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Abstract(s)
A marcação é a etapa do processo produtivo destinada à personalização e rastreabilidade
do cliente através da impressão de texto e/ou imagens nas rolhas de cortiça, que podem ser
marcadas a fogo, a laser e/ou a tinta. Esta etapa torna-se desafiante uma vez que são ainda pouco
conhecidos os mecanismos por detrás de cada um dos tipos de marcação, que atuam sobre a
superfície da cortiça e as inúmeras variáveis que a influenciam.
O presente trabalho encontra-se dividido em dois projetos. O 1.º projeto visa avaliar as
principais causas da libertação de pó durante o processo de marcação, nos Estados Unidos da
América, a tinta oxidativa e apresentar alternativas para solucionar o problema. O 2.º projeto
surge com o objetivo de dar continuidade ao estudo da rugosidade superficial, direcionado para
a etapa da retificação, a fim de avaliar e controlar este parâmetro, que influencia a qualidade da
marcação.
No 1.º projeto foram avaliadas caraterísticas da rolha, nomeadamente a capilaridade, o teor
de peróxido de hidrogénio, agente de branqueamento utilizado na etapa da lavação, e o teor de
pó e procedeu-se a ensaios de marcação a tinta oxidativa. Dentro dos fatores estudados, foi
possível verificar que as rolhas continham uma quantidade de peróxidos, 0,8 mg/L, acima do
valor admissível pela empresa Amorim Cork, S.A, menor ou igual a 0,1 mg/L. O teor elevado
de peróxidos aliado ao tempo de permanência das rolhas em condições adversas durante o
transporte para os Estados Unidos da América leva à degradação da superfície da rolha de
cortiça, causando problemas na marcação das rolhas no cliente final. Neste estudo, verificou-se
que o recurso a um enxaguamento após oxidação se demonstrou eficiente na remoção do teor
de peróxidos, obtendo-se um valor abaixo de 0,1 mg/rolha, valor máximo admissível pela
empresa Amorim Cork, S.A. Nos ensaios de marcação, em Portugal, não ocorreram problemas.
No 2.º projeto foi estudado o processo de retificação das rolhas. A ponçagem é a fase que
influencia diretamente a rugosidade, uma vez que recorre a uma mó, de quatro pedras giratória,
para o acabamento do corpo das rolhas. No presente trabalho foram utilizadas três
configurações de mós em três tipos de rolha microaglomerada. O estudo revelou que é crucial
o passo de limpeza destas pedras, uma vez que, após a limpeza, verifica-se sempre uma
diminuição no valor médio da rugosidade das rolhas. Nos vários casos estudados a rugosidade
nas rolhas aumenta 24 horas após a limpeza da mó. Para além disso, verificou-se que, nas
condições do estudo, para o acabamento superficial pretendido, é necessário que a cadência da
ponçagem não ultrapasse os 75 %, cerca de 6.750 - 7.500 rolhas/h.
Branding is the stage of the production process aimed at personalisation and customer traceability through the printing of text and/or images on cork stoppers, which can be marked by fire, laser and/or ink. This stage is challenging because of the mechanisms that act on the surface of the cork behind the branding and the numerous variables that influence them are still poorly understood. This work is divided into two projects. The first project aims to assess the main causes of dust release during the marking process in the United States of America using oxidizing paint, and to present alternatives for solving the problem. The 2nd project aims to continue the study of surface roughness, focusing on the grinding stage, in order to assess and control this parameter, which influences the quality of the marking. In the first project, the characteristics of the cork stopper were assessed, namely capillarity, the content of hydrogen peroxide, the bleaching agent used in the washing stage, and the dust content, and oxidative paint marking tests were carried out. Among the factors studied, it was found that the stoppers contained a quantity of peroxides, 0.8 mg/L, above the value permitted by Amorim Cork, S.A., which is less than or equal to 0.1 mg/L. The high peroxide content combined with the time the stoppers spent in adverse conditions during transportation to the United States led to degradation of the surface of the cork stopper, causing problems when marking the stoppers for the end customer. In this study, the use of a post-oxidation rinse proved to be efficient in removing the peroxide content, achieving 0.0 mg/cork. In the marking tests in Portugal, there were no problems during marking for the US customer. In the second project, the cork stopper rectification process was studied. Stoning is the phase that directly influences roughness, as it uses a four-stone rotating grinding wheel to finish the body of the stoppers. In this study, three configurations of grinding wheels were used on three types of micro-agglomerated stoppers. The study revealed that the step of cleaning these stones is crucial since after cleaning there is always a decrease in the average roughness of the stoppers. In the various cases studied, the roughness of the stoppers increased 24 hours after cleaning the grinding wheel. In addition, it was found that, under the conditions of the study, in order to achieve the desired surface finish, the punching rate mustn’t exceed 75 percent, around 6,750 - 7,500 stoppers/h.
Branding is the stage of the production process aimed at personalisation and customer traceability through the printing of text and/or images on cork stoppers, which can be marked by fire, laser and/or ink. This stage is challenging because of the mechanisms that act on the surface of the cork behind the branding and the numerous variables that influence them are still poorly understood. This work is divided into two projects. The first project aims to assess the main causes of dust release during the marking process in the United States of America using oxidizing paint, and to present alternatives for solving the problem. The 2nd project aims to continue the study of surface roughness, focusing on the grinding stage, in order to assess and control this parameter, which influences the quality of the marking. In the first project, the characteristics of the cork stopper were assessed, namely capillarity, the content of hydrogen peroxide, the bleaching agent used in the washing stage, and the dust content, and oxidative paint marking tests were carried out. Among the factors studied, it was found that the stoppers contained a quantity of peroxides, 0.8 mg/L, above the value permitted by Amorim Cork, S.A., which is less than or equal to 0.1 mg/L. The high peroxide content combined with the time the stoppers spent in adverse conditions during transportation to the United States led to degradation of the surface of the cork stopper, causing problems when marking the stoppers for the end customer. In this study, the use of a post-oxidation rinse proved to be efficient in removing the peroxide content, achieving 0.0 mg/cork. In the marking tests in Portugal, there were no problems during marking for the US customer. In the second project, the cork stopper rectification process was studied. Stoning is the phase that directly influences roughness, as it uses a four-stone rotating grinding wheel to finish the body of the stoppers. In this study, three configurations of grinding wheels were used on three types of micro-agglomerated stoppers. The study revealed that the step of cleaning these stones is crucial since after cleaning there is always a decrease in the average roughness of the stoppers. In the various cases studied, the roughness of the stoppers increased 24 hours after cleaning the grinding wheel. In addition, it was found that, under the conditions of the study, in order to achieve the desired surface finish, the punching rate mustn’t exceed 75 percent, around 6,750 - 7,500 stoppers/h.
Description
Keywords
cork branding micro-agglomerated stoppers peroxide content roughness