Effects of Different Cooling Methods on the Specific Energy Consumption when Drilling CFRP/Ti6Al4V Stacks

Abstract As the current trend in the manufacturing industry is moving toward cleaner production and sustainable manufacturing, selecting a proper cooling method is of vital importance to reduce the environmental and economical impacts of machining processes. Thus, one of the biggest challenges a manufacturer faces when machining titanium-composite stacks is whether or not to use coolant, and, if so, how to apply it effectively. Therefore, it is important to know how the application of coolants to machined composite stack surfaces affects the kinetics of cutting and how the cut surfaces interact with the coolant. The aim of this paper is to study the cutting energy distribution in drilling CFRP/Ti6Al4V stacks under different cooling conditions and to optimize the machining process in order to reduce the energy consumption. A series of drilling tests using TiAlN-coated drill bits under dry and MQL conditions were conducted to quantify the specific cutting energy consumption of each stacked phase. The results indicate that the use of vegetable-based lubricating oil can effectively reduce the energy consumed on the the friction work between the drill bit and the machined hole wall, which leads to a decrease in drilling torque and specific cutting energy. To achieve better hole quality and energy efficiency, large feed rates under MQL conditions are recommended.