Abstract
Lightweight materials are finding plentiful applications in various engineering sectors due to their high strength-to-weight ratios. Hole-making is an inevitable requirement for their structural applications, which is often marred by thermal damages of the drill causing unacceptable shortening of tool life. Efficient cooling of the tool is a prime requirement for enhancing the process viability. The current work presents a novel technique of cooling only the twist drill between drilling of holes with no effect of the applied cryogenic coolant transferred to the work material. The technique is applied in the drilling of two commonly used high-strength lightweight materials: carbon fibers reinforced polymer (CFRP) and an alloy of titanium (Ti-6Al-4V). The efficacy of the cooling approach is compared with those of conventionally applied continuous cryogenic cooling and no-cooling. The effectiveness is quantified in terms of tool wear, thrust force, hole quality, specific cutting energy, productivity, and consumption of the cryogenic fluid. The experimental work leads to a finding that between-the-holes cryogenic cooling possesses a rich potential in curbing tool wear, reducing thrust force and specific energy consumption, and improving hole quality in drilling of CFRP. Regarding the titanium alloy, it yields a much better surface finish and lesser consumption of specific cutting energy.
Highlights
Hole-making in alloys and composites is a primary requirement of their structural applications
The analysis suggests that the between-the-holes mode of cryogenic cooling is an economical option as compared to the continuous mode when low-to-medium cutting speeds are involved, such as for the drilling of Ti-6Al-4V
The novel cooling technique is pitched against the conventional continuous mode of cryogenic cooling and no-cooling approach in drilling of a titanium alloy and carbon fibers reinforced polymer (CFRP) composite
Summary
Hole-making in alloys and composites is a primary requirement of their structural applications. Just like other machining processes, drilling generates process heat, which should be efficiently dissipated to keep the progress of tool wear in check and obtain cutting of highquality holes [1]. The situation is even more troublesome in drilling of high-strength materials because they are cut with an expense of higher cutting energy and, generate stronger heat flux in the cutting regions. Application of cryogenic cutting fluids have yielded positive outcomes, but the ratios of the fluid volume consumed to the amount of heat dissipated are considered too high to make the process viable. The ratios are unacceptably high due to the lack of the fluids’ access to the cutting lips of the tool. The infelicitous situation calls for an innovative way of applying cutting fluids for the sake of more efficient heat dissipation and better drilling viability
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