Network part program approach based on the STEP-NC data structure for the machining of multiple fixture pallets

partially_open4noThe adoption of alternative process plans, that is, process plans that include alternative ways of machining a workpiece, can improve system performance through a better management of resource availability. Unfortunately even if this opportunity is deeply analysed in literature, it is not frequently adopted in real manufacturing practice. In order to fill this gap, this article presents the network part program (NPP) approach for the machining of multiple fixture pallets. The NPP approach is based on the STEP-NC data structure which supports nonlinear sequences of operations and process flexibility. In the NPP approach, a machining system supervisor defines the machining sequences and generates the related part programs just before the execution of the pallet. This article provides an approach with high scientific value and industrial applicability based on the integration of new and existing process planning methods. A real industrial case study is considered in order to show that in real applications the final quality is unaffected by the change of the sequence of the operations due to the employment of nonlinear process plans. Since the results appear very encouraging, the proposed approach is a possible solution to accelerate the adoption of nonlinear process planning in real manufacturing practice.S. Borgia; S. Pellegrinelli; S. Petro'; T. TolioBorgia, Stefano; Pellegrinelli, Stefania; Petro', Stefano; Tolio, TULLIO ANTONIO MARI

Modelos para sequenciação de padrões em problemas de corte de stock

Tese de doutoramento em Engenharia Industrial e de SistemasIn this thesis, we address an optimization problem that appears in cutting stock operations research called the minimization of the maximum number of open stacks (MOSP) and we put forward a new integer programming formulation for the MOSP. By associating the duration of each stack with an interval of time, it is possible to use the rich theory that exists in interval graphs in order to create a model based on the completion of a graph with edges. The structure of this type of graphs admits a linear ordering of the vertices that de nes an ordering of the stacks, and consequently decides a sequence for the cutting patterns. The polytope de ned by this formulation is full-dimensional and the main inequalities in the model are proved to be facets. Additional inequalities are derived based on the properties of chordal graphs and comparability graphs. The maximum number of open stacks is related with the chromatic number of the solution graph; thus the formulation is strengthened by adding the representatives formulation for the vertex coloring problem. The model is applied to the minimization of open stacks, and also to the minimum interval graph completion problem and other pattern sequencing problems such as the minimization of the order spread (MORP) and the minimization of the number of tool switches (MTSP). Computational tests of the model are presented.Nesta tese e abordado um problema de optimização que surge em operações de corte de stock chamado minimização do número máximo de pilhas abertas (MOSP) e e proposta uma nova formulação de programação inteira. Associando a duração de cada pilha a um intervalo de tempo, e possível usar a teoria rica que existe em grafos de intervalos para criar um modelo baseado no completamento de um grafo por arcos. A estrutura deste tipo de grafos admite uma ordenação linear dos vértices que define uma ordenação linear das pilhas e, por sua vez, determina a sequência dos padrões de corte. O politopo definido por esta formulação tem dimensão completa e prova-se que as principais desigualdades do modelo são facetas. São derivadas desigualdades adicionais baseadas nas propriedades de grafos cordais e de grafos de comparabilidades. O número máximo de pilhas abertas está relacionado com o número cromático do grafo solução, pelo que o modelo e reforçado com a formulação por representativos para o problema de coloração de vértices. O modelo e aplicado a minimização de pilhas abertas, e também ao problema de completamento mínimo de um grafo de intervalos e a outros problemas de sequenciação de padrões, tais como a minimização da dispersão de encomendas (MORP) e a minimização do número de trocas de ferramentas (MTSP). São apresentados testes computacionais do modelo.Fundação para a Ciência e a Tecnologia (FCT), programa de financiamento QREN-POPH-Tipologia 4.1-Formação Avançada comparticipado pelo Fundo Social Europeu e por fundos do MCTES (Bolsa individual com a refer^encia SFRH/BD/32151/2006) entre 2006 e 2009, e pela Escola Superior de Estudos Industriais e de Gest~ao do Instituto Polit ecnico do Porto (Bolsa PROTEC com a refer^encia SFRH/BD/49914/2009) entre 2009 e 2010

Single line for assembly just-in-sequence multiple models

Programa Doutoral em Líderes para as Indústrias TecnológicasThe automotive industry is under a deep competitive reorganization process that manifests itself both on the demand and on the supply side. The competitiveness of this reorganization is highly dependent on a flexible production system, able to produce on demand, different vehicles (models) on a single assembly line. Due to demand requirements, production has to adjust faster to new models, each one with a large number of individual feature variants, and complexity grows in production. In addition, lean manufacturing principles introduced Just-in-Sequence as a further key issue of modern automotive production. In order to explore the single line concept related with the Just-in- Sequence principle, Car Sequencing policies avoiding blockage and starvation caused by product variety are needed. The main goal of this project was the development of a mathematical model and a computational tool to define the car sequence in the final assembly line in a daily production run. The car sequence depends on the daily demand, called the production mix, and should avoid line stoppages and minimize the number of workers needed to complete the sequence in the minimum time. This goal was achieved and we have created a new exact approach for Car Sequencing that considers limited capacity, special markets priorities and clustering of colors. An Integer Programming model was developed, but when considering clustering colors it became more complex and hard to solve. To overcome this difficulty a heuristic procedure was presented. Results show that the use of this new heuristic integrated with the exact integer model is a good approach for the Car Sequencing problems. The models were run in the software IBM ILOG 12.2 framework in a Intel® Core™2 Duo CPU T9600 Toshiba laptop @ 2.80GHz with 6 GB of RAM and we obtained good results for the heuristic in less than half an hour, for three hundred cars and seventeen options. As a result of our work we show that the clustering of colors improves the performance of the global manufacturing system and that our tool can be used daily for Car Sequencing in automotive companies.Atualmente, a indústria automóvel encontra-se sobre profunda reorganização como resultado das alterações na procura dos automóveis. Estas reestruturações serão tanto mais competitivas quanto mais flexível for o sistema de produção, tendo capacidade de se adaptar a diferentes procuras, de diferentes variantes de carros com graus de complexidade diferentes e sendo capaz de produzir estes carros numa linha única. Os princípios Lean introduziram o conceito just-in-sequence como a chave para a modernização e para a capacidade de adaptação a esta nova realidade da indústria automóvel. O conceito de linha única associada ao conceito just-in-sequence levou à procura de políticas de sequenciação de carros que evitassem o bloqueio e a paragem das linhas. O principal objetivo desta tese de doutoramento foi desenvolver um modelo matemático e uma ferramenta computacional para definir a sequência dos carros na montagem final, num dia de produção. A sequência de carros depende da procura diária e deve evitar paragens de linha e minimizar o número de operários necessários para completar a sequência no mínimo tempo possível. Este objetivo foi alcançado e foi desenvolvida uma nova abordagem exata para sequenciar carros considerando capacidade limitada, prioridades para mercados especiais e o agrupamento de carros da mesma cor. Foi desenvolvido um modelo de programação inteira, mas quando se considerou o agrupamento de carros da mesma cor, o modelo tornou-se mais complexo e difícil de resolver. Por este motivo, foi criado um modelo heurístico integrado com o modelo inteiro exato, que resulta numa boa abordagem para os problemas de sequenciação. Os modelos foram testados no software IBM ILOG 12.2 num computador Intel® Core™2 Duo CPU T9600 Toshiba laptop @ 2.80GHz with 6 GB of RAM e obtiveram-se bons resultados em menos de meia hora, para trezentos carros e dezassete opções. Como resultado deste trabalho demonstramos que agrupar os carros por cores na montagem final melhora a performance global do sistema de produção e que a nossa ferramenta pode ser usada diariamente para sequenciar os carros a produzir na montagem final da indústria automóvel.The author, Cláudia Sofia Rodrigues Duarte, was supported by the Portuguese Foundation for Science and Technology (SFRH / BD / 43010 / 2008) and the MIT Portugal Program

Algorithms and Methods for Designing and Scheduling Smart Manufacturing Systems

This book, as a Special Issue, is a collection of some of the latest advancements in designing and scheduling smart manufacturing systems. The smart manufacturing concept is undoubtedly considered a paradigm shift in manufacturing technology. This conception is part of the Industry 4.0 strategy, or equivalent national policies, and brings new challenges and opportunities for the companies that are facing tough global competition. Industry 4.0 should not only be perceived as one of many possible strategies for manufacturing companies, but also as an important practice within organizations. The main focus of Industry 4.0 implementation is to combine production, information technology, and the internet. The presented Special Issue consists of ten research papers presenting the latest works in the field. The papers include various topics, which can be divided into three categories—(i) designing and scheduling manufacturing systems (seven articles), (ii) machining process optimization (two articles), (iii) digital insurance platforms (one article). Most of the mentioned research problems are solved in these articles by using genetic algorithms, the harmony search algorithm, the hybrid bat algorithm, the combined whale optimization algorithm, and other optimization and decision-making methods. The above-mentioned groups of articles are briefly described in this order in this book

Flexible Stock Allocation and Trim Loss Control for Cutting Problem in the Industrial-Use Paper Production

We consider a one-dimensional cutting stock problem (CSP) in which the stock widths are not used to fulfill the order but kept for use in the future for the industrial-use paper production. We present a new model based on the flexible stock allocation and trim loss control to determine the production quantity. We evaluate our approach using a real data and show that we are able to solve industrial-size problems, while also addressing common cutting considerations such as aggregation of orders, multiple stock widths, and cutting different patterns on the same machine. In addition, we compare our model with others, including trim loss minimization problem (TLMP) and cutting stock problem (CSP). The results show that the proposed model outperforms the other two models regarding total flexibility and trim loss ratio

A New Decision Model for Reducing Trim Loss and Inventory in the Paper Industry

In the paper industry, numerous studies have explored means of optimizing order allocation and cutting trim loss. However, enterprises may not adopt the resulting solutions because some widths of the inventory exceed or are less than those required for acceptable scheduling. To ensure that the results better suit the actual requirements, we present a new decision model based on the adjustment of scheduling and limitation of inventory quantity to differentiate trim loss and inventory distribution data. Differential analysis is used to reduce data filtering and the information is valuable for decision making. A numerical example is presented to illustrate the applicability of the proposed method. The results show that our proposed method outperforms the manual method regarding scheduling quantity and trim loss

A Polyhedral Study of Mixed 0-1 Set

We consider a variant of the well-known single node fixed charge network flow set with constant capacities. This set arises from the relaxation of more general mixed integer sets such as lot-sizing problems with multiple suppliers. We provide a complete polyhedral characterization of the convex hull of the given set

Planning and Scheduling Optimization

Although planning and scheduling optimization have been explored in the literature for many years now, it still remains a hot topic in the current scientific research. The changing market trends, globalization, technical and technological progress, and sustainability considerations make it necessary to deal with new optimization challenges in modern manufacturing, engineering, and healthcare systems. This book provides an overview of the recent advances in different areas connected with operations research models and other applications of intelligent computing techniques used for planning and scheduling optimization. The wide range of theoretical and practical research findings reported in this book confirms that the planning and scheduling problem is a complex issue that is present in different industrial sectors and organizations and opens promising and dynamic perspectives of research and development

A Bibliometric Analysis of Operations Research and Management Science

Bibliometric analysis is the quantitative study of bibliographic material. It provides a general picture of a research field that can be classified by papers, authors and journals. This paper presents a bibliometric overview of research published in operations research and management science in recent decades. The main objective of this study is to identify some of the most relevant research in this field and some of the newest trends according to the information found in the Web of Science database. Several classifications are made, including an analysis of the most influential journals, the two hundred most cited papers of all time and the most productive and influential authors. The results obtained are in accordance with the common wisdom, although some variations are found.European Commission PIEF-GA-2011-300062 Chilean Government 116028