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The effects of liquid-CO2 cooling, MQL and cutting parameters on drilling performance
Abstract
An investigation is made into the effects of liquid carbon dioxide (LCO2) cooling, minimum-quantity lubrication (MQL) and cutting speed in drilling. Experimental measurements of torque, thrust force and temperature are made over a wide range of process and operating conditions. The resulting empirical models are used to quantify the individual contributions of the controlled parameters on drilling performance, and to facilitate temperature-based process optimization. Of particular interest is the need to carefully adjust the LCO2 flow rate for any combination of MQL flow rate and cutting speed. The optimization is validated both in simulation and actual drilling tests.
... Such advanced solutions to cooling and lubrication have not yet been explored in the grinding of cemented carbides. This work focuses on investigating the LCO 2 solution, as this technology has proven superior in other machining applications, such as in drilling [12] and milling [13]. Even though the pressure in LCO 2 cylinder is nearly 6 MPa (60 bar), it is likely that the air barrier formed around a grinding wheel rotating at high speed would prevent the LCO 2 from entering the grinding zone and causing it to be diverted elsewhere. ...
... Strojniški vestnik -Journal of Mechanical Engineering 69(2023)[11][12][435][436][437][438][439][440][441][442][443] ...
Despite extensive research on grinding of cemented carbide, few studies have examined abrasive machining of this material using small-diameter super abrasive tools (also known as grinding pins/points), especially with respect to varying cooling-lubrication methods. This study therefore focuses on a comparative experimental investigation of three such methods - dry, emulsion, and lubricated liquid carbon dioxide (LCO2-MQL). The performance of these methods and the resulting grindability are examined in terms of grinding forces, force ratios, specific energy, and through the analysis of wheel loading. The results show that LCO2-MQL grinding has lower grinding forces (normal forces – 8 % to 145 % lower than dry grinding, and 18 % to 33 % lower than emulsion grinding and tangential forces – 4 % to 66 % lower than dry grinding and 28 % to 78 % lower than emulsion grinding) and specific energy 24 % to 51 % lower compared to dry grinding and 64 % to 69 % lower than emulsion grinding, indicating its potential for efficient material removal. However, a challenge with high wheel loading was observed with LCO2-MQL, likely due to the lack of oxygen in the CO2 grinding atmosphere. Despite this issue, the LCO2-MQL method shows potential for efficient operations, especially at higher aggressiveness values where the lowest specific energies were achieved. These results provide new insights into various aspects of cooling-lubrication methods in the pin grinding of cemented carbides.
... Their study found that CO 2 snow had a higher heat transfer coefficient (1347 W/m 2 ○ C) compared to subzero MQL (486 W/m 2 ○ C), reducing tool wear and improving surface finish. Sterle et al. 138 (Table III). Sivalingam et al. 141 showed that hybrid MQL and CO 2 cutting environments improved machinability, reducing cutting forces by 28%-39%, enhancing surface finish, and extending tool life by minimizing wear. ...
In recent years, sustainability has evolved profoundly and garnered significant global attention, establishing itself as a pivotal topic in contemporary research. In line with this development, the present review thoroughly examines existing studies on machining processes employing minimum quantity lubrication (MQL). The growing imperative for sustainable practices has driven researchers to reassess alternative lubrication techniques within machining operations. Although conventional lubri-cooling agents continue to be widely used for machining engineering alloys, an expanding body of research demonstrates that the incorporation of vegetable oils, nanofluids, and nanoplatelets into MQL systems can yield superior performance compared to traditional methods. The review presents an overview of recent developments and advancements related to MQL technology and provides a rigorous analysis of the performance of vegetable oils and nanofluids as metalworking fluids. This study also demonstrates that eco-friendly MQL approaches can be a sustainable alternative to traditional flood lubrication and serves as a meaningful resource to move toward greener machining solutions.
... This improved evacuation was made possible by better chip breakability and therefore chip morphology was reported under cryogenic machining. [16]; [17]. ...
Liquid carbon dioxide (LCO2) based cryogenic cooling has shown promising results in terms of wear reduction, productivity increase and energy efficiency when machining high-temperature materials. For process-safe use with low pulsation, CO2 must be fed in the liquid state to cool the process zone. LCO2 is typically stored in riser bottles in which gaseous and liquid aggregate state coexist. A preliminary study has already shown that the liquefied state of the CO2 can be stabilized by pre-cooling. In this paper, the influence of a heat exchanger as a pre-cooling system on the cooling capacity of the CO2 is investigated and the required energy consumption is compared to unstabilized CO2, pressure increased CO2 and compressed air. It has been shown that pre-cooling leads to a more energy-efficient increase in the cooling capacity of the CO2 compared to pressure increased CO2.
Cryogenic minimum quantity lubrication
Liquid carbon dioxide
Density enhancement
Cooling capacity
Machining
Energy effiency
... Sterle et al. [144] studied the effects of LCO 2 cooling + MQL in drilling the 42CrMo4 steel (31 HRC). The main findings show that LCO 2 cooling improved chip evacuation but provided poor lubrication in Cooling lubrication methods [133]. ...
The extensive range of steel types and classifications results in a diverse set of properties such as plasticity, heat resistance, strength, and corrosion resistance. This diversity enables the creation of alloys with varying machinability, from easy to hard-to-cut. This review focuses on the intricate interplay between mechanical characteristics of steel and machinability indicators such as tool wear, tool life, material removal rate (MRR), and chip formation. This review also highlights innovative strategies to enhance steel's machinability through the manipulation of cutting conditions. These approaches range from dry cutting to sophisticated cooling systems such as minimum quantity lubrication (MQL), cryogenic lubrication (CL), and high-pressure cooling (HPC). Additionally, the impact of tool design, including geometry and surface texturing, is scrutinized, along with the deployment of advanced tool materials and coatings. Furthermore, the paper investigates the efficacy of assisted machining techniques, including vibrational, thermal, and hybrid methods. A comprehensive review of advanced machining operations (encompassing turning, drilling, milling, and grinding) elucidates the potential improvements in surface integrity and machinability of steel. The review also addresses the challenges and future opportunities in this domain. In conclusion, the exploration into the machinability of steel underscores its significance as a versatile material in various industries. By understanding and optimizing the machining dynamics and employing innovative strategies, there is potential to further enhance the properties and machinability of steel alloys. This review provides valuable data compilation for researchers, engineers, and industry professionals seeking to advance the utilization of a large array of steel variants in manufacturing processes.
... Additionally, worth mentioning that other environmentally friendly lubrication-cooling strategies such as cryogenic can contribute to controlling cutting temperatures and reducing cutting tool wear [30]. However, the initial cost for implementing the cryogenic cooling must be considered, as well as its lower efficiency in terms of lubrication capacity, especially compared to the MQL technique [31,32]. ...
The cutting fluid application in turning process using the MQL technique is a viable option to optimize the process in terms of cutting tool performance and machined part characteristics; in addition, the MQL technique is environmentally friendly. In this work, the influence of cutting speed (vc), feed rate (f), and lubrication-cooling condition (dry and MQL) in the turning of AISI 1045 steel was investigated. For this, the cutting tool wear, the surface roughness, the electrical current required by the machine tool, and the chip morphology were analyzed. The maximum flank wear values (VBBmax) showed that the MQL technique can reduce the wear of cutting tools. The values of the roughness parameter Ra indicated low influence of the application of the MQL technique on the surface finish. The greatest influence on this output variable was exerted by feed rate (f). The increase in cutting speed (vc) and feed (f) values increased the measured electric current. The application of the MQL technique was able to reduce the electrical current values required by the machine tool, which are directly proportional to the cutting efforts. Analysis of chip morphology showed that for all cutting conditions adopted, segmented chips were formed. The analysis of the front and back surfaces presented results that corroborate the analyzes of wear, roughness, and electric current. Therefore, it was possible to infer that the application of the MQL technique can reduce friction, temperature, and cutting efforts, as well as being able to change the chip morphology.
... Therefore, a comparative analysis of cutting forces and tool wear dynamics achieved by commercially available industrial drill bit without cooling capabilities and its modified version with a built-in cooling channel was conducted in this experimental study. Due to the expected positive influence of internally cooled drill bits on the dynamics of particle formation and friction reduction in the cutting zone [4][5][6][7], the aim of this study was to determine to what extent the cooling medium affects the reduction of cutting forces and tool wear in stone drilling. ...
Drill bits with internal cooling capabilities are still not employed in stone machining practices within shop floor environments. Therefore, a conventional industrial drill bit used in stone machining was subject to a redesign wherein an axial cooling channel was machined throughout its body. A comparison was drawn between the standard drill bit without cooling capabilities and the redesigned drill bit, which used compressed air as a cooling medium. The experiment was performed by drilling three types of stone samples varying in hardness with nine combinations of cutting speed and feed rate. During the machining process, two types of process signals were continuously measured—namely, cutting forces and vibrations. Additionally, the cutting edges of the drill bits were inspected after a specific number of drilling cycles using a vision system. The primary objective of this study was to compare the cutting forces and tool wear dynamics achieved by those two drill bits. Furthermore, the usage of vibration signals in the classification of stone hardness during machining with an internally cooled drill bit was additionally analyzed. The results of this study unveiled improvement in minimizing cutting forces, vibrations, and the intensity of tool wear when utilizing an internally cooled drill bit. Even though the machining system generally exhibited lower vibrations, vibration signals again demonstrated commendable efficacy in classifying stone hardness.
... For example, temperature reduction ability of flood assisted milling is not desirable in all conditions. Such outcome can be accredited to the poor infiltration of the high pressured and abundant fluid into the interfaces of cutting tool and chip [58]. On the other hand, MQL system is found much more effective over conventional methods which give an idea about the supportive function of the pressurized air to send the oil particles into the vacancies of interfaces. ...
Because of their biodegradable and regenerative properties, cellulose nanocrystals derived primarily from naturally occurring cellulose fibers serve as a sustainable and environmentally beneficial material for most applications. Although these nanocrystals are inherently hydrophilic, they can be surface functionalized to suit a wide range of demanding requirements, such as those associated with the creation of high-performance nanocomposites in hydrophobic polymer matrices. Therefore, the present work deals with the application of cellulose-based biodegradable nanocrystals as a lubricant in the machining of PPS composites. In this study, milling process was considered to investigate the influence of the sustainable lubricating conditions on the machinability indexes of PPS composites. As a novel cooling approach, water-based solutions enriched by cellulose nanocrystals with different reinforcements (0.25%, 0.5%, and 1%) were used over known methods such as MQL, conventional flood, and dry. According to the research outcomes, cellulose nanocrystals-based nanofluids provided satisfying contributions on retarding the tool wear and reducing the cutting temperatures considerably. Despite the surface-related results such as roughness, topography and texture are promising for the developed strategy; further investigations will be useful to determine ideal water-particle concentration to improve the quality of the machined surface.
... Some newly developed cooling conditions have also been utilized for machining Ti-6Al-4V. Cryogenic cooling conditions such as low-temperature liquid nitrogen and low-temperature CO 2 were utilized for improving cutting performance in machining Ti-6Al-4V [15][16][17]. The deep cryogenic and high-pressure cooling devices are expensive, and complex compared to the SJC and MQL cooling devices. ...
TiAlN-coated carbide tools have been used to machine Ti-6Al-4V alloys in aviation workshops. However, the effect of TiAlN coating on surface morphology and tool wear in the processing of Ti-6Al-4V alloys under various cooling conditions has not been reported in the public published literature. In our current research, turning experiments of Ti-6Al-4V with uncoated and TiAlN tools under dry, MQL, flood cooling, and cryogenic spray jet cooling conditions were carried out. The machined surface roughness and tool life were selected as the two main quantitative indexes for estimating the effects of TiAlN coating on the cutting performance of Ti-6Al-4V under various cooling conditions. The results showed that TiAlN coating makes it hard to improve the machined surface roughness and tool wear of a cutting titanium alloy at a low speed of 75 m/min compared to that achieved by uncoated tools. The TiAlN tools presented excellent tool life in turning Ti-6Al-4V at a high speed of 150 m/min compared to that achieved by uncoated tools. From the perspective of obtaining finished surface roughness and superior tool life in high-speed turning Ti-6Al-4V, the selection of TiAlN tools is feasible and reasonable under the cryogenic spray jet cooling condition. The dedicative results and conclusions of this research could guide the optimized selection of cutting tools in machining Ti-6Al-4V for the aviation industry.
... The device is shown in Figure 10. The results showed that: LCO 2 proved more efficient at lower drilling temperatures and LCO 2 + MQL combination performed better in reducing temperature [54]. There are two photosensitive elements in the two-color pyrometer, and each element is sensitive to different wavelengths of infrared radiation. ...
Drilling is regarded as the most complex manufacturing process compared with other conventional machining processes. During the drilling process, most of the energy consumed in metal cutting is converted to heat and increases temperature considerably. The resulting thermal phenomena are important since they influence the mode of deformation, the final metallurgical state of the machined surface, and the rate of tool wear. Hence, understanding the temperature characteristics in the drilling process is crucial for enhancing the drill performance and process efficiency. Extensive efforts have been conducted to measure and control the drilling tool temperature successively. However, very few studies have been conducted from a comprehensive perspective to review all the efforts. To address this gap in the literature, a rigorous review concerning the state-of-the-art results and advances in drilling tool temperature is presented in this paper by referring to the wide comparisons among literature analyses. The multiple aspects of drilling tool temperature are precisely detailed and discussed in terms of theoretical analysis and thermal modeling, methods for temperature measuring, the effect of cutting parameters, tool geometries and hole-making methods on temperature and temperature controlling by different cooling methods. In conclusion, several possible future research directions are discussed to offer potential insights for the drilling community and future researchers.
... Boughdiri et al. [118] made experiments on the effects of thrust force, torque and hole quality of machining parameters when punching GLARE 2B laminates. Sterle et al. [119] worked on a study on the effects of liquid carbon dioxide cooling, cutting speed and minimum amount of lubrication on the process outputs (thrust force, temperature and torque) in the drilling process of 42CrMo4 steel material. Manickam and Partipan [120] studied the effects of cutting parameters on the process outputs when drilling AISI 317L material. ...
This review paper summarizes the application of smart manufacturing systems utilized in drilling and hole machining processes. In this perspective, prominent sensors such as vibration, cutting forces, temperature, current/power and sound used in the contemporary indirect and direct tool condition monitoring systems are handled one-by-one according to their applications during machining of holes. Thus, it is aimed to show several operations with the application stages and literature papers which utilize the sensorial data such as grinding, reaming, broaching, boring, tapping, drilling and countersinking. The novel side of this paper is summarizing the all-hole machining processes utilizing sensor systems while benefitting their predictive ability for improved machinability characteristics such as surface integrity, tool wear, dimensional accuracy, chip morphology.
... It has been observed that the cooling and lubrication cost comprises 7-17% of total machining cost which can go up to 20% for cutting difficult-to-cut material [4]. This cost includes the labor cost to handle the lubricant/coolant, energy cost for recirculation, coolant/lubricant cost, cost of equipment required to circulate coolant/lubricant, and waste disposal [5]. Figure 1 describes the bifurcation of costs involved in machining as well as cutting fluids used in machining operations of automobile industries [6]. ...
In the present scenario, citizens' concern about environment preservation creates a necessity to mature more ecological and energy-efficient manufacturing processes and materials. The usage of glass fiber reinforced polymer (GFRP) is one of the emerging materials to replace the traditional metallic alloys in the automotive and aircraft industries. However, it has been comprehended to arise a sustainable substitute to conventional emulsion-based coolants in machining processes for dropping the destructive effects on the ecosystem without degrading the machining performance. So, in this study, the comparison of the two sustainable cutting fluid approaches, i.e., dry and LCO 2 , has been presented based on machining performance indicators like temperature, modulus of cutting force, tool wear, surface roughness, power consumption, and life cycle assessment (LCA) analysis for end milling of GFRP. The cutting condition of LCO 2 has been found to be superior in terms of machining performance by providing 80% of lower cutting zone temperature, tool wear, 5% lower modulus of cutting force, and reduced surface roughness with 9% lower power consumption that has been observed in the case of LCO 2 in comparison with dry machining. However, to compress the CO 2 for converting in liquid form, a higher amount of energy and natural resources is consumed resulting in a higher impact on the environment in comparison with dry machining. Considering the 18 impact categories of ReCiPe midpoint (H) 2016, 95% higher values of impacts have been observed in the case of LCO 2 in comparison with dry machining.
Minimum quantity lubrication (MQL) is an effective method for addressing technical challenges associated with high cutting loads during machining. Although much research has explored the ability of MQL to reduce cutting forces, intuitive analyses of its developmental trends, leading researchers, and research hotspots remain limited. To address this, a bibliometric analysis was conducted on studies related to MQL and its role in cutting force reduction. Data from the Web of Science Core Collection database, covering the period from January 1, 2008, to December 31, 2023, were analyzed. Bibliometric tools such as VOSviewer, Scimago Graphica, and Bibliometrix were used to visually assess publication trends, source journals, countries, institutions, authors, references, and keywords. The results show that India leads in publication output with 231 papers, while Li CH from China is the most cited author, with 3200 citations. A detailed clustering analysis of keywords and their representative research areas was performed, summarizing the current findings on the effects of processing parameters on cutting forces. The study also analyzed the optimization of machining parameters to minimize cutting forces, identifying relatively optimal conditions. Finally, challenges and potential solutions were discussed, providing theoretical and technical guidance for the industrial application of MQL.
In orthopedic surgery, precise bone screw insertion is crucial for stabilizing fractures, necessitating a preliminary cortical bone drilling procedure. However, this process can induce temperatures exceeding 70°C due to the low thermal conductivity of cortical bone, potentially leading to thermal osteonecrosis. Furthermore, significant cutting forces and torque pose risks of tool breakage and bone damage, underlining the need for high precision and optimal processing parameters. Traditionally, drilling relies on the surgeon's experience and often results in imprecise outcomes due to inconsistent feed rates. Therefore, this study proposes the use of a 6-axis robot for controlled drilling, offering precise control over angular velocities and consistent feed rates. Additionally, explore the use of cryogenic liquid nitrogen (LN2) as a novel cooling method compared to conventional saline solutions, examining its efficacy under various cutting conditions. The results demonstrate that LN2 cooling conditions lead to a reduction in thrust and torque under specific processing conditions, and facilitate smoother chip evacuation. Additionally, LN2 significantly lowers the peak temperature around the drilling site, thus minimizing the risk of thermal osteonecrosis. Consequently, the use of a 6-axis robot provides consistent feed rates, and LN2 cooling achieves optimal processing conditions, enabling a more controlled and effective drilling process.
Sustainable machining practices including dry cutting, cryogenic cooling (Cryo), and minimum quantity lubrication (MQL) techniques play an essential role in minimizing the extensive utilization of mineral-based cutting fluids, which can harm our ecology and health. However, the insufficient cooling and lubrication competencies of these eco-friendly strategies have some limitations that restrict their implementation in large-scale industrial applications. High-temperature generation in dry environment is associated with rapid tool wear and deteriorated surface quality. MQL at a high cutting speed usually requires better cooling capability; nevertheless, the inefficient lubrication mechanism offered by cryogenic environment affects the metal cutting performance and increases the machining cost. In this regard, hybrid lubrication technique was introduced to utilize the combined benefits of Cryo and MQL strategies for curtailing the thermal–mechanical damage associated with the tool and workpiece material. This paper reviews literature on sustainable hybrid lubrication techniques under three main topics, i.e., (a) Cyo-MQL lubrication fundamentals, (b) active heat transfer mechanisms, and (c) machinability performance in different machining processes, which includes tool life, cutting force, surface roughness, and microstructure characterization. Three data basis Google Scholar, Scopus, and Web of Sciences have been used to select relevant research articles on hybrid lubrication techniques. It is summarized that utilization of hybrid lubrication technique in different machining processes cannot only create a sustainable workpiece environment but can also remarkably improve the surface quality and material characteristics along with extending tool life and reducing cutting force.
Difficult-to-cut materials such as titanium alloys, high-temperature alloys, metal/ceramic/polymer-matrix composites, hard and brittle materials, as well as geometrically complex components such as thin-walled structures, micro channels and complex surfaces, are widely used in aerospace community. Mechanical machining is the main material removal process and responsible for the vast majority of material removal for aerospace components. Nevertheless, it encounters many problems in terms of severe and rapid tool wear, low machining efficiency, and deteriorated surface integrity. Nontraditional energy-assisted mechanical machining is a hybrid process in which nontraditional energies, e.g., vibration, laser, electric, etc., are applied to improve the machinability of local material and decrease burden of mechanical machining. It provides a feasible and promising way for improving machinability and surface quality, reducing process forces, and prolonging tool life, etc. However, systematic reviews of this technology are lacking with respect to the current research status and development direction. This paper reviews recent progress in nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in aerospace community. It focuses on the processing principles, material responses under nontraditional energy, resultant forces and temperatures, material removal mechanisms and applications of these processes including vibration-, laser-, electric-, magnetic-, chemical-, cryogenic cooling-, and hybrid nontraditional energies-assisted mechanical machining. Eventually, a comprehensive summary of the principles, advantages and limitations for each hybrid process is provided, and future perspectives on forward design, device development and sustainability of nontraditional energy-assisted mechanical machining processes are discussed.
Carbon fibre reinforced polymer/titanium stacks (CFRP/Ti6Al4V) are employed in aeronautics due to their
excellent weight-to-strength ratio and corrosion properties. However, these same material properties present
challenges for hole making which cannot be solved using conventional water-based metalworking fluids (MWFs),
as they cause degradation of the composite. Moreover, environmental and health concerns require exploration of
alternative cooling/lubrication solutions. In this study, a controlled mixture of liquid carbon dioxide (LCO2) and
minimum quantity lubrication (MQL) was supplied through the drilling tool. The effect of varying LCO2 and MQL
flow rates was evaluated on cutting forces, temperatures, and several hole quality outputs. The optimal flow rates
were then determined through multi-objective optimisation. The results show that the cooling/lubrication flow
rate greatly affects the measured outputs, and that supplying LCO2 + MQL with optimised flow rates helps
achieve superior quality holes in CFRP, Ti6Al4V and CFRP/Ti6Al4V stacks.
Comparative studies of variation in cutting conditions and cutter nomenclature on the surface morphology and the integrity of slot milled nimonic 263 alloy S Gowthaman-This content was downloaded from IP address 152.58.71.214 on 16/05 Abstract. Duplex stainless steel (DSS) 2205 is considered difficult to cut machine materials. Therefore, an advanced cooling technique, such as a hybrid Liquid carbon dioxide (LCO 2)-Minimum quantity of lubrication (MQL) approach, is proposed for drilling duplex stainless steel 2205. In this research study, parametric optimization was performed by using the Response surface method (RSM) with the box-Behnken design of the matrix. For parametric optimization, select three input parameters: drill diameter, spindle speed, and feed rate, while hole deviation and cylindricity error are output responses. The Analysis of variances (ANOVA) test showed that spindle speed is the major factor that influences both responses, e.g., hole deviation and cylindricity error, with contributions of 38.90% and 59.42%, respectively. The modeling and predictive abilities of developed Fuzzy logic system (FLS) and Artificial neural network (ANN) to the comparison of experimental results. It was also found that the predicted values from regression analysis, artificial neural networks, fuzzy logic interfaces, and the proposed method were in good agreement with actual experiment results. Also, the Artificial neural network model provides a minimum % of error of 1.36% and 2.44 %, respectively responses compared to other models.
Cryogenic cooling has excellent cooling and poor lubrication, while minimum quantity lubrication (MQL) has vice versa. Therefore, eco-friendly hybrid lubri-coolants are getting attention nowadays to achieve sufficient cooling and lubrication for high-speed machining hard-to-cut materials. In this research, ethanol, Blaser oil, and hybrid ethanol-Blaser oil lubri-coolants with and without dry ice are compared regarding machinability performance measures i.e., tool flank wear. For in-depth analysis, scanning electron microscope (SEM), Electron deposition Spectroscopy (EDS) line, point and ED-mapping was used to analyze workpiece chemical elemental deposition on tool flank edge. Experimental findings have shown that compared to dry conditions, the hybrid ethanol-ester oil-dry ice significantly improved the tool life up to 66%, ester oil for 57%, and ethanol for 43%, respectively. More important, SEM of flank wear has shown adhesion, micro-chipping, and abrasion as dominant wear phenomena, when face milling Ti-6Al-4 V under hybrid lubri-coolants.
AA7075 aluminum alloy has the same hardness as steel but its weight is only about one-third that of steel. Thanks to this outstanding advantage, this material is widely applied in many different fields, especially in the field of automobile and aviation. Therefore, it is very necessary to study the multi-objective optimization when machining this material. In this article, a study on multi-objective optimization when drilling this material is presented. The experiments were conducted in accordance with a matrix designed by the Taguchi method. Spindle speed and feed rate were two parameters of which optimal values should be determined. Reference Ideal Method (RIM) was used to solve the multi-objective problem. The purpose of this study is to determine the values of the above two cutting parameters to simultaneously ensure the maximum value of Material Removal Rate (MRR), the minimum value of Diameter Error (DE) and the very minimum value of Roundness Error (RE). In addition, the effect of cutting parameters on DE and RE was also discovered. Finally, the directions for further study were also mentioned in this paper.
An investigation is made into the lubrication capabilities of solid-lubricated liquid carbon dioxide (LCO2) in comparison to flood lubrication, straight LCO2 and oil-lubricated LCO2 (MQL). The coefficient of friction is determined via tribological experiments, similar to machining, using an open tribometer which features an uncoated carbide insert sliding against a workpiece. Tribological experiments reveal superior performance of solid-lubricated LCO2. The milling experiments as well indicate that solid-lubricated LCO2 significantly reduces wear. The machined-surface topography is examined using high-magnification SEM, which shows no presence of adhered solid particles on the workpiece surface, providing a completely dry machining process.
New techniques are presented for Delaunay triangular mesh generation and element optimisation. Sample points for triangulation are generated through mapping (a new approach). These sample points are later triangulated by the conventional Delaunay method. Resulting triangular elements are optimised by addition, removal and relocation of mapped sample points (element nodes). The proposed techniques (generation of sample points through mapping for Delaunay triangulation and mesh optimisation) are demonstrated by using Mathematica software. Simulation results show that the proposed techniques are able to form meshes that consist of triangular elements with aspect ratio of less than 2 and minimum skewness of more than 45 degrees.
The quantification of the heat flow distribution in the cutting zone is still a not solved problem in particular if cooling lubrication is involved. The publication introduces a model extended measuring approach in order to monitor heat and coolant flows in the milling process under CO2 – MQL cooling lubrication. The system featured a telemetry system in order to transmit the temperature measured by a tool-embedded thermocouple. By further data post processing of the temperature, the heat flow into the tool was inversely determined by comparison of the measured temperature a distinct point with analytically modeled, transient temperatures.
Ti-6Al-4V is commonly used especially in aerospace and biomedical industries. This alloy is known as a difficult-to-cut material. Due to its poor thermal properties, the heat generated during machining processes traps near material deformation zones. This causes detrimental high temperatures for the cutting tools. This article combines the analytical and FEM modeling techniques to estimate the temperature evolution of carbide tools in Ti-6Al-4V drilling. In this article, a novel thermocouple based temperature measurement setup is also introduced. Moreover, the simulated and measured temperatures under various cutting conditions for the drilling of Ti-6Al-4V are presented for the validation.
A novel single-channel supply of pre-mixed (a) liquid carbon dioxide (LCO2) and (b) oil – delivered via minimum quantity lubrication (MQL) – represents a significant advancement in cryogenic-machining technology. In this proof-of-concept study, an attempt is made to advance the understanding of the oil solubility in LCO2 and to analyze the oil-droplets and their impact on machining performance. The results indicate that the physical and chemical properties of oil distinctively affect its solubility in LCO2. The achieved solubility further influences the achievable oil-droplet size and distribution and tool life.
A sustainable approach to increase the productivity in milling of difficult-to-cut materials is the use of internal cryogenic cooling combined with minimum quantity lubrication (MQL). There are various systems available on the market to control the flow of the cryogenic and the MQL medium. These systems are usually based on a delivery of the media through two separate channels. Moreover, a single channel system, which uses the solubility of oil in supercritical CO2 is state of the art. Compared to a two-channel system the geometry of the cooling lubrication channels is simplified, the tools are more stable and easier to manufacture. Furthermore, there is no negative interaction between the CO2 and MQL jets. Instead of supercritical CO2 (SCCO2), liquid CO2 (LCO2) is easier to handle and widely available. Therefore, this paper presents fundamental investigations of the solubility of liquid oil in LCO2. In addition, an innovative single channel system was designed, implemented and tested in milling process of Ti6Al4V.
This paper presents a novel approach for coupling of thermal FE and CFD simulations to predict the temperature distribution in the cutting process. The developed FSI model considers experimentally validated workpiece temperature to simulate the heat convection interactions in drilling operations. This innovative method allows not only for the common analysis of the flow behaviour, but additionally for the detailed investigation of the temperature distribution within the cutting fluid. The simulation provides indications for an insufficient fluid supply of the cutting edge and the results can contribute significantly to the further optimisation of thermally high stressed cutting tools and processes.
The energy consumption of machining operations is significantly influenced by the cooling strategy. In cases of high-performance drilling, high thermal stress on the tool makes adequate cooling necessary. Only cryogenic machining provides the option of lubricant-free processing, resulting in low tool wear, even at high removal rates, due to significant reductions in tool temperatures. Compared to actual tests, verified finite-element process models showed that suitable tool geometry, especially in terms of the positions of the cooling channels, is fundamental for efficient cryogenic drilling. The process model developed is based on a new combination of different approaches for modeling a cryogenically cooled tool.
This study investigates the workpiece temperature in minimum quantity lubrication (MQL) deep hole drilling. An inverse heat transfer method is developed to estimate the spatial and temporal change of heat flux on the drilled hole wall surfaces based on the workpiece temperature measured using embedded thermocouples and analyzed using the finite element method. The inverse method is validated experimentally in both dry and MQL deep-hole drilling conditions and the results show good agreement with the experimental temperature measurements. This study demonstrates that the heat generated on the hole wall surface is significant in deep hole drilling. In the example of deep hole drilling of ductile iron, the level of thermal power applied on the hole wall surface is about the same as that on the hole bottom surface when a 10 mm drill reached a depth of 120 mm. [DOI:10.1115/1.4005794]
The temperature at the bottom surface of a hole being drilled is measured by using an infrared-radiation pyrometer equipped with two optical fibers. One of the optical fibers is inserted into the oil hole of an internal coolant carbide drill and passes through the machine-tool spindle. This optical fiber is connected to another optical fiber at the end of the spindle. Infrared rays radiating from the bottom surface of the hole being drilled are accepted and transmitted to the pyrometer by the two optical fibers. Temperature increases as drilling progresses, and it increases considerably near the bottom surface of the workpiece. In case of a 10-mm-thick carbon–steel workpiece, temperature reaches 190, 250, and 340 °C at drilling depths of 6, 8, and 10 mm, respectively. To investigate the effect of the increase in temperature on drill wear, a series of 10-mm-deep blind holes are drilled in workpieces with thicknesses of 10 and 25 mm. Tool wear is greater when the drill cuts a hole at the bottom of a 10-mm workpiece than that when the drill cuts a hole at the mid-depth of a 25-mm workpiece. This indicates that the rapid increase in temperature near the bottom of the workpiece effects the progress of drill wear.
In this study, we analyzed the high temperature tribological behavior of AlCrTiN coatings deposited on WC substrates by low cathodic arc technique. The coatings chemical composition, Al 31at.%, Cr 16at.%, Ti 7at.% and N 46at.%, and the bonding state were evaluated by X-ray photoelectron spectroscopy. The mechanical properties of the coatings were studied by scratch-test and nanohardness depth sensing indentation. The morphology of the coatings surface, ball scars, wear tracks and wear debris as well as the oxidized samples was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The structure was analyzed using X-ray diffraction (XRD). Wear testing was carried out using a high temperature tribometer (pin-on-disc) with alumina balls as counterparts. The evaluation of the friction coefficient with the number of cycles (sliding distance) was assessed at different temperatures and the wear rates of the coatings and balls were determined; the maximum testing temperature was 800°C. The coating showed an excellent thermal stability and wear resistance. The friction reached a maximum at 500°C and then decreased, whereas the wear rate was negligible up to 600°C and increased significantly at higher temperatures.
A model is developed for predicting the heat that flows into the workpiece during dry drilling processes. The model can be applied to any drill of known geometry. The measured drilling thrust and torque are used as inputs in an oblique cutting analysis, and an advection heat partition model is developed to calculate heat flux loads on a finite element model of the workpiece. Experiments using embedded thermocouples have verified that the model accurately predicts the temperature field in the workpiece for a range of drilling speeds and feeds.
In drilling, the temperature of the cutting edges of a drill is measured using a two-color pyrometer with an optical fiber. A cemented carbide drill with a diameter of 10 mm is used as a cutting tool, and carbon steel, cast iron and aluminum die-cast alloy are used as work materials. The temperature distribution along the cutting edge of a drill is measured and the influence of spindle speed and feed rate on the tool temperature is investigated. The maximum tool temperature is observed during the drilling of carbon steel. The effect of oil mist supplied from oil holes in the drill on the tool temperature is examined and the result is compared to that in turning and end milling. The temperature reduction in oil mist turning is approximately 5%, while in oil mist end milling it is 10–15% and that in oil mist drilling is 20–25% compared to the temperature in dry cutting.
This paper presents a study of the temperature reached during drilling of the titanium alloy Ti6Al4V, employing class K10 carbide drills with and without hard coating (TiAlN, CrCN or TiCN). The main object of this study was to evaluate the temperature for different coated tools under the condition of application of minimal quantity of lubricant (MQL). The drilling process was chosen to evaluate the effect of the lubrication obtained with MQL, where the lubricant was applied either with an external nozzle or internally through the drill. The results show potential for drilling with MQL applied internally through the tool. For drilling with MQL applied with an external nozzle, the process was restricted to small depths and limited with reference to the requirements of the surface quality of the hole.
The micro-scale temperature fields in the cutting of two AISI 4140 steels with different machinability ratings were measured. A custom infrared microscope was constructed; each pixel was calibrated separately to reduce measurement uncertainty. Orthogonal cutting experiments were performed on a high speed machining center with surface speeds up to 500 m min−1 and uncut chip thicknesses ranging from 0.1 mm to 0.3 mm. The results indicate that in certain critical regions of the thermal field, improved machinability correlates with significant reductions in temperature that exceed measurement uncertainties. Such micro-scale temperature measurements will help to design materials with further improved machinability.
Thermo-mechanical Effects in Drilling Using Metal Working Fluids and Cryogenic Cooling and Their Impact on Tool Performance
- Outerio