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Análise Estatística de um Processo de Fabrico com Dois Fornecedores e respetiva Estabilização de Geometria Singular - Caso de Estudo
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O tema abordado é derivado do ramo automóvel, o caso de estudo presente abordou a
produção de barras de tejadilho quanto à sua geometria.
A questão envolvida na necessidade do estudo, remete-nos para um problema envol-
vente do paradigma fabril, a produção Just in Time (JIT) e a matéria-prima.
A produção JIT implica que todos os processos reduzam stocks, convergindo num
ritmo de produção certo, que não possui margem para erros e exige uma disponibilidade
de matérias-primas e qualidade de serviço elevada.
O alumínio é a matéria-prima utilizada nas barras de tejadilho, tem capacidades muito
apreciadas na indústria automóvel. Toda a produção gira em torno do tratamento térmico,
que altera as suas características.
A necessidade surge porque existe uma incompatibilidade destes dois pontos, o JIT
que corre contra o tempo e o alumínio que precisa do tempo de tratamento ideal.
A produção física de barras de tejadilho, especificamente, envolve três atividades: a
dobragem dos perfís, o tratamento térmico e a maquinação dos mesmos. São processos
que dependem de um grande número de variáveis, mas principalmente da condição da
matéria-prima referida.
O estudo presente requerido pela entidade, envolveu a geometria final das barras e
uma abordagem que a tentasse resolver ou, pelo menos, compreendê-la melhor. Deste
modo, desenvolveu-se um estudo de 5 meses, decorridos de Fevereiro a Junho do presente
ano, onde os três primeiros foram parte da integração no ambiente fabril com os respec-
tivos processos e para a concepção do teste - que tentou abranger o maior número de
questões possíveis, já os últimos dois meses espelharam a realização do teste e a análise
de resultados.
O estudo recaíu sobre a geometria final do produto. Deste modo, procurou-se analisar
algumas característica e processos envolventes.
A característica do material deveria ser medida por meio de ensaios de tracção.
No processo de dobragem, sendo um dos processos fulcrais, usou-se uma metodologia
que garantisse sempre a mesma forma de estar por parte da máquina a fim de encontrar
respostas sobre o processo e a reação da matéria-prima ao mesmo. Operou-se por meio
do sistema de medição da fábrica - constitídos por um gabarito de dobragem e um relógio
comparador. O Termo endurecimento, é a atividade intermédia, trata de aplicar o envelhecimento
acelerado por meio de um forno e temperaturas elevadas, capacitando o alumínio a de-
senvolver as suas funções à posteriori.
A maquinação, é o último processo e ilustra a geometria final como resultado do
aspecto do produto final. A análise destes resultados foi executada por meio do sistema
de medição, que tem por objetivo, simular a viatura. O sistema de medição consiste num
gabarito de maquinação e num relógio comparador.
Os dados recolhidos são alvo de análises de variâncias para refletir o comportamento
do material. Existiu ainda lugar para analisar um processo visual, a pintura, realizada e
analisada do mesmo modo que a maquinação. Foi desenvolvida devido ao facto de ser
uma atividade que poderia comprometer a geometria.
Todos estes pontos reduzem-se a dois fatores, o tratamento térmico e as característica
do alumínio.
Devido a estes pontos, foi possível realizar medições em todas as fases do processo,
atividade após atividade, concluindo, deste modo, que as característica e a condição do
material são os pontos a ter em consideração.
The subject of this dissertation derived from automotive sector, and the case study in question regarded the production of roof bars in terms of its geometry. This study focuses on the paradigm in factories, the Just In Time production and raw materials. The JIT production forces all processes to reduce stocks, merging into the right pro- duction rhythm, that does not have any error margins and demands high availability of raw materials and services. Aluminum is the raw material used in the roof bars, which has features that are very appreciated in the automotive industry and all the production swirls around its heat treatment, which change features. The need for this study exists because there is an incompatibility between the rushing caused by JIT and the time needed to get ideal features to be used. The physical production of roof bars, specifically, involves three activities: the bending of the profiles, the heat treatment and the milling. All of these depend on a great number of variables, but the most significative is the condition of the raw material. The present study ordered by the entity, involved the final geometry of the bars and an approach that tried to fix or, at least, understand it better. This way, a study was developed for 5 months, from February to June of the present year, where the three first months were focus on the factory, engaging in the industrial process and the conception of the test – which tried to involve the maximum number of variables. In the last two months of this study, the tests were made as well as the analyses of the results. The study concerned on the final geometry of the product. Thereby, it was necessary to observe some features of the industrial processes. The features should be measured by traction tests. In the bending process, it was used a methodology that could guarantee the unifor- mity of the process. The operation was conducted with the factory measuring system – composed by a bending template and a dial gauge. The aging treatment is the intermediate activity, it uses an oven and high tempera- tures to accelerate the aging rate of the aluminium to assure that the specimen gets the characteristics of an old one. The milling is the last process and it illustrates the final look on the product. The analysis of these results was executed using a measuring system that simulates the vehicle. This system consists on the bending template and the dial gauge. The data gathered is analyzed in terms of its variance to reflect on the materials’s behavior. All production is reduced to the heat treatment and the features of aluminium. Due to this, was possible to measure all the phases in the processes, activity after activity and conclude that the features and the condition of the aluminium is the most important one.
The subject of this dissertation derived from automotive sector, and the case study in question regarded the production of roof bars in terms of its geometry. This study focuses on the paradigm in factories, the Just In Time production and raw materials. The JIT production forces all processes to reduce stocks, merging into the right pro- duction rhythm, that does not have any error margins and demands high availability of raw materials and services. Aluminum is the raw material used in the roof bars, which has features that are very appreciated in the automotive industry and all the production swirls around its heat treatment, which change features. The need for this study exists because there is an incompatibility between the rushing caused by JIT and the time needed to get ideal features to be used. The physical production of roof bars, specifically, involves three activities: the bending of the profiles, the heat treatment and the milling. All of these depend on a great number of variables, but the most significative is the condition of the raw material. The present study ordered by the entity, involved the final geometry of the bars and an approach that tried to fix or, at least, understand it better. This way, a study was developed for 5 months, from February to June of the present year, where the three first months were focus on the factory, engaging in the industrial process and the conception of the test – which tried to involve the maximum number of variables. In the last two months of this study, the tests were made as well as the analyses of the results. The study concerned on the final geometry of the product. Thereby, it was necessary to observe some features of the industrial processes. The features should be measured by traction tests. In the bending process, it was used a methodology that could guarantee the unifor- mity of the process. The operation was conducted with the factory measuring system – composed by a bending template and a dial gauge. The aging treatment is the intermediate activity, it uses an oven and high tempera- tures to accelerate the aging rate of the aluminium to assure that the specimen gets the characteristics of an old one. The milling is the last process and it illustrates the final look on the product. The analysis of these results was executed using a measuring system that simulates the vehicle. This system consists on the bending template and the dial gauge. The data gathered is analyzed in terms of its variance to reflect on the materials’s behavior. All production is reduced to the heat treatment and the features of aluminium. Due to this, was possible to measure all the phases in the processes, activity after activity and conclude that the features and the condition of the aluminium is the most important one.
Descrição
Palavras-chave
Análise de Variância Alumínio Barras de Tejadilho Dobra por Extensão Controlo Estatístico do Processo