Special Issue "New Findings and Approaches in Machining Processes"

A special issue of Journal of Manufacturing and Materials Processing (ISSN 2504-4494).

Deadline for manuscript submissions: closed (31 December 2018)

Special Issue Editors

Guest Editor
Prof. Dr. Luis Norberto López de Lacalle

Department of Mechanical Engineering, Aeronautics Advanced Manufacturing Center (CFAA), Faculty of Engineering of Bilbao, Alameda de Urquijo s/n, 48013 Bilbao, Spain
Website | E-Mail
Interests: machining of superalloys; additive manufacturing; welding; coatings; machining; manufacturing of aeroengine components; vibrations in manufacturing processes
Guest Editor
Dr. Amaia Calleja

Department of Mechanical Engineering, Aeronautics Advanced Manufacturing Center (CFAA), Faculty of Engineering of Vitoria, Nieves Cano 12, 01006 Vitoria, Spain
Website | E-Mail
Interests: machining of superalloys; additive manufacturing; welding; coatings; machining; manufacturing of aeroengine components; vibrations in manufacturing processes

Special Issue Information

Dear Colleagues,

Since the 1990s, the world of machining has been increasing in size, achieving more quality and productivity. In fact, substrate grades and new coatings for cutting tools have been launched to the market to improve quality and productivity in all machining operations. The evolution has been constant, and some recent data and surveys defined that metal removal rates have doubled in the last twenty years. On the other hand, machining is key to performing the final operations to achieve the precision required by designers. A mistaken or error in a final machining operation can lead to an expensive wrong part (scrap) and a consequent waste of time and money. To date, machining and grinding are unique approaches to reach a few micrometers in final dimensions.

Sustainability in manufacturing is also a concern, and the so-called “machining green” approaches have been proposed, in lines such as the reduction of coolants and energy, reuse of chips and even reuse of cutting tool substrates. Classical journals sometimes forget that real industry is always making extensive efforts in daily continuous improvements (kaizen, in Japanese) and not looking for breakthrough advances in machining. This Special Issue can be a way to show the present state-of-the-art and recent advances.

Machining is applied by modern machine tools controlled using 4.0 CNC controls. The relation of machining performance with respect to machine characteristics is also a constant topic in the scientific literature. On the other hand, workers and machinists are facing new challenges in training and knowledge. The human factor is key in the transformation of the “art” and “craft” of machining in the “applied science” of metalworking. Traditional points of view regarding classical tool life study or part quality finishing are giving place to more creative approaches, e.g. high-feed milling, trochoidal milling, orbital drilling, abrasive polishing, combination of machining with other non-conventional processes and many others.

Thus, machining was the main operation to improve by the father of modern metalworking FW Taylor at the dawn of XX century, and it is still a key technology in the early years of the XXI. The special issue is open to new findings and approaches, taking into account the following points:

  • New cutting tools
  • Benchmarking of machining processes
  • Solutions for difficult-to-cut alloys
  • Techniques to improve the cutting edge
  • Machine tools for high performance machining
  • Vibration problems in machining
  • Coatings and new grades for tool materials
  • Multitasking machines, a key for productivity and precision
  • Tool wear and tool life
  • Iron casting machining
  • Solutions for stainless steels
  • Thermal, high-pressure, hybrid assisted processes.
  • Use of new 4.0 and analytics in machining
  • New lubricoolant approaches
  • Sustainability in machining: green machining
  • Power consumption in machining
  • Workers trained with new machinist skills

Prof. Dr. Luis López de Lacalle
Dr. Amaia Calleja
Guest Editors

Manuscript Submission Information

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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. Journal of Manufacturing and Materials Processing is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) is waived for well-prepared manuscripts submitted to this issue. 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

  • cutting tools
  • machining
  • machine tools
  • coolants
  • multitasking machines
  • CN machines

Published Papers (18 papers)

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Research

Open AccessArticle
Reliability of Cutting Edge Radius Estimator Based on Chip Production Rate for Micro End Milling
J. Manuf. Mater. Process. 2019, 3(1), 25; https://doi.org/10.3390/jmmp3010025
Received: 18 February 2019 / Revised: 16 March 2019 / Accepted: 18 March 2019 / Published: 20 March 2019
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Abstract
In this paper, the reliability of a new online cutting edge radius estimator for micro end milling is evaluated. This estimator predicts the cutting edge radius by detecting the drop in the chip production rate as the cutting edge of a micro end [...] Read more.
In this paper, the reliability of a new online cutting edge radius estimator for micro end milling is evaluated. This estimator predicts the cutting edge radius by detecting the drop in the chip production rate as the cutting edge of a micro end mill slips over the workpiece when the minimum chip thickness (MCT) becomes larger than the uncut chip thickness (UCT), thus transitioning from the shearing to the ploughing dominant regime. This study proposes a method of calibrating the cutting edge radius estimator by determining two parameters from training data: a ‘size filtering threshold’ that specifies the smallest-size chip that should be counted, and a ‘drop detection threshold’ that distinguishes the drop in the number of chips at the actual critical feedrate from the number drops at the other feedrates. This study then evaluates the accuracy of the calibrated estimator from testing data for determining the ‘critical feedrate’—the feedrate at which the MCT and UCT will be equal. It is found that the estimator is successful in determining the critical feedrate to within 1 mm/s in 84% of trials. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Kinematically Coupled Force Compensation—Experimental Results and Advanced Design for the 1D-Implementation
J. Manuf. Mater. Process. 2019, 3(1), 24; https://doi.org/10.3390/jmmp3010024
Received: 31 December 2018 / Revised: 22 February 2019 / Accepted: 27 February 2019 / Published: 18 March 2019
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Abstract
Typically, the feed dynamics of machine tools are limited to reduce excitations of machine structure oscillations. Consequently, the potential increase in productivity provided by electrical direct drives cannot be exploited. The novel approach of the Kinematically Coupled Force Compensation (KCFC) combines the principles [...] Read more.
Typically, the feed dynamics of machine tools are limited to reduce excitations of machine structure oscillations. Consequently, the potential increase in productivity provided by electrical direct drives cannot be exploited. The novel approach of the Kinematically Coupled Force Compensation (KCFC) combines the principles of redundant axes and force compensation to achieve an increase in the machine’s feed dynamics. Because the drive reaction forces are directly applied to the machine frame, they cancel out each other perfectly if the relative motion at the Tool Centre Point (TCP) is split according to the mass ratio of the slides. In this paper, the principle of KCFC is introduced briefly and possible improvements in the design of machine structures and control are presented. The results of experimental investigations obtained by means of a 1D-KCFC Test Bed illustrate the effectiveness of the principle. Moreover, a further increase of the compensation quality can be achieved by decoupling the force flow from the machine frame, by means of elastic elements. Finally, an outlook on future research with reference to the 1D-implementation as well as possible applications of the KCFC in highly productive processes is given. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Process Stability during Laser Beam Welding with Beam Oscillation and Wire Feed
J. Manuf. Mater. Process. 2019, 3(1), 17; https://doi.org/10.3390/jmmp3010017
Received: 20 December 2018 / Revised: 24 January 2019 / Accepted: 28 January 2019 / Published: 1 February 2019
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Abstract
Beam oscillation in laser material processing makes it possible to influence process behavior in terms of energy distribution, stability, melt pool dynamics and solidification. Within the setup presented here, the beam is oscillated transverse to the welding direction, and the filler wire is [...] Read more.
Beam oscillation in laser material processing makes it possible to influence process behavior in terms of energy distribution, stability, melt pool dynamics and solidification. Within the setup presented here, the beam is oscillated transverse to the welding direction, and the filler wire is fed to the melt pool of a butt joint with an air gap. One advantage of this setup is the large gap bridging ability. Certain parameter sets lead to the so-called buttonhole welding method, which allows laser welding of smooth and nearly ripple-free seams. Observations showed a transition area between conventional keyhole and buttonhole welding in which the process is destabilized. Welds made with parameter sets from this area contain critical seam defects. Welding experiments with high-speed video recording and a simplified analytical model about the wire-beam interaction have helped to elucidate the mechanisms behind this. EN AW-6082 sheet material in 1.5 mm thickness and ML 4043 filler wire with 1.2 mm diameter were used. The investigations lead to the conclusion that partially melted wire segments result at certain parameter relations which hinder the formation of a buttonhole. If these segments are prevented, buttonhole welding occurs. In the transition area, these segments are very small and can lead to the detachment of a buttonhole, resulting in the named seam defects. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Application of Carbon Dioxide Snow in Machining of CGI using an Additively Manufactured Turning Tool
J. Manuf. Mater. Process. 2019, 3(1), 15; https://doi.org/10.3390/jmmp3010015
Received: 24 December 2018 / Revised: 18 January 2019 / Accepted: 21 January 2019 / Published: 23 January 2019
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Abstract
The application of conventional cooling lubricants for the tribological conditioning of machining processes involves high additional costs and health risks. The application of a cryogenic carbon dioxide (CO2) snow cooling strategy is an economical and environmentally sound alternative for oily cooling [...] Read more.
The application of conventional cooling lubricants for the tribological conditioning of machining processes involves high additional costs and health risks. The application of a cryogenic carbon dioxide (CO2) snow cooling strategy is an economical and environmentally sound alternative for oily cooling emulsions since it has a high cooling effect as well as a residue-free sublimation. This article introduces a laser additive manufactured tool holder with an integrated dual nozzle which enables CO2-snow jet application. Initially this work focuses on the characterization and the selection of a suitable nozzle geometry. The modular tool body features an adapted channel structure for process-reliable and targeted CO2-snow cooling for turning processes. This enables the simultaneous cooling of the rake and flank face with CO2-snow, as well as the application of cryogenic multi-component cooling of the rake face. In the context of this study, the focus lies on the technological evaluation of three different supply strategies during the continuous turning of compacted graphite iron CGI-450 at increased cutting speed. It was established that an efficient rake face cooling is indispensable to achieve a low thermal tool load, and thus lower crater wear behavior. Therefore, this study contributes to an improvement in cryogenic machining processes regarding the design of additively manufactured tool bodies for process-reliable CO2-snow cooling, as well as for the selection of supply strategies to minimize the thermomechanical tool load. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Metallurgical Analysis of Chip Forming Process when Machining High Strength Bainitic Steels
J. Manuf. Mater. Process. 2019, 3(1), 10; https://doi.org/10.3390/jmmp3010010
Received: 18 December 2018 / Revised: 16 January 2019 / Accepted: 17 January 2019 / Published: 19 January 2019
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Abstract
In the following work, we propose a metallurgical approach to the chip formation process. We focus on a turning application of high strength steel in which chips are produced by adiabatic shear bands that generate cutting force signals with high frequency components. A [...] Read more.
In the following work, we propose a metallurgical approach to the chip formation process. We focus on a turning application of high strength steel in which chips are produced by adiabatic shear bands that generate cutting force signals with high frequency components. A spectral analysis of these signals is applied and highlights peaks above 4 kHz depending on the cutting conditions. A microscopic analysis on the chip sections provided data on chip breaking and serration mechanisms. Shear band spacing and excitation frequency of the whole cutting system were calculated and gave a good correlation with cutting forces spectra. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
High Seam Surface Quality in Keyhole Laser Welding: Buttonhole Welding
J. Manuf. Mater. Process. 2018, 2(4), 78; https://doi.org/10.3390/jmmp2040078
Received: 18 October 2018 / Revised: 8 November 2018 / Accepted: 12 November 2018 / Published: 14 November 2018
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Abstract
Keyhole laser welding experiments with 1.5 mm thick aluminum sheets (EN AW-6082) were carried out with transversal beam oscillation and wire feeding. A circular cavity, which was named buttonhole, formed directly behind the laser spot at certain oscillation frequencies. The welding states “no [...] Read more.
Keyhole laser welding experiments with 1.5 mm thick aluminum sheets (EN AW-6082) were carried out with transversal beam oscillation and wire feeding. A circular cavity, which was named buttonhole, formed directly behind the laser spot at certain oscillation frequencies. The welding states “no buttonhole”, “unstable buttonhole”, and “stable buttonhole” were distinguished. The melt pool dynamics were experimentally analyzed and correlated with the resulting roughness and waviness of the seam surfaces. Criteria for stable buttonhole welding were derived. On the basis of the cavity radii relations, it is shown that capillary pressure conditions can explain the movement of the buttonhole with the process. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Evaluation of an Analytical Model in the Prediction of Machining Temperature of AISI 1045 Steel and AISI 4340 Steel
J. Manuf. Mater. Process. 2018, 2(4), 74; https://doi.org/10.3390/jmmp2040074
Received: 25 September 2018 / Revised: 18 October 2018 / Accepted: 20 October 2018 / Published: 24 October 2018
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Abstract
This paper evaluates a physics-based analytical model in the prediction of machining temperature of AISI 1045 steel and AISI 4340 steel. The prediction model was developed based on the Johnson-Cook constitutive model (J-C model) and mechanics of the orthogonal cutting process. The average [...] Read more.
This paper evaluates a physics-based analytical model in the prediction of machining temperature of AISI 1045 steel and AISI 4340 steel. The prediction model was developed based on the Johnson-Cook constitutive model (J-C model) and mechanics of the orthogonal cutting process. The average temperatures at two shear zones were predicted by minimizing the difference between calculated stresses using the J-C model and calculated stresses using the mechanics model. In this work, (1) the influence of input Johnson-Cook model constants, cutting force, and chip thickness on the accuracy of predictions are investigated with sensitivity analyses, in which multiple sets of available J-C constants and varying cutting force and chip thickness are used for the temperature prediction in machining AISI 1045 steel. The larger the input deviation, the larger prediction deviation. The temperature at the primary shear zone is more susceptible to the deviation of inputs than the temperature at the secondary shear zone. (2) The machining temperatures are also predicted in machining AISI 4340 steel using cutting tools with various specifications to demonstrate its predictive capability. Good agreements are observed upon validation to available experimental data in the literature. (3) Lastly, the advantage and limitation of the temperature model are discussed with comparison other analytical temperature models. Considering the reliable and easily measurable input requirements and sufficient predictive capability, this temperature model can be employed for effective and efficient machining temperature prediction. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Optimization of Parameters on Robotized Gas Metal Arc Welding of LNE 700 High-Strength Steel
J. Manuf. Mater. Process. 2018, 2(4), 70; https://doi.org/10.3390/jmmp2040070
Received: 22 September 2018 / Revised: 11 October 2018 / Accepted: 12 October 2018 / Published: 16 October 2018
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Abstract
The main aim of this study is to determine the best process parameters for the robotized Gas Metal Arc Welding (GMAW) of LNE 700 advanced high-strength steel. This article evaluates some quality criteria such as the microhardness, the heat-affected zone (HAZ) and the [...] Read more.
The main aim of this study is to determine the best process parameters for the robotized Gas Metal Arc Welding (GMAW) of LNE 700 advanced high-strength steel. This article evaluates some quality criteria such as the microhardness, the heat-affected zone (HAZ) and the convexity in the welded joints. The assays are performed using an experimental design, based on the Taguchi method. The analysis of the results identified some factors of greatest influence and how best to combine them to determine an optimum condition for welding LNE 700 high strength steel. Moreover, the influence of welding parameters on quality criteria is determined. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Machining of Iron-Carbon Alloys by the Use of Poly-Crystalline Diamond Cutting Inserts with Internal Cooling
J. Manuf. Mater. Process. 2018, 2(3), 57; https://doi.org/10.3390/jmmp2030057
Received: 26 July 2018 / Revised: 14 August 2018 / Accepted: 28 August 2018 / Published: 31 August 2018
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Abstract
Poly-crystalline diamond (PCD) is an extremely tough, synthetically produced cutting tool material, which offers outstanding capabilities concerning wear behavior in abrasive cutting environments. Currently, the primary application of PCD cutting tools is the machining of non-ferrous materials, as the diamond’s carbon high affinity [...] Read more.
Poly-crystalline diamond (PCD) is an extremely tough, synthetically produced cutting tool material, which offers outstanding capabilities concerning wear behavior in abrasive cutting environments. Currently, the primary application of PCD cutting tools is the machining of non-ferrous materials, as the diamond’s carbon high affinity towards iron causes diffusion effects while cutting steel with rising temperature. This effect significantly reduces tool life. To lower the occurring temperature of the cutting process, and therefore avoid the reaction of carbon and iron, a thermal functionalization of the cutting inserts has been investigated. The results give insight into making PCD cutting tools economically usable for the machining of iron-carbon materials. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Analysis of the Process Parameter Influence in Laser Cladding of 316L Stainless Steel
J. Manuf. Mater. Process. 2018, 2(3), 55; https://doi.org/10.3390/jmmp2030055
Received: 15 June 2018 / Revised: 26 July 2018 / Accepted: 13 August 2018 / Published: 15 August 2018
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Abstract
Laser Cladding is one of the leading processes within Additive Manufacturing technologies, which has concentrated a considerable amount of effort on its development. In regard to the latter, the current study aims to summarize the influence of the most relevant process parameters in [...] Read more.
Laser Cladding is one of the leading processes within Additive Manufacturing technologies, which has concentrated a considerable amount of effort on its development. In regard to the latter, the current study aims to summarize the influence of the most relevant process parameters in the laser cladding processing of single and compound volumes (solid forms) made from AISI 316L stainless steel powders and using a coaxial nozzle for their deposition. Process speed, applied laser power and powder flow are considered to be the main variables affecting the laser cladding in single clads, whereas overlap percentage and overlapping strategy also become relevant when dealing with multiple clads. By setting appropriate values for each process parameter, the main goal of this paper is to develop a processing window in which a good metallurgical bond between the delivered powder and the substrate is obtained, trying simultaneously to maintain processing times at their lowest value possible. Conventional metallography techniques were performed on the cross sections of the laser tracks to measure the effective dimensions of clads, height and width, as well as the resulting dilution value. Besides the influence of the overlap between contiguous clads and layers, physical defects such as porosity and cracks were also evaluated. Optimum process parameters to maximize productivity were defined as 13 mm/s, 2500 W, 30% of overlap and a 25 g/min powder feed rate. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Using the Segmented Iterative Learning Control Method to Generate Volumetric Error-Compensated Part Programs for Three-Axis CNC Milling Machine Tools
J. Manuf. Mater. Process. 2018, 2(3), 53; https://doi.org/10.3390/jmmp2030053
Received: 17 July 2018 / Revised: 10 August 2018 / Accepted: 10 August 2018 / Published: 13 August 2018
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Abstract
This study proposes using the iterative learning control method to adjust the volumetric error-compensated tool path, where the working volume motion accuracy of three-axis computerized numerical control (CNC) milling machine tools is increased by segmented modification of the part program. As the three-axis [...] Read more.
This study proposes using the iterative learning control method to adjust the volumetric error-compensated tool path, where the working volume motion accuracy of three-axis computerized numerical control (CNC) milling machine tools is increased by segmented modification of the part program. As the three-axis CNC milling machine tools generally have volumetric error of working volume, this study refers to the measured and established table of volumetric errors and uses the method of the modifying part program for volumetric error compensation of machine tools. This study proposes using part-program single-block positioning segmented for volumetric error compensation, as the generated compensated part program with multiple compensated blocks can effectively compensate the volumetric error of working volume in the tool moving process. In terms of the compensated tool path computing method, this study uses the iterative learning control (ILC) method and refers to compensated tool path and volumetric errors along the compensated tool path for iterative computation. Finally, a part program with multiple blocks is modified by the converged optimal compensated tool path, in order that the modified part program has higher-precision volumetric error compensation effect. The simulation result shows that the rate of improvement of error of the volumetric error compensation method proposed in this study is 70%. The result of cutting tests shows that the average rate of improvement of the straightness error of the test workpiece is 60%, while the average rate of improvement of height error is 80%. Therefore, the results of simulation and cutting tests can prove the feasibility of using the ILC method for segmented modification of the volumetric error-compensated part programs proposed in this study. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Molecular Dynamics Simulation Study of Liquid-Assisted Laser Beam Micromachining Process
J. Manuf. Mater. Process. 2018, 2(3), 51; https://doi.org/10.3390/jmmp2030051
Received: 29 June 2018 / Revised: 30 July 2018 / Accepted: 6 August 2018 / Published: 9 August 2018
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Abstract
Liquid Assisted Laser Beam Micromachining (LA-LBMM) process is an advanced machining process that can overcome the limitations of traditional laser beam machining processes. This research involves the use of a Molecular Dynamics (MD) simulation technique to investigate the complex and dynamic mechanisms involved [...] Read more.
Liquid Assisted Laser Beam Micromachining (LA-LBMM) process is an advanced machining process that can overcome the limitations of traditional laser beam machining processes. This research involves the use of a Molecular Dynamics (MD) simulation technique to investigate the complex and dynamic mechanisms involved in the LA-LBMM process both in static and dynamic mode. The results of the MD simulation are compared with those of Laser Beam Micromachining (LBMM) performed in air. The study revealed that machining during LA-LBMM process showed higher removal compared with LBMM process. The LA-LBMM process in dynamic mode showed lesser material removal compared with the static mode as the flowing water carrying the heat away from the machining zone. Investigation of the material removal mechanism revealed the presence of a thermal blanket and a bubble formation in the LA-LBMM process, aiding in higher material removal. The findings of this study provide further insights to strengthen the knowledge base of laser beam micromachining technology. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Process Forces Analysis and a New Feed Control Strategy for Drilling of Unidirectional Carbon Fiber Reinforced Plastics (UD-CFRP)
J. Manuf. Mater. Process. 2018, 2(3), 46; https://doi.org/10.3390/jmmp2030046
Received: 17 May 2018 / Revised: 10 July 2018 / Accepted: 11 July 2018 / Published: 13 July 2018
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Abstract
Reliable machining of carbon fiber-reinforced plastics (CFRP) is the key for application of these lightweight materials. Due to its anisotropy, CFRP is a very difficult material to machine because of occurring delamination and fiber-pullouts. The tool design is especially crucial to minimize and [...] Read more.
Reliable machining of carbon fiber-reinforced plastics (CFRP) is the key for application of these lightweight materials. Due to its anisotropy, CFRP is a very difficult material to machine because of occurring delamination and fiber-pullouts. The tool design is especially crucial to minimize and to avoid these processing errors. In this paper a process analysis for drilling is shown for better understanding of the chip formation. Drilling of unidirectional CFRP enables the investigation of the effect of fiber orientation on the chip formation process. In theory, the amount of cut fibers and the cutting angle to the main cutting edge determine the cutting force. Experimental tests with varied macroscopic drill geometries verify this theory. Based on these detected relationships, the tool loads can be calculated for a successful tool design. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Assessment of Cutting Performance of Cemented Tungsten Carbide Drills in Drilling Multidirectional T700 CFRP Plate
J. Manuf. Mater. Process. 2018, 2(3), 43; https://doi.org/10.3390/jmmp2030043
Received: 21 May 2018 / Revised: 3 July 2018 / Accepted: 4 July 2018 / Published: 9 July 2018
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Abstract
The drilling of carbon fiber reinforced polymer (CFRP) plate is very critical in its structural applications in aeronautical, aerospace, and automobile industries. For ensuring the good quality of drilled holes in terms of least drilling damage and prolonged tool life, suitable selection of [...] Read more.
The drilling of carbon fiber reinforced polymer (CFRP) plate is very critical in its structural applications in aeronautical, aerospace, and automobile industries. For ensuring the good quality of drilled holes in terms of least drilling damage and prolonged tool life, suitable selection of drill geometry and material, and drilling parameters—such as cutting speed and feed rate—are imperative in the drilling of CFRP plate. This study aims to evaluate the cutting performance of conventional two-flute twist drills made of cemented tungsten carbide YG6X (WC-6 wt % Co) for the dry drilling of the multidirectional T700 CFRP plate. The effects of varying cutting speed and tool wear pattern on the drilling performance are analyzed. The drilling performance is assessed in terms of hole quality by the qualitative and quantitative analysis of drilling-induced delamination and hole diameter. Furthermore, the correlation between the tool wear progression and the drilled hole quality is established. Through this assessment, a suitable set of drilling parameters, i.e., cutting speed of 9000 rpm and feed rate of 400 mm/min, is proposed for producing the best quality holes for multidirectional T700 CFRP plate. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Development of a New Forced Cooling Technology Using a High-Pressure Coolant for Machining Difficult-To-Machine Materials
J. Manuf. Mater. Process. 2018, 2(2), 39; https://doi.org/10.3390/jmmp2020039
Received: 9 May 2018 / Revised: 30 May 2018 / Accepted: 6 June 2018 / Published: 12 June 2018
Cited by 1 | PDF Full-text (2866 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, titanium and nickel alloys have become relevant in the production of aeronautic and astronautic parts. Since both nickel and titanium alloys have a very small thermal conductivity, the used tool will suffer huge damage from the heat generated during a [...] Read more.
In recent years, titanium and nickel alloys have become relevant in the production of aeronautic and astronautic parts. Since both nickel and titanium alloys have a very small thermal conductivity, the used tool will suffer huge damage from the heat generated during a grinding process. Therefore, there is a requirement for a durable tool with excellent cooling capacity. In this research, a new forced cooling technology that uses high-pressure coolant for machining difficult-to-machine materials was developed and evaluated. Here, a through hole on the rake face near the turning tool tip was machined by electrical discharge machining. Then, high-pressure coolant was supplied to the turning tool from the machined hole. Several values of pressure were experimentally performed. It is concluded from the results that the technology could effectively cool the area near the tip of a turning tool, and that the chip was also effectively removed by the high-pressure coolant. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Effect of Laser Welding Process Parameters and Filler Metals on the Weldability and the Mechanical Properties of AA7020 Aluminium Alloy
J. Manuf. Mater. Process. 2018, 2(2), 33; https://doi.org/10.3390/jmmp2020033
Received: 7 April 2018 / Revised: 26 May 2018 / Accepted: 29 May 2018 / Published: 1 June 2018
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Abstract
This research work aims at finding the optimum process parameters for the laser welding of AA7020 aluminium alloys. The use of 7xxx series alloys is limited because of weldability problems, such as hot cracking, porosity, and softening of the fusion zone despite its [...] Read more.
This research work aims at finding the optimum process parameters for the laser welding of AA7020 aluminium alloys. The use of 7xxx series alloys is limited because of weldability problems, such as hot cracking, porosity, and softening of the fusion zone despite its higher specific strength-to-weight ratio. AA7020 aluminium alloy was welded while varying the process parameters so as to obtain optimal welding efficiency. The welded samples were analysed to reveal the microstructure, defects, and mechanical properties of the welded zone. The samples were prepared from a plate of AA7020, which was hot rolled at a temperature of 470 °С to a thickness of 1 mm. The welding was carried out at an overlap of 0.25 mm, duration of 14 ms and argon shield gas flow rate of 15 L/min. Process parameters, such as peak power, welding speed, and pulse shaping, were varied. The samples were welded with Al-5Ti-B and Al-5Mg as filler metals. The welding speed, peak power, and pulse shaping have a great influence on the weldability and hot cracking susceptibility of the aluminium alloy. Al-5Ti-B improves the microstructure and ultimate tensile strength of AA7020 aluminium alloy. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
Multi-Criteria Assessment of Machining Processes for Turbine Disc Slotting
J. Manuf. Mater. Process. 2018, 2(2), 32; https://doi.org/10.3390/jmmp2020032
Received: 2 May 2018 / Revised: 22 May 2018 / Accepted: 23 May 2018 / Published: 28 May 2018
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Abstract
Many different process chains are possible to manufacture profiled grooves in turbine discs. Broaching with high speed steel tools is still state of the art today but as a consequence of the rising demand for aero engines, the disc manufacturers are striving for [...] Read more.
Many different process chains are possible to manufacture profiled grooves in turbine discs. Broaching with high speed steel tools is still state of the art today but as a consequence of the rising demand for aero engines, the disc manufacturers are striving for alternative high performance processes to increase both flexibility and productivity in the manufacturing of these safety critical features. Broaching machines are oftentimes at a bottleneck in the production of rotating turbine discs. Several other machining processes have been discussed in the context of slotting, such as broaching with carbide tools, milling, water jet machining, W-EDM and grinding. Within this paper a multi-criteria assessment approach is presented dealing with slotting processes. The assessment comprehends economical, ecological, flexibility and productivity criteria, and is based on data gathered with an aero engine OEM. The technological aspects such as tool life and productivities are based on real machining tests that have been carried out within the project HoFePro. The assessment is conducted for multiple profile shapes that represent different sizes and geometrical complexities of profiled grooves. The manufacturing processes within the assessment include broaching with HSS and carbide, milling with ceramics and carbide (side and end) as well as profile milling with carbide tools. The underlying workpiece material is a nickel-based alloy. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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Open AccessArticle
New Observations on High-Speed Machining of Hardened AISI 4340 Steel Using Alumina-Based Ceramic Tools
J. Manuf. Mater. Process. 2018, 2(2), 27; https://doi.org/10.3390/jmmp2020027
Received: 1 April 2018 / Revised: 28 April 2018 / Accepted: 30 April 2018 / Published: 3 May 2018
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Abstract
High-speed machining (HSM) is used in industry to improve the productivity and quality of the cutting operations. In this investigation, pure alumina ceramics with the addition of ZrO2, and mixed alumina (Al2O3 + TiC) tools were used in [...] Read more.
High-speed machining (HSM) is used in industry to improve the productivity and quality of the cutting operations. In this investigation, pure alumina ceramics with the addition of ZrO2, and mixed alumina (Al2O3 + TiC) tools were used in the dry hard turning of AISI 4340 (52 HRC) at different high cutting speeds of 150, 250, 700 and 1000 m/min. It was observed that at cutting speeds of 150 and 250 m/min, pure alumina ceramic tools had better wear resistance than mixed alumina ones. However, upon increasing the cutting speed from 700 to 1000 m/min, mixed alumina ceramic tools outperformed pure ceramic ones. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to investigate the worn cutting edges and analyze the obtained results. It was found that the tribo-films formed at the cutting zone during machining affected the wear resistances of the tools and influenced the coefficient of friction at the tool-chip interface. These observations were confirmed by the chip compression ratio results at different cutting conditions. Raising cutting speed to 1000 m/min corresponded to a remarkable decrease in cutting force components in the dry hard turning of AISI 4340 steel. Full article
(This article belongs to the Special Issue New Findings and Approaches in Machining Processes)
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J. Manuf. Mater. Process. EISSN 2504-4494 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
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