UNIVERSIDADE FEDERAL DE SANTA CATARINA DEPARTAMENTO DE ENGENHARIA MECÂNICA
Francisco Ratusznei
SYSTEM RECONFIGURATION FOR CYLINDRICAL LASER CLADDING APPLICATION
Florianópolis 2019
SYSTEM RECONFIGURATION FOR CYLINDRICAL LASER CLADDING APPLICATION
Francisco Ratusznei
SYSTEM RECONFIGURATION FOR CYLINDRICAL LASER CLADDING APPLICATION
Dissertação submetida ao Programa de Pós-Graduação em Engenharia Mecânica da Universidade Federal de Santa Catarina para a obtenção do Grau de Mestre em Engenharia Mecânica. Orientador: Prof. Dr. Eng. Milton Pereira
Coorientador: Prof. Dr.-Ing. Walter Lindolfo Weingaertner
Florianópolis 2019
Ficha de identificação da obra elaborada pelo autor, através do Programa de Geração Automática da Biblioteca Universitária da UFSC.
Ratusznei, Francisco
System Reconfiguration for Cylindrical Laser Cladding Application / Francisco Ratusznei ; orientador, Milton Pereira, coorientador, Walter Lindolfo Weingaertner, 2019.
100 p.
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós Graduação em Engenharia Mecânica, Florianópolis, 2019.
Inclui referências.
1. Engenharia Mecânica. 2. Sistema Laser. 3. Reconfigurável. 4. Laser Cladding. 5. Interpolação Cilíndrica. I. Pereira, Milton . II. Weingaertner, Walter Lindolfo . III. Universidade Federal de Santa Catarina. Programa de Pós-Graduação em Engenharia Mecânica. IV. Título.
Dedico a meus pais Jorge R. Ratusznei e Sílvia Ap. D. Ratusznei
AGRADECIMENTOS
O sucesso deste projeto foi possível graças à liderança por parte dos orientadores, ao trabalho colaborativo do grupo, à assistência da equipe e laboratórios externos, às fundações de fomento, ao apoio prestado pelos familiares e à graça de Deus.
As orientações prestadas pelo co-orientador Walter Lindolfo Weingaertner e pelo orientador Milton Pereira, foram fundamentais para definir claramente o escopo do projeto desde o início. A assistência durante o desenvolvimento do projeto, brainstorms e a orientação contínua direcionaram o esforço para alcançar o objetivo do trabalho.
A equipe do laboratório colaborou dia a dia, desde o auxílio em tarefas complementares, como práticas de metalografia, treinamento sobre a operação CNC e ajuda na redação desta dissertação. Tarefas menos elegantes, como o levantamento de equipamentos pesados e artifícios técnicos aplicados em máquinas defeituosas foram práticas igualmente compartilhadas. Momentos humorísticos ajudaram a dissolver a desilusão e a angústia recorrentes.
O apoio de laboratórios externos como o LABSOLDA, LABCONF, LABTERMO e LABMAT foi essencial frente à ausência de alguns materiais e equipamentos os quais foram prontamente disponibilizados.
O apoio institucional provido pela Capes (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) foi muito importante para facilitar as condições de sustento pessoal e concentrar o foco exclusivamente nas questões da pesquisa, tornando o esforço pela sobrevivência uma preocupação secundária.
O reconhecimento por parte da família sobre a importância do aprimoramento pessoal, estudos e vida intelectual foi fundamental, tão importante quanto o suporte financeiro frequentemente provido. Finalmente, às vezes na vida, ao contrário do que propõe uma metodologia de projetos, é preciso iniciar uma nova fase sem muita certeza sobre a capacidade pessoal de finaliza-la ou mesmo sem possuir todos os meios para tal. Neste contexto, a providência divina foi a única explicação para o sucesso em situações de total derrota e impotência.
A moderação na defesa da verdade é serviço prestado à mentira.
RESUMO
Componentes cilíndricos são comuns em aplicações industriais e muitos deles exigem tratamentos especiais para prolongar sua vida útil. O revestimento de superfícies via laser cladding foi reconhecida como sendo significativamente benéfica em relação às técnicas convencionais. No entanto, esse processo ainda exige pesquisa e desenvolvimento, por exemplo, a superfície recoberta pode apresentar desvios indesejáveis, tanto geométricos como de forma. Neste contexto, a cinemática do equipamento e a estratégia de deposição são centrais para a qualidade do revestimento. Infelizmente, as linhas de pesquisa e desenvolvimento de materiais com laser no Brasil sofrem com a falta de instalações adequadas para lidar com aplicações de alta potência, mesmo havendo uma demanda representativa deste campo. Neste sentido, o alto custo de equipamentos comerciais requer o desenvolvimento de sistemas laser pelos próprios institutos. Desde 2010, o Laboratório de Mecânica de Precisão (LMP) começou a atuar em pesquisas de processamento a laser. O sistema laser até então disponível tinha a capacidade de operar em três eixos de movimento simultâneo em uma configuração XYZ linear – adequado para superfícies planas. Este trabalho busca a reconfiguração do sistema laser para interpolação cilíndrica, a fim de permitir a aplicação de revestimentos em superfícies de revolução externamente. Na primeira parte do trabalho é apresentada uma contextualização da tecnologia laser, histórico, definição, aplicações e normas de segurança. Nesta fase ainda, o processo de recobrimento, ou laser cladding é destacado, assim como as superligas e os equipamentos que utilizados para a sua aplicação. Em seguida é a presentada uma revisão sobre sistemas modulares. Na sequência, a metodologia de projetos para sistemas mecânicos de precisão reconfiguráveis, que será utilizada neste trabalho, é descrita e tem suas etapas detalhadas. Após a descrição da metodologia, segue-se sua aplicação. A primeira fase do projeto em questão consiste na implementação da metodologia para orientar o aprimoramento do equipamento e satisfazer os requisitos iniciais do projeto. Em seguida, a construção do equipamento é apresentada, onde os novos módulos necessários foram integrados ao sistema existente por meio de interfaces, preservando as capacidades originais de acordo com a metodologia. Na última fase, após alguns ensaios metrológicos, foram aplicados os revestimentos de INCONEL 625, primeiramente sobre placas planas de aço AISI 1020 e, posteriormente, sobre um substrato cilíndrico. A seção transversal das deposições foi analisada para avaliar a consistência geométrica da aplicação. Os resultados obtidos por meio da avaliação
metrológica e das aplicações em condições reais demonstraram a competência do sistema de interpolação para guiar o sistema laser em trajetórias cilíndricas. O aprimoramento do equipamento permite que novas linhas de pesquisa sejam exploradas, não somente em recobrimento de superfícies cilíndricas, mas também, por exemplo, soldagem de tubos a laser e inclusive aplicações em materiais reflexivos – em virtude da possibilidade de rotação do cabeçote laser. Finalmente, são listadas algumas melhorias e sugestões para trabalhos futuros.
Palavras-chave: Sistema Laser, Reconfigurável, Modular, Estratégias de Deposição, Laser Cladding, INCONEL 625, Interpolação Cilíndrica.
RESUMO EXPANDIDO
Introdução
Quando o laser foi inventado na década de 1960, não foi encontrada uma aplicação imediata para a nova tecnologia. No entanto, desde o início havia a expectativa de que a descoberta pudesse ser usada para resolver problemas que ainda não nem existiam. Nos anos 80, grupos de pesquisa relataram que revestimentos quando aplicados a laser poderiam apresentar vantagens em relação aos processos convencionais. Inicialmente, as aplicações de revestimento a laser eram limitadas a pequenas áreas e formas complexas. O incremento na potência de saída, as reduções no custo e o aumento da confiabilidade tornaram possíveis o recobrimento de áreas maiores. Neste campo, surge o Laser cladding, um processo de revestimento que foi que possível graças à convergência de áreas tecnológicas como, materiais, robótica, software e, principalmente, processamento a laser. No contexto brasileiro, a pesquisa a laser está atrasada em relação às outras partes do mundo, isso é motivado principalmente pelo alto custo dos equipamentos e pela infraestrutura necessária. Outra razão para o atraso da pesquisa laser em geral é a escassez de recursos humanos especializados. Mesmo assim, há uma demanda considerável de pesquisa e desenvolvimento envolvendo esta técnica, particularmente para indústrias de petróleo/gás e marítimas. Em muitas situações o custo não é o único problema relacionado aos processos a laser. Como esse campo ainda está em fase de desenvolvimento, sistemas de posicionamento especiais e equipamentos com características específicas podem não estar disponíveis no mercado. Nesse sentido, o desenvolvimento de equipamentos personalizados pode ser necessário. Os processos a laser em geral estão intimamente relacionados à automação, uma vez que os processos de alta potência não são executadas à mão por razões de segurança. No campo industrial, isso é ainda mais importante porque a necessidade de um controle eficiente aumenta a produtividade e a qualidade. Metodologias modulares e reconfiguráveis podem auxiliar na implementação de unidades de laser econômicas. A abordagem modular pode reduzir o tempo de projeto, resultando em sistemas funcionais e totalmente automatizados. Novamente, o uso de módulos padrão ou comerciais, por exemplo, braços robóticos, pode ter grande impacto na flexibilidade e complexidade do processo, permitindo a pesquisa de estratégias especiais. Neste contexto, o custo final de um sistema a laser completo pode ser reduzido pela reutilização de módulos de automação e movimentação de outros campos
da fabricação. O LMP (Laboratório de Mecânica de Precisão) trabalha há muitos anos na pesquisa e desenvolvimento de sistemas de mecânica de precisão, processos de fabricação convencionais e não convencionais. Muitos projetos são conduzidos conjuntamente com empresas locais, resultando em soluções fundamentais para a indústria bem como recursos humanos altamente especializados. Em 2010, o projeto Rede Metalúrgica, financiado pela FINEP (Financiadora de Estudos e Projetos), permitiu o início da implantação de uma instalação laser de alta potência. Este evento confirmou o novo campo de pesquisa do laboratório, iniciado em uma parceria com universidades e institutos de pesquisa alemães e suíços. Em seu trabalho, Gutjahr (2016) desenvolveu uma unidade laser de alta potência, integrando um controle numérico industrial com características modulares e reconfiguráveis, além de fornecer toda a infraestrutura necessária, como o ambiente de operação, instalação de sistemas de segurança e área de trabalho; focado em aplicações como, Laser Cladding, soldagem e tratamento térmico. O projeto liderado por Gutjahr (2016) foi bem-sucedido, mas o cronograma de mestrado não foi longo o suficiente para cobrir todas as possíveis aplicações deste complexo sistema, o qual se destinava a processamento de superfícies planas. Por este motivo, este trabalho procura a atualização do sistema laser para expandir as capacidades de processamento para formas cilíndricas. Objetivos
O objetivo deste trabalho é a atualização do sistema laser de 10 kW (SL1) existente, seguindo os princípios de modularidade e reconfigurabilidade, para permitir o processo de revestimento (laser cladding) de superfícies cilíndricas, mantendo as capacidades originais de processamento em superfícies planas. As atividades específicas relacionadas ao projeto são: a) Definir os requisitos para realizar a tarefa, b) Selecionar novos módulos, c) Fabricar as interfaces para integrar os novos módulos ao sistema original, d) Montar e integrar os módulos ao sistema, e) Qualificar o sistema, f) Validar o sistema aplicando um processo de Laser Cladding em condições reais sobre uma superfície cilíndrica.
Metodologia
Como já mencionado, este projeto é uma extensão de outro realizado por GUTJAHR (2016), o qual utilizou a metodologia PRODIP (Processo de Desenvolvimento Integrado de Produtos) desenvolvida pelo NeDIP (Núcleo de Desenvolvimento Integrado de Produtos) da UFSC (Universidade Federal de Santa Catarina). Para o propósito deste projeto, uma metodologia de projeto reconfigurável foi aplicada. Uma
Metodologia de Projeto de Sistemas de Precisão Reconfigurável desenvolvida por PEREIRA (2004) foi compilada seguindo os princípios de projeto de produtos modulares somado às características de sistemas reconfiguráveis. Esta metodologia consiste de uma sequência de passos lógicos que vão desde a definição da tarefa a ser executada, passando pela seleção de módulos e análise de efeitos incidentais, chegando por fim a um equipamento modular e reconfigurável. A característica modular é o núcleo da metodologia, baseada em módulos independentes básicos – que são obtidos a partir de equipamentos existentes, comprados ou adaptados. Os sistemas modulares visam produzir uma variedade de produtos por meio da combinação de componentes intercambiáveis e independentes, denominados módulos. Sistemas de Manufatura Reconfigurável (RMS), por sua vez, combinam a alta produtividade das linhas dedicadas, mas com maior flexibilidade de modo a reagir de forma rápida e eficiente às mudanças impostas pelo mercado.
Resultados e Discussão
Neste trabalho, um sistema laser reconfigurável foi desenvolvido, construído e qualificado. O sistema foi reconfigurado com sucesso para a operação com 4 eixos, capaz de revestir componentes cilíndricos. Novos módulos foram selecionados, interfaces foram fabricadas e integradas ao sistema original, preservando os recursos originais. O sistema a laser foi finalmente validado em condições reais pela aplicação de uma estratégia especial de laser cladding. O sistema laser original (SL-1) foi construído para processar somente superfícies planas, mas desde o início, houve a preocupação no sentido de uma futura reconfiguração, o que facilitou o presente processo de reconfiguração. O atual sistema laser é agora composto de duas áreas de trabalho: uma mesa XY para operações em superfície plana e de um eixo rotacional. A metodologia reconfigurável foi fundamental para orientar adequadamente o projeto. Na primeira etapa, apoiada pela equipe, foram determinadas as restrições do equipamento. Após isso, os módulos disponíveis foram selecionados. As interfaces necessárias para integrar os módulos ao sistema foram fabricadas utilizando material e maquinário do LMP, os recursos de outros laboratórios também foram muito importantes. Quase todos os componentes e interfaces foram fabricados, o que contribuiu para o baixo custo do projeto. Um modelo CAD do sistema foi imprescindível para auxiliar a montagem, já que o tamanho e a complexidade do sistema exigiam uma instalação muito cuidadosa. Para fins de validação, em primeiro lugar foi realizada uma movimentação em vazio para verificar possíveis conflitos e depois dois experimentos em condições reais. Para a
primeiro experimento, o logotipo do LMP foi gravado com sucesso em um tubo de aço de 350 mm de diâmetro. Nesta ocasião, confirmou-se a capacidade do sistema em operar em ambas as direções. Somente uma pequena influência de folga foi verificada. Para o experimento final, uma estratégia especial para o processo de laser cladding foi aplicada sobre um eixo de aço de 40 mm de diâmetro. A estratégia em particular foi estudada simultaneamente à reconfiguração do sistema laser. A estratégia em questão foi muito conveniente para avaliar as capacidades dinâmicas e de posicionamento do sistema, uma vez que requer o reposicionamento do cabeçote laser. Uma seção transversal do eixo revestido foi analisada usando um editor de imagens e os resultados revelaram a competência do sistema para revestir componentes cilíndricos.
Considerações Finais
O sistema pôde interpolar com sucesso dois eixos para processar geometrias cilíndricas com precisão aceitável. Os desvios detectados nos ensaios não são prejudiciais aos processos em questão, uma vez que a qualidade final de uma deposição é muito mais influenciada por outras questões, por exemplo, solidificação, contração, tensão superficial e outros aspectos metalúrgicos. Por fim, conforme sugerido por Gutjhar (2016), muitas operações manuais foram automatizadas pela equipe durante a reconfiguração: O fornecimento de gás e o alimentador de pó, antes ativados manualmente, foram configurados como códigos G. Isso é muito importante, porque o gás e o injetor de pó podem ser ligados e desligados durante a execução do programa, o que diminui a possibilidade de erros humanos, o que melhora a segurança e economiza recursos. Uma entrada analógica foi configurada, isso permite que a potência do laser ou a velocidade de varredura sejam alteradas durante o processo, o que é central para experimentos tais como alimentação dinâmica de arame/pó, controle adaptativo e controle em tempo real. A emissão de laser pulsado também foi habilitada, o sistema precisou de configurações em nível de software e hardware para selecionar esta condição, agora a pesquisa focada em laser pulsado pode ser iniciada.Ao final do projeto, o sistema laser foi capaz de atender aos requisitos iniciais
Palavras-chave: Sistema Laser, Reconfigurável, Modular, Estratégias de Deposição, Laser Cladding, INCONEL 625, Interpolação Cilíndric
ABSTRACT
Cylindrical components are common on industrial applications and many of them requires coating protection to extend its lifetime. The application of protective coatings via laser cladding was recognized to be significantly beneficial over conventional techniques. However, this process still demands research and development, for instance, the resultant surface can present undesirable geometric and form deviations. In this context, the equipment kinematics and the deposition strategy are central to the cladding quality. Unfortunately, the Brazilian R&D on laser materials processing suffers from the lack of adequate facilities to deal with high power laser applications, even so, there is a considerable demand for this field. In this sense, the high cost of commercial equipment requests the development of laser systems by the own institutes. Since 2010, the Precision Engineering Laboratory (LMP) started researching laser applications. The current Laser System available is capable of three axes simultaneous movement on a XY table setup - suitable for flat surfaces. This work seeks the Laser System reconfiguration for cylindrical interpolation in order to produce laser cladding application externally on revolution surfaces. The first phase consists of a project methodology implementation to orientate the equipment upgrade to satisfy the requirements. Then, the new modules necessary were integrated in the existent system via proper interfaces preserving the original capabilities. In the last phase, after some metrological tests, INCONEL 625 clads were applied, first over AISI 1020 flat plates and after that, over a cylindrical substrate. The cross section of the cladded layers were analyzed to evaluate the clad geometry consistence. The results testified the interpolation competence to guide the laser cladding system for cylindrical trajectories also allowing the research team to prospect more laser processes.
Keywords: Laser System Reconfiguration, Modular System, Laser Cladding Strategy, INCONEL 625, Cylindrical Interpolation.
LIST OF FIGURES
Figure 2.1 - The intensity profile of a Gaussian beam. Adapted from (HITZ;
EWING; HECHT, 2012). ...36
Figure 2.2 - Penetration of electromagnetic radiation thru the human eye (GUIDE... 2019). ...39
Figure 2.3 - Coaxial and lateral laser cladding powder supply (SCHNEIDER, 1998). ...40
Figure 2.4 - Coating of oil drilling tool by laser cladding (TOYSERKANI; KHAJEPOUR; CORBIN, 2004) ...42
Figure 2.5 - Laser cladding set up using robotic arm (DING; DWIVEDI; KOVACEVIC, 2017). ...47
Figure 2.6 - Milling machine arrangements (STOETERAU, 2004). ...48
Figure 2.7 - Hybrid manufacturing machine (HYBRID…2018). ...49
Figure 2.8 - Function and modules types in modular and mixed systems (PAHL; BEITZ, 1996). ...51
Figure 2.9 - General view of the reconfigurable project methodology. Adapted from (PEREIRA, 2004). ...58
Figure 2.10 - Step 1 detail. Adapted from (PEREIRA, 2004). ...61
Figure 2.11 - Step 2 detail. Adapted from (PEREIRA, 2004). ...62
Figure 2.12 - Step 3 detail. Adapted from (PEREIRA, 2004). ...62
Figure 2.13 - Step 4 detail. Adapted from (PEREIRA, 2004). ...63
Figure 2.14 - Step 5 detail. Adapted from (PEREIRA, 2004). ...64
Figure 2.15 - Step 6 detail. Adapted from (PEREIRA, 2004). ...65
Figure 2.16 - Step 7 detail. Adapted from (PEREIRA, 2004). ...65
Figure 3.1 - Laser system global function. Adapted from (GUTJAHR, 2016). .68 Figure 3.2 - Functional synthesis of the system. Adapted from (GUTJAHR, 2016). ...70
Figure 3.3 - Movement processing diagram. ...72
Figure 3.4 - Coordinate System According to DIN 66217 (DIN, 1975). ...73
Figure 3.5 - Room layouts ...76
Figure 3.6 - The CAD model for the rotary unity (A axis). ...77
Figure 3.7 - The U axis unity. ...78
Figure 3.8 - Frame structure reconfiguration for the U axis. ...78
Figure 3.9 – Interfaces integration with the system. ...79
Figure 3.10 - Interfaces used for the integration. ...80
Figure 3.11 - Interface evaluation matrix. ...80
Figure 3.12 - Laser head tilting. ...81
Figure 3.13 - Laser System CAD assembly. ...83
Figure 3.14 – Laser system reconfiguration before and after. ...84
Figure 3.15 - Motor Tuning Result for the A axis. ...85
Figure 3.16 - Motor Tuning for the X axis. ...85
Figure 3.17 - Gauge setup for the U axis. ...86
Figure 3.18 - Tryout Result. ...87
Figure 3.20 - Laser Cladding Strategy. ... 89 Figure 3.21 - Real situation of laser cladding application. ... 90 Figure 3.22 - Cross section of one cladded component. ... 91 Figure 3.23 - CNC rotary table. ... 92 Figure 3.24 - Hybrid laser-TIG welding. ... 92
LIST OF TABELES
Table 2.1 - INCONEL 625 Composition (INCONEL... 2018) ...44 Table 2.2 - Laser system configuration for some labs (DAVIM, 2013). ...47 Table 2.3 - RMS as a combination of dedicated and flexible systems
(PEREIRA, 2004). ...54 Table 2.4 - List of documents to assist the methodology. Adapted from ...59 Table 2.5 - List of tools to assist the methodology. Adapted from ...60 Table 3.1 - Project requirement. ...71 Table 3.2 – Modules required to compose the laser system. ...73 Table 3.3 - Specifications for each module. ...74 Table 3.4 - Measurements results. ...91
LIST OF ABBREVIATIONS AND ACRONYMS ABNT Associação Brasileira de Normas Técnicas
CAD Computer Aided Design CAM Computer Aided Manufacturing CNC Computer Numerical Control CVD Chemical Vapor Deposition DIN Deutsches Institut für Normung
DML Dedicated Manufacturing Lines
DOF Degrees of Freedom
ECP External Command Panel FMS Flexible Manufacturing Systems HAZ Heat Affected Zone
ILT Fraunhofer-Institut für Lasertechnik
IPT Fraunhofer-Institut für Produktionstechnologie
ISO International Organization for Standardization IWF Institut für Werkzeugmaschinen und Fertigung
LASER Light Amplification by Stimulated Emission of Radiation LMP Laboratório de Mecânica de Precisão
LZH LASER Zentrum Hannover
MCP Main Command Panel
MPE Maximum Permissible Exposure
NeDIP Nucleo de Desenvolvimento Integrado de Produtos
PLC Programmable Logic Controller
PRODIP Processo de Desenvolvimento Integrado de Produtos
PVD Physical Vapor Deposition
RMS Reconfigurable Manufacturing System
TIG Tungsten Inert Gas
UFSC Universidade Federal de Santa Catarina
LIST OF SYMBOLS
P [W] Incident Power
Pabs [W] Absorbed Power
A [-] Absorptivity
I [W] Laser Intensity at a Given Point
I0 [W] Laser Intensity in the Center of the Beam
x [m] Distance from the Center
w [m] Beam Radius
CONTENT 1 INTRODUCTION ... 31 1.1 OBJECTIVES ... 32 1.1.1 General Objective ... 32 1.1.2 Specific Objectives ... 32 1.2 Problem Context ... 33 2 REVIEW OF CONTENT ... 35 2.1 Laser ... 35 2.2 Laser Safety ... 37 2.2.1 Laser Classification ... 37 2.3 Laser Cladding ... 39 2.3.1 Process Description ... 40 2.3.2 Applications ... 41 2.3.3 Defects... 42 2.3.4 Laser Cladding of Superalloys ... 43 2.3.5 Laser Cladding Processing Units ... 45 2.4 Modular Systems ... 49 2.4.1 Classification of Modules ... 50 2.4.2 Modules Benefits ... 51 2.4.3 Modules Combination ... 53 2.5 Reconfigurable Manufacturing Systems ... 54 2.5.1 Characteristics of RMS ... 56 2.6 Project Methodology ... 57
3 RECONFIGURABLE SYSTEMS PROJECT
METHODOLOGY APPLIED TO LASER CLADDING
EQUIPMENT IMPROVEMENT ... 67 3.1 Laser Cladding System Reconfiguration ... 67 3.2 Definitions of the Task to Be Accomplished... 68 3.3 Kinematic Evaluation ... 71 3.4 Module Need Identification ... 73 3.5 Modules Selection ... 74 3.5.1 Modules ... 77 3.6 Interface Evaluation ... 79 3.7 Conception Assembly ... 82 3.8 Task Execution ... 88 3.9 Final Comments ... 91 4 CONCLUSIONS ... 93 4.1 Suggestions for Future Projects ... 95 REFERENCES ... 97
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1 INTRODUCTION
When the laser was invented in the 1960’s, the researches didn´t find an immediate application. However, they realize that the new technology could be used to solve problems that still not exist. The unique features exhibit by the laser light can be applied to many areas. As soon it appeared, adapted versions started to take shape. As the laser power increased, material processing areas started to be benefited from the laser technology (TOYSERKANI; KHAJEPOUR; CORBIN, 2004).
In the 1980’s research groups reported the use of laser cladding for wear and corrosion resistance being advantageous over other coating processes. The main reason is the possibility to achieve optimum qualities, such as to minimize the heat affected zone and dilution, in comparison with other conventional techniques (CALLEJA et al., 2014). Initially, applications of laser cladding were limited to small areas and complex shapes. The increment in the output power, reductions in the cost of laser power, and increase of the reliability, make depositions over larger areas cost acceptable (ION, 2005).
Laser metal deposition or laser cladding is an emerging manufacturing process. This breakthrough is due to the convergence of technological areas such as materials, robotics, software and specially, laser processing. The application of wear and corrosion resistant coatings via laser cladding was recognized to be significantly beneficial over conventional techniques.
Laser cladding is extensively used in hardfacing and corrosion protection. This demand is particularly important for the gas and oil industry, since the surface protection is mandatory for industrial components in this field. In this specific case, cladding process with Inconel 625 demonstrates high corrosion resistance and ductility (ABIOYE; MCCARTNEY; CLARE, 2015).
Laser processes are closely related to automation, since high power laser applications are not performed by hand for safety reasons. In the industrial field, this is even more important because the need for an efficient process control to increase productivity and quality. In this context, robotic systems and numeric control have been standing out.
In the Brazilian context, the laser research is late comparing to the other parts of the world, this is mostly motivated by the high cost of the equipment and the infrastructure required to assist a laser process unity. Other reason for the laser research delay in general, is the scarcity of specialized human resources on laser processing. Even so, there is a
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considerable demand of research and development of these processes, particularly for oil/gas and marine industries (GUTJAHR, 2016).
Luckily, the final cost of a complete laser system can be decreased by the reusing of automation and movement modules from other manufacture fields. Modular and reconfigurable methodologies can assist the implementation of cost effective laser unities. The modular approach can reduce the design time, achieving various functional systems and fully automated (OGIN; LEVASHKIN; YARESKO, 2017).
Sometimes, the cost isn’t the only issue related to laser applications. Because this is still a growing field, special positioning system and equipment with particular characteristics may not be available in the market. In this sense, the development of personalized equipment can be necessary. Again the use of standard or commercial modules, for instance robotic arms, can greatly impact on the process flexibility and complexity, allowing the research of special strategies (DING; DWIVEDI; KOVACEVIC, 2017).
1.1 OBJECTIVES 1.1.1 General Objective
The objective of this work is the upgrade of the existent 10 kW laser system (SL1), following the principles of modularity and reconfigurability, to allow the cladding process of cylindrical surfaces and maintaining the original capabilities of flat surface processing.
1.1.2 Specific Objectives
The specific activities related with the project are:
a) Define the requirements to perform the assignment; b) Select new modules to accomplish the task required; c) Fabricate the interfaces to integrate the new modules with
the original system;
d) Assembly and integrate the modules with the system; e) Qualification of the system to operate accordingly; f) Validate the system by applying a real condition laser
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1.2 Problem Context
The LMP (Precision Engineering Laboratory – Laboratório de Mecânica de Precisão) have been working for many years on the research and development of precision engineering systems, conventional and advanced manufacturing processes. Many projects are managed side by side with local companies in a dynamic partnership, resulting on key solutions to the industry and high specialized human resources.
By 2010 the project Metallurgic Network founded by FINEP (Projects and Studies Founding – Financiadora de Estudos e Projetos) allowed the implementation of a high power laser facility. This event confirmed the new research field of the lab, which has started with a partnership with German and Swiss universities and research institutes (IPT, ILT, IPK, LZH and IWF Inspire), but still requires multiple steps to be accomplished.
In this context, it was necessary the implementation of complementary projects in order to permit the high power laser operation. Some low budget PC based numeric commanded systems have been developed, but none of them were suitable to fulfill the initial project scope, mainly due to the complex structure reconfiguration required (JUNIOR, 2013; GUTJAHR, 2016).
In his work, Gutjahr (2016) developed a high power laser system unity, integrating an industrial numeric control with modular and reconfigurable characteristics, as well as provided all the infrastructure required, with the operation environment, safety facility and working area; focused on laser applications: laser cladding, welding and heat treatment.
The project leaded by Gutjahr (2016) has been successful, but the master degree schedule available was not long enough to cover all the potential applications of such complex system. For this reason, this present work seeks the laser system upgrade in order expand the laser processing capabilities –for cylindrical shapes processing.
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2 REVIEW OF CONTENT 2.1 Laser
LASER is an acronym for “Light Amplification
by Stimulated Emission of Radiation”. There are three basic differences between a laser beam and a regular light emission. A laser beam is highly directional (it has a small divergence), in other words, a laser beam can be focused to a small spot, it is composed by just one color (monochromatic), and finally the light waves are aligned while in an ordinary light beam, the waves propagate randomly. These characteristics can be summarized as “coherence”: (a) same wave length, (b) same direction, and (3) same phase.
Coherence makes the laser beam special; it allows focusing the light energy precisely which is useful for measurement and optical purposes. The uses include CD and barcode readers, recreative and military purposes and for this present case, material processing (HITZ; EWING; HECHT, 2012)
One of the most important aspects of laser technology is the interaction between mater and a laser beam. Despite the effort and the content produced up to now, laser processing still remains a challenge. The reason for that is because the interaction of light with mater is complicated and not fully understood.
The result of a laser interaction is determined by the power absorbed within the workpiece and, for metallic materials, the radiation energy is generally converted into heat. The absorptivity is defined as the ratio of power deposited within the workpiece and the incident power according to Equation 2.1:
𝐴 =𝑃𝑎𝑏𝑠
𝑃 (2.1)
The absorptivity can admit values between 0 and 1 which depends on the material properties and the following factors:
Properties of the laser: wavelength, polarization;
The ambient conditions: process gas, surrounding material; The surface properties: roughness; morphology;
The geometry of the piece: thickness, boundaries; Local heat, phase changes, laser induced plasma; The optical constants of the material;
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The temperature which affects the other parameters.
Precise values for absorption are determined experimentally. Computational models are only reasonable under ideal conditions. Computing absorption can only be made approximately because physical and chemical surface properties cannot be accomplished with enough precision (POPRAWE, 2011).
The laser interaction with the matter also depends on the spatial distribution of the energy light. When a flashlight beam reaches a wall, a light spot is produced; a closer view of the spot reviews that the intensity of the light decreases in the peripheral area away from the center of the spot. A similar effect is verified on a laser spot. This means that inside a laser spot, the light intensity is not the same. Many energy distributions can be found, one in particular is the Gaussian.
The term “Gaussian” is applied because the intensity profile of the laser spot is described by Gaussian distribution, according to Equation 2.2 (HITZ; EWING; HECHT, 2012).
𝐼 = 𝐼0𝑒 −2𝑥2
𝑤2
⁄ (2.2)
Where 𝐼0 is the intensity at the center of the laser beam, x is the distance from the center and w, the beam radius. The edge of the beam is mathematically defined as the point where the intensity is 13% or 1 𝑒⁄ 2 of the maximum value. This intensity energy distribution means that the intensity of a laser spot is higher in the center and reduces along the spot radius. The Figure 2.1 illustrates the intensity profile for a Gaussian laser beam.
Figure 2.1 - The intensity profile of a Gaussian beam. Adapted from (HITZ; EWING; HECHT, 2012).
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2.2 Laser Safety
Safety is an important issue around laser systems. This includes the personnel safety, facilities, the own system and the staff around, which are not connected directly with the system operation. High radiation levels and toxic gases are common inside laser processing rooms. However, the hazards can be minimized by following standard precautions.
2.2.1 Laser Classification
The risks of a direct laser-human interaction are related mainly with the laser power and frequency. The ANSI Z 136 standard series divide the laser into five categories according to the power and risks to the skin and eye contact:
a) Class 1 and 1M: visible or invisible radiation, at any circumstance, can cause damage by direct contact with the laser beam;
b) Class 2 and 2M: low power visible lasers up to 1 mW. The direct interaction with the eye is not allowed;
c) Class 3: visible and invisible laser beam, the power between 1 mW and 5 mW, the naked eye operation is not recommended, because they can cause harm to the retina. It ranges from the infrared to the ultraviolet.
d) Class 3B: visible and invisible radiation with power between 5 mW and 500mW, they are considered medium power and can cause damage to the human eye when directly incident. They can be reflected, but the reflection is not critic and do not offer fires risk.
e) Class 4: lasers above 500 mW, visible and invisible radiation, they can cause harm to the skin and eye. The reflection can cause fire risk (ANSI, 2009).
The classification of the risks depends on the laser interaction with its surrounding and can be listed as follows:
a) Possibility of eye and skin damage;
b) Consequent effects during the laser interaction – oxidation, radiation, toxic gases;
c) Level of access;
d) Possibility of human exposition to the laser beam (ANSI, 2009);
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The characterization of access level by the personnel is central to define the safety precautions. The standard classify the operation environment as follows:
a) Unrestricted: free access and no need for safety glasses; b) Restricted: limited access, the use of protection is mandatory as
well as operation advices, visual notices and safety precautions boards. Applicable to the class 3B and superior;
c) Controlled: the access, permanence and operation into the facility are supervised. The precautions cited on b) are valid. Applicable to the class 4;
d) Excluded: the access to the process room is allowed, but the permanence is forbidden during the laser emission;
e) Inaccessible: it is impossible to access the process environment due to the physical reduced dimensions (ANSI, 2009).
The laser system enclosure, the absence of windows and the extreme precaution during the operation, including the access control, pursue the risk minimization to the operator. If these methods were impracticable, administrative control and individual protections should be applied (ANSI, 2009).
The most severe harm to the humans during the laser operation is associated with the direct incidence of the laser beam or its reflection into the eye. The most effective protection is, in fact, the total enclosure of the process and in the second place, the use of safety glasses (depending on the risk classification). The eye damage caused by the laser is potentially irreversible and are directly related with the beam characteristic, particularly the wavelength. The Figure 2.2 presents the parts of the human eye affected according to the laser wavelength (GUIDE... 2019).
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Figure 2.2 - Penetration of electromagnetic radiation thru the human eye (GUIDE... 2019).
The laser safety glasses are developed to cover the 3B and 4 classes, while they are mandatory for the 1M, 2M and 3 on special conditions. The lenses are manufactured to absorb laser light of a particular wavelength to reduce, consequently, the maximum permissible exposure (MPE). The absorption by the human skin was neglected until ultraviolet (UV) lasers became popular. The UV light has a high dispersion capability, even thru the air particles. This means that the exposition is not restricted only to the laser beam, but to entire surround environment. In these cases, skin protection is recommended, for instance, special gloves, in case of presence inside the processing room (GUIDE... 2019).
2.3 Laser Cladding
Toyserkani, Khajepour, Corbin, (2005) emphasize that the literature indicates many terminologies to laser cladding based on its diversified applications. For coating applications, terms such as “laser coating”, “laser powder deposition” or “laser surfacing” are used as synonyms. In prototyping by pre-placed powder laser cladding calls the technology “selective laser sintering of metals” or “direct metal laser sintering”. Despite the variations, all the names share the same principle: “deposition of powder particles melted by a laser heat source on a substrate”. This processes will be termed as “laser cladding” from now on throughout this text.
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Poprawe (2011) highlights the unique proprieties associated with this technology:
Metallurgical bonding between substrate and deposited material;
Low porosity and bonding defects; Minimized heat input and distortion;
Suitable for iron, cobalt, nickel, titanium, aluminum, copper and other metallic base alloys;
Automated production of high precision layers.
2.3.1 Process Description
Laser cladding utilizes a laser heat source to deposit a layer on a substrate. It associates distinct technologies such as, laser processing, computer-aided design, robotics and powder metallurgy. The deposited material can be transferred by powder injection, pre-placed powder, or by wire feeding. Powder injection has been demonstrated the most effective (TOYSERKANI, KHAJEPOUR, CORBIN, 2005). Typically, the powder grain size varies between 20 and 100 µm. The carrier gas, which feds the powder into the interaction area, is usually argon or helium. The gas also acts as a shielding gas (POPRAWE, 2011). Figure 2.3 illustrates the process described before.
Figure 2.3 - Coaxial and lateral laser cladding powder supply (SCHNEIDER, 1998).
Co-axial Powder Supply Laser Beam
Shielding Gas Powder and
Carrier Gas Powder and
Carrier Gas Shielding
Gas Lateral Powder Supply
Laser Beam
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Lateral powder injection is the simplest and least expensive. On the other hand, this injector configuration presents a directional effect on the coating drops shape and a lower powder efficiency. This fact made the side injector not suitable for complex geometries.
The second type of injection creates a coaxial powder flow by means of a special nozzle. Despite the higher cost and complexity in comparison to the lateral injection, the coaxial can reach difficult access points and move in any direction. The disadvantage of the coaxial injector is that the laser beam and the powder flow are fixed in relation to one another. This mean that changing the beam´s focus requires displacing the powder nozzle and, consequently the focus of the powder jet. The resulting flow can became too thick or too thin (DAVIM, 2013).
2.3.2 Applications
The main applications for laser cladding are coatings and parts repair. The fundamental characteristics that allow laser cladding to contribute with these fields are the possibility of achieving a low heat input, dealing with a variety of materials and the automation.
Cladding consists of a layer deposited onto a substrate’s surface, which combines characteristics from the coating and the substrate. The clads are capable to provide corrosion resistance and the substrate provides the load capacity. Surface characteristics such as, abrasive, erosive, corrosive, wear and oxidation resistance, also low friction and high hardness surfaces are achievable.
Refurbishment and repair of high cost components such as tools, turbine blades, rolling mills it is another application for laser cladding. Conventional welding methods introduce thermal distortion and can be destructive (crack, porosity, very short life). Laser cladding can provide repair on many alloys that are considered unweldable by conventional methods (TOYSERKANI, KHAJEPOUR, CORBIN, 2005).
There is still the possibility of fast modification of molds and inserts for plastic injection. Also, the petrochemical industry, offshore drilling, sugar industry, steel and energy are increasingly using laser cladding to protect and repair components such as gears, shafts, and drilling components.
Figure 2.4 illustrates the coating of an oil-drilling toll by means of laser cladding (POPRAWE, 2011).
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Figure 2.4 - Coating of oil drilling tool by laser cladding (TOYSERKANI; KHAJEPOUR; CORBIN, 2004).
Finally, Toyserkani, Khajepour and Corbin, (2005) points out that rapid tooling is getting attention from manufactures once they are looking for technologies that are able to produce high-cost components and tools at low manufacturing costs and with a short manufacturing time.
2.3.3 Defects
Ion, (2005) summarizes the most common imperfection found in laser cladding and some recommendations about them:
Lack of fusion – this defect is more often observed at the toes of adjacent overlapping clads, mainly when the ratio thickness/width is high. The powder feed and traverse rate enables molten clad to flow properly in order to form an overlap with high integrity.
Cracking – this is a frequent problem because the alloys solidify to produce a high hardness coating, generally hard particles act as stress concentrators. Another reason for cracking is the thermal stress developed due to the temperature gradients. A third reason is the non-uniform thermal expansion. One solution involves substrate preheating.
Distortion – residual stress is the main cause for distortion. In order to reduce this effect, the power of the laser beam can be reduced or it can be applied through a pulsed regime. Finally, the substrate can be pre bent to compensate the distortion.
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Porosity – one reason is related to surface contamination which reduces the wetting ability of the molten clad. A good cleaning eliminates this imperfection. Fine porosity is caused by degassing as the clad solidifies. Coarse porosity depends on the geometry. Specific regions can solidify before others and promote enclosed gas pockets. Agitation can prevent this type of defect.
Dilution – in order to achieve a strong bond, a small amount of substrate must be melted, about 5%. However, the molten substrate mixes with the clad, causing elements migration that reduces corrosion resistance. Dilution can be controlled by power, feed rate and scanning speed balance.
2.3.4 Laser Cladding of Superalloys
The development of the stainless steels at the beginning of 20th century satisfied the need for high-temperature materials in the first moment. When its limits were found, the metallurgical community come up with what might be called “super-alloys” of stainless. Following, the World War II demanded the invention and adaption of alloys for gas turbines. In 1920 the superalloy industry adapted the cobalt alloy, used in dentistry, to high temperature requirements of aircraft engines. Also, nickel-chromium alloys could be found at that date.
Numerous definitions for superalloys can be found in the technical literature. In terms of composition, most of the sources refer to nickel, cobalt or iron as a base material, the Group VIII A elements is also mentioned. The high temperature application is the most remarkable characteristic attributed to superalloys. The operational temperature can vary – Donachie and Donachie (2002) indicates temperatures above 540°C, other authors, 650°C and 0,7 of the melting point was also pointed as a typical maximum operating temperatures. Other qualities frequently referred are good surface stability, corrosion, oxidation and creep resistance (KRACKE, 2012).
Among the most successful superalloys, figures the INCONEL 625, which is a commercial name for a particular nickel-chromium alloy largely applied for its corrosion resistance, strength and fabricability, working temperatures can range from cryogenic to 982°C. The strength of INCONEL is due to the stiffening effect of molybdenum and niobium into the nickel-chromium matrix. This set of elements is also responsible
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for superior resistance to high corrosive environments and high temperature including oxidation and carburization.
The resistance to pitting and crevice corrosion, corrosion-fatigue, chloride-ion corrosion and high tensile strength makes INCONEL widely applicable for seawater environments. It can be used to manufacture propeller blades, exhaust ducts and under water instrument components. Thermal fatigue strength, resistance to oxidation and good weldability of INCONEL 625 makes it appropriate for aerospace components: engine exhaust, fuel and hydraulic tubing, heat exchangers, compressor vanes, turbine rings and more.
INCONEL 625 is largely accepted in the chemical field due to its outstanding corrosion resistance under a large range of pressures and temperatures. It can be used in thinner-walled vessels and tubing due to its high strength. Other applications are heat exchangers, reaction vessels and dilatations columns. The resistance to temperatures inside reactors is among other reasons why the 625 alloy is being applied on nuclear plants (INCONEL 625). Table 2.1 summarizes the INCONEL alloy 625 composition.
Table 2.1 - INCONEL 625 Composition (INCONEL... 2018) Component Composition Limits, %
Ni 58 min Cr 20-23 Mo 8-10 Fe 5 max Nb+Na 3,15 – 4,15 Co 1 max Mn 0,5 max Si 0,5 max Al 0,4 max Ti 0,4 max C 0,1 max S 0,015 max P 0,015 max
Superalloys are commonly used as coatings and not just as solid parts. Industrial components may demand complex and contradictory requirements, for instance crack and wear resistance combined. In this case, a monolithic component could become either very expensive or unachievable. This issue can be solved by using combined materials (TUSHINSKY et al., 2013).
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The coating must improve the surface proprieties, for instance, wear and corrosion resistance. The application optimized materials over regular substrates result on cost savings. The most popular thermal coating methods are plasma spraying, arc welding and flame spraying. All of them apply heat to melt the coating material over the substrate – which can be melted or not. The attachment is guaranteed either by adhesive or fusion bounding.
The laser technology can also be applied to process superalloys and can be advantageous:
Better control of the energy supply; Possibility of local treatment;
Minimum distortion due to low heat input;
Fine microstructure due to the high heat/cooling rates;
There are no contact forces in the substrate, since the process is contactless;
Minimum dilution of the substrate;
Stronger bond between the work piece and the coating; Porosity free layers and homogeneous elements distribution
can be achieved (SCHNEIDER, 1998). 2.3.5 Laser Cladding Processing Units
One fundamental difference between machining and AM (additive manufacturing) is the absence of contact between the tool and the part for AM. In terms of movement system, this is a very important fact, because the forces involved during the cutting process for conventional manufacturing processes demand a much higher machine stiffness. In fact, there is no much information about the influence of movement system accuracy on the final quality for laser cladding – and additive manufacturing in general – as well as standards or recommendations about this topic. One reason is the relatively novelty of this field. Also, machining use to be the last phase of a part production, so the quality of the final product is highly related to the machine tool used. Laser cladding – and many additive process – requires post processing since the final surface can be rough for most applications. Researches are much more concentrated on process parameters, such as, laser power, scan speed, feed rate etc.
Laser cladding can be applied on many fields and different applications require specific positioning devices. For this reason, an appropriate positioning system must be chosen in order to reach required
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velocities (typically between 1mm/s and 20mm/s), cover the total workspace and provide maneuverability for the toolpaths. The most popular positioning systems for laser cladding are the CNC tables or multi-DOF (degrees of freedom) manipulators. For both systems, the movement dynamics must be carefully take into consideration to achieve proper accelerations and velocities for different trajectory points.
When a robotic arm is used, the singularity of the joints can be a limit for the trajectory. A singularity occurs when “one or more joints no longer represents independent controlling variables, causing a limitation on the workspace of the robot” (TOYSERKANI; KHAJEPOUR; CORBIN, 2004).
The number of degrees of freedom is an important aspect for complex shapes parts produced by laser cladding, because, in these cases, it is necessary to deposit the layers in a non-planar way. Figure 2.2 presents a photo and a schematic of a laser cladding system using a 6-axis robotic arm and an additional 2-axis tilt and rotary table as a movement unity. The number of DOF makes this setup flexible to process complex shapes, but also presents some disadvantages:
The fiber, which conducts the laser beam, can’t be bended to small radii, because the fragile fibers inside could crack. This fact limits the freedom which the arm can move and rotate; There is a higher probability of the laser beam be reflected or
scape for the workspace reaching undesirable areas inside the processing room. So, it is important to take this concern into consideration when the paths are programed;
Robotic arms are still more expensive in comparison whit linear guides and can face dynamic issues for high velocity and acceleration;
Most applications does not require the motion possibilities offered by such system. In many cases, just simple trajectories are enough to satisfy the research requirement. For many cladding processes, the toolpaths consist of simple lines – which can be accomplished with 2 ½ axes – or a regular helical interpolation.
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Figure 2.5 - Laser cladding set up using robotic arm (DING; DWIVEDI; KOVACEVIC, 2017).
CNC motions system can be successfully reconfigured to a laser motion system. It is possible to design functional setups in terms of automation, working area, layout, auxiliary functions and positioning. (OGIN; LEVASHKIN; YARESKO, 2017).
Table 2.2 presents the laser system configuration for some institutes and universities along the world. Davim (2013) suggests at least three-axis interpolation in order to reach any point in space and more two axes are necessary to orientate to a specific direction. Also, other features are necessary, for instance, laser, powder and gas switch (on/off).
Table 2.2 - Laser system configuration for some labs (DAVIM, 2013).
Process Laser Material
Feeding
CNC Workstation
Laser Engineered Net Shaping 2.4 kW CW Nd:YAG Laser Co-axial 5-axis Freeform Laser Consolidation (LIU; DUPONT, 2003) 1 kW pulsed Nd:YAG Laser Lateral 3-axis Directed Light Fabrication (MILEWSKI et al., 1998) 2 kW CW Nd:YAG Laser Co-axial 5-axis Shape Deposition Manufacturing 2.4 kW CW Nd:YAG Laser
Lateral 5-axis CNC mill Laser Direct Casting 2.8 kW CW Co-axial 4-axis fully
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(CHAM et al., 2002) Nd:YAG Laser integrated CNC Selective Laser Cladding (BENDEICH et al., 2006) 5 kW CW CO2 Laser Lateral 3-axis workstation Automated Laser Fabrication (ALIMARDANI et al., 2010) 1 kW CW Fiber Laser Lateral 5-axis workstation
Conventional machine tools have being adapted for additive manufacturing in general, mainly at research centers, since the cost of a complete system could be prohibitive. Sometimes, the type of application requires a specific dynamic, toll path, workspace and so on. In this cases, the reconfiguration of an existent CNC system can fulfil the need. Machine tools are available on a variety of layouts and their accuracy can even be over the need for AM. Figure 2.6 presents some setups possibilities for milling machines. The number of axes and their setting can be optimized baser on the process kinematics, constructive requirements and the manufacturing process limits. The variety of existent layouts provide a large source of movement unities to be used for laser application systems.
Figure 2.6 - Milling machine arrangements (STOETERAU, 2004). The machine tool structure is a base for the other elements which will built the overall equipment. These elements can be, guides, measuring and safety system for instance. The modern machine tool design consists of integrating specific subsystems, which can proceed
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from distinct manufacturers. The domain of every aspect of the production is not necessary (STOETERAU, 2004).
This modular approach was central to adapt conventional machine tools commonly applied on machining, into AM systems. Also, it possibilities the emergence of the hybrid manufacturing, the combination of subtractive and additive process into one single machine as illustrated in Figure 2.7, where both process can be performed. This sort of equipment is potentially important for repairing – since it is possible to add material (NAGEL; LIOU, 2012).
Figure 2.7 - Hybrid manufacturing machine (HYBRID…2018). 2.4 Modular Systems
Modular systems aim to produce a variety of products by means of a combination of interchangeable and independent components, named modules. In this topology, different system conceptions generate different products, attending specific problems. This contrast affects several aspects of the product, for instance, production scale, different functions, aesthetics or even specific functions of the product (KAMRANI; SA'ED, 2002).
Pahl and Beitz (1996) define:
By modular products we refer to machines, assemblies and components that fulfil various overall functions through the combination of distinct function units (building blocks) or modules (PAHL; BEITZ, 1996, p. 495).
The quality of the interfaces is central for modular systems, because it guarantees the integration between the modules and the final quality of the product. The interfaces also affect the interchangeability between the modules, the assembly, maintenance and the substitution of defective unities (PEREIRA, 2004).
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2.4.1 Classification of Modules
At this point it is important to differentiate the types of modules referring to their respective functions into a modular system:
Basic: those are fundamental functions, fulfilling overall tasks or in combination with other functions, generally, they can’t be variable.
Auxiliary: these functions are auxiliary modules joined to the basic modules.
Special: those are implemented by “possible modules”, responsible for specific sub functions, they can be understood as additions or accessories.
Adaptive: those functions are necessary as means of adaptations with other systems and variable external conditions.
Customer – Specific: these functions are implemented by non-modules and they are designed individually for specific duties. When they are necessary, the system became a mixed system, because the combination of modules and non-modules (PAHL; BEITZ, 1996).
The Figure 2.8 illustrates the modules classification. The modules are divided into essentials, which includes basic and auxiliary modules, possible modules, which includes special and adaptive modules and even non-modules leading to mixed systems.
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Figure 2.8 - Function and modules types in modular and mixed systems (PAHL; BEITZ, 1996).
2.4.2 Modules Benefits
Ulrich and Tung (1991) present the advantages of the modularity: Scale economy of components – the modularity allows the use
of some components and systems on many products. This is possible due to the patronization.
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Products changing – by changing some modules it is possible to provide the products with new operational characteristics, changing the product life span;
Products diversity – the modularity permits the creation of a variety of products by the combination of a small group of different components;
Development time planning – the modularity facilitates the project of products, due to the high adaptation possibilities; Task split – after the interface definition, the components can
be fabricated by different companies, which decreases the deadlines;
Project focused on the production – the product division into independent components allows the production and designing to became specialized and focused. If some module requires a special characteristic, the remaining modules may not;
Components test and verification – the tests and verifications became more simple since each component is a particular functional element, its function is well defined and the tests are much more simple;
Different demand – the material use can be differentiated, the components can be grouped by similar rate of fail or replacement, ensuring a uniform reposition;
Ease to install, produce and use – the modularity facilitates the production, assembly and use. The production and assembly are easier, because the components are treated as modules and so, they can be fabricated and assembled separately from one another. The use is facilitated, because the conception of the product is focused on the customer suggestion;
Easier to maintain, diagnose, repair and discard – again, all these aspects are accomplished due to the modules. The diagnose, repair, components replacement is facilitated, because is a matter of replacing the defective module temporally while the original is being fixed.
However, there are also some disadvantages of the modular systems:
Static architecture of the product – innovations can be very challenging
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Performance optimization – the performance is limited by the level of modularity imposed to the product.
Easy to copy – the copy of the product is facilitated;
Unities variable costs increase – a sub utilized module increase the final cost of the product;
Similar products – few differences between the product lines can be negative to the customer acceptance (ULRICH; TUNG, 1991).
2.4.3 Modules Combination
Ulrich and Tung (1991) describe how the modules can be associated:
Component swapping Modularity – distinct products, from a particular family, are created by the combination of two or more alternative components.
Component Sharing Modularity – in this category, different products from distinct families are created by the combination of different modules sharing the same basic component. There a close relationship with the patronization, for instance the bearings, they are applied on a variety of different equipment. Fabricate to Fit Modularity – one or more standard components are used along with one or more additional components with uncountable variations, generally, the variations are associated to the physical dimensions.
Bus Modularity – when one module can be associated to a different number of basic components. The standard interface allows the number and localization of components to be changed.
All these concepts and classifications refer to a very wide definition of modular systems. The theory behind modular system requires specific directions to the product to be developed. The methodology applied can be completely different from one product to another (PEREIRA, 2004).
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2.5 Reconfigurable Manufacturing Systems
The fast technology changing on manufacturing systems demands easy actualization equipment and promptly integrable functions. These conditions require a manufacturing approach which permits a fast new product families launch, with a quick production capacity, able to be adapted to the market demands. Also, an immediate integration of new functions and technologies already existent. Finally, an easy product volume adaptation to a specific market segments (MEHRABI; ULSOY; KOREN, 2000).
Most of the companies use dedicated or flexible manufacturing systems. Dedicated Manufacturing Lines (DML) or transfer lines, are dedicated to mass production. Each line is dedicated to produce only one component, with a high productivity. The high demand makes the cost of each component decrease.
Flexible Manufacturing Systems (FMS) can produce a verity of products, with a flexible production volume and shape, using the same system. Frequently, this system is composed by costly computer numeric control (CNC) machines. The productivity is lower than a dedicated machines and consequently, the cost by each component produced (KOREN et al., 1999).
In this context, raises the Reconfigurable Manufacturing System (RMS), which combines the high productivity from the dedicated lines with the flexibility form the flexible manufacturing capable, also, to react quickly and efficiently to the imposed changes. Table 2.3 summarizes the particularities of each system.
Table 2.3 - RMS as a combination of dedicated and flexible systems (PEREIRA, 2004).
Characteristic DML RMS FMS/CNC
Machine Structure Fix Adjustable Fix
System focus Component Family of
components Machine
Production capacity No Yes Yes
Flexibility No Adaptable General
Simultaneous tools
operation Yes Yes No
In this approach, the system and equipment project is oriented to an adjustable structure, in order to allow a scale changing for different market demands and the system shifting to produce new components. The
