Evaluation of a Novel Controlled Cutting Fluid Impinging Supply System When Machining Titanium Alloys  
[PERSON]  
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[PERSON]  
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[PERSON]  
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[PERSON]  
2 School of Mechanical and Systems Engineering, Newcastle University, Newcastle Upon Tyne NE1 7 RU, UK; [EMAIL_ADDRESS] (Correspondence: [EMAIL_ADDRESS]; Tel. : +44-191-243-7834 223  
dermatitis, and cancers) [12; 13; 14; 15; 16]. Vegetable Oils (VOs)-based cutting fluids are superior alternatives due to their high biodegradability [17] and the distinctive chemical structure of the vegetable oil's molecules, which may be heavy, long, and dipolar in nature. Uniformity and super-density are other unique properties of vegetable oil molecules, which afford a thick, tenacious and vigorous film layer that offers VOs a superior ability to absorb contact pressure [18; 19; 20; 21; 22]. VOs base stocks have high thermal conductivities of up to 0.172 W/m\(\cdot\)K and a low coefficient of friction (e.g., 0.03 for soybean oil) compared to 0.125 W/m\(\cdot\)K and 0.07, respectively, for mineral oils [23; 24; 25]. An adequate understanding of cutting fluid application methods in machining operations may significantly enhance heat dissipation and thus improve the surface quality of machined parts. Several cooling supply methods were introduced to control the temperature in the cutting zone to improve productivity and increase the overall performance of machining processes. Six main cooling strategies are used in machining operations [26; 27]. Conventional flood/wet cooling is a common supply method used in machine shop floors. This method provides a steady-state stream of fluid to the machining zone with flow rates ranging from 10 L/min for single point tools to 225 L/min for multiple tool cutters [28]. Flood cooling was evaluated against minimum quantity lubrication (MQL) and dry cutting while turning hardness steel (EN-31). A reduction (about 57.14%) in the chip-tool interface temperature was obtained when flood cooling was used [29]. However, high cutting fluid consumption and low fluid penetration, particularly at higher cutting speeds, are the main drawbacks [30]. High pressure cooling (HPC) was also introduced where cutting fluids are applied at high pressure up to 200 bars through customised nozzles to provide a powerful jet of fluid into the machining zone. The cooling performance of HPC was compared with flood cooling during cutting Inconel 718 using the SiAlON cutting tool. It was found that HPC was immensely helpful to extend tool life and improve chip breaking [31]. However, the high cost of pumping systems and equipment for micro-particle filtering (i.e., <20 \(\upmu\)m) are the main disadvantages [30; 32]. Minimum quantity lubrication (MQL), compressed air, oil mist and cryogenic cooling were also considered as alternative cooling supply techniques to reduce the amount of cutting fluid delivered. MQL was found a useful lubricating method to enhance surface quality and tool life, while cryogenic cooling was found very effective in reducing tool wear and lengthening tool life. However, high costs associated with these cutting fluid supply systems are the principal limitation [33; 34; 35; 36; 37]. Additionally, nozzle position plays a vital role in machining operations and considerably affects tool life and cutting performance. [PERSON] et al. [38] studied the influence of nozzle positions of 45\({}^{\circ}\) and 135\({}^{\circ}\) in relation to feed direction when milling Al5083 using the MQL cooling supply method. The results showed that the nozzle position at 135\({}^{\circ}\) achieved lower tool flank wear of 0.098 and 0.095 mm at 0.04 and 0.06 ml/min cooling rates, respectively. The 45\({}^{\circ}\) nozzle orientation showed inferior flank wear values of 0.14 and 0.12 mm at 0.04 and 0.06 ml/min, respectively, after a 158 m cutting length. It was found that nozzle placement is crucial in order to obtain the optimum effect of MQL cooling.