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Sustainability Assessment of Advanced Machining Technologies
Abstract
Efficient cooling and lubrication techniques are required to obtain sustainable machining of difficult-to-cut materials, which are the pillars of aerospace, automotive, medical and nuclear industries. Cryogenic machining with the assistance of lubricated Liquid Carbon Dioxide (LCO2) is a novel approach for sustainable manufacturing without the use of harmful water-based metalworking fluids (MWFs). In case of unavoidable use of MWFs under high pressure, such as turning finishing processes of difficult-to-cut materials, the pulsating high pressure delivery of MWFs prolongs the tool life and enables the control over chip length to prevent surface damage of high value-added parts. In this paper, sustainability assessment of both advanced principles was carried out, considering overall costs and operational safety. Experimental tests were executed on difficult-to-cut materials in comparison to conventional flood lubrication. For both techniques, longer tool life compared to flood lubrication was observed additional cleaner production and higher part quality led to reduced long-term overall costs. These advanced machining technologies are also operation safe, proving to be a sustainable alternative to conventional machining.
... Sterle et al. analyzed the pulsating HP CF supply strategy in comparison to HP CF supply and cryogenic machining concerning economic and ecological aspects [27]. Turning experiments in Inconel 718 with pulsating HP CF supply were carried out with a feed f = 0.28 mm, a cutting speed v c = 50 m/min, and a depth of cut a p = 0.5 mm. ...
... In summary, the pulsating HP CF supply was identified as a suitable technology to achieve chip breakage during finish turning of Inconel 718 by Bergs et al. and Sterle et al. [14,[25][26][27]. Bergs identified basic correlations between the cutting parameters, the pulsation parameters, and the resulting chip length l s [25]. ...
High-pressure cutting fluid supply is a proven technology for chip breaking when turning difficult-to-cut materials, such as Inconel 718. However, the technology is usually not suitable for the finish turning of safety-critical parts in aero engines. The acting force of the cutting fluid jet on the back of the chip causes chip breaking. The broken chips are then accelerated by the cutting fluid jet towards the workpiece surfaces where they cause damage on impact. One approach to minimize surface damage is a specific increase in the chip length. The center of gravity of the chips with an adjusted length is shifted out of the focus where the cutting fluid jet hits the chips. Hence, the already finished surface is subjected to fewer impacts of the chips. In this study, the adjustment of the chip length by pulsating high-pressure cutting fluid supply to prevent surface damage was investigated. A valve unit was used to generate two alternating cutting fluid supply pressure levels in certain time intervals. During the low-pressure stage, the force of the cutting fluid jet does not lead to chip breakage and the chip length increases until the valves switch and the high-pressure stage is released. The focus of this work was the analysis of the relationship between the duration of the low-pressure and high-pressure time intervals and the chip length. Additionally, the influence of the depth of cut, the feed, and the cutting speed on the chip length during pulsating high-pressure cutting fluid supply was investigated. Finally, a case study was carried out to evaluate the effectiveness of the pulsating high-pressure cutting fluid supply technology. Therefore, the shoulder surface of a demonstrator part was finished by face turning. Following, the cylindrical surface was finished with a continuous and pulsating high-pressure cutting fluid supply with varied supply parameters. Microscopic analyses of the surface prove that the pulsating high-pressure cutting fluid supply prevents the surface from being damaged by the impacts of chips.
... Sustainable press tools can help improve sustainability in the manufacturing industry and reduce their environmental impact. These studies collectively underscore this potential [12]. ...
The design and material selection used during the manufacturing process significantly impact the environment due to their energy consumption and waste production, including carbon dioxide emissions. This study used the LCA tool eco-indicator to evaluate the environmental impact of producing clothes-hanging machines. Two different press tool designs were analyzed, each using other materials for punch and die. The results indicate that the press tool design 2 with SKD11 punch and die is suitable for long-term use but emits the highest CO 2 emissions at 102.33 kg CO 2 . In contrast, the press tool design 1 with S45C punch and die is suitable for short-term use but emits the lowest CO 2 emissions at 69.72 kg CO 2 .
... Coolant was supplied externally using a nozzle with an internal diameter of 0.8 mm, as seen in Fig. 3a. The LCO2 and MQL were supplied through a single channel using the Arclub One LCO2 system [18], which ensured a flow rate of 0.2 kg/min for LCO2 and 40 mL/h for MQL. ...
Lightweight materials like Carbon Fiber Reinforced Polymers (CFRPs) present certain challenges, mainly regarding the resultant surface integrity of the holes. Different techniques such as optimized tool geometries, machining techniques and cooling/lubricating techniques have been tested for improving surface integrity on CFRPs. Unfortunately using coolants presents certain challenges when machining CFRPs, as the moisture absorption can degrade the mechanical properties of the composite, on top of the environmental and health hazards created by water and oil based metalworking fluids. Therefore, this study aims to evaluate the influence of environmentally friendly liquid carbon dioxide (LCO2) based cooling/lubricating conditions and Polycrystalline Diamond (PCD) drill bit geometries (point angle) on the delamination when drilling CFRP composites. The results showed significant influence of the tool geometry and cooling condition on the surface integrity of CFRPs, especially in the case of the former.
... Andererseits erhöht sich die Komplexität des Systems durch die Druck-und Temperaturerhöhung. Im Bereich der Zerspanung konnte nachgewiesen werden, dass es keines homogenen Mischungsverhältnisses bedarf, um die Wirkstelle effizient kühlen und schmieren zu können[89,94,155,156]. Dennoch können sich Inhomogenitäten im Zeitverlauf signifikant auf den Prozess auswirken. ...
Die kryogene Kühlung ist eine Kühlschmierstrategie zur Bearbeitung schwerzerspanbarer Werkstoffe. Diese Kühlmethode findet durch die Absenz eines Schmierstoffs bisher keine breite industrielle Anwendung. Die Forschungsschwerpunkte dieser Arbeit liegen in der Entwicklung und Erprobung eines Systems zur Beimischung eines Schmiermittels in ein kryogenes Medium. Als Kryogen dient flüssiges Kohlenstoffdioxid. Durch verschiedene Funktionsnachweise konnte gezeigt werden, dass eine homogene Vermischung des Schmierstoffs mit dem CO2 nicht notwendig ist, um einen gleichmäßigen Schmiermittelauftrag zu erreichen. Anschließende Untersuchungen zur kryogenen Minimalmengenschmierung beim Drehen von Ti-6Al-4V, X5CrNi18-10 und 42CrMo4 sowie beim Fräsen von XCrNiMoTi17-12-2 und Ti-6Al-4V verdeutlichen den Einfluss unterschiedlicher Schmierstoffe. Die Prozessanalyse belegt, dass native Schmierstoffe die Werkzeugstandzeit und das Zeitspanvolumen gegenüber synthetischen und mineralischen Produkten beim Fräsen erhöhen können. Eine Analyse der Energieeffizienz zeigt, dass durch längere Werkzeugstandzeiten der Energiebedarf mit der kryogenen Minimalmengenschmierung im Vergleich zur konventionellen Nassbearbeitung reduziert werden kann. Die kryogene Minimalmengenschmierung bietet dadurch beträchtliche Potenziale zur Etablierung einer nachhaltigen Produktion.
... Furthermore, transition from conventional flood lubrication to LCO 2 assisted machining, if the nonpolar oil (oil 2) is used in pre-mixed LCO 2 + MQL, reflects in 44.7 % lower running costs, as the tool life is significantly prolonged (conventional flood lubrication; L f = 13.6 m and LCO 2 assisted machining; L f = 36.6 m) [16]. ...
Single-channel supply of pre-mixed liquid carbon dioxide (LCO2) and minimum quantity lubrication (MQL) represents a state-of-the-art LCO2 assisted machining. However, to fully understand and optimize cooling and lubrication provided by the LCO2 + MQL, a fundamental media flow analysis is essential, yet not researched enough. Therefore, in this paper, media flow velocity and oil droplet size were analysed in supplying line and at the nozzle outlet using high-speed camera and proprietary single-channel system. Results indicate that pre-mixed media flow velocity is mainly influenced by the LCO2 expansion rate upon the nozzle outlet, wherein oil droplet size is largely dependent on the solubility between oil and LCO2. Media flow velocity increases significantly from an average of 40 m/s in the supplying line to the excess of 90 m/s at the nozzle outlet due to the pressure drop and LCO2 expansion. Furthermore, this volume expansion causes the oil droplet to increase to the point of critical, unstable droplet size. Afterward, the unstable oil droplet breaks up into smaller oil droplets. It was found, that nonpolar oil, with greater solubility in LCO2, compared to the polar oil, provides droplets as small as 2 μm in diameter. Smaller oil droplets positively reflect on tool wear and tool life in LCO2 assisted machining, as the longest tool life was achieved by using the nonpolar oil for pre-mixed LCO2 + MQL.
In machining processes, there are contradictions between high efficiency and environmentally-friendly machining. This indicated that there is a major potential for sustainable machining to both increase efficiency and protect ecological balance. For this, the employment of effective methods has become imperative to reduce resource use. In this way, the use of analysis and optimization tools to select the tool material, cutting parameters, cooling/lubrication conditions, etc., will be a benefit for minimizing waste without sacrificing efficiency. In the literature, researchers have used various methods to reveal the requirements of sustainability. However, reaching the concept of sustainable machining by using one more than technique confuses the readers. Therefore, it was deemed necessary to present and discuss the current methods, models and analyzes in a comprehensive review paper. In this context, this paper reviewed the previously published works, especially focusing on sustainability and energy consumption modeling methods in machining operations. At the end of the study, it was seen that LCA provides a systematic and quantitative view of the system and thus can act as a decision support tool. Moreover, it can give an idea to the manufacturers about the improvement of the process and the areas of innovation. However, the method has several disadvantages such as relatively expensive and specific software, obtaining inventory data, impractical to use, time-consuming and requires large amounts of data. Various mathematical models and algorithms have been developed to deal with the complex situations and offer a more practical use compared to LCA. However, it is difficult to state that clear results have been achieved thanks to these models. It was seen that in complex machining processes, only approximate results can be found with models, which leads to questioning the reliability of the models.
It should be reminded that in the general classification of hybrid shaping processes.
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.
Increasing demand for difficult-to-cut materials challenge conventional cooling techniques to their limit. The durability of the tool is often reduced and cutting parameters such as feed rate or depth of cut have to be adjusted with a negative impact on productivity. Therefore, innovative cooling technologies have to be developed and integrated into new and existing machining equipment. The article describes the development of a hybrid cooling concept offering the flexibility to assign conventional or cryogenic cooling to incremental process steps. The developed cryogenic cooling supply system controls the flow of liquid carbon dioxide regarding density, flow rate and temperature before the lubrication media is injected by a high precision pump into the same tube. This approach significantly reduces the integration effort especially for internal cooling before being applied to a drilling process with a rotating tool of 50CrMo4. The challenges for the integration in the machine tool consist in the interface between spindle and tool holder and the tool itself due to the potential expansion of CO2 leading to undesired cooling before reaching the tool center point. Therefore, each interface has been investigated and requirements for cryogenic-compatible tools have been defined. Finally, different lubrication fluids combined with CO2-based cryogenic cooling have been investigated regarding tool durability for a milling process of Ti6Al4V. The results show that different oils have significant impact on the process performance offering a perspective for further research.
Hard turning with minimal fluid application is a recently developed technique to alleviate the problem associated with cutting fluid. During this process, very small quantity of cutting fluid is applied as a narrow high velocity pulsing jet at the cutting zone. As the quantity of cutting fluid is very small, some auxiliary cooling of tool using heat pipe was attempted in the present work to enhance heat dissipation and thus improving cutting performance. Heat pipe was installed in vertical position in contact with the tool for extracting more heat from the tool. The influence of heat pipe cooling of tool on the cutting performance was analyzed by Taguchi's design of experiments. It was observed that the use of heat pipe in minimal fluid application reduced cutting temperature and tool wear to a maximum of 22% and 15%, respectively, in comparison with conventional hard turning with minimal fluid application without the aid of heat pipe. It appears that heat pipe can be successively employed as a mean of cooling the tool during hard turning with minimal fluid application.
Recently the concept of hard turning has gained much attention in the metal cutting industry. In hard turning, multiple operations can be performed in single step, thereby it replaces the traditional process cycle. But it involves very large quantities of cutting fluid. Procurement, storage and disposal of cutting fluid involve expenses and environmental problem. Pure dry turning is a solution to this problem as it does not require any cutting fluid at all. But pure dry turning requires ultra hard cutting tools and extremely rigid machine tools, and also it is difficult to implement in the existing shop floor as the machine tool may not be rigid enough to support hard turning. In this context, turning with minimal fluid application is a viable alternative wherein, extremely small quantities of cutting fluid are introduced at critical contact zones as high velocity pulsing slugs, so that for all practical purposes it resembles pure dry turning and at the same time free from all the problems related to large scale use of cutting fluid as in conventional wet turning. In this study, fluid application parameters that characterize the minimal fluid application scheme were optimized and its effect on cutting performance and tool vibration was studied. From the results, it was observed that minimal fluid application in the optimized mode brought forth low vibration levels and better cutting performance.
This paper shows current research results in the field of high-pressure lubricoolant supply and cryogenic cooling. Since the performance of a high-pressure lubricoolant supply in turning titanium and nickel-based alloys has been proven in many previous papers, this paper focuses on the quantification of the potential in turning different steels, namely quenched and tempered but also stainless steels in comparison to the conventional flood cooling. Since energy efficiency is very crucial, pressure and flow rate have to be adjusted carefully and in accordance with the cutting parameters in order to guarantee best results using only a minimal amount of energy. Moreover the effects of cryogenic cooling with CO2 will be evaluated in comparison to high-pressure cooling and conventional flood cooling. In the field of cryogenic cooling with CO2, cutting tests were carried out under variation of the CO2-flow rate in order to find the minimum required value for a certain machining task with the overall aim to prevent waste of the CO2. Especially in cryogenic cooling technologies, many fundamental research regarding the working mechanisms but also further developments in cutting tool and machine tool technology are still necessary to make this technology ready for industrial use.
Difficult-to-cut materials like Inconel 718 are used for aerospace, steam turbine, bearing industry, nuclear and automotive applications. In machining, friction and heat generation at the cutting zone are the frequent problems, which affect the tool life and surface finish. Heat generation pose limitations during the turning of such modern materials due to their peculiar characteristics such as poor thermal conductivity, high strength at elevated temperature, resistance to wear and chemical degradation. A good understanding of the methods of lubrication/cooling at the cutting zone, reduction of heat generation will lead to efficient and economic machining of these modern materials. This paper presents use of compressed cold carbon dioxide for cooling at machined affected zone. Effect of cold compressed carbon dioxide as coolant on process forces, surface roughness, micro hardness, specific cutting pressure has been studied in comparison to dry turning for same set of cutting parameters.
Abstract This paper shows a new milling concept, Walter Cryo tecTM. With this concept, the internal multi-channel supply of cryogenic media as well as other media e.g. cold air, MQL or cutting emulsion by means of a special machine tool spindle and an adapted cutting tool is supported. Cutting tests with different cooling and lubrication strategies were carried out. The effects of these strategies are compared. The paper focuses on the quantification of the potential of cryogenic machining with CO2 in milling of high temperature high strength stainless steel. The major benefits are higher cutting data, higher material removal rates and less tool wear. Besides the economic effects, the environmental advantages are shown.
This experimental work is carried out to investigate the performance and influence of cryogenic coolants such as CO2 (carbon dioxide) and LN2 (liquid nitrogen) on cutting temperature, cutting force, tool wear, surface finish and chip morphology in machining of AISI 1045 steel compared to wet machining. The results proved that the application of cryogenic coolants reduced the cutting temperature drastically which resulted in appreciable improvement in surface finish of the product and reduced tool wear. The use of cryogenic LN2 reduced the cutting temperature about 3–17% when compared to CO2 coolant. Application of CO2 reduced the cutting forces and improved the surface finish of the machined part to an extent about 2–12% and 2–14% respectively when compared to the use of cryogenic LN2 coolant. Tool wear was found to be less on the application of CO2 compared to the wet and LN2 machining conditions.
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 discusses an investigation into the capability of liquid nitrogen (LN 2 ) and liquid carbon dioxide (LCO 2 ) as a coolant in machining. A comparative analysis of the heat-transfer rate was made utilizing cooling of a controlled heat source with an integrated temperature sensor. The analysis was coupled with experimental in-process temperature measurements in cryogenic milling of titanium alloy Ti-6Al-4V (ß). The results indicate that cooling capability differs between these two cryogenic media, in both the observed cooling rate as well as in the achieved steady-state temperature.
In this study, the effect of supercritical carbon dioxide cooling with Minimum Quantity Lubrication (scCO2+MQL) on tool wear and surface integrity of AISI 304 L austenitic stainless steel in milling was investigated. A series of machining experiments based on a Design of Experiments (DoE) was carried out at various combinations of cutting parameters to investigate the effect of cutting speed and feed rate on tool wear, near-surface residual stresses, surface roughness and microhardness. The results were compared with the experimental results obtained from milling with flood coolant. A significant improvement in tool life was observed in milling with the scCO2+MQL using multilayer coated tungsten carbide inserts. The tool life in terms of cutting time increased by ∼324%, in comparison to a baseline flood coolant. Further, a decrease in surface roughness value (Ra) by about 30%, from 1.09 µm for flood coolant to 0.78 µm after face milling with scCO2+MQL was seen. Additionally, the Ra value slightly increased after machining, for both cooling methods with the increase of cutting speed of ∼19%. The observed changes in Ra value were discussed in terms of a built-up-edge (BUE) formation. There were no apparent differences in surface microhardness between both cooling methods. However, the surface microhardness increased with feed rate after milling with both scCO2+MQL and flood coolant due to the increased strain hardening. Also, there was no significant difference in residual stresses after milling, neither with scCO2+MQL nor the flood coolant. The surface residual stress values obtained in the transverse and longitudinal directions were consistent with a predictive model with errors of around 3–8%.
Cryogenically assisted manufacturing processes are emerging as environmentally-benign, toxic-free, hazardless operations, producing functionally superior products. This paper presents an overview of major cryogenic manufacturing processes, summarizing the state-of-the-art and significant developments during the last few decades. It begins with a summary of historic perspectives, including definitions, scope, and proceeds to analysis of process mechanics and material performance covering tribological and thermo-mechanical interactions, followed by surface integrity, product quality and performance in cryogenic manufacturing. Process analysis and applications includes machining, forming and grinding. Economic, safety and health issues are then discussed. Finally, progress in developing predictive performance models and future outlook are presented.
Minimum quantity lubricant (MQL) machining is an emerging cooling technology that ensures green machining. In this research work, an innovative design for the application of MQL in the form of pulse jet was created, following the development of that applicator. The surface milling of AISI 4140 steel, heat treated to 40 HRC, was investigated with pulse jet minimum quantity lubricant applicator using VG-68 grade straight cut cutting oil as the cutting fluid in respect of cutting force, surface roughness and tool flank wear with machining time. Four flute carbide end mill cutter was used to investigate the change in tool wear, and compared with that of the dry condition. The result and analysis indicate that this pulse jet MQL applicator can be utilized in hard milling operation to ensure better surface finish and minimal tool wear and cutting force.
Machining with minimal fluid application is a new technique for reducing the usage of cutting fluid that ensures green manufacturing on shop floor. During minimal fluid application, a high velocity minimal pulsing jet of proprietary cutting fluid was applied at the tool work interface. In the present work an auxiliary high velocity minimal pulsing jet of water was applied at the top side of the chip in addition to the pulsing jet of cutting fluid at the tool work interface during turning of hardened AISI 4340 steel. The effect of auxiliary pulsing jet of water on the top side on cutting performance is investigated in comparison with conventional turning with minimal fluid application. From the experimental results, it was observed that the presence of an auxiliary jet of water on the top side of the chip promoted chip curl by Rebinder effect. Increase in chip curl resulted in less tool chip contact length thereby reduces the friction, cutting force and cutting temperature.
This paper investigates the cooling and lubrication properties of supercritical carbon dioxide (scCO2) sprays as potential substitutes for aqueous emulsions and straight oils used in the metalworking industry today. Sprays of rapidly expanding scCO2 act to cool and lubricate machining and forming processes by delivering a mixture of dry ice and lubricant deep into the cutting/forming zone. In this work, experiments with turning, milling, drilling, thread cutting, and thread forming were performed with scCO2 and other metalworking fluids (MWFs) to evaluate their relative performance with respect to tool wear and machining torque. Observations reveal that scCO2–MWFs are more effective in removing heat from the tool-workpiece interface than conventionally delivered (flood) aqueous MWFs as well as other gas-based MWF sprays. In addition, scCO2–MWFs delivered in lubricant-expanded phase, where scCO2 is used to increase volume of lubricant in the spray field, are shown to provide better lubricity than straight oils and oil-in-air minimum quantity lubrication (MQL) sprays. As a result, scCO2–MWFs can reduce tool wear and improve machining productivity in a wide range of manufacturing operations leading to appreciable improvements in the economics of manufacturing. Also given that CO2 is a recovered waste gas that is non-toxic, scCO2–MWFs can improve the environmental and worker health performance of manufacturing operations.
This paper aims at improving the understanding of cryogenic assistance in machining Ti6Al4V and Inconel718 with carbide tools. It especially intends to investigate the cooling and/or lubrication capabilities of a nitrogen jet under extreme contact conditions using a dedicated tribometer. Whereas neither liquid nor gas nitrogen is able to decrease friction coefficient and adhesion on Ti6Al4V, it is proved to be efficient on Inconel718 with a prevailing effect of the liquid phase. In both cases, applying gas nitrogen already decreases the amount of heat transmitted to the pin but this can be drastically enhanced by using liquid nitrogen. Finally, this work provides quantitative data regarding friction coefficient under dry and cryogenic conditions that can be implemented in numerical cutting models.
This two part paper presents general issues, methods and a case study for achieving production sustainability on a machining technology level. In order to tackle these issues, the paper promotes sustainable production via the alternative machining technologies, namely cryogenic and high pressure jet assisted machining that have a high potential to cut costs and improve competitiveness by reducing resource consumption and thus creating less waste. The general issues of sustainable technologies pointed out with a comparative case study life cycle assessment performed for alternative machining processes are covered in part I of the work, concluding that future of sustainable production is going to entail the use of alternative machining technologies to reduce consumption rates, environmental burdens, and health risks simultaneously, while increasing performances and profitability. As an upgrade to this part, overall cost evaluation is covered by a case study in part II of this work.
Environmental concerns call for the reduced use of cutting fluids in metal cutting practice. New cutting techniques are to be investigated to achieve this objective. Hard turning with Minimal Fluid application (HTMF) is one such technique, which can alleviate the pollution problems associated with cutting fluids. In the present work a specially formulated cutting fluid was applied as a high velocity, thin pulsed jet at the immediate cutting zones at an extremely low rate of 2 ml/min using a fluid application system developed for this purpose during turning of hardened steel. The performance of HTMF is studied in comparison with that of conventional hard turning in wet and dry form.
This paper investigates the application of the high-pressure jet assistance (HPJA) in rough turning of Inconel 718 with coated carbide tools. The region of operability, which sets the boundaries of the process parameters, has been experimentally determined using the tool–material pair (TMP) methodology. The assessment of HPJA machining performance is based on response surface methodology (RSM), which integrates a design of experiment (DOE) and a regression modelling technique for fitting a model to experimental. This leads to a new insight into the influence of the cutting process on chip breakability, cutting forces, contact length, surface finish and tool temperature, which are the key machining performance measures.
Traditional machining methods are still very important in machining mechanical parts, although many non-traditional machining methods, such as electrical discharge machining, laser burning, and water jet abrasion, have been used extensively. In traditional machining processes, cutting fluid plays a very important role. It not only cools down the cutting tool and target parts, by which the cutting tool achieves a longer life and the target parts obtain better quality, but it also acts as a lubricant, decreasing the friction force between the tool rake and the machined material. In traditional machining process, cutting fluid accounts for 15–30% of the total cutting costs [Kamiya, Y., 1996. Safety and environmental control in flexible manufacturing system. Journal of mechanics and cutting tools, 40 (2), 24–30 (in Japanese)]. Although current cutting fluid provision systems work well most of the time, high productivity machining encourages use of high cutting velocity and feed rate. As a result, conventional or low-pressure cutting fluid provision methods are not sufficiently efficient to penetrate the cutting zone. Therefore, cutting fluids with better performance are required. In this study, a new cutting fluid supply method, which uses a specially designed device to provide pulsed delivery of cutting fluid, has been introduced. This method greatly improves cutting performance. Experimental results showed that pulsed cutting fluid significantly decreased the cutting force needed and achieved better cutting surface quality.
The vast majority of machining operations exploit the good cooling and lubricating characteristics of cooling lubricants (CL). But, as costs for waste disposal increase, companies are now being forced to implement strategies in order to reduce the amount of CL used in their production lines. The most logical measure which can be taken to eliminate all of the problems associated with the use of CL is dry machining. In most cases, however, a machining operation without lubricant finds acceptance only when it is possible to guarantee that the part quality and machining times achieved in wet machining are equalled or surpassed. The introduction of dry machining techniques may also include the use of minimal quantities of lubricant (MQL). The following paper deals with the most recent developments in dry cutting.
Applying cutting fluid in a metal-cutting process can reduce the rate of tool wear and improve surface quality. However, cutting fluid has negative effects on the working environment and the use of cutting fluid also increases the total production cost. Therefore, there is a need to reduce the use of cutting fluid during machining. To serve that purpose, a minimal-cutting-fluid technique was studied. In the present work the cutting fluid was applied in a form of a high-velocity, narrow, pulsed jet at a rate of 2 ml/min. The performance of machining with pulsed-jet application was studied in high-speed milling of hardened steel, compared to dry machining and machining with flood application. The results clearly show that compared to dry machining and machining with flood application, machining with pulsed-jet application lowers cutting forces, reduces tool wear, increases tool life, and improves surface roughness, especially when machining with high cutting velocity. Moreover, the amount of cutting fluid consumed at the rate of 2 ml/min is a drastic reduction compared to flood application. Also, no harmful oil mist is generated during the pulsed-jet application. In conclusion, the pulsed-jet application can be applied to milling process of hardened steel using ball end mills; it reduces the negative effects to the environment, improves machining performances, and consequently reduces total production cost.
This paper reviews some of the main developments in cutting technology since the foundation of CIRP over fifty years ago. Material removal processes can take place at considerably higher performance levels in the range up to Qw = 150 – 1500 cm3/min for most workpiece materials at cutting speeds up to some 8.000 m/min. Dry or near dry cutting is finding widespread application. The superhard cutting tool materials embody hardness levels in the range 3000 – 9000 HV with toughness levels exceeding 1000 MPa. Coated tool materials offer the opportunity to fine tune the cutting tool to the material being machined. Machining accuracies down to 10 μm can now be achieved for conventional cutting processes with CNC machine tools, whilst ultraprecision cutting can operate in the range < 0.1 μm. The main technological developments associated with the cutting tool and tool materials, the workpiece materials, the machine tool, the process conditions and the manufacturing environment which have led to this advancement are given detailed consideration in this paper. The basis for a roadmap of future development of cutting technology is provided.
Modern machining processes face continuous cost pressures and high quality expectations. To remain competitive a company must continually identify cost reduction opportunities in production, exploit economic opportunities, and continuously improve production processes. A key technology that represents cost saving opportunities related to cooling lubrication, and simultaneously improves the overall performance of cutting operations, is dry machining. The elimination of, or significant reduction in, cooling lubricants affects all components of a production system. A detailed analysis and adaptation of cutting parameters, cutting tools, machine tools and the production environment is mandatory to ensure an efficient process and successfully enable dry machining.
During metal machining the rotating machine tool or grinding wheel is generating fine droplets and vapor which can cause occupational health problems. A new continuous measuring method was developed to detect both droplets and vapor of metalworking fluid mist and to provide information about the droplet size distribution. According to this method, an air sample of the metalworking fluid mist is segregated by impactors of different cut sizes, carried out in several successive passes. In each pass the droplets that are not collected in the impactor are fed into an evaporator that immediately evaporates all droplets, and subsequently the sample is analyzed in-line by a Flame Ionization Detector (FID). By subtraction of the value measured at the respectively next smaller fraction, the oil amount of the metalworking fluid mist found in a certain droplet size range is obtained. The metalworking fluid mist is thus segregated according to the droplet size, and a definite cut size between droplet and vapor can be defined, below which we can say "vapor". This method was calibrated with Di-2-Ethylhexyl-Sebacat (DEHS) as equivalence substance for further measurements applied on various metalworking fluids.
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