Atomization-based Cutting Fluid Research Articles

An Investigation on the Performance of the Ultrasonic Atomization-Based Cutting Fluid (uACF) Spray System

Nowadays, due to limited resources and manufacturers desire to keep manufacturing costs at the lowest level, minimum quantity lubrication systems stand out. Ultrasonic atomization-based cutting fluid (uACF) spray system, which is one of the minimum quantity lubrication methods, attracts attention with its low production cost and much lower cutting fluid consumption compared to conventional cooling systems. A limited number of studies have been carried out to demonstrate the performance of this innovative, compact and environmentally friendly system under real cutting conditions. uACF system was compared with spray cooling (SPR), compressed air cooling (AIR) and dry machining (DRY) conditions using similar machining parameters. Cutting speed and feed rate were selected as machining parameters. The effect of the machining parameters on the cutting force (Fc), cutting temperature (Tc), average surface roughness (Ra) and chip shrinkage coefficient (ξ) were compared with other systems. The study concluded that the uACF system can outperform or compete with different cooling methods in all performance outputs with the right choice of cutting parameter combination. In addition, the study also revealed the effects of cutting speed and feed rate levels on performance outputs under different cooling conditions. In the light of the data obtained from the study, it is concluded that the uACF system provides a good performance under real cutting conditions with a low amount of cutting fluid consumption (0.5 ml/min) with low operating cost and has a high utilisation potential.

Evaluation of the efficiency of an ultrasonic atomization-based coolant (uACF) spray system in external turning using different nozzle tips

Recently, the atomization-based coolant (ACF) spray system has shown promising cooling and lubrication effects in machining, but its effectiveness on machining processes has not yet been adequately studied. This paper proposes a new compact system which is developed based on the ultrasonic atomization of metalworking fluid used in machining and called the Ultrasonic Atomization-based Cutting Fluid (uACF) spray system. This study aims that, on turning AISI 1050 plain carbon steel, the effectiveness of the uACF spray system made with simple, economical, and accessible equipment is evaluated by comparing it with different cooling conditions. In this study, three different nozzle outlet tips called long wide nozzle (LWN), long narrow nozzle (LNN), and flat wide nozzle (FWN) have been used in the uACF system. Several experiments have been conducted to study the effects of the nozzle outlet tips on performance characteristics such as the main cutting force (Fc), cutting temperature (Tc), average surface roughness (Ra), and chip compression ratio (ζ). In addition, similar tests were also made for dry (DRY), compressed air (AIR), and dense coolant spraying (SPR) conditions and the test results were compared with each other. It was determined that there were statistically significant differences between the conditions of the uACF system and other classical cooling conditions. The uACF system created significant differences, especially in Fc and Tc. It was determined that the use of FWN in the uACF system was more effective than SPR on Fc, and was as effective as SPR on Tc. While the fluid consumption rate of FWN in the uACF system is 1.5 ml/min, the SPR has a fluid consumption of 20 ml/min. It has been found that the uACF spray system with a lower fluid consumption outperforms other cooling conditions, thus further enhancing the performance of the environmentally friendly production process. The effectiveness and potential of the uACF spray system on machining processes possess high efficiency and cost-effective benefits to substitute the traditional cooling-lubrication applications. The results obtained from this study have the potential to be helpful to other researchers for a similar type of study and a guide for further research on the development of different cooling systems.

Wear behaviour of whisker-reinforced ceramic tools in the turning of Inconel 718 assisted by an atomized spray of solid lubricants

Atomization-based cutting fluid (ACF) is well acknowledged as an alternative to dry cutting. However, ACF is restricted to the machining of mild materials owing to higher heat generation, shearing and frictional is the principal source of the tool wear under difficult-to-cut alloys. The applicability of ACF is explored in aggressive machining by the addition of 0.2 wt% of molybdenum disulfide and graphite powder as solid lubricants in vegetable oil. The performance of whisker-reinforced ceramic tools regarding wear progression, surface roughness, and vibration analysis under dry and ACF was compared. Findings have shown 50–65% less flank wear, and 39–51% less surface roughness under ACF due to solid lubricants at a tool-chip interface that limited notching and fracture of tool edge.

Study of Film Formation on Grooved Tools in an Atomization-Based Cutting Fluid Delivery System for Titanium Machining

The purpose of this paper is to study the effect of cutting tool surface geometry and the atomization-based cutting fluid (ACF) spray parameters on the characteristics of the thin film formed in an ACF delivery system. A computational model is developed using three submodels that are used to predict the carrier gas flow, droplet trajectories and the film formation, respectively. The model is validated through film thickness measurements using a laser displacement sensor. Turning inserts with chip-breaking grooves along with a conventional flat insert are used to study the effect of cutting tool surface geometry on the model-predicted film characteristics, including film thickness and velocity. Machining experiments are also conducted to investigate the effect of film characteristics on the machining performance in terms of tool wear, which show that the tool wear is minimum at a certain desired film thickness value and large film velocity value. Carrier gas pressure and cutting fluid flow rate are also varied to study the effect of ACF spray parameters on the film characteristics. Increase in the fluid flow results in increase in both film thickness and velocity, while an increase in the gas pressure results in the reduction of the film thickness but an increase in the film velocity.

Finish turning of Ti-6Al-4V with the atomization-based cutting fluid (ACF) spray system

Product quality and productivity are important factors in manufacturing industries, especially when dealing with cumbersome materials like titanium. Cooling and lubrication effects offered by the associated metalworking fluid application system play a vital role in determining these factors, especially during finish cutting. Recently, the atomization–based cutting fluid (ACF) spray system has shown promising cooling and lubrication effects during rough turning of titanium at the macro–scale, but yet to be examined during finish cutting (e.g., depth of cut and feed rate 0.2mm or lower). This paper aims to study the effect of the ACF spray system on machining performance during finish turning of Ti-6Al-4V. In the first set of experiments, two spray parameters (viz., gas velocity and flow rate) and cutting parameters (viz., cutting speed, feed rate and depth of cut) are varied to select the most suitable condition for the application of the ACF spray system. Machining outputs are evaluated in terms of nose wear, cutting temperature, surface roughness, roundness error, chip morphology, and part hardness. A separate set of experiments is then performed to compare the performance of the ACF spray system against compressed air (dry) and flood coolant conditions. It is found that, even a lower fluid flow rate of 1.5mL/min (10vol.%) at a lower gas velocity of the spray system outperforms the other two coolant conditions, thus further enhancing the performance of environmentally-friendly manufacturing process.

A Thermal Model to Predict Tool Temperature in Machining of Ti–6Al–4V Alloy With an Atomization-Based Cutting Fluid Spray System

In this study, a heat transfer model of machining of Ti–6Al–4V under the application of atomization-based cutting fluid (ACF) spray coolant is developed to predict the temperature of the cutting tool. Owing to high tool temperature involved in machining of Ti–6Al–4V, the model considers film boiling as the major heat transfer phenomenon. In addition, the design parameters of the spray for effective cooling during machining are derived based on droplet–surface interaction model. Machining experiments are conducted and the temperatures are recorded using the inserted thermocouple technique. The experimental data are compared with the model predictions. The temperature field obtained is comparable to the experimental results, confirming that the model predicts tool temperature during machining with ACF spray cooling satisfactorily.

Improving the performance of milling of titanium alloys using the atomization-based cutting fluid application system

The research presented in this paper investigates the effectiveness of the atomization-based cutting fluid (ACF) spray system in end-milling of titanium alloy, Ti–6Al–4V. To that end, the study has been conducted in two phases. In the first phase, experiments have been carried out to select suitable spray parameters. A numerical model of the ACF spray system has also been developed to gain a physics-based understanding of the cutting fluid film formation on a rotating tool surface and its role in providing cooling and lubrication at the cutting interface. In the second phase, experiments have been conducted to compare the machinability of titanium for different cutting fluid application methods, viz., dry cutting, flood cooling and ACF spray system, on the basis of five machinability parameters, including, tool life, tool wear, cutting forces, surface roughness and chip morphology. Experimental results show that the application of the ACF spray system results in uniform tool flank wear, lower cutting forces and higher surface finish and the tool life extends up to 75% over flood cooling. Additionally, chip morphology analysis reveals that using ACF spray system leads to the formation of shorter and thinner chips, as compared to those when flood cooling is used.

On Cutting Temperature Measurement During Titanium Machining With an Atomization-Based Cutting Fluid Spray System

The poor thermal conductivity and low elongation-to-break ratio of titanium lead to the development of extreme temperatures (in excess of 550 °C) localized in the tool–chip interface during machining of its alloys. At such temperature level, titanium becomes highly reactive with most tool materials resulting in accelerated tool wear. The atomization-based cutting fluid (ACF) spray system has recently been demonstrated to improve tool life in titanium machining due to good cutting fluid penetration causing the temperature to be reduced in the cutting zone. In this study, the cutting temperatures are measured both by inserting thermocouples at various locations of the tool–chip interface and the tool–work thermocouple technique. Cutting temperatures for dry machining and machining with flood cooling are also characterized for comparison with the ACF spray system temperature data. Findings reveal that the ACF spray system more effectively reduces cutting temperatures over flood cooling and dry conditions. The tool–chip friction coefficient indicates that the fluid film created by the ACF spray system also actively penetrates the tool–chip interface to enhance lubrication during titanium machining.

Study of Droplet Spray Behavior of an Atomization-Based Cutting Fluid Spray System for Machining Titanium Alloys

The atomization-based cutting fluid (ACF) spray system has been found to be effective for improving the tool life and overall productivity during the machining of titanium alloys like Ti–6Al–4 V. The aim of this research is to study droplet spray characteristics of an ACF spray system including droplet entrainment zone (e.g., angle and distance) and droplet-gas co-flow development regions with respect to three ACF spray parameters, viz., droplet and gas velocities, and spray distance. ACF spray experiments are performed by varying droplet and gas velocities. Machining experiments are performed in order to understand the effect of the droplet spray behavior on the machining performance, viz., tool life/wear, and surface roughness during turning of a titanium alloy, Ti–6Al–4 V. The flow development behavior with respect to the spray distance is studied by modeling the droplets entrainment mechanism. The model is validated by the ACF spray experiments. Experiments and the modeling of flow development behavior reveal that a higher droplet velocity and a smaller gas velocity result in smaller droplet entrainment angle leading to a gradual and early development of the co-flow, and a better distribution of the droplets across the jet flare. Machining experiments also show that a higher droplet velocity, a lower gas velocity and a longer spray distance significantly improve tool life and surface finish.

Characterization of Fluid Film Produced by an Atomization-Based Cutting Fluid Spray System During Machining

The atomization-based cutting fluid (ACF) spray system has recently been proposed as a cooling and lubrication solution for machining hard to machine materials (e.g., titanium alloys). On the tool rake face, the ACF spray system forms a thin film from cutting fluid that penetrates into the tool–chip interface to improve tool life. The objective of this work is to characterize this thin fluid film in terms of thickness and velocity for a set of ACF spray parameters. ACF spray experiments are performed by varying impingement angle to observe the nature of the spreading film and to determine the film thickness at different locations after impingement of the droplets. It is observed that the film spreads radially outward producing three fluid film development zones (i.e., impingement, steady, and unsteady). The steady zone is found to be between 3 and 7 mm from the focus (impingement point) of the ACF spray for the set of parameters investigated. An analytical 3D thin fluid film model for the ACF spray system has also been developed based on the Navier–Stokes equations for mass and momentum. The model requires a unique treatment of the cross-film velocity profile, droplet impingement, and pressure distributions, as well as a strong gas–liquid shear interaction. The thickness profiles predicted by the analytical film model have been validated. Moreover, the model predictions of film velocity and chip flow characteristics during a titanium turning experiment reveal that the fluid film can easily penetrate into the entire tool–chip interface with the use of the ACF spray system.

Effect of fluid concentration in titanium machining with an atomization-based cutting fluid (ACF) spray system

The aim of this work is to investigate the effect of metal-working fluid (MWF) concentration on the machining responses including tool life and wear, cutting force, friction coefficient, chip morphology, and surface roughness during the machining of titanium with the use of the ACF spray system. Five different concentrations from 5 to 15% of a water-soluble metalworking fluid (MWF) were applied during turning of a titanium alloy, Ti–6Al–4V. The thermo-physical properties such as viscosity, surface tension and thermal conductivity of these concentrations were also measured. The test results demonstrate that the tool life first extends with the increase in MWF concentration and then drops with further increase. At low concentration (e.g., 5%), a lack of the lubrication effect causes to increase in a higher friction at the tool–chip interface resulting in severe chipping and tool nose/flank wear within a short machining time. On the other hand, at high concentration, the cooling effect is less. This increases cutting temperature and a faster thermal softening/chipping/notching of the tool material and higher friction at the tool–chip–workpiece interaction zones resulting in early tool failure. A good balance between the cooling and the lubrication effects seems to be found at the 10% MWF concentration as it offers the best machining performance. However, machining with flood coolant is observed to perform the best in the range of 5–7%.

Analysis of Droplet Spreading on a Rotating Surface and the Prediction of Cooling and Lubrication Performance of an Atomization-Based Cutting Fluid System

Droplet spreading on a rotating surface has been modeled with an aim to design an efficient atomization-based cutting fluid (ACF) system for micromachining processes. To this end, single-droplet impingement experiments are conducted on a rotating surface to capture the 3D shape of a droplet upon impingement. A parameterization scheme is then developed to mathematically define the 3D shape of droplet upon impingement. The shape information is used to develop an energy-based model for droplet spreading. The droplet spreading model captures the experimental results within 10% accuracy. The spreading model is then used to predict the cooling and lubrication for an ACF-based microturning process. The model captures the cooling and lubrication trends observed in microturning experiments. A parametric study is conducted to identify the significant factors affecting the performance of an ACF system. Droplet speed is found to have a dominant effect on both cooling and lubrication performance, particularly, with a low surface tension fluid for cooling and a low surface tension and high viscosity fluid for lubrication.

Design and evaluation of an atomization-based cutting fluid spray system in turning of titanium alloy

Tool life has been a vital issue in machining titanium alloys. Recently, an atomization-based cutting fluid (ACF) application has been found to be an effective approach for cooling and lubrication in micromachining operations. In this study, an ACF spray system is developed for macro-scale turning of Ti–6Al–4V. The spray system is designed to minimize interaction between the fluid droplets, and the gas nozzle to control the divergence of the fluid droplets. Experiments are conducted to study the effect of five specific ACF spray parameters including fluid flow rate, spray distance, impingement angle, and type and pressure level of the droplet carrier gas on cutting forces, tool life, and chip characteristics. It has been observed that the combination of lower pressure (150psi) air-mixed CO2 with a higher flow rate (20ml/min) and a larger spray distance (35mm) produces a significantly longer tool life and broken chips. The results also reveal that the ACF spray system can extend tool life up to 40–50% over flood cooling.

Droplet Behavior on a Rotating Surface for Atomization-Based Cutting Fluid Application in Micromachining

The droplet behavior on a rotating surface has been studied to better understand the physics underlying atomized cutting fluid application. To this end, microturning experiments are carried out and the cutting performance evaluated for varying cutting fluids and at different droplet speeds. Microturning experiments indicate that a cutting fluid with low surface tension and low viscosity generates lower cutting temperatures, whereas a fluid with low surface tension and high viscosity generates lower cutting forces. Single-droplet impingement experiments are also conducted on a rotating surface using fluids with different surface tension and viscosity values. Upon impact, the droplet shape is observed to be a function of both the droplet speed and the surface speed. The spreading increases with increased surface speed owing to the tangential momentum added by the rotating surface. Spreading is observed to also increase with a decrease in fluid surface tension and does not change with the fluid viscosity. The evaporation rate is observed to increase for a rotating surface owing to convective heat transfer. Low surface tension and low viscosity are observed to increase the evaporation rate. It is concluded that a fluid with low surface tension and low viscosity is an effective coolant of the cutting zone, whereas a fluid with low surface tension and high viscosity is effective for lubrication.