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Machining: State-of-the-Art 2022

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A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Casting, Forming and Heat Treatment".

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 26288

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Dr. Francisco J. G. Silva

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Guest Editor

Department of Mechanical Engineering, ISEP–School of Engineering, Polytechnic of Porto, 4200-072 Porto, Portugal
Interests: tribology; coatings; manufacturing processes
Special Issues, Collections and Topics in MDPI journals

Dr. Filipe Fernandes

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ISEP - Scool of Engineering, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal
Interests: hard coatings; machining; materials characterization; corrosion
Special Issues, Collections and Topics in MDPI journals

Dr. Vitor Fernando Crespim Sousa

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Guest Editor

ISEP–School of Engineering, Polytechnic Institute of Porto, 4249-015 Porto, Portugal
Interests: manufacturing processes; machining; tool wear; tribology; parameters optimization; tool coatings; machining forces analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Machining remains one of the most important manufacturing processes in the worldwide context, being used every time surface finishing needs to be almost perfect due to contact with other parts. Machining processes have evolved significantly, as have the tools associated with them. The optimization of machining parameters has been a largely studied subject but remains a challenge because every day, new materials and alloys are being developed, new tool shapes are being created, and new coatings are used in their surfaces. Moreover, uncountable subjects around machining are being developed every day. Indeed, materials are evolving continuously, as are their tools and coatings; chips resulting from machining processes are increasingly studied; machining trajectories in CNC machines have experienced a deep evolution; more and more studies are being conducted on how to increase productivity; micromachining is extensively studied; EDM phenomena are increasingly explored; robotics around machining processes are progressively developed; and the Industry 4.0 is invading machining processes and operations through cloud computing, decentralized decision-making systems, and machine-learning processes. The automation of processes passing from CAD to CAM is also growing rapidly. Thus, there are several interesting topics undergoing development every day. This Special Issue aims to accumulate the most recent advances through original high-quality works that are able to disseminate the new evolutions and trends in machining processes, from the conventional to the most advanced processes.

Dr. Francisco J. G. Silva
Dr. Filipe Daniel Fernandes
Dr. Vitor Fernando Crespim Sousa
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Machining and machinability
Turning
Milling
Drilling
Grinding
EDM
Laser machining
Micro-machining
High-speed machining
Tools
Coated tools
Tool wear
Lubrication in machining processes
Vibrations and temperature monitoring
Study of the chip formation
Stresses in machining
Simulation in machining
Sustainable machining
Productivity in machining
Machine-learning
Machining in Industry 4.0

Related Special Issue

Metal Machining—Recent Advances, Applications and Challenges in Metals (13 articles)

Published Papers (12 papers)

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Editorial

Jump to: Research, Review

5 pages, 196 KiB

Open AccessEditorial

Machining: State-of-the-Art 2022

by Francisco J. G. Silva, Filipe Fernandes and Vitor F. C. Sousa

Metals 2023, 13(6), 1036; https://doi.org/10.3390/met13061036 - 29 May 2023

Viewed by 882

Abstract

Although additive manufacturing is gaining prominence in the market, many applications require very high levels of precision, which are currently not attainable by additive manufacturing [...] Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

Research

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19 pages, 6065 KiB

Open AccessArticle

On the Influence of Binder Material in PCBN Cutting Tools for Turning Operations of Inconel 718

by Francisco Matos, Tiago E. F. Silva, Vitor F. C. Sousa, Francisco Marques, Daniel Figueiredo, Francisco J. G. Silva and Abílio M. P. de Jesus

Metals 2023, 13(5), 934; https://doi.org/10.3390/met13050934 - 11 May 2023

Cited by 1 | Viewed by 1142

Abstract

Inconel 718 is a highly valued material in the aerospace and nuclear industries due to the fact of its exceptional properties. However, the processing of this material is quite difficult, especially through machining processes. Machining this material results in rapid tool wear, even when low material removal rates are considered. In this study, instrumented turning experiments were employed to evaluate the machinability of Inconel 718 alloy using PCBN tools while assessing the usage of two distinct binder phases, TiN and TiC, for those cutting tools. It was found that the tool life was highly sensitive to the cutting speeds but also affected by the workpiece mechanical properties. At lower cutting speeds, notch wear significantly impacted the tool integrity, whereas at higher cutting speeds, flank wear was the primary failure mode of the tool. The flank wear of the tools with TiN-based binder outperformed TiC by almost 30%, presenting a more consistent behavior when machining. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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22 pages, 6420 KiB

Open AccessArticle

Wear Behavior Phenomena of TiN/TiAlN HiPIMS PVD-Coated Tools on Milling Inconel 718

by Vitor F. C. Sousa, Filipe Fernandes, Francisco J. G. Silva, Rúben D. F. S. Costa, Naiara Sebbe and Rita C. M. Sales-Contini

Metals 2023, 13(4), 684; https://doi.org/10.3390/met13040684 - 30 Mar 2023

Cited by 10 | Viewed by 1308

Abstract

Due to Inconel 718’s high mechanical properties, even at higher temperatures, tendency to work-harden, and low thermal conductivity, this alloy is considered hard to machine. The machining of this alloy causes high amounts of tool wear, leading to its premature failure. There seems to be a gap in the literature, particularly regarding milling and finishing operations applied to Inconel 718 parts. In the present study, the wear behavior of multilayered PVD HiPIMS (High-power impulse magnetron sputtering)-coated TiN/TiAlN end-mills used for finishing operations on Inconel 718 is evaluated, aiming to establish/expand the understanding of the wear behavior of coated tools when machining these alloys. Different machining parameters, such as cutting speed, cutting length, and feed per tooth, are tested, evaluating the influence of these parameters’ variations on tool wear. The sustained wear was evaluated using SEM (Scanning electron microscope) analysis, characterizing the tools’ wear and identifying the predominant wear mechanisms. The machined surface was also evaluated after each machining test, establishing a relationship between the tools’ wear and production quality. It was noticed that the feed rate parameter exerted the most influence on the tools’ production quality, while the cutting speed mostly impacted the tools’ wear. The main wear mechanisms identified were abrasion, material adhesion, cratering, and adhesive wear. The findings of this study might prove useful for future research conducted on this topic, either optimization studies or studies on the simulation of the milling of Inconel alloys, such as the one presented here. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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15 pages, 2805 KiB

Open AccessArticle

Using an Artificial Neural Network Approach to Predict Machining Time

by André Rodrigues, Francisco J. G. Silva, Vitor F. C. Sousa, Arnaldo G. Pinto, Luís P. Ferreira and Teresa Pereira

Metals 2022, 12(10), 1709; https://doi.org/10.3390/met12101709 - 12 Oct 2022

Cited by 5 | Viewed by 1672

Abstract

One of the most critical factors in producing plastic injection molds is the cost estimation of machining services, which significantly affects the final mold price. These services’ costs are determined according to the machining time, which is usually a long and expensive operation. If it is considered that the injection mold parts are all different, it can be understood that the correct and quick estimation of machining times is of great importance for a company’s success. This article presents a proposal to apply artificial neural networks in machining time estimation for standard injection mold parts. For this purpose, a large set of parts was considered to shape the artificial intelligence model, and machining times were calculated to collect enough data for training the neural networks. The influences of the network architecture, input data, and the variables used in the network’s training were studied to find the neural network with greatest prediction accuracy. The application of neural networks in this work proved to be a quick and efficient way to predict cutting times with a percent error of 2.52% in the best case. The present work can strongly contribute to the research in this and similar sectors, as recent research does not usually focus on the direct prediction of machining times relating to overall production cost. This tool can be used in a quick and efficient manner to obtain information on the total machining cost of mold parts, with the possibility of being applied to other industry sectors. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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15 pages, 5350 KiB

Open AccessFeature PaperArticle

Delamination of Fibre Metal Laminates Due to Drilling: Experimental Study and Fracture Mechanics-Based Modelling

by Francisco Marques, Filipe G. A. Silva, Tiago E. F. Silva, Pedro A. R. Rosa, António T. Marques and Abílio M. P. de Jesus

Metals 2022, 12(8), 1262; https://doi.org/10.3390/met12081262 - 27 Jul 2022

Cited by 6 | Viewed by 1772

Abstract

Fibre metal laminates (FML) are significantly adopted in the aviation industry due to their convenient combination of specific strength, impact resistance and ductility. Drilling of such materials is a regular pre-requisite which enables assembly operations, typically through rivet joining. However, the hole-making operation is of increased complexity due to the dissimilarity of the involved materials, often resulting in defects (i.e., material interface delamination), which can significantly compromise the otherwise excellent fatigue strength. This work explores the potential of three different drill geometries, operating under variable cutting speeds and feeds on CFRP-AA laminates. In addition, the usage of sacrificial back support is investigated and cutting load, surface roughness and delamination extension are examined. In order to predict delamination occurrence, ADCB tests are performed, enabling the calculation of fracture energy threshold. Drill geometry presents a very significant influence on delamination occurrence. The usage of specific step-tools with secondary cutting edge showed superior performance. Despite its simplicity, the applied critical force threshold model was able to successfully predict interface delamination with good accuracy. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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26 pages, 4641 KiB

Open AccessFeature PaperArticle

Build-Up an Economical Tool for Machining Operations Cost Estimation

by Francisco J. G. Silva, Vitor F. C. Sousa, Arnaldo G. Pinto, Luís P. Ferreira and Teresa Pereira

Metals 2022, 12(7), 1205; https://doi.org/10.3390/met12071205 - 15 Jul 2022

Cited by 4 | Viewed by 1914

Abstract

Currently, there is a lack of affordable and simple tools for the estimation of these costs, especially for machining operations. This is particularly true for manufacturing SMEs, in which the cost estimation of machined parts is usually performed based only on required material for part production, or involves a time-consuming, non-standardized technical analysis. Therefore, a cost estimation tool was developed, based on the calculated machining times and amount of required material, based on the final drawing of the requested workpiece. The tool was developed primarily for milling machines, considering milling, drilling, and boring/threading operations. Regarding the considered materials, these were primarily aluminum alloys. However, some polymer materials were also considered. The tool first estimates the required time for total part production and then calculates the total cost. The total production time is estimated based on the required machining operations, as well as drawing, programming, and machine setup time. A part complexity level was also introduced, based on the number of details and operations required for each workpiece, which will inflate the estimated times. The estimation tool was tested in a company setting, comparing the estimated operation time values with the real ones, for a wide variety of parts of differing complexity. An average error of 14% for machining operation times was registered, which is quite satisfactory, as this time is the most impactful in terms of machining cost. However, there are still some problems regarding the accuracy in estimating finishing operation times. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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30 pages, 8153 KiB

Open AccessArticle

Investigations on the Wear Performance of Coated Tools in Machining UNS S32101 Duplex Stainless Steel

by Vitor F. C. Sousa, Francisco J. G. Silva, Ricardo Alexandre, Gustavo Pinto, Andresa Baptista and José S. Fecheira

Metals 2022, 12(6), 896; https://doi.org/10.3390/met12060896 - 25 May 2022

Cited by 2 | Viewed by 1568

Abstract

Due to their high mechanical property values and corrosion resistance, duplex stainless steels (DSSs) are used for a wide variety of industrial applications. DSSs are also selected for applications that require, especially, high corrosion resistance and overall good mechanical properties, such as in the naval and oil-gas exploration industries. The obtention of components made from these materials is quite problematic, as DSSs are considered difficult-to-machine alloys. In this work, the developed wear during milling of the UNS S32101 DSS alloy is presented, employing four types of milling tools with different geometries and coatings. The influence of feed rate and cutting length variations on the tools’ wear and their performance was evaluated. The used tools had two and four flutes with different coatings: TiAlN, TiAlSiN and AlCrN. The cutting behavior of these tools was analyzed by collecting data regarding the cutting forces developed during machining and evaluating the machined surface quality for each tool. After testing, the tools were submitted to SEM analysis, enabling the identification of the wear mechanisms and quantification of flank wear, as well as identifying the early stages of the development of these mechanisms. A comparison of all the tested tools was made, determining that the TiAlSiN-coated tools produced highly satisfactory results, especially in terms of sustained flank wear. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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Review

Jump to: Editorial, Research

28 pages, 8334 KiB

Open AccessReview

A Critical Review on Fiber Metal Laminates (FML): From Manufacturing to Sustainable Processing

by Rúben D. F. S. Costa, Rita C. M. Sales-Contini, Francisco J. G. Silva, Naiara Sebbe and Abílio M. P. Jesus

Metals 2023, 13(4), 638; https://doi.org/10.3390/met13040638 - 23 Mar 2023

Cited by 9 | Viewed by 2953

Abstract

Composite materials such as Fiber Metal Laminates (FMLs) have attracted the interest of the aerospace and automotive industries due to their high strength to weight ratio, but to use them as structures it is necessary to master the manufacturing and wiring techniques of these materials. Therefore, this paper aims to address and summarize the drilling and milling processes in FMLs based on a literature review of papers published from 2000 to 2023. Parameters used in multi-material manufacturing and machining such as drilling and milling, tool geometry, tool coating, lubricants and coolants published by researchers were analyzed, compared and discussed. Machining process parameters related to sustainability were also analyzed. A SWOT analysis was carried out and discussed to identify opportunities for improvement in the machining process. There are opportunities to develop the surface treatment of aluminum alloys, such as testing other combinations than those already used, testing non-traditional surface treatments and manufacturing modes, and developing sustainable techniques during the FML manufacturing process. In the area of tooling, the opportunities are mainly related to coatings for tools and changing machining parameters to achieve an optimum finished part. Finally, to improve the sustainability of the process, it is necessary to test coated drills under cryogenic conditions to reduce the use of lubricants during the machining process. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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31 pages, 2803 KiB

Open AccessReview

A Comprehensive Review on the Conventional and Non-Conventional Machining and Tool-Wear Mechanisms of INCONEL^®

by A. F. V. Pedroso, V. F. C. Sousa, N. P. V. Sebbe, F. J. G. Silva, R. D. S. G. Campilho, R. C. M. Sales-Contini and A. M. P. Jesus

Metals 2023, 13(3), 585; https://doi.org/10.3390/met13030585 - 13 Mar 2023

Cited by 15 | Viewed by 2626

Abstract

Nickel-based superalloys, namely INCONEL^® variants, have had an increase in applications throughout various industries like aeronautics, automotive and energy power plants. These superalloys can withstand high-temperature applications without suffering from creep, making them extremely appealing and suitable for manufactured goods such as jet engines or steam turbines. Nevertheless, INCONEL^® alloys are considered difficult-to-cut materials, not only due to their superior material properties but also because of their poor thermal conductivity (k) and severe work hardening, which may lead to premature tool wear (TW) and poor final product finishing. In this regard, it is of paramount importance to optimise the machining parameters, to strengthen the process performance outcomes concerning the quality and cost of the product. The present review aims to systematically summarize and analyse the progress taken within the field of INCONEL^® machining sensitively over the past five years, with some exceptions, and present the most recent solutions found in the industry, as well as the prospects from researchers. To accomplish this article, ScienceDirect, Springer, Taylor & Francis, Wiley and ASME have been used as sources of information as a result of great fidelity knowledge. Books from Woodhead Publishing Series, CRC Press and Academic Press have been also used. The main keywords used in searching information were: “Nickel-based superalloys”, “INCONEL^® 718”, “INCONEL^® 625” “INCONEL^® Machining processes” and “Tool-wear mechanisms”. The combined use of these keywords was crucial to filter the huge information currently available about the evolution of INCONEL^® machining technologies. As a main contribution to this work, three SWOT analyses are provided on information that is dispersed in several articles. It was found that significant progress in the traditional cutting tool technologies has been made, nonetheless, the machining of INCONEL^® 718 and 625 is still considered a great challenge due to the intrinsic characteristics of those Ni-based-superalloys, whose machining promotes high-wear to the tools and coatings used. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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20 pages, 2608 KiB

Open AccessReview

Hybrid Manufacturing Processes Used in the Production of Complex Parts: A Comprehensive Review

by Naiara P. V. Sebbe, Filipe Fernandes, Vitor F. C. Sousa and Francisco J. G. Silva

Metals 2022, 12(11), 1874; https://doi.org/10.3390/met12111874 - 02 Nov 2022

Cited by 13 | Viewed by 3903

Abstract

Additive manufacturing is defined as a process based on the superposition of layers of materials in order to obtain 3D parts; however, the process does not allow achieve the adequate and necessary surface finishing. In addition, with the development of new materials with superior properties, some of them acquire high hardness and strength, consequently decreasing their ability to be machined. To overcome this shortcoming, a new technology assembling additive and subtractive processes, was developed and implemented. In this process, the additive methods are integrated into a single machine with subtractive processes, often called hybrid manufacturing. The additive manufacturing process is used to produce the part with high efficiency and flexibility, whilst machining is then triggered to give a good surface finishing and dimensional accuracy. With this, and without the need to transport the part from one machine to another, the manufacturing time of the part is reduced, as well as the production costs, since the waste of material is minimized, with the additive–subtractive integration. This work aimed to carry out an extensive literature review regarding additive manufacturing methods, such as binder blasting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet laminating and vat polymerization, as well as machining processes, studying the additive-subtractive integration, in order to analyze recent developments in this area, the techniques used, and the results obtained. To perform this review, ScienceDirect, Web of Knowledge and Google Scholar were used as the main source of information because they are powerful search engines in science information. Specialized books have been also used, as well as several websites. The main keywords used in searching information were: “CNC machining”, “hybrid machining”, “hybrid manufacturing”, “additive manufacturing”, “high-speed machining” and “post-processing”. The conjunction of these keywords was crucial to filter the huge information currently available about additive manufacturing. The search was mainly focused on publications of the current century. The work intends to provide structured information on the research carried out about each one of the two considered processes (additive manufacturing and machining), and on how these developments can be taken into consideration in studies about hybrid machining, helping researchers to increase their knowledge in this field in a faster way. An outlook about the integration of these processes is also performed. Additionally, a SWOT analysis is also provided for additive manufacturing, machining and hybrid manufacturing processes, observing the aspects inherent to these technologies. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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22 pages, 4094 KiB

Open AccessReview

Green Metalworking Fluids for Sustainable Machining Operations and Other Sustainable Systems: A Review

by Muhammad Azhar Ali Khan, Muzafar Hussain, Shahrukh Khan Lodhi, Bouchaib Zazoum, Muhammad Asad and Abdulaziz Afzal

Metals 2022, 12(9), 1466; https://doi.org/10.3390/met12091466 - 31 Aug 2022

Cited by 9 | Viewed by 2358

Abstract

Many efforts have been made over the years to minimize the usage of mineral oil-based MWFs. This includes the trail of its alternatives, such as vegetable oil-based MWFs, nanofluids, etc. These alternatives have shown comparable results to mineral oil-based MWFs in producing a better surface finish and machining efficiency. Apart from the conventional flooding of MWFs, several alternative techniques have been developed by researchers to minimize or eliminate the usage of MWFs, including dry machining, high pressure coolant technique, minimum quantity lubrication, etc. which have also demonstrated promising results. This review attempts to highlight the drawbacks of mineral oil-based MWFs and to assess the applicability of vegetable oil-based MWFs in machining applications. Furthermore, other sustainable machining techniques are discussed in the literature review section, which highlight the main issues associated with the mentioned machining operations and their shortcomings based on the most recent literature. From the comprehensive and critical review that was performed, we inferred that the alternative methods are not mature enough at this stage and that they fall behind in some associated outcomes, some of which may be the tribological properties, surface finish or surface roughness, the cutting forces, the amount of working fluid consumed, etc. More efforts are still needed to fully eliminate the use of MWFs. Moreover, the applications of nanofluids in machining operations have been reviewed in this paper. We concluded from the critical review that nanofluids are an emerging technology which have found their place in machining applications due to their excellent thermophysical properties, but are still in their developmental stage, and more detailed studies are needed to make these a cost-effective solution. Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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28 pages, 4076 KiB

Open AccessReview

A Review of CO₂ Coolants for Sustainable Machining

by Leon Proud, Nikolaos Tapoglou and Tom Slatter

Metals 2022, 12(2), 283; https://doi.org/10.3390/met12020283 - 05 Feb 2022

Cited by 11 | Viewed by 2572

Abstract

In many machining operations, metalworking fluids (MWFs) play an invaluable role. Often, proper application of an intelligent MWF strategy allows manufacturing processes to benefit from a multitude of operational incentives, not least of which are increased tool life, improved surface integrity and optimised chip handling. Despite these clearly positive implications, current MWF strategies are often unable to accommodate the environmental, economic and social conscience of industrial environments. In response to these challenges, CO₂ coolants are postulated as an operationally viable, environmentally benign MWF solution. Given the strong mechanistic rationale and historical evidence in support of cryogenic coolants, this review considers the technological chronology of cryogenic MWF’s in addition to the current state-of-the-art approaches. The review also focuses on the use of CO₂ coolants in the context of the machining of a multitude of material types in various machining conditions. In doing so, cryogenic assisted machining is shown to offer a litany of performance benefits for both conventional emulsion (flood) cooling and near dry strategies, i.e., minimum quantity lubrication (MQL), as well as aerosol dry lubrication (ADL). Full article

(This article belongs to the Special Issue Machining: State-of-the-Art 2022)

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