Processo de retificação de cerâmica avançada combinado à mitigação de riscos à saúde dos colaboradores usando uma técnica alternativa de lubrirrefrigeração
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Data
2023-06-30
Autores
Fernandes, Lucas de Martini
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
As cerâmicas avançadas tornaram possíveis diversas aplicações que eram inconcebíveis anos atrás. A utilização atual na indústria aeroespacial é um dos exemplos de sucesso de aplicação, sendo ainda o material altamente desejado em diversos tipos de indústria, tais como de defesa, automotiva e biomédica, devido às suas ótimas propriedades de elevada força específica, resistência à corrosão, estabilidade em elevadas temperaturas, baixa dilatação térmica, entre outras propriedades, entretanto, o alto custo de manufatura atrapalha o crescimento deste mercado. Para estes materiais, a maneira mais usual de obter a geometria final de uma peça nas tolerâncias desejadas é por meio de retificação com rebolos diamantados, visto que a retificação costuma ser o processo selecionado quando são necessárias superfícies ou geometrias de elevada qualidade ou se materiais frágeis precisam ser usinados. Um dos sistemas que representa elevado custo na operação de retificação é o de lubri-refrigeração, que, de acordo com diversos estudos feitos por outros autores, representa entre 16 – 20% do custo total, enquanto a ferramenta costuma entre 4 – 7%. Além destes fatos, o uso de fluido convencional é ainda responsável por uma grande quantidade de emissão de dióxido de carbono equivalente, considerando desde fabricação até descarte do material, por este motivo, sendo importante encontrar caminhos mais sustentáveis, ao mesmo tempo que visando obter viabilidade econômica. Assim, este trabalho explora a retificação cilíndrica externa de mergulho em peças do material alumina 96%, utilizando rebolo diamantado e com algumas variações de método de lubri-refrigeração (convencional, MQL e MQL + WCJ) e de velocidade de avanço (0,25; 0,5 e 0,75 mm/min), visando análise do desempenho dos métodos em diferentes condições de taxa de remoção de material, sendo feita a ponderação de três aspectos relacionados à ecoeficiência: qualidade da peça (nos parâmetros desvio de circularidade e rugosidade, junto à análise em microscópio confocal), custos da operação (para o qual foram coletados parâmetros tais como desgaste diametral do rebolo; relação G; potência demandada) e emissão de carbono equivalente, temas de grande relevância no mundo atual e para futuros de curto e longo prazo. Os resultados obtidos indicaram ótimo desempenho da condição MQL + WCJ nos quesitos custo total e emissão de dióxido de carbono equivalente, enquanto tendo menor desempenho que o sistema convencional no quesito qualidade da peça, sendo uma escolha interessante quando não é necessária alta taxa de remoção de material, visando as vantagens dos quesitos ambiental e custo. O uso de apenas MQL mostrou resultados ambientais consideravelmente melhores do que o sistema convencional, entretanto, nos critérios qualidade da peça e custos, não teve bons resultados, sendo possivelmente viável em condição de baixa taxa de remoção de material, enquanto a lubri-refrigeração convencional apresentou os melhores resultados de qualidade de peça e em elevadas taxas de remoção de material, tendo em detrimento o maior nível de emissão de dióxido de carbono equivalente, independente da velocidade de avanço analisada, e riscos de saúde aos operadores, assim como ambientais.
Advanced ceramics have made possible various applications which were virtually inconceivable years ago. Current application on the aerospace industries is a successful example of use of the material. Some other fields in which the material is highly desired are defense, automotive and biomedical industries owing to their excellent properties such as high specific strength, corrosion resistance, wear resistance, high-temperature stability, low thermal expansion, among others, however, the high manufacturing cost has hampered the growth of advanced ceramics’ market. For these materials, the most usual way to obtain the final geometry of a piece is grinding with grinding wheel using diamond grits, since grinding is usually the selected process when high quality surface / geometry or brittle material machining is required. The coolant-lubricant system plays a major role on the grinding process costs, which, according to studies of different authors, represents generally 16 – 20% of the total operation costs, while the tool costs are usually on the range of 4 – 7%. Besides these facts, the conventional fluid usage is also responsible for a considerable share of the carbon dioxide equivalent emissions, considering operations required from the oil production until its disposal. For this reason, it’s important the achievement of more sustainable ways, along with economic feasibility. Therefore, this work explores the plunge cylindrical external grinding process on alumina 96% workpieces using diamond grinding wheel and applying some coolant-lubricant methods (conventional, MQL and MQL + WCJ) and different feed rates (0.25, 0.50 and 0.75 mm/min), aiming performance analysis of each method on different material removal rates conditions, in which three aspects are weighted: workpiece quality (surface roughness and roundness error parameters, along with confocal microscopy analysis), operation costs (which considered some parameters such as wheel diametral wear, G-ratio and consumed power) and carbon dioxide equivalent emission, topics which present great relevance in the current world and for short and long term futures. The results obtained presented great performance of the MQL + WCJ condition regarding total cost and carbon dioxide equivalent emission, while had worse performance than conventional method on workpiece quality, which is an interesting choice when high material removal rates are not required, aiming the good environmental and lower cost benefits. The MQL condition showed environmental results considerably better than conventional system, however, had the worst performance regarding workpiece quality and total costs, which may be feasible on low material removal rate conditions, while the conventional system had the best performance in terms of workpiece quality and for high material removal rates, but the worst performance (for all feed rates analyzed) in carbon dioxide equivalent emission, besides the risks that this products presents to the machine operators and to the environment.
Advanced ceramics have made possible various applications which were virtually inconceivable years ago. Current application on the aerospace industries is a successful example of use of the material. Some other fields in which the material is highly desired are defense, automotive and biomedical industries owing to their excellent properties such as high specific strength, corrosion resistance, wear resistance, high-temperature stability, low thermal expansion, among others, however, the high manufacturing cost has hampered the growth of advanced ceramics’ market. For these materials, the most usual way to obtain the final geometry of a piece is grinding with grinding wheel using diamond grits, since grinding is usually the selected process when high quality surface / geometry or brittle material machining is required. The coolant-lubricant system plays a major role on the grinding process costs, which, according to studies of different authors, represents generally 16 – 20% of the total operation costs, while the tool costs are usually on the range of 4 – 7%. Besides these facts, the conventional fluid usage is also responsible for a considerable share of the carbon dioxide equivalent emissions, considering operations required from the oil production until its disposal. For this reason, it’s important the achievement of more sustainable ways, along with economic feasibility. Therefore, this work explores the plunge cylindrical external grinding process on alumina 96% workpieces using diamond grinding wheel and applying some coolant-lubricant methods (conventional, MQL and MQL + WCJ) and different feed rates (0.25, 0.50 and 0.75 mm/min), aiming performance analysis of each method on different material removal rates conditions, in which three aspects are weighted: workpiece quality (surface roughness and roundness error parameters, along with confocal microscopy analysis), operation costs (which considered some parameters such as wheel diametral wear, G-ratio and consumed power) and carbon dioxide equivalent emission, topics which present great relevance in the current world and for short and long term futures. The results obtained presented great performance of the MQL + WCJ condition regarding total cost and carbon dioxide equivalent emission, while had worse performance than conventional method on workpiece quality, which is an interesting choice when high material removal rates are not required, aiming the good environmental and lower cost benefits. The MQL condition showed environmental results considerably better than conventional system, however, had the worst performance regarding workpiece quality and total costs, which may be feasible on low material removal rate conditions, while the conventional system had the best performance in terms of workpiece quality and for high material removal rates, but the worst performance (for all feed rates analyzed) in carbon dioxide equivalent emission, besides the risks that this products presents to the machine operators and to the environment.
Descrição
Palavras-chave
Retificação, Cerâmica avançada, Rebolo diamantado, MQL, WCJ, Ecoeficiência, Grinding, Advanced ceramics, Diamond grinding wheel, Eco-efficiency