O problema integrado de programação de produção e dimensionamento de lotes em ambiente fowshop consiste em estabelecer tamanhos de lotes de produção e alocar máquinas para processá-los dentro de um horizonte de planejamento, em uma linha de produção com máquinas dispostas em série. O problema considera que a demanda deve ser atendida sem atrasos, que a capacidade das máquinas deve ser respeitada e que as preparações de máquinas são dependentes da sequência de produção e preservadas entre períodos do horizonte de planejamento. O objetivo é determinar uma programação de produção visando minimizar os custos de preparação de máquina, de produção e de estoque. Um modelo matemático da literatura é apresentado assim como procedimentos para obtenção de limitantes inferiores. Além disso, abordamos o problema por meio de distintas versões da metaheurística Times Assíncronos (A-Teams). Os procedimentos propostos foram comparados com heurísticas da literatura baseadas em Programação Inteira Mista (MIP). As metodologias desenvolvidas e os resultados obtidos são apresentados nesta dissertação / The integrated production scheduling and lot sizing problem in a fowshop environment consists in establishing production lot sizes and alocate machines to process them inside a planning horizon, in a production line with machines arranged in series. The problem considers that demand must be met without backlogging, the capacity of the machines must be respected, machine setup are sequence-dependent and preserved between periods of the planning horizon. The objective is to determine a production schedule to minimize the setup, production and inventory costs. A mathematical model from the literature is presented as well as procedures for obtaining lower bounds. In addition, we propose to address the problem through different versions of the metaheuristic Asynchronous Teams (A-Teams). The procedures were compared with literature heuristics based on Mixed Integer Programming (MIP). The developed methodologies and the obtained results are presented in this dissertation

A indústria de fundição produz uma vasta gama de itens com presença na cadeia produtiva de vários setores da economia. São gerados pelo setor, desde itens simples de uso doméstico até itens sofisticados, utilizados por indústrias de base e pelo setor de autopeças. Por ser um segmento muito importante para a economia brasileira, estudos visando melhorar sua eficiência são fundamentais para assegurar sua competitividade em relação ao cenário mundial. Segundo a literatura, um dos principais fatores que influenciam sua produtividade é o planejamento da produção. Nos últimos anos, os investimentos nesta área vem aumentando e tem recebido mais atenção do ponto de vista acadêmico. Esta dissertação aborda o planejamento da produção em fundições de pequeno porte, cujas principais decisões são: decidir quais ligas fundir nos fornos disponíveis e quais itens devem ser vazados a partir das ligas fundidas. Uma questão ainda não considerada na literatura é a obrigatoriedade de completar a produção de todos os itens de um pedido para que este seja considerado atendido e entregue ao cliente. No entanto, em muitos casos reais, um pedido não pode ser atendido parcialmente, ou seja, os itens que compõem esse pedido podem fazer parte de um mesmo item final. Em outros casos, o pedido pode ser atendido parcialmente, mas incorre-se em custos adicionais de expedição. Esta dissertação busca preencher esta lacuna, para tanto, propomos: (1) um modelo matemático para tratar o problema de planejamento da produção de pedidos em fundições de pequeno porte; (2) um modelo para tratar a possibilidade de múltiplas entregas para o problema estudado. Além disso, também é proposta uma heurística Relax-and Fix (relaxe-e-fixe) para a solução do problema integrado / The foundry industry produces plenty of different items present in various sectors of the economy. Such items range from simple household gadgets to sophisticated devices used by basic industries and the auto parts sector. This industry is important for the Brazilian economy and studies aiming at the improvement of its efficiency are fundamental to ensure its competitiveness worldwide. As highlighted in the literature, an important factor that influences the production in the sector is the produiction planning.; In recent years, the investments in this area have been increasing and more attention has been drawn by academic studies. This dissertation deals with the production planning in small foundries, whose major decisions are the determination of the alloys to the merged and items to be produced. A question that still has not considered in the literature is the obligation to complete the production of the orders to be delivered to the client. However, in many real cases, an order cannot bi partially delivered, that is, the pieces, which are parts of the order, may be pats of the final product. In other cases, the order may be partially delivered, but with additional expedition costs. In this dissertation the objective is close that question, so we propose: (1) a mathematical model for production-planning problem of complete orders for small foundry industry; (2) a mathematical model to treat the possibility of partial delivery to the sama problem. Furthermore, we proppose a Relax-and-Fix heuristic for the integrated model

O problema de dimensionamento de lotes determina um plano de produção que apoia às tomadas de decisões, a médio prazo, em meios industriais. Este plano de produção indica as quantidades de cada item que devem ser produzidas em cada período do horizonte de planejamento, de acordo com um objetivo dado e satisfazendo a demanda dos clientes. Diversos métodos de solução foram propostas na literatura, considerando a dificuldade de solução de algumas classes de problemas e a necessidade de métodos que gerem soluções de alta qualidade em um tempo computacional adequado. Neste trabalho, abordamos heurísticas baseadas na formulação matemática (LP-and-fix, relax-and-fix e fix-and-optimize), uma metaheurística (algoritmo de abelhas) e dois métodos híbridos, utilizados na solução de dois problemas distintos de dimensionamento de lotes multiestá- gio com limitação de capacidade. Consideramos também, a utilização de três formulações da literatura, para verificar a influência de cada uma sobre as abordagens de solução verificadas. Os resultados computacionais demonstraram que os métodos baseados na formulação matemática do problema se mostraram eficientes, mas limitados normalmente a ótimos locais, enquanto os métodos híbridos puderam superar estes ótimos locais, utilizando conceitos da metaheurística algoritmo de abelhas para isto. Além disso, pudemos verificar a influência de uma formulação \"forte\" sobre as soluções geradas pelas abordagens de solução, demonstrando que métodos baseados em relaxação linear conseguem obter maiores vantagens deste tipo de formulação, mas outras abordagens podem ou não obter estas vantagens, dependendo do problema abordado / The lot-sizing problem determines a production plan, which supports the decision making, in the medium term, at the industrial environment. This production plan indicates the amounts of each item to be produced in each period of the planning horizon, according to a given objective and satisfying customer\'s demand. Diverse solution methods have been proposed in the literature, considering the difficulty of solving some problem classes and the need of methods to generate solutions quickly. In this work, we develop matheuristics (LP-and-fix, relax-and-fix and fix-and-optimize), one metaheuristic (bees algorithm) and two hybrid methods, used to solve two different multilevel capacitated lot-sizing problems. We also consider the use of three different formulations of the literature to verify the influence of each one on the solutions approaches. The computational results show that the matheuristics proved to be efficient, but usually limited to local optima, while the hybrid methods could escape from these local optima, using concepts of bees algorithm to do this. Additionally, we test the effect of a tight formulation on the solutions approaches, demonstrating that LP-based heuristics can obtain further advantages from this type of formulation, but other approaches can take these advantages, depending on the problem addressed

Nessa dissertação apresentamos um problema de programação da produção, motivado por uma indústria alimentícia caracterizada pela perecibilidade dos produtos, sequenciamento da produção dos lotes e pela necessidade de sincronização de recursos escassos para operação das linhas de produção. Em indústrias desse ramo, existem altos custos associados a estocagem dos produtos, a fim de evitar sua perda, de modo que é essencial a boa gestão dos processos industriais e do estoque. Modelos matemáticos de programação inteira mista foram desenvolvidos para tratar o problema, bem como o estudo da inclusão de diversas restrições da literatura para o tratamento da perecibilidade. Testes computacionais foram realizados para as validações dos modelos matemáticos, entretanto, devido à dificuldade de determinar soluções de boa qualidade pelo solver de otimização, foram propostos métodos heurísticos baseados na formulação matemática. Com o objetivo de mostrar o desempenho das heurísticas, comparamos as suas performances na resolução de instâncias da literatura e exemplares baseados no cenário produtivo da indústria com os resultados do solver. / In this dissertation we present a lot sizing and scheduling problem motivated by a food industry characterized by the perishability of the products, sequencing the production of the lots and by the need of synchronization of scarce resources for the operation of the production lines. In this type of industry, there are high costs associated with stocking the products in order to avoid their loss, so that good management of industrial processes and inventory is essential. Mathematical models of mixed integer programming were developed to treat the problem, as well as the study of the inclusion of several restrictions of the literature for the treatment of perishability. Computational tests were performed for the validations of the mathematical models, however, due to the difficulty of determining solutions of good quality by the optimization solver, heuristic methods based on the mathematical formulation were proposed. In order to show the performance of the heuristics, we compare their performances in solving instances of the literature and exemplars based on the productive scenario of the industry with the results of solver.

Volvo GTO is currently interested in reducing their batch sizes at the press operation in Umeå. Where a large number of different cab parts are currently produced for trucks on two different production lines that interact with each other. The reason for wanting to reduce the batch sizes is to reduce their warehousing costs, free up factory space for other activities and to create a more dynamic production that can respond to market changes rapidly. In the thesis work, the effects of changes in batch size in the press lines has been anal- ysed with both qualitatively and quantitatively methods. The analyses have been based on finding the smallest possible batch size for the stamped articles. This follows lean production where unnecessary waste of resources should be avoided, and Just-In-Time production should be sought. By testing the current production using batch sizes close to the theoretical minimum, we obtain and can analyse the various processes that are affected by changed batch sizes. These analyses are delimited to the effects after the two press lines and then mainly on the different types of inventories and processes that occur after press lines. The conclusion we can draw from this analysis is that there are many parameters that weigh into the definition of an optimal batch size from a cost perspective. This is be- cause it is a large production organisation with many sub-processes. Results show that the setup costs increases from smaller batch sizes and are not matched by the profits from less inventory holding cost. But since inventory space in the plant is in high demand the gained space from smaller batch sizes could be profitable long term. There is several other advantages that could justify reduced batch sizes on both press lines like shorter lead times, less overproduction and movements. Smaller batch sizes may confront some problems in the QC control process, outer setup, quality issues and increase visibility. / Volvo GTO Umeå är i dagsläget intresserade av att minska sina batchstorlekar i pressli- norna. I dagsläget produceras en större mängd olika hyttdelar till lastbilar på två olika produktionslinor som samspelar med varandra. Anledningen till att man vill minska sina batchstorlekar är för att sänka sina lagerhållningskostnader, frigöra fabriksyta till andra aktiviteter samt att uppnå en mer dynamisk produktion som snabbare kan svara till marknadsförändringar. I arbetet har flödet efter dessa presslinor analyserats både kvalitatitvt och kvantitativt. Analyserna i arbetet har utgått från att hitta den minsta möjliga batchstorleken för ar- tiklarna. Detta ligger i linje med lean principen där onödigt resursslöseri skall undvikas, och Just-In-Time produktion bör eftersträvas. Genom att testa den nuvarande produktionsstrukturen med batchstorlekar nära teo- retiskt minimum analyserar vi de olika processer som påverkas av förändrade batch- strolekar och hur de kostnaderna kopplade till processerna påverkas. Dessa analyser grundar sig på det som sker efter pressverksamheten och då främst olika typer av lager och förädlingsprocesser. Den slutsats vi kan dra från denna analys är att det finns många parametrar som väger in vid definieringen av en optimal batchstorlek ur ett kostnadsperspektiv. Detta eftersom det är en stor produktionsapparat med många delprocesser. De slutsatser som dras är att mindre batchstorlekar ökar ställkostnader och matchas in av de konkreta vinsterna i minskade lagerhållnadskostnader. Men då yta i fabriken är i hög efterfrågan kan ytan värderas så högt att det finns långsiktiga vinster att minska batchstorlekarna. Det finns också flertalet andra fördelar som skulle kunna rättfärdiga minskade batchstorlekar på båda presslinorna så som kortare ledtider, mindre överproduktion och färre förflyttningar. Mindre batchstorlekar kan också synliggöra problem i kvalitetskontrollprocessen, yttre ställ, kvalitetsproblem och öka visibilitet.

This thesis presents a case study of mathematical production scheduling optimization applied on Arla Foods AB’s production of dairy products. The scheduling was performed as a possible remedy for problems caused by overcrowded finished goods warehouse. Based on the scheduling, conclusions were made on whether the existing two-shift production is sufficient or if an additional night shift should be introduced. In parallel, an empirical and theoretical analysis on the perceived effects of night shift work on employees was conducted. For the optimization, mixed integer programming was used to model the production context through a discrete time scheduling lot-sizing model developed in this thesis. The model developed and implemented on Arla Foods AB contributes to the research field through its feature of relatively low complexity enabling scheduling of extensive production systems when applied in industrial contexts where products may be categorized. The thesis concludes that mathematical production scheduling can solve Arla Foods AB’s production problematics and suggests reallocation of the existing shifts for the purpose of reduced costs and acceptable warehouse levels. This reallocation would incur production during inconvenient hours whereas management remedies reducing negative effects of night shift work are identified. / Denna avhandling innefattar en studie av matematisk optimering av produktionsscheman applicerad på Arla Foods ABs produktion av mejeriprodukter. Schemaläggningen utfördes som en möjlig lösning på produktionsproblematik orsakad av överfyllda färdigvarulager. Utifrån de optimerade produktionsschemana drogs slutsatser kring om dagens produktionsstruktur på två skift är tillräcklig eller om introduktion av ett andra nattskift skulle vara fördelaktig. Parallellt med detta presenteras en empirisk och teoretisk studie kring de produktionsanställdas uppfattning kring effekter av att arbeta nattskift. För optimeringen har heltalsoptimering (eng: mixed integer programming) använts för modellering av produktionen genom en produktionsplaneringsmodell med diskret tidsrepresentation (eng: discrete time scheduling lot-sizing model ) som utvecklas i denna avhandling. Denna model, som även appliceras på Arla Foods ABs produktion, presenteras i detalj och karaktäriseras av låg komplexitet vilket möjliggör schemaoptimering av omfattande produktionssystem givet att produktportföljen kan kategoriseras i produktgrupper med liknande egenskaper ur ett produktionsperspektiv. Avhandlingen fastslår att matematisk optimering av produktionsscheman har potential att lösa produktionsproblematiken på Arla Foods AB och föreslår en reallokering av den nuvarande produktionen för minskade kostnader och utjämnade nivåer i färdigvarulager. Produktionsomläggningen skulle innebära produktion under obekväm arbetstid vilket föranleder en analys av initiativ som har potential att minska de negativa effekterna av nattskiftarbete för de produktionsanställda.

This dissertation aims to provide models which will help companies make sustainable logistics management and transportation decisions. These models are extensions of the economic lot sizing model with the availability of multiple replenishment modes. The objective of the models is to minimize total replenishment costs and emissions. The study provides applications of these models on contemporary supply chain problems. Initially, the impact of carbon regulatory mechanisms on the replenishment decisions are analyzed for a biomass supply chain under fixed charge replenishment costs. Then, models are extended to consider multiple-setups replenishment costs for age dependent perishable products. For a cost minimization objective, solution algorithms are proposed to solve cases where one, two or multiple replenishment modes are available. Finally, using a bi-objective model, tradeoffs in costs and emissions are analyzed in a perishable product supply chain.

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In this paper, we will show that the economic lot-sizing problem with rework of defectives is NP-hard. Therefore, we reduce it to the well-known PARTITION problem. This is in line with the findings for similar models that in-vestigate lot-sizing with remanufacturing.

There have been several infamous incidences where world-renowned corporations have been caught by surprise when a low-tier downstream supplier has been publicly found to be non-compliant with basic corporate social responsibilities (CSR) codes. In such instances, the company reputation, and consequently financial health, suffer greatly. Motivated by the advances in predictive modeling, we present a predictive analytics model for detecting possible supplier deviations before they become a corporate liability. The model will be built based on publicly available data such as news and online content. We apply text mining and machine learning tools to design a corporate social responsibility "early warning system" on the upstream side of the supply chain. In our literature review we found that there is a lack of studies that focus on the social aspect of sustainability. Our research will help fill this gap by providing performance measures that can be used to build prescriptive analytics models to help in the selection of suppliers. To this end, we use the output of the predictive model to create a supplier selection optimization model that takes into account CSR compliance in global supply chain context. We propose a heuristic to solve the problem and computationally study its effectiveness as well as the impact of introducing CSR on procurement costs as well as ordering and supplier selection patterns. Our models provide analytics tools to companies to detect supplier deviance behaviour and act upon it so as to contain its impact and possible disruptions that can shake the whole supply chain. / Thesis / Master of Science (MSc)