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Abstract(s)
No contexto industrial atual de elevada competitividade e exigência do mercado, empresas dedicadas à produção de tubos e outros produtos através da extrusão, como é o caso da empresa X, reconhece a necessidade de garantir que os parâmetros de qualidade dos seus produtos atinjam os níveis definidos, para que se assegure a conformidade e a satisfação do cliente. Neste caso, o diâmetro interno dos tubos, que é uma das características cruciais do produto final, tem demonstrado desde a abertura da empresa, uma grande variabilidade, o que leva à instabilidade do processo.
Neste sentido foi conduzido antes do estudo principal, um estudo de controlo estatístico do processo, para avaliar as suas capacidades. Com a aplicação de cartas de controlo 𝑋̅−𝑅 e do cálculo dos índices 𝐶𝑝 e 𝐶𝑝𝑘, verificou-se que o processo se encontra sob controlo estatístico. No entanto, os valores extremamente baixos dos índices indicam uma descentralização e baixa capacidade do processo, dificultando o cumprimento dos requisitos da qualidade.
Como resposta a estas dificuldades, desenvolveu-se um Design of Experiments (DoE) com base no método de Taguchi, com o objetivo de otimizar os parâmetros do processo de extrusão e reduzir a variabilidade do processo para se atingir a qualidade necessária. Selecionaram-se os fatores, velocidade da extrusora, número de vias, temperatura do Pin e Die e velocidade do forno, e organizaram-se numa matriz ortogonal 𝐿8, sendo que para as 8 experiências a realizar se retiraram 2 respostas para cada uma. As respostas em estudo (diâmetro interno e espessura) são do tipo “Nominal é melhor” o que implica que os valores das respostas têm de estar em torno de um valor alvo definido pela empresa. A análise dos resultados incluiu a construção de gráficos de efeito médio relativamente à resposta e à razão S/N, análise das interações entre os fatores e ainda uma análise da variância (ANOVA) para identificar os efeitos estatisticamente mais relevantes.
Os fatores significativos obtidos para o diâmetro interno foram então, a velocidade do forno, a relação entre a velocidade da extrusora e a temperatura do Pin e Die e a relação entre o número de vias e a velocidade do forno. Já para a espessura obtiveram-se as mesmas, mas ao invés da velocidade do forno, foi selecionada a relação entre o número de vias e a temperatura do Pin e Die.
In today's highly competitive and demanding industrial market, companies dedicated to the production of pipes and other products through extrusion, such as the company in question, recognize the need to ensure that the quality parameters of their products reach the defined levels, in order to ensure compliance and customer satisfaction. In this particular case, the internal diameter of the tubes, which is one of the crucial characteristics of the final product, has shown great variability since the company opened, leading to process instability. A statistical control study of the process was carried out before the main study to assess its capabilities. By applying the 𝑋̅−𝑅 control charts and calculating the 𝐶𝑝 and 𝐶𝑝𝑘 indices, it was found that the process is under statistical control.However, the extremely low index values indicate decentralization and low process capacity, making it difficult to meet quality requirements. In response to these difficulties, a Design of Experiments (DoE) was developed based on the Taguchi method, with the aim of optimizing the parameters of the extrusion process and reducing the variability of the process in order to achieve the required quality. The factors, extruder speed, number of lanes, Pin and Die temperature and oven speed, were selected and organized in an 𝐿8 orthogonal matrix, with 2 answers for each of the 8 experiments to be carried out. The responses under study (internal diameter and thickness) are of the ‘Nominal is better’ type, which means that the response values must be around a target value defined by the company. The analysis of the results included the construction of average effect graphs in relation to the response and the S/N ratio, analysis of the interactions between the factors and also an analysis of variance (ANOVA) to identify the most statistically relevant effects. The significant factors obtained for the internal diameter were the oven speed, the relationship between the extruder speed and the Pin and Die temperature and the relationship between the number of lanes and the oven speed. For the thickness, the same was obtained, but instead of the oven speed, the ratio between the number of lanes and the Pin and Die temperature was selected.
In today's highly competitive and demanding industrial market, companies dedicated to the production of pipes and other products through extrusion, such as the company in question, recognize the need to ensure that the quality parameters of their products reach the defined levels, in order to ensure compliance and customer satisfaction. In this particular case, the internal diameter of the tubes, which is one of the crucial characteristics of the final product, has shown great variability since the company opened, leading to process instability. A statistical control study of the process was carried out before the main study to assess its capabilities. By applying the 𝑋̅−𝑅 control charts and calculating the 𝐶𝑝 and 𝐶𝑝𝑘 indices, it was found that the process is under statistical control.However, the extremely low index values indicate decentralization and low process capacity, making it difficult to meet quality requirements. In response to these difficulties, a Design of Experiments (DoE) was developed based on the Taguchi method, with the aim of optimizing the parameters of the extrusion process and reducing the variability of the process in order to achieve the required quality. The factors, extruder speed, number of lanes, Pin and Die temperature and oven speed, were selected and organized in an 𝐿8 orthogonal matrix, with 2 answers for each of the 8 experiments to be carried out. The responses under study (internal diameter and thickness) are of the ‘Nominal is better’ type, which means that the response values must be around a target value defined by the company. The analysis of the results included the construction of average effect graphs in relation to the response and the S/N ratio, analysis of the interactions between the factors and also an analysis of variance (ANOVA) to identify the most statistically relevant effects. The significant factors obtained for the internal diameter were the oven speed, the relationship between the extruder speed and the Pin and Die temperature and the relationship between the number of lanes and the oven speed. For the thickness, the same was obtained, but instead of the oven speed, the ratio between the number of lanes and the Pin and Die temperature was selected.
Description
Keywords
Extrusão Qualidade Design de Experiências Taguchi Otimização Borracha Extrusion Quality Design of Experiments Optimization Rubber