Abstract:The high percentage of the refrigeration costs (17%) in the operational production costs, the ecological subjects, the lawlegal demands related to the preservation of the environment and the human health justify the recent researches about the restriction towards the use of abundant cutting fluid in machining processes. However, it is important to point out that the use of a minimal mist lubrication (mixture of air and oil) has been possible in production processes for machining, due to the technological devel… Show more
“…Three levels of flow rate and air pressure were used: 20, 40, and 60 ml/h and 1, 2, and 3 bars. The choice of those levels was based on previous studies on MQL drilling of aluminum alloys which applied flow rates in the range of 10 to 100 ml/h and in some cases up to 250 ml/h [8,9,[59][60][61][62][63][64][65][66][67][68].…”
Conventional twist drilling is a widely used machining process for creating holes in aerospace and automobile structures. Drilling at room temperature can sometime affect the quality of machined holes due to increased thermal effects on the workpiece. Thermal effects can be a cumbersome when machining composites and fiber metal laminates due to their different thermal expansion coefficients, which may introduce additional stress in the structure. Thermal machining effects can be minimized using coolants supplied either directly or indirectly to the cutting tool-workpiece interaction zone, to remove away part of the generated heat. The use of coolants adds extra costs for handling, disposal, and environmental impact. Therefore, environmentally friendly cooling technologies are replacing conventional cooling methods to reduce costs and impact on the environment. In addition, the selection of machining parameters has great influence on the hole quality. This paper investigates the impact of drilling parameters and two modern cooling technologies namely cryogenic liquid nitrogen and minimum quantity lubrication on the hole perpendicularity error of fiber metal laminates commercially known as GLARE® (Glass Laminate Aluminum Reinforced Epoxy). It was also found that applying cryogenic liquid nitrogen or minimum quantity lubrication does not lead to an improvement in hole perpendicularity error in GLARE® laminates.
“…Three levels of flow rate and air pressure were used: 20, 40, and 60 ml/h and 1, 2, and 3 bars. The choice of those levels was based on previous studies on MQL drilling of aluminum alloys which applied flow rates in the range of 10 to 100 ml/h and in some cases up to 250 ml/h [8,9,[59][60][61][62][63][64][65][66][67][68].…”
Conventional twist drilling is a widely used machining process for creating holes in aerospace and automobile structures. Drilling at room temperature can sometime affect the quality of machined holes due to increased thermal effects on the workpiece. Thermal effects can be a cumbersome when machining composites and fiber metal laminates due to their different thermal expansion coefficients, which may introduce additional stress in the structure. Thermal machining effects can be minimized using coolants supplied either directly or indirectly to the cutting tool-workpiece interaction zone, to remove away part of the generated heat. The use of coolants adds extra costs for handling, disposal, and environmental impact. Therefore, environmentally friendly cooling technologies are replacing conventional cooling methods to reduce costs and impact on the environment. In addition, the selection of machining parameters has great influence on the hole quality. This paper investigates the impact of drilling parameters and two modern cooling technologies namely cryogenic liquid nitrogen and minimum quantity lubrication on the hole perpendicularity error of fiber metal laminates commercially known as GLARE® (Glass Laminate Aluminum Reinforced Epoxy). It was also found that applying cryogenic liquid nitrogen or minimum quantity lubrication does not lead to an improvement in hole perpendicularity error in GLARE® laminates.
“…Thus, because the effect of MQL on the process is mainly lubrication and it presents a very small cooling ability to the tool (Braga et al, 2003), it will not cause thermal cracks generation and J. of the Braz. Soc.…”
Section: Results Of the Third Phase -Experiments With Minimum Quantitmentioning
It is estimated that around 65% of the cost of a die or mould is related to the machining processes. Moreover, the literature says that 70% of the time spent in the machining processes of this kind of parts is used in finishing and semi-finishing operations. The high complexity of the machined surfaces makes mandatory the use of ball nose tools, with large overhang, what increases vibration in the process. These problems have to be minimized, since dies and moulds demand a very good surface finish and tight dimensional tolerances. A frequently used strategy to attenuate these problems is to carry out semi-finishing operations with cutters containing circular inserts, because these inserts produce smooth transitions among the passes and a smaller and more uniform stock material for the finishing operation. The main goal of this work is to evaluate the performance of rounded inserts of carbide and cermet in the semi-finishing milling (called toroidal milling) of H13 steel with hardness of 50 HRc. The influence of radial depth of cut, cutting speed and feed per tooth on tool life will also be considered. It also intends to test the feasibility of using minimum quantity of lubricant (MQL) technique instead of dry cutting in this kind of machining operation
“…al. [12] used this technique on drilling Aluminum-Silicon alloy (323) with carbide drills, without coating. The authors concluded that MQL could reduce the temperature on the chip formation zone, maintaining it at levels low enough to avoid tool material deterioration.…”
Trabajar los aceros endurecidos siempre ha sido un desafío para el corte de metales, particularmente en las operaciones de roscado. En el presente trabajo se mide la temperatura del acero AISI H13 endurecido, realizándose ensayos sin lubricación (seco) y dos sistemas con lubricación: aceite lubricante en grandes cantidades y mínima cantidad de líquido (minimum quantity of fluid MQF) a 20 ml/h, en ambos casos se utilizó aceite integral mineral. El roscado se realiza sobre probetas de prueba de 100 x 40 mm con 14 mm de espesor y dureza de 55 HRc. Para medir la temperatura se utiliza la técnica de termocuplas situadas muy próximas al diámetro mayor del hilo de rosca (a 0.1, 2.5 y 5 mm de distancia). Se utilizan tres termocuplas a lo largo del espesor de la probeta de prueba a 3.0, 7.0 y 11.0 mm desde la entrada del roscado. Se hacen dos réplicas del registro de la temperatura para cada condición de corte ensayada. Se utiliza un modelo teórico-analítico de conducción de calor para evaluar la temperatura en la interfase de la probeta de prueba, determinar el flujo de calor y el coeficiente de convección. El menor incremento de la temperatura y del calor se observa al utilizar el método lubricante en grandes cantidades, seguido por el de MQF, al comparar con la condición en seco. El efecto es directamente proporcional a la cantidad de lubricante aplicado, siendo también significativo con el sistema MQF al compararlo con el corte en seco. Palabras clave: Roscado, conducción del calor, cantidad mínima del líquido (MQL), acero AISI H13, temperatura.
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