Sistemas de programação com capacidade finita dos recursos constituem uma alternativa interessant... more Sistemas de programação com capacidade finita dos recursos constituem uma alternativa interessante para a programação detalhada da produção. Neste artigo, apresenta-se um protótipo desenvolvido em planilhas que, via simulação por eventos diiscretos, realiza a programação detalhada das operações em um ambiente de produção do tipo Job Shop. Primeiramente, utilizam-se três das mais reconhecidas regras de despacho (FIFO, SPT e EDD), além do emprego da técnica chamada carregamento lateral, para gerar soluções iniciais do problema. A partir daí, o usuário pode modificar qualquer das sequências anteriores, gerando novas soluções. Todas podem ser comparadas mediante o uso de indicadores e gráficos de Gantt. Destaca-se que, devido à facilidade de visualização gráfica e interação com o usuário, o modelo proporciona uma visão integrada do problema de programação detalhada. Ainda que seja apenas um protótipo, oferece um panorama global das especificações e funcionalidades necessárias de um sist...
Brazilian journal of operations & production management, 2018
This work seeks to explore and demonstrate the use of Agent Based Simulations (ABS) in modelling ... more This work seeks to explore and demonstrate the use of Agent Based Simulations (ABS) in modelling and simulating supply chains. Such methodology was applied to develop a model to evaluate the impact of current tax policies in soy supply chain in Brazil. The model brought interesting insights on how the country’s current tax structure induces logistics and tributary trade-offs, therefore generating a suboptimal grain distribution. This is accomplished by going through the conception and implementation of an Agent Based Model. First there is the definition and delimitation of the main agents acting upon soy’s supply chain, such as producers, trader and consumers. Those agents then have their behaviors studied and translated into programable patterns. Finally, the model considers the environmental interactions with the mentioned players, including the effects of infrastructure capacities, transportation costs, storage costs and tax legislation. After quantitative and behavioral validati...
The demand for nuclear fuel for research reactors is increasing worldwide. However, some nuclear ... more The demand for nuclear fuel for research reactors is increasing worldwide. However, some nuclear fuel factories have small production volumes. There is a gap in the literature regarding how to expand capacity of those facilities in a safe and reliable way. Thus, the purpose of this work is to propose and validate a conceptual model to increase the production capacity of these factories. We addressed factories that produce plate-type fuel elements loaded with LEU U3Si2-Al, which are typically used in nuclear research reactors. We collected data from a real nuclear fuel plant and applied the model to that data, i.e., we set up a case study. We developed two different strategies for the use of the model, thus generating several production scenarios. Each scenario is an experiment of the different possibilities to enlarge the capacity. We applied discrete events simulation in order to cover all production scenarios. Our tests indicated significant increases in productive capacity, thus ...
Este artigo apresenta modelos de simulação para análise do efeito do estoque intermediário em Sis... more Este artigo apresenta modelos de simulação para análise do efeito do estoque intermediário em Sistemas de Produção Puxada. Inicialmente, são apresentados dois modelos de filas isoladas, um modelo clássico de filas e outro equivalente para produção puxada. A seguir, apresentam-se os modelos com postos de atendimento em série (flow shop), onde os lotes percorrem seqüencialmente m postos de atendimento deixando o sistema com a conclusão da operação no último posto. Neste cenário, dois mecanismos de produção puxada são implementados: CONWIP e Kanban. Estes modelos foram implementados considerando quatro estações de trabalho e tempos de operação exponencial e normal. A partir da simulação, verifica-se o efeito do limite de estoque intermediário no tempo de ciclo (lead time) e na capacidade de produção (vazão) da linha. Estes modelos foram implementados em planilhas Microsoft Excel, com uso da linguagem Visual Basic, que provaram ser ferramentas bastante úteis na implementação dos modelos...
Objetivo: Desenvolver um modelo de análise para o Planejamento e Controle da Produção (PCP) em Pe... more Objetivo: Desenvolver um modelo de análise para o Planejamento e Controle da Produção (PCP) em Pequenas e Médias Empresas (PMEs) que operam com a estratégia de Produção Contra Pedido e verificar o impacto da formalização dos processos e da mensuração de resultados no PCP das PMEs. Método: Este trabalho utilizou a pesquisa-ação para validar um modelo de análise do PCP em 3 PMEs. Foram criadas equipes de melhoria em cada empresa e aplicadas técnicas como a visita técnica, observação participante e entrevistas focadas para mapeamento e análise dos processos de PCP. Fundamentação teórica: Ao analisar a literatura, foi possível mapear três principais características das operações das PME's: (1) Planejamento e Controle da Produção deficientes, (2) informalidade na execução das operações e (3) falta de mensuração de resultados. O modelo de análise proposto neste trabalho parte de um entendimento de que as caraterísticas (2) e (3) explicam (1) em grande medida. Resultados: A formalizaçã...
Abstract The lot sizing and scheduling (LSS) problem has motivated much research in production pl... more Abstract The lot sizing and scheduling (LSS) problem has motivated much research in production planning and control. However, while there are many papers on modelling this problem, there is scant research on how it is addressed in the industry. We present a survey of Brazilian industry practices in LSS, intending to understand the problem faced by operations managers, drawing parallels with academic findings to identify gaps between theory and practice and opportunities for future research. We confirm that the main objective of practitioners in companies operating under MTS strategy is to maximise service level, followed by inventory reduction. Availability of raw material, demand uncertainty and safety stock levels, lack of decision support software and the impact of sequence-dependent set-up times are other major concerns highlighted by the practitioners. Lastly, we confirmed that despite the relevant body of research on this problem, there is still a large gap between theory and practice.
Brazilian Journal of Operations & Production Management, 2015
This paper discusses which benefits the use of APS may bring to the S&OP, and the critical factor... more This paper discusses which benefits the use of APS may bring to the S&OP, and the critical factors for the successful implementation. A case study was conducted in a major dairy company in the Brazilian food industry. Positioned in an environment of high market competition and narrow profit margins, the company strives for operational excellence, aimed at inventory reduction and increased service level. This supply chain includes several plants and has recently been through the deployment of an APS to support its S&OP process. The research has identified the main benefits of the APS: greater confidence and accuracy in planning, and better balancing of inventory throughout the supply chain. The deployment project went through specific difficulties that delayed its schedule. The study reinforces the importance of fully support from senior managers and the commitment of the planning staff to meet the challenges of customization and integration of the new system.
This paper provides a simulation model to study the effect of the work-in-process control on due ... more This paper provides a simulation model to study the effect of the work-in-process control on due date performance in job shop environment. The due date performance is measured by both the number of tardy jobs and the total tardiness. The simulation runs include different shop configurations (flow shop and general job shop), workloads and sequencing rules. As expected, the results reveal that due date performance is highly dependent on the work-in-process, particularly after the system reaches saturation. Nevertheless, the model is very useful to show job shop managers the effect of the work-in-process control in the due date meeting performance.
Sistemas de programação com capacidade finita dos recursos constituem uma alternativa interessant... more Sistemas de programação com capacidade finita dos recursos constituem uma alternativa interessante para a programação detalhada da produção. Neste artigo, apresenta-se um protótipo desenvolvido em planilhas que, via simulação por eventos diiscretos, realiza a programação detalhada das operações em um ambiente de produção do tipo Job Shop. Primeiramente, utilizam-se três das mais reconhecidas regras de despacho (FIFO, SPT e EDD), além do emprego da técnica chamada carregamento lateral, para gerar soluções iniciais do problema. A partir daí, o usuário pode modificar qualquer das sequências anteriores, gerando novas soluções. Todas podem ser comparadas mediante o uso de indicadores e gráficos de Gantt. Destaca-se que, devido à facilidade de visualização gráfica e interação com o usuário, o modelo proporciona uma visão integrada do problema de programação detalhada. Ainda que seja apenas um protótipo, oferece um panorama global das especificações e funcionalidades necessárias de um sist...
Brazilian journal of operations & production management, 2018
This work seeks to explore and demonstrate the use of Agent Based Simulations (ABS) in modelling ... more This work seeks to explore and demonstrate the use of Agent Based Simulations (ABS) in modelling and simulating supply chains. Such methodology was applied to develop a model to evaluate the impact of current tax policies in soy supply chain in Brazil. The model brought interesting insights on how the country’s current tax structure induces logistics and tributary trade-offs, therefore generating a suboptimal grain distribution. This is accomplished by going through the conception and implementation of an Agent Based Model. First there is the definition and delimitation of the main agents acting upon soy’s supply chain, such as producers, trader and consumers. Those agents then have their behaviors studied and translated into programable patterns. Finally, the model considers the environmental interactions with the mentioned players, including the effects of infrastructure capacities, transportation costs, storage costs and tax legislation. After quantitative and behavioral validati...
The demand for nuclear fuel for research reactors is increasing worldwide. However, some nuclear ... more The demand for nuclear fuel for research reactors is increasing worldwide. However, some nuclear fuel factories have small production volumes. There is a gap in the literature regarding how to expand capacity of those facilities in a safe and reliable way. Thus, the purpose of this work is to propose and validate a conceptual model to increase the production capacity of these factories. We addressed factories that produce plate-type fuel elements loaded with LEU U3Si2-Al, which are typically used in nuclear research reactors. We collected data from a real nuclear fuel plant and applied the model to that data, i.e., we set up a case study. We developed two different strategies for the use of the model, thus generating several production scenarios. Each scenario is an experiment of the different possibilities to enlarge the capacity. We applied discrete events simulation in order to cover all production scenarios. Our tests indicated significant increases in productive capacity, thus ...
Este artigo apresenta modelos de simulação para análise do efeito do estoque intermediário em Sis... more Este artigo apresenta modelos de simulação para análise do efeito do estoque intermediário em Sistemas de Produção Puxada. Inicialmente, são apresentados dois modelos de filas isoladas, um modelo clássico de filas e outro equivalente para produção puxada. A seguir, apresentam-se os modelos com postos de atendimento em série (flow shop), onde os lotes percorrem seqüencialmente m postos de atendimento deixando o sistema com a conclusão da operação no último posto. Neste cenário, dois mecanismos de produção puxada são implementados: CONWIP e Kanban. Estes modelos foram implementados considerando quatro estações de trabalho e tempos de operação exponencial e normal. A partir da simulação, verifica-se o efeito do limite de estoque intermediário no tempo de ciclo (lead time) e na capacidade de produção (vazão) da linha. Estes modelos foram implementados em planilhas Microsoft Excel, com uso da linguagem Visual Basic, que provaram ser ferramentas bastante úteis na implementação dos modelos...
Objetivo: Desenvolver um modelo de análise para o Planejamento e Controle da Produção (PCP) em Pe... more Objetivo: Desenvolver um modelo de análise para o Planejamento e Controle da Produção (PCP) em Pequenas e Médias Empresas (PMEs) que operam com a estratégia de Produção Contra Pedido e verificar o impacto da formalização dos processos e da mensuração de resultados no PCP das PMEs. Método: Este trabalho utilizou a pesquisa-ação para validar um modelo de análise do PCP em 3 PMEs. Foram criadas equipes de melhoria em cada empresa e aplicadas técnicas como a visita técnica, observação participante e entrevistas focadas para mapeamento e análise dos processos de PCP. Fundamentação teórica: Ao analisar a literatura, foi possível mapear três principais características das operações das PME's: (1) Planejamento e Controle da Produção deficientes, (2) informalidade na execução das operações e (3) falta de mensuração de resultados. O modelo de análise proposto neste trabalho parte de um entendimento de que as caraterísticas (2) e (3) explicam (1) em grande medida. Resultados: A formalizaçã...
Abstract The lot sizing and scheduling (LSS) problem has motivated much research in production pl... more Abstract The lot sizing and scheduling (LSS) problem has motivated much research in production planning and control. However, while there are many papers on modelling this problem, there is scant research on how it is addressed in the industry. We present a survey of Brazilian industry practices in LSS, intending to understand the problem faced by operations managers, drawing parallels with academic findings to identify gaps between theory and practice and opportunities for future research. We confirm that the main objective of practitioners in companies operating under MTS strategy is to maximise service level, followed by inventory reduction. Availability of raw material, demand uncertainty and safety stock levels, lack of decision support software and the impact of sequence-dependent set-up times are other major concerns highlighted by the practitioners. Lastly, we confirmed that despite the relevant body of research on this problem, there is still a large gap between theory and practice.
Brazilian Journal of Operations & Production Management, 2015
This paper discusses which benefits the use of APS may bring to the S&OP, and the critical factor... more This paper discusses which benefits the use of APS may bring to the S&OP, and the critical factors for the successful implementation. A case study was conducted in a major dairy company in the Brazilian food industry. Positioned in an environment of high market competition and narrow profit margins, the company strives for operational excellence, aimed at inventory reduction and increased service level. This supply chain includes several plants and has recently been through the deployment of an APS to support its S&OP process. The research has identified the main benefits of the APS: greater confidence and accuracy in planning, and better balancing of inventory throughout the supply chain. The deployment project went through specific difficulties that delayed its schedule. The study reinforces the importance of fully support from senior managers and the commitment of the planning staff to meet the challenges of customization and integration of the new system.
This paper provides a simulation model to study the effect of the work-in-process control on due ... more This paper provides a simulation model to study the effect of the work-in-process control on due date performance in job shop environment. The due date performance is measured by both the number of tardy jobs and the total tardiness. The simulation runs include different shop configurations (flow shop and general job shop), workloads and sequencing rules. As expected, the results reveal that due date performance is highly dependent on the work-in-process, particularly after the system reaches saturation. Nevertheless, the model is very useful to show job shop managers the effect of the work-in-process control in the due date meeting performance.
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