Retificação por corte interrompido do aço temperado ABNT 4340, com rebolo de CBN, utilizando refrigeração abundante e alta velocidade
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Data
2018-08-03
Autores
Tarrento, Gilson Eduardo
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Embora os processos de corte interrompido sejam comumente utilizados em operações de usinagem como torneamento, existe uma carência na literatura de trabalhos sobre a retificação de peças com geometria interrompida. Desta forma, o objetivo deste trabalho foi avaliar os efeitos dos impactos controlados entre o rebolo de CBN e as peças fabricadas com aço ABNT 4340, durante o processo de retificação por meio de corte interrompido variando-se a quantidade de rasgos da peça, utilizando 2 tipos diferentes de refrigeração (abundante e alta velocidade). Para a realização deste trabalho, foi utilizada uma retificadora cilíndrica CNC fabricada pela empresa Sulmecânica, modelo RUAP515H. O corpo de prova foi confeccionado com aço ABNT 4340 e o delineamento foi para aplicação do método de refrigeração abundante e otimizado por meio de alta velocidade (velocidade do jato de fluido igual à velocidade de corte), com 3 valores de velocidade de mergulho, sendo 0,25 mm/min., 0,50 mm/min. e 0,75 mm/min, sendo que para cada uma destas condições, foram utilizadas 4 diferentes geometrias, considerando peças com 0, 2, 6 e 12 ranhuras. Estabeleceu-se para cada condição de quantidade de ranhura da peça, um ensaio com 2 repetições para cada geometria, num total de 3 ensaios para cada condição ensaiada. Foi possível concluir que o aumento da velocidade de mergulho elevou a rugosidade e desvios de circularidade das peças, além de promover maior desgaste do rebolo. O aumento da velocidade de mergulho também elevou os níveis de emissão acústica, potência consumida e vibração da máquina. Para os corpos de prova com geometria interrompida, concluiu-se que as ranhuras contribuíram para a captura e transporte do fluido de corte para a área de contato, melhorando o sistema de refrigeração. Não foram constatadas evidências metalográficas que apontassem para ocorrência de danos microestruturais, causados por princípios térmicos ou mecânicos nas peças retificadas.
Although interrupted cutting processes are commonly used in machining operations such as turning, there is a lack in the literature about studies on the grinding of parts with interrupted geometry. Thus, the objective of this thesi was to evaluate the effects of the controlled impact between the CBN grinding wheel and the workpiece during the grinding process by means of interrupted cutting by varying the number of grooves of the workpiece. For this investigation, a cylindrical CNC grinding machine of Sulmecânica company, model RUAP515H was used. The test workpiece was made with ABNT 4340 steel and the design was for the application of the abundant cooling method and optimized by means of high speed (fluid jet velocity equal to the cutting speed), with 3 values of feed-rate, being 0.25 mm/min, 0.50 mm/min and 0.75 mm/min, and for each of these conditions, 4 different geometries were used, considering pieces with 0, 2, 6 and 12 grooves. Two replicates for each geometry was set up for each grooves quantity condition of the part in a total of 3 tests for each condition tested. It was possible to conclude that the increase of the feed-rate raised the roughness and deviations of roundness of the pieces, besides promoting greater wear of the grinding wheel. Increased feed-rate also increased acoustic emission levels, power consumption and machine vibration. For the workpieces with interrupted geometry, it was concluded that the grooves contributed to the capture and transport of the cutting fluid to the contact area, improving the cooling system. No metallographic evidence was found to indicate microstructural damage caused by thermal or mechanical principles in the ground pieces.
Although interrupted cutting processes are commonly used in machining operations such as turning, there is a lack in the literature about studies on the grinding of parts with interrupted geometry. Thus, the objective of this thesi was to evaluate the effects of the controlled impact between the CBN grinding wheel and the workpiece during the grinding process by means of interrupted cutting by varying the number of grooves of the workpiece. For this investigation, a cylindrical CNC grinding machine of Sulmecânica company, model RUAP515H was used. The test workpiece was made with ABNT 4340 steel and the design was for the application of the abundant cooling method and optimized by means of high speed (fluid jet velocity equal to the cutting speed), with 3 values of feed-rate, being 0.25 mm/min, 0.50 mm/min and 0.75 mm/min, and for each of these conditions, 4 different geometries were used, considering pieces with 0, 2, 6 and 12 grooves. Two replicates for each geometry was set up for each grooves quantity condition of the part in a total of 3 tests for each condition tested. It was possible to conclude that the increase of the feed-rate raised the roughness and deviations of roundness of the pieces, besides promoting greater wear of the grinding wheel. Increased feed-rate also increased acoustic emission levels, power consumption and machine vibration. For the workpieces with interrupted geometry, it was concluded that the grooves contributed to the capture and transport of the cutting fluid to the contact area, improving the cooling system. No metallographic evidence was found to indicate microstructural damage caused by thermal or mechanical principles in the ground pieces.
Descrição
Palavras-chave
Corte interrompido, Métodos de refrigeração, Rebolo de CBN, Retificação, Interrupted cutting, CBN grinding wheel, Cooling methods, Grinding