Minimization of total tardiness in no-wait flowshop production systems with preventive maintenance

Efficient business organizations must balance quality, cost, and time constraints in competitive environments. Reflecting the complexity of this task, we consider manufacturing systems including several stages of production chains requiring time measurement. When production scheduling is not prioritized in such enterprises, several negative effects may occur. A corporation may suffer financial penalties as well as negative brand exposure, and thus may find its credibility challenged. Therefore, in this study, we propose constructive methods to minimize a total tardiness criterion, considering preventative maintenance constraints to reflect the reality of industrial practice, focusing on a no-wait flowshop environment in which jobs are successively processed without operational interruptions. In addition to proposing constructive methods to solve the no-wait flowshop production scheduling problem, a metaheuristic is presented as an approach to improve results obtained by constructive methods. Computational experiments were designed and performed to compare several production scheduling algorithms. Among various constructive heuristics considered, an algorithm called HENLL using an insertion logic showed the best performance. The proposed metaheuristic is based on the iterated greedy (IG) search method, and the results obtained demonstrated significant improvement compared to the heuristics alone. It is expected that this study may be used by production planning and control (PPC) professionals to apply the proposed method to schedule production more efficiently. We show that the proposed method successfully presented a better solution in relation to total tardiness, considering the above mentioned environment

Bounded dynamic programming approach to minimize makespan in the blocking flowshop problem with sequence dependent setup times

This paper aims at presenting an algorithm for solving the blocking flow shop problem with sequence dependent setup times (BFSP-SDST) with minimization of the makespan. In order to do so, we propose an adapted Bounded Dynamic Programming (BDP-SN) algorithm as solution method, since the problem itself does not present a significant number of sources in the state-of-art references and also because Dynamic Programming and its variants have been resurfacing in the flowshop literature. Therefore, we apply the modified method to two sets of problems and compare the results computationally and statistically for instances with a MILP and a B&B method for at most 20 jobs and 20 machines. The results show that BDP-SN is promising and outperforms both MILP and B&B within the established time limit. In addition, some suggestions are made in order to improve the method and employ it in parallel research regarding other branches of machine scheduling

Contribuitions for the m-machine blocking flow shop scheduling problem with sequence-dependent setup times and hirarquical objective-functions subject to preventive maintenance total cost

O problema de programação de operações ou scheduling é um processo de decisão que desempenha um papel crucial em muitas indústrias de manufatura e de serviços. Sua essência concentra-se nas atividades de alocação e sequenciamento. Neste contexto, é de grande importância o desenvolvimento de técnicas que auxiliem na tomada de decisão da sequência de produção. De acordo com a revisão de literatura realizada nesta pesquisa, análises e proposição de técnicas de solução para o denominado ambiente de produção flow shop sem estoques intermediários entre as máquinas (bloqueio) vem ganhando notoriedade nas últimas décadas, na sua maioria, sem a adição de restrições adicionais. Levando-se em conta a lacuna encontrada na literatura para esta área, nesta tese são propostos métodos de solução para o problema de programação de operações em ambientes flow shop com m máquinas, considerando bloqueio, tempos de setup dependentes da sequência e ocorrência de manutenção preventiva. As funções-objetivo tratadas foram a minimização da duração total da programação e do tempo total de fluxo dado que o custo total de manutenção preventiva exigido pela sequência não ultrapasse um dado valor. Um modelo de programação linear inteira mista (MILP) e formas de cálculo das datas de início e término das tarefas. Uma busca local para avaliação do reposicionamento das MPs foi desenvolvida para minimização da função-objetivo. Métodos heurísticos (construtivos e metaheurísticas) encontrados para os problemas de minimização da duração total da programação (Cmax) e do tempo total de fluxo (Σ iCi) foram adaptados e propostos, no intuito de minimizar as funções-objetivo. Os métodos foram implementados e testados em dois cenários de ocorrência de manutenções preventivas, com instâncias de problemas de pequeno, médio e grande portes. Resultados estatísticos mostraram que em comparação com o MILP proposto, as metaheurísticas Iterated Greedy e GRASP(HPF2) obtiveram os melhores desempenhos para a minimização de Cmax e de ΣiCi, respectivamente, em problemas de pequeno porte. Para problemas de médio e grande portes, Iterated Greedy e Variable Block Insertion Heuristic (VBIH) apresentaram o melhor desempenho geral nos dois cenários avaliados. Por fim, pode-se constatar experimentalmente que a busca local proposta obteve melhorias significativas e expressivas na qualidade da solução gerada pelas metaheurísticas, o que sugere seu uso como parte da metodologia de solução dos problemas estudados.Scheduling is a decision process that plays a crucial role in many manufacturing and service industries. Its essence focuses on allocation and sequencing decisions. In this context, it is of great importance the development of techniques that can be used as a support to the decision making of the production sequence. According to the literature review carried out in this research, analysis and proposition of solution techniques for the so-called blocking flow shop scheduling problem has gained notoriety over the last decades, mostrly without the additional constraints. Taking into account the gap found in the literature for this area, in this thesis is addressed the m-machine blocking flow shop scheduling problem, with sequence-dependent setup times, preventive maintenance operations occurrences and minimization of hierarchical objective functions. The research aims to propose solution techniques to minimize the makespan (Cmax) and the total flow time (ΣiCi) given that the preventive maintenance total cost required by the sequence does not exceed a given value. A mixed integer linear programming (MILP) and forms of objective-fucntion computation were proposed. A local search for MP rescheduling was developed, aiming to minimize the objective-functions. Heuristic methods of the literature for the minimization of Cmax and ΣiCi have been adopted to minimize the preventive maintenance total cost and the hierarquical objective-functions of the approached problems. The methods were implemented and tested over two preventive maintenance instance problems configurations. Statistical results showed that, compared to the proposed MILP, the Iterated Greedy and GRASP(HPF2) obtained the best performances for the Cmax and ΣiCi minimization, respectively. For medium and large problems, Iterated Greedy and VBIH showed the best overall performances in both evaluated scenarios. Finally, it can be seen that the proposed local search significantly improved the quality solution generated by the metaheuristics, which suggests its use as part of the solution methodology of the problems studied here

Heuristics methods for the no-wait flow shop problem with preventive maintenance constraints and makespan minimization

O problema de programação de operações em ambiente no-wait flow shop tem sido abordado desde a década de 60. Por se tratar de um ambiente em que as tarefas devem ser processadas continuamente e sem interrupções entre uma máquina e outra, um tempo de espera entre o início da tarefa anterior e o início da tarefa atual deve ser determinado na primeira máquina. Neste sentido, uma vez que a tarefa inicia seu processamento, as máquinas devem estar disponíveis para que atendam a restrição de no-wait. Portanto, operações de manutenção preventiva são necessárias para que a programação seja atendida sem maiores problemas. Este trabalho aborda dois problemas: no-wait flow shop e no-wait flow shop com operações de manutenção preventiva. O critério de desempenho adotado foi a duração total da programação (makespan). Por meio de uma revisão de literatura, mecanismos de construção de soluções foram identificadas e classificadas e, baseando-se em tais, novos métodos heurísticos construtivos simples e compostos foram propostos para o problema no-wait flow shop e uma heurística composta foi desenvolvida considerando as operações de manutenção preventiva. Experimentações computacionais para os dois problemas foram realizadas para fins de comparação e avaliação dos métodos propostos com os métodos heurísticos construtivos da literatura. Para o problema Fm|no - wait|Cmax resultados evidenciaram que as heurísticas propostas H4GPSLLS e MH4GPSLLS superaram as heurísticas da literatura em qualidade de solução, com diferença estatisticamente significativa no nível de 5% de significância. Para o problema Fm|no - wait, m(k)|Cmax, pode-se constatar que a heurística BIHLS e as heurísticas H4GPSLLS e MH4GPSLLS apresentaram desempenho superior com diferença estatística significativa no nível de 5% de significância em comparação as heurísticas da literatura.The no-wait flow shop scheduling problem has been studied since 60\'s. In this environment, jobs must be processed continuously without interruption between one machine and another, and because of this, a delay between the start time of the previous job and the start time of the current job must be determined in the first machine. In this sense, since a job starts its processing, the machines must be available to respect the no-wait constraint. Therefore, preventive maintenance operations are needed. This work adresses two problems: the m machine no-wait flow shop and the m machine no-wait flow shop with preventive maintenance operations. The performance measure adopted was the makespan. By means of a literature review, mechanisms of solution construction were identified and classified. New simple and composite constructive heuristics were proposed to the no-wait flow shop problem and a new composite constructive heuristic was developed considering the preventive maintenance operations. Computational experiments and their respective analyses for both problems were carried out to compare and evaluate the performance between the proposed methods and the constructive heuristics of the literature. Regarding Fm|no - wait|Cmax problem, results show that the proposed heuristics H4GPSLLS and MH4GPSLLS outperformed the heuristics of the literature in quality of the solution and is statistically significative to 5% of significance level. To the Fm|no - wait, m(k)|Cmax problem it can be seen that the proposed heuristic BIHLS and H4GPSLLS and MH4GPSLLS outperformed the heuristics of the literature and is statistically better to 5% of significance level

Procedure structuring for programming aircraft maintenance activities

Purpose – This paper aims to exemplify the use of project management tools in the scheduling of aircraftmaintenance activities. This process is known as maintenance, repair and overhaul and it has gainedimportance within the aeronautical sector due to its expected growth in the coming years; however, it alsofaces increasing competitiveness in its market. This fact gives rise to the need of acting in maintenancemanagement and seeking lower costs while maintaining the quality of the service provided. The purpose ofthis paper is to propose the structuring of a procedure that aims to reduce the total maintenance time(downtime) and guarantee the delivery of the aircraft on time.Design/methodology/approach – The paper, through a case study at a Brazilian aircraft maintenancecenter, used critical path method and critical chain project management, the latter being derived from thetheory of constraints, with the purpose of analyzing resources systematically and synchronizing the activitiesin the precedence network.Findings – As a result, it is shown that downtime can be reduced from 11 to 5 days and improvements areproposed to achieve greater market competitiveness.Originality/value – This paper demonstrates the competitive advantage that resulted from the applicationof project management tools in the aircraft maintenance planning and execution