Silvio Alexandre De Araujo

• PhD
• Full Professor at São Paulo State University

This paper studies the process of cutting steel bars in a truck suspension factory with the objective of reducing its inventory costs and material losses. A mathematical model is presented that focuses on decisions for a medium-term horizon (4 periods of 2 months). This approach addresses the one-dimensional 3-level integrated lot sizing and cuttin...

In this paper, an integration of the one-dimensional cutting stock problem with an operational problem that arises in the manufacture of concrete poles is studied. Seeing that poles have a steel structure, different thicknesses of steel bars can be used in their manufacture. This variety in combining the materials to produce the structure of the po...

In this paper, an automotive spring factory is studied to optimize its hardening process. The assignment of items to the hardening furnace is treated as a one-dimensional cutting stock problem, an approach not found in the literature. To make a feasible decision in this assignment, the activity that follows the furnace, i.e. the bending of the item...

In this paper, we present a new mixed integer programming formulation for two-dimensional guillotine cutting and packing problems based on a strip decomposition of the rectangular spaces. The formulation covers most of the main related problems in the literature by setting parameters accordingly. The strip concept commonly used for problems with a...

We study bin-packing and lot-sizing decisions in an integrated way. Such a problem appears in several manufacturing settings where items first need to be cut and next assembled into final products. One of the main novelties of this research is the modeling of the complex setup operations in the cutting process, which is modeled using a bin-packing...

This study looks at a real-world production planning problem that arises in a Brazilian lattice slab factory. Based on its production, which comprises a process in two stages, the main concerns of the factory are the waste of steel trusses in the first stage, setups and inventory costs in the second stage. The proposed mathematical model is based o...

In this paper the cutting stock problem minimizing saw cycles is considered. In this context where objects can be cut simultaneously the trade-off between raw material and machine utilization costs is of major interest. Different processing times for each cutting pattern are considered, according to the number of items on it, different from previou...

In this paper, we study the one-dimensional multi-period cutting stock problem with setup costs on cutting patterns. We present pattern-based and pseudo-polynomial formulations for the problem. Reformulations are also proposed to improve the lower bounds. We then present a thorough theoretical analysis to establish the strength of the various propo...

This research looks at the production planning of hollow-core slabs integrated to the optimisation problem of the use of moulds. Considering the production process of these structures, two mathematical models are proposed for the arising problem, which consists of a one-dimensional multi-period cutting stock problem with innovative aspects regardin...

O problema de corte de estoque apresenta importância reconhecida tanto no meio acadêmico, como industrial. Diversas características operacionais peculiares podem ser verificadas em diferentes sistemas de produção. Este trabalho contribui no estudo de três características operacionais e suas integrações com processos de corte unidimensionais, motiva...

O problema de corte de estoque (PCE) apresenta importância reconhecida e crescente, tanto no meio acadêmico, como industrial. Por estar tipicamente imerso em processos produtivos, diversas características operacionais podem ser verificadas em diferentes sistemas de produção. Este artigo propõe-se a contribuir no estudo de uma característica operaci...

Neste trabalho abordamos um problema real identificado no processo produtivo de indústrias de embalagens de papelão ondulado. O setor de planejamento e controle da produção emite boletins que trazem as características relativas às chapas que serão produzidas. A produção destas chapas é feita no corrugador, onde bobinas são instaladas, de acordo com...

Sugarcane is a product of great economic relevance and, as well as its use for the production of different types of sugar, it is also a renewable source for the production of bio‐fuels, other bio‐products, and electricity. In this context, efficient planning and technology changes are necessary to ensure high productivity, competitiveness and harmo...

In many productive processes, two important problems arise in the production planning: the lot-sizing problem and the cutting stock problem. Generally, companies deal with these problems separately but, by considering them in an integrated way, better results can be obtained. In this paper, the integrated lot-sizing and three-dimensional cutting st...

In this paper, a manufacturer of automotive springs is studied in order to reduce inventory costs and losses in the steel bar cutting process. For that, a mathematical model is proposed considering parallel machines and operational constraints, besides the demand, inventory costs and limits for items and final products. This one-dimensional integra...

The standard blending problem consists of combining components to produce a final product with a given demand, while satisfying specific criteria with respect to the global blend and minimizing the total cost. The Bill-Of-Material (BOM) (or recipe) indicates which components are used and in which proportion. Typically, there is some flexibility in...

In this paper, we address a two-stage integrated lot-sizing, scheduling and cutting stock problem with sequence-dependent setup times and setup costs. In production stage one, a cutting machine is used to cut large objects into smaller pieces, in which cutting patterns are generated and used to cut the pieces, and should be sequenced in order to ob...

This paper presents a literature classification and a detailed computational study analysing the impact of considering the possibility of setup carryover and crossover when solving the lot sizing problem. This problem is an extension of the standard Capacitated Lot Sizing Problem. A setup carryover is defined as the possibility to begin a period wi...

This paper addresses the integration of the lot-sizing problem and the one-dimensional cutting stock problem with usable leftovers (LSP-CSPUL). This integration aims to minimize the cost of cutting items from objects available in stock, allowing the bringing forward production of items that have known demands in a future planning horizon. The gener...

This work is related to the lot sizing problem with flexible parallel machines, which basically consists in determining the quantity of items to be produced, on each of the machines, in a finite time horizon, satisfying a given demand. This problem has an economic origin and involves costs of production, inventory and setup. In the standard problem...

This paper addresses the problem of multiple manufacturing modes integrated into the cutting stock problem, based on a real-life application of the concrete pole manufacturing. The main aim is to propose, formulate and test this integrated problem, which can be applied to the construction industry and other contexts of multiple manufacturing modes...

In this paper we address a reel allocation problem that appears in a corrugated cardboard packaging company. Given a production plan which incorporates customer orders and a set of reels in stock, the decision is how to allocate these reels to the corrugator to produce the ordered corrugated cardboard sheets, aiming to minimize the number of reels...

We analyze machine flexibility in the context of the flexible job shop problem. In general, the decisions about machine flexibility are taken in advance (the data sets already contain this information). Based on a mathematical model from literature, we proposed an extension that, aiming to minimize the makespan, considers the possibility of investi...

The aim of this paper is to classify the literature related to the integration between the lot-sizing and cutting stock problem. A deterministic mathematical model, that considers multiple dimensions of integration and comprises several aspects found in practice, is proposed. This model is used as a framework to classify the current literature in t...

The bus driver scheduling problem (BDSP) under study consists in finding a set of duties that covers the bus schedule from a Brazilian public transportation bus company with the objective of minimizing the total cost. A deterministic 2-phase heuristic algorithm is proposed using multiple assignment problems that arise from a model based on a weight...

The lot sizing problem with setup crossover is an extension of the standard big bucket capacitated lot sizing problem (CLSP). The general idea is that the first setup operation of each planning period can already start in the previous period, if not all the capacity is used in that previous period. This provides more flexibility in the planning and...

Two important optimization problems occur in the planning and production scheduling in paper industries: the lot sizing problem and the cutting stock problem. The lot sizing problem must determine the quantity of jumbos of different types of paper to be produced in each machine over a finite planning horizon.These jumbos are then cut in order to me...

Two important optimization problems occur in the planning and production scheduling in paper industries: the lot sizing problem and the cutting stock problem. The lot sizing problem must determine the quantity of jumbos of different types of paper to be produced in each machine over a finite planning horizon. These jumbos are then cut in order to m...

Diversas são as aplicações da Pesquisa Operacional nos campos do conhecimento visando a otimização de processos. O uso de técnicas eficientes no planejamento e programação da produção em indústrias, almejando aumentar sua produtividade e a qualidade dos produtos, são cada vez mais frequentes, e na construção civil não é diferente. Este trabalho abo...

The integrated lot sizing and cutting stock problem is studied in the context of furniture production. The goal is to capture the interdependencies between the determination of the lot size and of the cutting process in order to reduce raw material waste and production and inventory costs. An integrated mathematical model is proposed that includes...

This study presents mixed integer programming (MIP) models for production lot-sizing problems with distribution costs using unit load devices such as pallets and containers. Problems that integrate production lot-sizing decisions and loading of the products in vehicles (bins) are also modelled, in which constraints such as weight limits, volume res...

O problema de escalonamento de condutores (PEC) consiste em distribuir de maneira eficiente o quadro de viagens de uma empresa de transporte coletivo entre os condutores disponíveis. Esse problema é comumente modelado como um problema de cobertura de conjunto — PCC (set covering problem). Nesse caso, um bom resultado para o PEC depende de uma boa c...

Production processes comprising both the lot-sizing problem and the cutting stock problem are frequent in various industrial sectors. However these problems are usually treated separately, which can generates suboptimal overall solution and consequently causes production losses. In this paper, we propose different mathematical models for the integr...

The cutting stock problems (PCE) are often found in furniture industries. In some of them, it is necessary to cut rectangular plates of wood into smaller rectangles that are parts of final products. The focus of this work is to evaluate different mathematical models to generate cutting patterns for the solution of the two-dimensional PCE using the...

The multiperiod cutting stock problem arises in the production planning and programming of many industries that have the cutting process as an important stage. Ordered items are required in different periods of a finite planning horizon. It is possible to bring forward or not the production of items. Unused inventory in a certain period becomes ava...

Neste trabalho propomos um modelo matematico para resolver o problema de dimensionamento de lotes de producao em uma industria de moveis. O problema proposto se caracteriza como multi-itens, multi-estagios com demanda dinâmica deterministica.

Dois importantes problemas de otimizacao matematica ocorrem no planejamento e programacao da producao em industrias papeleiras: o problema de dimensionamento de lotes e o problema de corte de estoque multiperiodo. O problema de dimensionamento de lotes deve determinar a quantidade de bobinas jumbos de diferentes tipos de papel a serem produzidos em...

Nowadays, Brazil is the largest producer of sugarcane, with an output of 632 million tons in the last harvest season (2014/2015). Out of this amount, 571.34 million tons of sugarcane were produced in the Center-South region of Brazil, generating approximately 31.99 million tons of sugar and 26.15 billion liters of ethanol. The number displayed for...

We study the multi-item capacitated lot sizing problem with setup times. Based on two strong reformulations of the problem, we present a transformed reformulation and valid inequalities that speed up column generation and Lagrange relaxation. We demonstrate computationally how both ideas enhance the performance of our algorithm and show theoretical...

Um importante problema de programação da produção surge em indústrias de papel, integrando o problema de corte de estoque ao dimensionamento de lotes. O problema de dimensionamento de lotes deve determinar a quantidade de bobinas jumbos de diferentes tipos de papel a serem produzidos em cada máquina, ao longo de um horizonte de planejamento finito....

We consider the capacitated lot sizing problem with multiple items, setup time and unrelated parallel machines. The aim of the article is to develop a Lagrangian heuristic to obtain good solutions to this problem and good lower bounds to certify the quality of solutions. Based on a strong reformulation of the problem as a shortest path problem, the...

This paper investigates the one-dimensional cutting stock problem considering two conflicting objective functions: minimization of both the number of objects and the number of different cutting patterns used. A new heuristic method based on the concepts of genetic algorithms is proposed to solve the problem. This heuristic is empirically analyzed b...

This paper considers the multi-plant lot sizing problem. Each item can be produced in any plant and it is possible to meet the demand of a particular plant with production from one (or several) other plants, in this case, incurs a transfer cost. The objective is todevelop strong formulations for this problem. Reformulations that based on the shorte...

In many production processes, a key material is prepared and then transformed into different final products. The lot sizing decisions concern not only the production of final products, but also that of material preparation in order to take account of their sequence-dependent setup costs and times. The amount of research in recent years indicates th...

In this paper, capacitated lot sizing problems in which the classical lot sizing decisions are made considering the transportation costs of the manufactured products were studied. These costs are related to the necessary number of pallets or trucks to pack and/or transport the products from the factory to the warehouse. Three extensions of a mixed...

This paper addresses the single stage lot-sizing problem in parallel machines. Each item can be produced on any machine, and incurs a setup time before to start the production. The objective of this paper is to obtain lower bounds of good quality for this problem. A solution method is developed based on a reformulation of the problem and the Lagran...

In this paper, some new constraints and an extended formulation are presented for a Lot Sizing and Scheduling Model proposed in the literature. In the production process considered a key material is prepared and is transformed into different final items. The sequencing decisions are related to the order in which the materials are processed and the...

This paper deals with the one-dimensional integer cutting stock problem, which consists of cutting a set of available objects in stock in order to produce ordered smaller items in such a way as to minimize the waste of material. The case in which there are various types of objects available in stock in limited quantities is studied. A new heuristic...

The aim of this work was to study a distribution and lot-sizing problem that considers costs with transportation to a company warehouse as well as, inventory, production and setup costs. The logistic costs are associated with necessary containers to pack produced items. The company negotiates a long-term contract in which a fixed cost per period is...

A lot sizing and scheduling problem prevalent in small market-driven foundries is studied. There are two related decision levels: (1) the furnace scheduling of metal alloy production, and (2) moulding machine planning which specifies the type and size of production lots. A mixed integer programming (MIP) formulation of the problem is proposed, but...

A lot sizing and scheduling problem from a foundry is considered in which key materials are produced and then transformed into many products on a single machine. A mixed integer programming (MIP) model is developed, taking into account sequence-dependent setup costs and times, and then adapted for rolling horizon use. A relax-and-fix (RF) solution...

This work consists of a case study in a large foundry, which has three molding lines and two sets of furnaces. The molding lines produce different types of items, which must be made of different alloys produced by the furnaces. In each period, the production programming in this foundry has two important levels of decision making which are linked: 1...

Atualmente, no Brasil, as fundições estão presentes em todas as regiões, produzindo desde peças simples de uso do-méstico até as mais sofisticadas, como autopeças de veícu-los e peças e/ou partes de máquinas e equipamentos de uso industrial. Segundo o relatório da ABIFA-Associação Bra-sileira de Fundição (2002), o setor produziu em novembro de 2002...

This article discusses a practical lot-sizing and scheduling problem in a foundry, involving two interrelated decision levels: furnace scheduling – in which a type of alloy is selected for production in each period, and molding machine planning – which specifies the quantity of each item to be manufactured in each period, i.e., lot-sizing. A mixed...

Este trabalho consiste no estudo de um problema prático que ocorre numa fundição que tem apenas um forno em operação por período, consistindo no gargalo do processo produtivo, e várias máquinas de moldagem que produzem diferentes tipos de itens com demandas conhecidas que devem ser feitos com diferentes ligas. Em cada período, a programação da prod...

This work presents a study on the resolution method of the single product lot sizing problem formulated by Trigeiro et al. (1989). This problem consists of determining the quantities to be produced in different periods of time, minimizing the sum of costs of production, setup and inventory. The quantity to be produced in each period should be suffi...

RESUMO Neste trabalho estuda-se algumas extensões de um trabalho anterior em que decisões relativas à minimização dos custos com transporte dos produtos fabricados são tomadas de forma integrada às decisões clássicas do problema de dimensionamento de lotes (minimização dos custos de produção, estoque e preparação). Os custos com transporte estão as...

To elaborate work schedules for telephonic attendance, the manipulation of a large volume of information is required, which makes the task more complex and subject to conflicts among the elements involved. The schedules of shifts, free times, vacations and duties are generated every month, but modifications in the course of the month can still occu...

This work deals with the Integer One Dimensional Cutting Stock Problem. Several well-known heuristics are implemented. These heuristics are used to develop a new heuristic method based on the Genetic Algorithms characteristics. Preliminary computational results are presented which to compare the new method with some classical methods and with anoth...

Resumo Neste trabalho, são implementados vários procedimentos meta-heurísticos para resolução do Problema de Partição de Números, que consiste num dos problemas clássicos de otimização combinatória cujo problema de decisão associado pertence à classe NP-difícil. Além de ter diversas aplicações práticas, este problema é freqüentemente usado como bas...

RESUMO Baseado em [3], este trabalho apresenta uma discussão de como a relação entre decomposição de Dantzig-Wolfe e relaxação lagrangiana pode ser explorado para desenvolver algoritmos combinando os pontos fortes de ambos os métodos. Afim de explicar os princípios gerais usamos o problema de dimensionamento de lotes em máquinas paralelas. O proble...

Este trabalho apresenta um estudo sobre problemas de dimensionamento de lotes monoestágios, que consistem em determinar as quantidades de itens a serem produzidos em diferentes períodos de tempo, de modo a minimizar a soma dos custos de produção, preparação e estoque. A quantidade produzida em cada período deve ser capaz de atender as demandas dos...