because of the high complex and intersected flow that the company has, the management intended to adopt another approach that takes dynamic information into consideration, therefore, building a simulation model is the solution, where according to Banks et al (2001) the simulation is a duplication of a real-world process or system and its behaviour as it progress during the time, which is a very useful method to evaluate complex systems, instead of using usual mathematical means used tools. The simulation model created by using Banks et al (2001) simulation methodology, and ExtendSim software help. The resulted model used as a tool that provides great assistance to the decision makers, in order to develop the Conwip system which applied in the manufacturing line under study, and to investigate “What if” scenarios. The result of this study obtained after performing two experiments, where the first experiment gives recommendation regarding the optimal upper bound of the total amount of work that can be used in Conwip system, with the use of sensitivity analysis, and the second experiment analyse the overall all effect on the system after separating the paths of high and low volume products. This project proves the powerful side of using the simulation in situations where it’s too hard or even impossible to improve the performance of a manufacturing line i.e. when large number of variables involved and affecting the system.

Práce se zabývá modelováním a simulací výrobních systémů řízených principem tahu (kanban, CONWIP). Analyzuje vzájemný vztah průtoku, operačních zásob a doby výroby. Zohledňuje stochastické vlivy a variabilitu procesů. Teoretické základy jsou aplikovány na příkladu výrobní linky CP1H ve společnosti Bosch Diesel.

Submitted by Mariana Dornelles Vargas (marianadv) on 2015-03-17T19:40:51Z No. of bitstreams: 1 metodo_quantificar.pdf: 1038017 bytes, checksum: 54f78fa2753a1dfe9d797dc88d1ed31e (MD5) / Made available in DSpace on 2015-03-17T19:40:51Z (GMT). No. of bitstreams: 1 metodo_quantificar.pdf: 1038017 bytes, checksum: 54f78fa2753a1dfe9d797dc88d1ed31e (MD5) Previous issue date: 2011-03-16 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / PROSUP - Programa de Suporte à Pós-Gradução de Instituições de Ensino Particulares / Em ambientes produtivos intermitentes que operam na condição ?produzir para estoque?, com fluxo convergente, a possibilidade de constituir estoques em processo (WIP), de produtos prontos, ou matérias-primas pode aumentar o grau de complexidade da gestão das operações e a necessidade de utilizar procedimentos de controle distintos para cada tipo de estoque. Ao focar no alinhamento da gestão dos estoques aos planos de demanda e capacidade, considerando um ambiente produtivo que emprega a abordagem Conwip, a presente pesquisa tem por finalidade propor um método estruturado que possibilite quantificar o nível de WIP do sistema produtivo, a partir da Simulação por Eventos Discretos e da técnica de Apoio Multicritério ELECTRE TRI. Esta pesquisa tem o intuito de contribuir com a geração de informações que subsidiem a tomada de decisão concernente à escolha de uma configuração de cenário que aluda a um nível de estoque em processo e de produtos prontos considerando o mix de produção sob estudo. Fundamentado na proposta desenvolvida nesta dissertação, o Método de Pesquisa pode ser caracterizado quanto aos procedimentos técnicos, pelo uso da Simulação Computacional e relativo à natureza dos dados, destaca-se o da abordagem essencialmente quantitativa, ou Pesquisa Quantitativa. O método proposto foi avaliado, quanto a sua estrutura e proposta, por especialistas das disciplinas de Simulação, Gestão de Sistemas Produtivos e Métodos Multicritério à Decisão. Uma aplicação do método em um sistema produtivo real também é apresentada / In intermittent productive systems that operate in the condition 'make to stock' with convergent flow, the possibility of generate work in process (WIP), finish good products or raw materials inventories can increase the degree of complexity of the management in the operations and the need of using procedures of different control for each stock type. Focusing in the alignment of the stocks to the demand and capacity plans, considering a productive system which uses the Conwip approach, this research describes a structured method that aims to quantify the level of WIP in the productive system, applying the Events Discrete Simulation and the technique nominated ELECTRE TRI. This research intends to contribute with the generation of information for decision support regarding the choice of work in process and finished goods stock levels, considering the production mix studied. Based in the proposal developed in this work, the Method of Research can be characterized, regarding the technical procedures, as Computational Simulation, and regarding the nature of the data, as Quantitative Research. The method proposed in this research was evaluated for specialists in the disciplines of Simulation, Administration of Production Systems and Multicriteria Decision Analysis. An application of the method in a real productive system is also presented.

As the effort of today’s industries to continuously move towards lean production, pull production system has been developed as one possible solution of lean. It is popularly known in the industry world, and is indeed a proven technique to achieve substantial savings on inventory, production cost incurred by manufactures all over the world. However, a careful understanding of pull production systems is required to access its suitability to a particular production setup. It is necessary to develop a proper way to implement pull production systems.             This study is based on a real life scenario in a leading driveline manufacturing company. The production system is studied in detail as regard to its production characteristic. A theoretical review is first made as research foundation. A careful analysis study within the company is conducted with all the existing constrains to figure out improvement opportunities. Eventually, from the applicability point of view, proposals of future pull production system implementation have been developed. The objective of the proposals is to minimize the identified weaknesses of the current system, including long lead time, low flexibility and unconnected flow.

In this thesis, a real world application of the constant work in process (Conwip) system in an electronics company is realized. The aim of the application is to reduce the work in process (WIP) inventory while maintaining the same throughput level. A model is developed to determine the constant work in process level of the Conwip system for the production lines in this company. The approximated mean value analysis approach is used for the solution. Real system data are collected before and after the Conwip application. Hypothesis tests are used to compare the WIP and the throughput levels of the Conwip system with the existing push control system for a pilot production line. Results of the hypothesis tests show that the Conwip production control system can signinifcantly reduce the WIP while maintaining the same throughput rate.

Denna rapport har haft som syfte att hjälpa företaget Swegon Operations AB att minska sina hanteringskostnader, bundet kapital och eventuell överproduktion. För att uppnå syftet gjordes värdeflödesanalyser vilka kartlade tre separata flöden för tre egentillverkade komponenter. Kombinerat med värdeflödesanalyserna skapades även en matematisk optimeringsmodell som positionerar Swegons arbetsstationer utifrån deras interna flöden. De skapade värdeflödesanalyserna gav ett underlag till fortsatt analys av hanteringskostnader, bundet kapital och överproduktion. Analysen visade på svårigheter att identifiera exakt var hanteringskostnader och överproduktion existerade; men högst bundet kapital fanns i färdigvarulagret. Svårigheten att identifiera brister i fabriken mynnade ut i två olika tillvägagångssätt för att uppfylla studiens syfte. Det första var att utföra fyra experiment i Swegons fabrik för att kunna förstå de studerade flödena bättre. De utförda experimenten baserades på beräkningar av säkerhetslagar via en programmerad algoritm samt analys av existerande mellanlager där överproduktion existerade. Det andra tillvägagångssättet var att identifiera hanteringskostnaderna mellan respektive produktionsstation och använda en matematisk modell för att positionera stationerna så att material transporteras så korta sträckor som möjligt. Resultaten från de fyra olika experimenten låg till grund för att minska hanteringskostnader och bundet kapital i ett av de studerade flödena samt överproduktion i vart och ett av de flöden som studerats. Experimenten utgjorde även en grund för att motivera en omplacering av en robot samt två manuella packningsstationer. För att identifiera hanteringskostnaderna mellan respektive produktionsstation skapades en matematisk modell baserad på heltalsprogrammering. Modellen användes därefter för att finna den optimala positioneringen för respektive produktionsstation. Den utförda analysen, experimenten och den matematiska modellen bidrog slutligen till att ta fram rekommendationer. Rekommendationerna bidrar till att sänka hanteringskostnader, minska det bundna kapitalet och reducera en viss del av den överproduktion som existerade för de tre studerade komponenterna. Den första rekommendationen är att Swegon ska sänka de nuvarande Kanban-nivåerna på deras produkter klassificerade som högvolym. Den andra rekommendationen är en omstrukturering av ett nuvarande flöde där övergång från en materialbehovsplanering till CONWIP samt omplacering av maskiner kommer bidra till att reducera hanteringskostnader, bundet kapital och överproduktion.