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Additive Manufacturing: Accuracy, Suitability, Sustainability and Costs

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A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Additive Manufacturing".

Deadline for manuscript submissions: closed (31 January 2020) | Viewed by 21978

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Special Issue Editor

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

Special Issue Information

Dear Colleagues,

Additive manufacturing is an emerging manufacturing process with huge potential. Many studies have recently been developed regarding the different approaches already made in terms of technology. However, in order to better explore the most recent developments, it is also necessary to study important aspects such as the accuracy of each technology, their suitability for particular applications, how the processes are sustainable, and the development of models able to predict the production cost regarding different technologies and equipment, as well as material, geometry of the parts, filling characteristics, and so on. This Special Issue intends to disseminate recent high-quality studies in this field, regarding the production of metallic parts by additive manufacturing. Theoretical and experimental works will be welcome, highlighting the differences between technologies and characteristics of the parts.

Prof. Francisco J. G. Silva
Guest Editor

Manuscript Submission Information

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Keywords

additive manufacturing
direct metal deposition
3D printing of metal alloys
costs
accuracy
sustainability
direct metal laser sintering
laser powder bed fusion

Published Papers (4 papers)

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Research

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17 pages, 4694 KiB

Open AccessFeature PaperArticle

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

by Rafael Barros, Francisco J. G. Silva, Ronny M. Gouveia, Abdollah Saboori, Giulio Marchese, Sara Biamino, Alessandro Salmi and Eleonora Atzeni

Metals 2019, 9(12), 1290; https://doi.org/10.3390/met9121290 - 30 Nov 2019

Cited by 77 | Viewed by 7466

Abstract

Residual stresses (RS) of great magnitude are usually present in parts produced by Laser Powder Bed Fusion (PBF-LB), mainly owing to the extreme temperature gradients and high cooling rates involved in the process. Those “hidden” stresses can be detrimental to a part’s mechanical properties and fatigue life; therefore, it is crucial to know their magnitude and orientation. The hole-drilling strain-gage method was used to determine the RS magnitude and direction-depth profiles. Cuboid specimens in the as-built state, and after standard solution annealing and ageing heat treatment conditions, were prepared to study the RS evolution throughout the heat treatment stages. Measurements were performed on the top and lateral surfaces. In the as-built specimens, tensile stresses of ~400 MPa on the top and above 600 MPa on the lateral surface were obtained. On the lateral surface, RS anisotropy was noticed, with the horizontally aligned stresses being three times lower than the vertically aligned. RS decreased markedly after the first heat treatment. On heat-treated specimens, magnitude oscillations were observed. By microstructure analysis, the presence of carbides was verified, which is a probable root for the oscillations. Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part’s core. Full article

(This article belongs to the Special Issue Additive Manufacturing: Accuracy, Suitability, Sustainability and Costs)

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18 pages, 14633 KiB

Open AccessArticle

An In Vivo Evaluation of Biocompatibility and Implant Accuracy of the Electron Beam Melting and Commercial Reconstruction Plates

by Khaja Moiduddin, Syed Hammad Mian, Mohammed Alkindi, Sundar Ramalingam, Hisham Alkhalefah and Osama Alghamdi

Metals 2019, 9(10), 1065; https://doi.org/10.3390/met9101065 - 30 Sep 2019

Cited by 4 | Viewed by 2299

Abstract

The use of additive manufacturing in medical applications has become more prevalent over the last decade. Studies have proved that reconstruction plates with a mesh structure enhance the biocompatibility and bone-ingrowth formation. However, limited studies have been reported in the customization and in vivo clinical assessment of mesh implants. The purpose of this study was to investigate the surgical treatment and implant fitting accuracy using three different reconstruction plates. Fifteen goats were divided into one control and three experimental groups (Groups 1, 2, and 3) with five in each group. An experimental segmental defect was created on these animals and was adopted with customized electron beam melting reconstruction titanium plates with mesh in Group 1 and without mesh in Group 2 and commercial reconstruction plate in Group 3. All the animals were subjected to radiographic analysis before and after surgery. The subjected animals were sacrificed after 3 months and the electron beam melting reconstruction plates were compared with the commercial plate based on clinical and histology analysis and implant fitting accuracy. Both the electron beam melting reconstruction plates (with mesh and without mesh) and commercial plates survived the three months post-operation, revealing good wound-healing with new bone formation and without any foreign-body reaction. The electron beam melting reconstructed plate with mesh (Group 1) was found to have a better implant fitting when compared to the other two groups. The average discrepancy between Groups 2 and 3 was not significant. Certainly, the commercial plate (Group 3) was found to have the least accuracy as compared to other electron beam melting reconstruction plates (Group 1 and Group 2). Custom design electron beam melting fabricated reconstruction plates possessed better functionality, aesthetic outcome, and long-term biocompatibility when compared to commercial plates. Animal results indicated that the electron beam melting plates with mesh (Group 1) were superior in comparison to the other two groups due to its ability to provide better bone-in-growth and osseointegration on its porous microstructure. Full article

(This article belongs to the Special Issue Additive Manufacturing: Accuracy, Suitability, Sustainability and Costs)

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22 pages, 6396 KiB

Open AccessArticle

Research on Four-Point Air Bending Process and Contour Detection Method for JCO Forming Process of LSAW Pipes

by Zhiyuan Zhang, Haoran Wang, Gaochao Yu and Jun Zhao

Metals 2019, 9(8), 859; https://doi.org/10.3390/met9080859 - 06 Aug 2019

Cited by 3 | Viewed by 3198

Abstract

Aiming at the forming efficiency and roundness of the longitudinal submerged arc welded (LSAW) pipes in JCO (J-shape to C-shape to O-shape) forming process, this paper proposes a four-point air bending process. Compared with the traditional three-point air bending process, The new process can provide a more uniform bending moment, does not need to crimp the edges of steel sheet, shorten the residual straight segment length, and lengthen the forming length in single pass. The mechanical model is established to analyze the static equilibrium conditions and elastic–plastic deformation. The process is simulated by using the software package ABAQUS, to find the maximum punch spacing, and further determine the formulation principles of other process parameters. In addition, a contour detection method for the LSAW pipes in forming process is proposed based on machine vision (planar-array CCD camera produced by Gray Point Corporation, Vancouver, Canada). This method can not only quickly detect the contour of each pass, but also splice the detected contours together to obtain the overall contour with the given splicing algorithm. According to the measured contour, the bending angle, radius, and roundness can be calculated, to correct the punch reduction in the next pass and improve the forming accuracy of the pipes. Finally, an experimental system is designed to verify the proposed four-point bending JCO forming process and contour detection method. The result shows that the error between the contour detection method and CMM (coordinate measuring machine) is less than 0.5% for the overall contour, the two experimental pipes require 13 and 15 passes respectively, the roundness of pipes are less than 1.1%, which is much better than that of traditional three-point bending JCO forming process. Full article

(This article belongs to the Special Issue Additive Manufacturing: Accuracy, Suitability, Sustainability and Costs)

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Review

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25 pages, 2579 KiB

Open AccessReview

Study of the Environmental Implications of Using Metal Powder in Additive Manufacturing and Its Handling

by Jon Iñaki Arrizubieta, Olatz Ukar, Marta Ostolaza and Arantza Mugica

Metals 2020, 10(2), 261; https://doi.org/10.3390/met10020261 - 17 Feb 2020

Cited by 47 | Viewed by 8372

Abstract

Additive Manufacturing, AM, is considered to be environmentally friendly when compared to conventional manufacturing processes. Most researchers focus on resource consumption when performing the corresponding Life Cycle Analysis, LCA, of AM. To that end, the sustainability of AM is compared to processes like milling. Nevertheless, factors such as resource use, pollution, and the effects of AM on human health and society should be also taken into account before determining its environmental impact. In addition, in powder-based AM, handling the powder becomes an issue to be addressed, considering both the operator´s health and the subsequent management of the powder used. In view of these requirements, the fundamentals of the different powder-based AM processes were studied and special attention paid to the health risks derived from the high concentrations of certain chemical compounds existing in the typically employed materials. A review of previous work related to the environmental impact of AM is presented, highlighting the gaps found and the areas where deeper research is required. Finally, the implications of the reuse of metallic powder and the procedures to be followed for the disposal of waste are studied. Full article

(This article belongs to the Special Issue Additive Manufacturing: Accuracy, Suitability, Sustainability and Costs)

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