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The infiltration and cooling effect of lubricant droplets in the cutting zone largely depend on setting minimum quantity lubricant (MQL) system parameters appropriately. The study determines the optimal spray angle and spray distance relying on the geometric position relationship between the nozzle and the overall cutting zone. A numerical model that combines computational fluid dynamics (CFD) and discrete phase model (DPM) is presented to simulate droplet transport process for dynamic milling and one-tooth milling by flow field distribution and droplet characteristics. The influences of different spray distances and spray angles on the infiltration process and cutting tool temperature are analyzed. The experiments aimed at verifying the results of the analysis are conducted by measuring cutting force, cutting temperature, surface roughness, surface microtopography and tool wear. The result indicates that the spray distance has a significant impact on the jet divergence, and insufficient lubrication or excessive lubrication is effectively avoided with the optimal cutting distance. Spraying in the direction of cutting-out promotes the accessibility of the lubricant and greater concentration of droplets in the cutting zone, especially later in the cutting process, which results in increased infiltration, reduced friction, and improved heat dissipation. Moreover, experiments demonstate that the optimal state of jetting in the direction of cutting-out is 46 °C lower than that of dry cutting, the surface roughness is reduced by 19.8%, and the wear amount is reduced by roughly 34%. This study has a better understanding of the setting of spray distance and spray angle in MQL milling and the development of equipment, which provides theoretical guidance for the optimization of MQL system parameters in practical applications.

The lower lead time and increasing demand for good quality parts require the industries to produce the parts manufactured sustainably with higher precision, improved productivity, and low cost using new techniques. Minimum quantity lubricant (MQL) is one of these techniques, which is economical and eco-friendly. This paper deals with the analysis and multi-response optimization of cutting process parameters of Aluminum alloy 6026-T9 in MQL and dry conditions using an integrated approach of composite desirability function and criteria importance through inter-criteria (CRITIC). The cutting parameters considered for the study are cutting speed, feed rate, depth of cut, and positive rank angle, while the responses are surface roughness profile (Ra, Rq, Rz), tool life and material removal rate. The type of insert used was a tungsten carbide, while the coolant was minimum quantity lubricant (MQL) vegetable oil (olive oil) performed at 150 mL/hr. Taguchi orthogonal array (L16) using sixteen experimental runs are designed for machining. Based on analysis of variance (ANOVA) it is identified that the most significant cutting process parameters for surface roughness profile (Ra, Rq, Rz) under both dry and MQL conditions are the feed rate, while for the tool life are cutting speed and feed rate and for material removal rate is cutting speed followed by depth of cut and feed rate. Under dry conditions the optimized levels obtained are cutting speed of 500 m/min, the feed rate of 0.3 mm/rev, depth of cut of 2 mm, and positive rake angle of 15°. However for MQL condition are cutting speed of 500 m/min, the feed rate of 0.4 mm/rev, depth of cut of 2 mm, and positive rake angle of 15°. Finally, the machined worked piece surface and inserts are morphologically characterized at different cutting parameters using scanning electron microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX).

• The cutting performance and the cutting fluid infiltration characteristics are analyzed during MQL milling. • The improvement effect of cutting performance in MQL milling is related to cutting parameters. • The increment in cutting parameters hampers the infiltration of cutting fluid into the tool-chip contact interface. • The three-stage infiltration models are established to ascertain the conditions of stable lubricating film formation. • The internal mechanisms of MQL infiltration and lubrication performance variation with cutting parameters are clarified. The insufficient infiltration of cutting fluid at the tool-chip contact interface during machining poses a substantial challenge to achieving clean and efficient cutting processes. Key to enhancing the infiltration efficiency of cutting fluids lies in understanding their penetrative characteristics within the tool-chip cutting region. Thus, analyzing the milling performance under varying lubrication environments and cutting parameters forms a fundamental prerequisite to this research. In this study, we experimentally investigated the influences of cutting parameters on cutting force and cutting temperature in dry and minimum quantity lubricant (MQL) milling. In addition, we presented the friction state at the tool-chip interface, incorporating the friction coefficient into our analysis. Moreover, we explored the infiltration characteristics of oil mist fluid within the tool-chip contact region via fluid simulations. The tool wear mechanisms under various lubrication conditions were also elucidated. Subsequently, we established three-stage infiltration models to ascertain the conditions conducive to the formation of stable lubricating films and revealed the internal mechanisms dictating MQL penetration. The results disclose that the cutting force, cutting temperature, and friction coefficient of MQL milling decrease by 10–25%, 9%, and 16% respectively at a cutting speed of v c = 100 m/min, feed rate of f z = 0.4 mm/rev, and axial cutting depth of a p = 0.3 mm. However, as cutting parameters increase, the MQL's ameliorative effect on cutting performance diminishes. The underlying cause for this is the expansion of the tool-chip contact length and the increased chip curling radius, which significantly obstruct the injection of MQL oil mist droplets, resulting in a weakened infiltration effect. In conjunction with the conditions necessary for lubricating film formation, it is evident that an increase in cutting parameters is detrimental to improving the infiltration capacity of the cutting fluid into the capillary. [ABSTRACT FROM AUTHOR]

Titanium and its alloys are associated with low density and excellent strength/weight ratio, biocompatibility in surgical implants, high mechanical strength at high temperatures and excellent corrosion resistance. The Ti6Al4V alloy is applied in the aerospace, biomedical, chemical, naval and petrochemical industries. However, these alloys present problems during machining and are therefore considered materials of difficult machinability at high cutting speeds. This paper aims to analyse the wear mechanisms in cutting tools using cemented carbide (H13A) and synthetic polycrystalline diamond (PCD) in the high-speed turning of Ti6Al4V alloy, under the following cooling conditions: dry, jet and minimum quantity lubricant (MQL). To measure wear, a microscope was used to measure flank wear in the tools. Next, the images of these tools were obtained using scanning electron microscopy for the identification of the wear mechanisms. According to the results, the variation in the cutting parameters (cutting speed and feed rate), type of tool material, as well as the cooling conditions significantly affects the behaviour of the wear mechanisms. The wear mechanisms presented in the cutting tools are not the result of one single mechanism, but a combination of many mechanisms. Overall, the primary type of wear is flank wear and the mechanisms are abrasion, adhesion and attrition (adherence and drag). [ABSTRACT FROM AUTHOR]

Precise, economical and sustainable cutting operations are highly desirable in the advanced manufacturing environment. For this aim, the present study investigated the influence of cutting parameters (i.e., the cutting speed (c), feed rate (f), depth of cut (d) and positive rake angle (p)) and sustainable cutting conditions (dry and minimum quantity lubricant (MQL)) on cutting forces (i.e., feed force (Ff), tangential forces (Ft), radial force (Fr) and resultant cutting forces (Fc) and shape deviations (i.e., circularity and cylindricity) of a 6026-T9 aluminum alloy. The type of lubricant and insert used are virgin olive oil and uncoated tungsten carbide tool. Turning experiments were performed on a TAKISAWA TC-1 CNC lathe machine and cutting forces were measured with the help of a Kistler 9257B dynamometer. Shape deviations were evaluated by means of a Tesa Micro-Hite 3D DCC 474 coordinate measuring machine (CMM). Experimental runs were planned based on Taguchi mixture orthogonal array design L16. Analysis of variance (ANOVA) was performed to study the statistical significance of cutting parameters. Taguchi based signal to noise (S/N) ratios are applied for optimization of single response, while for optimization of multiple responses Taguchi based signal to noise (S/N) ratios coupled with multi-objective optimization on the basis of ratio analysis (MOORA) and criteria importance through inter-criteria correlation (CRITIC) are employed. ANOVA results revealed that feed rate, followed by a depth of cut, are the most influencing and contributing factors for all components of cutting forces (Ff, Ft, Fr, and Fc) and shape deviations (circularity and cylindricity). The optimized cutting parameters obtained for multi responses are c = 600 m/min, f = 0.1 mm/rev, d = 1 mm and p = 25°, while for cutting conditions, MQL is optimal.

Turning continues to be the largest segment of the machining industry, which highlights the continued demand for turned parts and the overall improvement of the process. The turning process has seen quite an evolution, from basic lathes using solid tools, to complex CNC (Computer Numerical Control) multi-process machines, using, for the most part, coated inserts and coated tools. These coatings have proven to be a significant step in the production of high-quality parts and a higher tool life that have captivated the industry. Continuous improvement to turning coated tools has been made, with many researches focusing on the optimization of turning processes that use coated tools. In the present paper, a presentation of various recently published papers on this subject is going to be made, mentioning the various types of coatings that have recently been used in the turning process, the turning of hard to machine materials, such as titanium alloys and Inconel, as well as the interaction of these coatings with the turned surfaces, the wear patterns that these coatings suffer during the turning of materials and relating these wear mechanisms to the coated tool’s life expectancy. Some lubrication conditions present a more sustainable alternative to current methods used in the turning process; the employment of coated tool inserts under these conditions is a current popular research topic, as there is a focus on opting for more eco-friendly machining options.

This paper presents a methodological tool to measure the sustainability index (SI) of industrial products and processes based on process variables, and denominated individual metrics in pairs and impacts on the technological, environmental, social and economic aspects, which are the pillars of sustainable manufacturing. The methodological assessment tool includes data normalization processes, evaluation by score importance according to elicited knowledge of researchers and experts about the subject, and aggregation of variables based on the sustainability aspect it belongs. Data normalization is applied to convert physical data measured in specific dimensionless scores for each variable. To prove the effectiveness of the methodological tool, a case study of a metal-mechanical industry that uses cutting fluid is presented and the effectiveness of this fluid is compared with the technique of applying cutting fluid flood regarding minimum quantity lubricant (MQL). [ABSTRACT FROM AUTHOR]

Abstract: The quality of machined components is currently of high interest, for the market demands mechanical components of increasingly high performance, not only from the standpoint of functionality but also from that of safety. Components produced through operations involving the removal of material display surface irregularities resulting not only from the action of the tool itself, but also from other factors that contribute to their superficial texture. This texture can exert a decisive influence on the application and performance of the machined component. This article analyzes the behavior of the minimum quantity lubricant (MQL) technique and compares it with the conventional cooling method. To this end, an optimized fluid application method was devised using a specially designed nozzle, by the authors, through which a minimum amount of oil is sprayed in a compressed air flow, thus meeting environmental requirements. This paper, therefore, explores and discusses the concept of the MQL in the grinding process. The performance of the MQL technique in the grinding process was evaluated based on an analysis of the surface integrity (roughness, residual stress, microstructure and microhardness). The results presented here are expected to lead to technological and ecological gains in the grinding process using MQL. [Copyright &y& Elsevier]

Abstract: In high speed milling process of wrought aluminium alloys, it is usual to observe the presence and growth of built up edge. In its presence, the lubrication and cooling of the edges are factors of great importance. Two techniques are used to avoid this problem: emulsion of oil in water, and spray of oil micro-drops in air. This technical communication refers to two aspects of these techniques. First, the efficiency of minimum quantity of lubricant (MQL) is assessed when compared to the inefficiency of emulsion techniques. This fact is assessed through computational fluid dynamics (CFD) simulation and experimental evidence. Second, the influence of the position of the injection nozzle in relation to the feed direction is experimentally studied. The possibility of minimising the consumption of cutting oil has also been analysed. [Copyright &y& Elsevier]

Precise, economical and sustainable cutting operations are highly desirable in the advanced manufacturing environment. For this aim, the present study investigated the influence of cutting parameters (i.e., the cutting speed (c), feed rate (f), depth of cut (d) and positive rake angle (p)) and sustainable cutting conditions (dry and minimum quantity lubricant (MQL)) on cutting forces (i.e., feed force (Ff), tangential forces (Ft), radial force (Fr) and resultant cutting forces (Fc) and shape deviations (i.e., circularity and cylindricity) of a 6026-T9 aluminum alloy. The type of lubricant and insert used are virgin olive oil and uncoated tungsten carbide tool. Turning experiments were performed on a TAKISAWA TC-1 CNC lathe machine and cutting forces were measured with the help of a Kistler 9257B dynamometer. Shape deviations were evaluated by means of a Tesa Micro-Hite 3D DCC 474 coordinate measuring machine (CMM). Experimental runs were planned based on Taguchi mixture orthogonal array design L16. Analysis of variance (ANOVA) was performed to study the statistical significance of cutting parameters. Taguchi based signal to noise (S/N) ratios are applied for optimization of single response, while for optimization of multiple responses Taguchi based signal to noise (S/N) ratios coupled with multi-objective optimization on the basis of ratio analysis (MOORA) and criteria importance through inter-criteria correlation (CRITIC) are employed. ANOVA results revealed that feed rate, followed by a depth of cut, are the most influencing and contributing factors for all components of cutting forces (Ff, Ft, Fr, and Fc) and shape deviations (circularity and cylindricity). The optimized cutting parameters obtained for multi responses are c = 600 m/min, f = 0.1 mm/rev, d = 1 mm and p = 25°, while for cutting conditions, MQL is optimal. [ABSTRACT FROM AUTHOR]

Turning continues to be the largest segment of the machining industry, which highlights the continued demand for turned parts and the overall improvement of the process. The turning process has seen quite an evolution, from basic lathes using solid tools, to complex CNC (Computer Numerical Control) multi-process machines, using, for the most part, coated inserts and coated tools. These coatings have proven to be a significant step in the production of high-quality parts and a higher tool life that have captivated the industry. Continuous improvement to turning coated tools has been made, with many researches focusing on the optimization of turning processes that use coated tools. In the present paper, a presentation of various recently published papers on this subject is going to be made, mentioning the various types of coatings that have recently been used in the turning process, the turning of hard to machine materials, such as titanium alloys and Inconel, as well as the interaction of these coatings with the turned surfaces, the wear patterns that these coatings suffer during the turning of materials and relating these wear mechanisms to the coated tool's life expectancy. Some lubrication conditions present a more sustainable alternative to current methods used in the turning process; the employment of coated tool inserts under these conditions is a current popular research topic, as there is a focus on opting for more eco-friendly machining options. [ABSTRACT FROM AUTHOR]