Special Issue "Additive Manufacturing Technologies and Applications"

A special issue of Technologies (ISSN 2227-7080). This special issue belongs to the section "Innovations in Materials Processing".

Deadline for manuscript submissions: closed (31 March 2017)

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Guest Editor
Dr. Salvatore Brischetto

ASTRA (Additive manufacturing for Systems and sTRuctures in Aerospace) group, Politecnico di Torino, Department of Mechanical and Aerospace Engineering, corso Duca degli Abruzzi 24, 10129 Torino, Italy
Website 1 | Website 2 | E-Mail
Phone: +39.011.090.6813
Fax: +39.011.090.6899
Interests: smart composite and FGM structures; multifield problems; hygro-thermal stress analysis; CNTs; inflatable structures; shell 3D and 2D numerical and exact solutions; additive manufacturing and UAVs
Co-Guest Editor
Prof. Dr. Paolo Maggiore

ASTRA (Additive manufacturing for Systems and sTRuctures in Aerospace) group, Politecnico di Torino, Department of Mechanical and Aerospace Engineering, corso Duca degli Abruzzi 24, 10129 Torino, Italy
Website | E-Mail
Interests: non linear system modeling; multidisciplinary design optimization; additive manufacturing applications; UAVs; paramteric CAD geometry optimization.
Co-Guest Editor
Mr. Carlo Giovanni Ferro

ASTRA (Additive manufacturing for Systems and sTRuctures in Aerospace) group, Politecnico di Torino, Department of Mechanical and Aerospace Engineering, corso Duca degli Abruzzi 24, 10129 Torino, Italy
Website | E-Mail
Interests: trabecular structures for aerospace applications; multidisciplinary design optimization; additive manufacturing; UAVs.

Special Issue Information

Dear Colleagues,

Additive Manufacturing is a well-known technology, patented firstly in 1984 by the French scientist Alain Le Mehaute. Its distinctive concept is of adding material with different methods (powder, wire and so on) instead of subtracting from a raw part. It has been widely introduced in the preliminary and conceptual design phase, thanks to the reduced production costs and realization time of a prototype. In the last few years, this technique has also been considered for low scale mass production due to some advantages. Firstly, this technique allows the construction of so-called evolutive shapes: Structures of complex design that are impossible or difficult to build with traditional milling or machining. Evolutive shapes are usually the result of a topological optimization. Therefore, important mass savings or increases in structure mechanical properties are obtained using this resource. The present Special Issue aims to publish papers in the area of Additive Manufacturing with particular attention on the different technologies employed and the several possible applications. Particular attention should be given to technologies, such as the Selective Laser Sintering (SLS) and the Fused Deposition Modeling (FDM), which, combined with the Computer Aided Design (CAD), could provide important advantages. Analytical, numerical and experimental knowledge and models are welcome to exploit the potential benefits offered by the 3D printing for the production of advanced structures and systems in aerospace, civil, mechanical and biomedical engineering sectors.

Dr. Salvatore Brischetto
Prof. Paolo Maggiore
Mr. Carlo Giovanni Ferro
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 papers will be 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. Technologies 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) for publication in this open access journal is 350 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

  • Additive Manufacturing (AM)
  • Fused Deposition Modelling (FDM)
  • Selective Laser Sintering (SLS)
  • Computer Aided Design (CAD)
  • Topological optimization
  • Analytical models
  • Numerical models
  • Experimental models
  • Advanced structures
  • Advanced materials
  • Advanced systems
  • Mechanical characterization
  • Prototype developing via AM

Published Papers (12 papers)

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Editorial

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Open AccessEditorial Special Issue on “Additive Manufacturing Technologies and Applications”
Technologies 2017, 5(3), 58; https://doi.org/10.3390/technologies5030058
Received: 8 September 2017 / Accepted: 11 September 2017 / Published: 12 September 2017
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Abstract
Additive Manufacturing (AM) is a well-known technology, first patented in 1984 by the French scientist Alain Le Mehaute [...]
Full article

Research

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Open AccessFeature PaperArticle Impact of DIY Home Manufacturing with 3D Printing on the Toy and Game Market
Technologies 2017, 5(3), 45; https://doi.org/10.3390/technologies5030045
Received: 16 May 2017 / Revised: 3 July 2017 / Accepted: 6 July 2017 / Published: 20 July 2017
Cited by 5 | PDF Full-text (4429 KB) | HTML Full-text | XML Full-text
Abstract
The 2020 toy and game market is projected to be US$135 billion. To determine if 3D printing could affect these markets if consumers offset purchases by 3D printing free designs, this study investigates the 100 most popular downloaded designs at MyMiniFactory in a
[...] Read more.
The 2020 toy and game market is projected to be US$135 billion. To determine if 3D printing could affect these markets if consumers offset purchases by 3D printing free designs, this study investigates the 100 most popular downloaded designs at MyMiniFactory in a month. Savings are quantified for using a Lulzbot Mini 3D printer and three filament types: commercial filament, pellet-extruded filament, and post-consumer waste converted to filament with a recyclebot. Case studies probed the quality of: (1) six common complex toys; (2) Lego blocks; and (3) the customizability of open source board games. All filaments analyzed saved the user over 75% of the cost of commercially available true alternative toys and over 90% for recyclebot filament. Overall, these results indicate a single 3D printing repository among dozens is saving consumers well over $60 million/year in offset purchases. The most common savings fell by 40%–90% in total savings, which came with the ability to make novel toys and games. The results of this study show consumers can generate higher value items for less money using the open source distributed manufacturing paradigm. It appears clear that consumer do-it-yourself (DIY) manufacturing is set to have a significant impact on the toy and game markets in the future. Full article
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Open AccessArticle Open Source Multi-Head 3D Printer for Polymer-Metal Composite Component Manufacturing
Technologies 2017, 5(2), 36; https://doi.org/10.3390/technologies5020036
Received: 1 March 2017 / Revised: 5 April 2017 / Accepted: 18 April 2017 / Published: 15 June 2017
Cited by 3 | PDF Full-text (13633 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
As low-cost desktop 3D printing is now dominated by free and open source self-replicating rapid prototype (RepRap) derivatives, there is an intense interest in extending the scope of potential applications to manufacturing. This study describes a manufacturing technology that enables a constrained set
[...] Read more.
As low-cost desktop 3D printing is now dominated by free and open source self-replicating rapid prototype (RepRap) derivatives, there is an intense interest in extending the scope of potential applications to manufacturing. This study describes a manufacturing technology that enables a constrained set of polymer-metal composite components. This paper provides (1) free and open source hardware and (2) software for printing systems that achieves metal wire embedment into a polymer matrix 3D-printed part via a novel weaving and wrapping method using (3) OpenSCAD and parametric coding for customized g-code commands. Composite parts are evaluated from the technical viability of manufacturing and quality. The results show that utilizing a multi-polymer head system for multi-component manufacturing reduces manufacturing time and reduces the embodied energy of manufacturing. Finally, it is concluded that an open source software and hardware tool chain can provide low-cost industrial manufacturing of complex metal-polymer composite-based products. Full article
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Open AccessArticle A Robust Multifunctional Sandwich Panel Design with Trabecular Structures by the Use of Additive Manufacturing Technology for a New De-Icing System
Technologies 2017, 5(2), 35; https://doi.org/10.3390/technologies5020035
Received: 29 January 2017 / Revised: 23 May 2017 / Accepted: 7 June 2017 / Published: 15 June 2017
Cited by 2 | PDF Full-text (3010 KB) | HTML Full-text | XML Full-text
Abstract
Anti-ice systems assure a vital on-board function in most aircraft: ice prevention or de-icing is mandatory for all aerodynamic surfaces to preserve their performance, and for all the movable surfaces to allow the proper control of the plane. In this work, a novel
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Anti-ice systems assure a vital on-board function in most aircraft: ice prevention or de-icing is mandatory for all aerodynamic surfaces to preserve their performance, and for all the movable surfaces to allow the proper control of the plane. In this work, a novel multi-functional panel concept which integrates anti-icing directly inside the primary structure is presented. In fact, constructing the core of the sandwich with trabecular non-stochastic cells allows the presence of a heat exchanger directly inside the structure with a savings in weight and an improvement in thermal efficiency. This solution can be realized easily in a single-piece component using Additive Manufacturing (AM) technology without the need for joints, gluing, or welding. The objective of this study is to preliminarily investigate the mechanical properties of the core constructed with Selective Laser Melting (SLM); through the Design of Experiment (DOE), different design parameters were varied to understand how they affect the compression behaviour. Full article
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Open AccessArticle Monitoring Approach to Evaluate the Performances of a New Deposition Nozzle Solution for DED Systems
Technologies 2017, 5(2), 29; https://doi.org/10.3390/technologies5020029
Received: 18 April 2017 / Revised: 19 May 2017 / Accepted: 25 May 2017 / Published: 31 May 2017
Cited by 2 | PDF Full-text (4138 KB) | HTML Full-text | XML Full-text
Abstract
Abstract: In order to improve the process efficiency of a direct energy deposition (DED) system, closed loop control systems can be considered for monitoring the deposition and melting processes and adjusting the process parameters in real-time. In this paper, the monitoring of
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Abstract: In order to improve the process efficiency of a direct energy deposition (DED) system, closed loop control systems can be considered for monitoring the deposition and melting processes and adjusting the process parameters in real-time. In this paper, the monitoring of a new deposition nozzle solution for DED systems is approached through a simulation-experimental comparison. The shape of the powder flow at the exit of the nozzle outlet and the spread of the powder particles on the deposition plane are analyzed through 2D images of the powder flow obtained by monitoring the powder depositions with a high-speed camera. These experimental results are then compared with data obtained through a Computational Fluid Dynamics model. Preliminary tests are carried out by varying powder, carrier, and shielding mass flow, demonstrating that the last parameter has a significant influence on the powder distribution and powder flow geometry. Full article
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Open AccessArticle Testbed for Multilayer Conformal Additive Manufacturing
Technologies 2017, 5(2), 25; https://doi.org/10.3390/technologies5020025
Received: 8 April 2017 / Revised: 18 May 2017 / Accepted: 19 May 2017 / Published: 24 May 2017
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Abstract
Over the last two decades, additive manufacturing (AM) or 3D printing technologies have become pervasive in both the public and private sectors. Despite this growth, there has been little to no deviation from the fundamental approach of building parts using planar layers. This
[...] Read more.
Over the last two decades, additive manufacturing (AM) or 3D printing technologies have become pervasive in both the public and private sectors. Despite this growth, there has been little to no deviation from the fundamental approach of building parts using planar layers. This undue reliance on a flat build surface limits part geometry and performance. To address these limitations, a new method of applying material onto or around existing surfaces with multilayer, thick features will be explored. Prior work proposes algorithms for defining conformal layers between existing and desired surfaces, however this work does not address the derivation of deposition paths, trajectories, or required hardware to achieve this new type of deposition. This paper presents (1) the derivation of deposition paths given a prescribed set of layers; (2) the design, characterization, and control of a proof-of-concept testbed; and (3) the derivation and application of time evolving trajectories subject to the material deposition constraints and mechanical constraints of the testbed. Derivations are presented in a general context with examples extending beyond the proposed testbed. Results show the feasibility of conformal material deposition (i.e., onto and around existing surfaces) with multilayer, thick features. Full article
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Open AccessArticle Customised Alloy Blends for In-Situ Al339 Alloy Formation Using Anchorless Selective Laser Melting
Technologies 2017, 5(2), 24; https://doi.org/10.3390/technologies5020024
Received: 31 March 2017 / Revised: 18 May 2017 / Accepted: 19 May 2017 / Published: 24 May 2017
PDF Full-text (5623 KB) | HTML Full-text | XML Full-text
Abstract
The additive manufacturing process Selective Laser Melting (SLM) can generate large thermal gradients during the processing of metallic powder; this can in turn lead to increased residual stress formation within a component. Metal anchors or support structures are required to be built during
[...] Read more.
The additive manufacturing process Selective Laser Melting (SLM) can generate large thermal gradients during the processing of metallic powder; this can in turn lead to increased residual stress formation within a component. Metal anchors or support structures are required to be built during the process and forcibly hold SLM components to a substrate plate and minimise geometric distortion/warpage due to the process induced thermal residual stress. The requirement for support structures can limit the geometric freedom of the SLM process and increase post-processing operations. A novel method known as Anchorless Selective Laser Melting (ASLM) maintains processed material within a stress relieved state throughout the duration of a build. As a result, metal components formed using ASLM do not develop signification residual stresses within the process, thus, the conventional support structures or anchors used are not required to prevent geometric distortion. ASLM locally melts two or more compositionally distinct powdered materials that alloy under the action of the laser, forming into various combinations of hypo/hyper eutectic alloys with a new reduced solidification temperature. This new alloy is maintained in a semi-solid or stress reduced state for a prolonged period during the build with the assistance of elevated powder bed pre-heating. In this paper, custom blends of alloys are designed, manufactured and processed using ASLM. The purpose of this work is to create an Al339 alloy from compositionally distinct powder blends. The in-situ alloying of this material and ASLM processing conditions allowed components to be built in a stress-relieved state, enabling the manufacture of overhanging and unsupported features. Full article
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Open AccessArticle Compression Tests of ABS Specimens for UAV Components Produced via the FDM Technique
Technologies 2017, 5(2), 20; https://doi.org/10.3390/technologies5020020
Received: 5 April 2017 / Revised: 2 May 2017 / Accepted: 3 May 2017 / Published: 5 May 2017
Cited by 1 | PDF Full-text (6226 KB) | HTML Full-text | XML Full-text
Abstract
Additive manufacturing has introduced a great step in the manufacturing process of consumer goods. Fused Deposition Modeling (FDM) and in particular 3D printers for home desktop applications are employed in the construction of prototypes, models and in general in non-structural objects. The aim
[...] Read more.
Additive manufacturing has introduced a great step in the manufacturing process of consumer goods. Fused Deposition Modeling (FDM) and in particular 3D printers for home desktop applications are employed in the construction of prototypes, models and in general in non-structural objects. The aim of this new work is to characterize this process in order to apply this technology in the construction of aeronautical structural parts when stresses are not excessive. An example is the construction of the PoliDrone UAV, a multicopter patented, designed and realized by researchers at Politecnico di Torino. For this purpose, a statistical characterization of the mechanical properties of ABS (Acrylonitrile Butadiene Styrene) specimens in compression tests is proposed in analogy with the past authors’ work about the tensile characterization of ABS specimens. A desktop 3D printer, including ABS filaments as the material, has been employed. ASTM 625 has been considered as the reference normative. A capability analysis has also been used as a reference method to evaluate the boundaries of acceptance for both mechanical and dimensional performances. The statistical characterization and the capability analysis are here proposed in an extensive form in order to validate a general method that will be used for further tests in a wider context. Full article
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Open AccessArticle In-Built Customised Mechanical Failure of 316L Components Fabricated Using Selective Laser Melting
Received: 31 January 2017 / Revised: 17 February 2017 / Accepted: 21 February 2017 / Published: 25 February 2017
Cited by 2 | PDF Full-text (3216 KB) | HTML Full-text | XML Full-text
Abstract
The layer-by-layer building methodology used within the powder bed process of Selective Laser Melting facilitates control over the degree of melting achieved at every layer. This control can be used to manipulate levels of porosity within each layer, effecting resultant mechanical properties. If
[...] Read more.
The layer-by-layer building methodology used within the powder bed process of Selective Laser Melting facilitates control over the degree of melting achieved at every layer. This control can be used to manipulate levels of porosity within each layer, effecting resultant mechanical properties. If specifically controlled, it has the potential to enable customisation of mechanical properties or design of in-built locations of mechanical fracture through strategic void placement across a component, enabling accurate location specific predictions of mechanical failure for fail-safe applications. This investigation examined the process parameter effects on porosity formation and mechanical properties of 316L samples whilst maintaining a constant laser energy density without manipulation of sample geometry. In order to understand the effects of customisation on mechanical properties, samples were manufactured with in-built porosity of up to 3% spanning across ~1.7% of a samples’ cross-section using a specially developed set of “hybrid” processing parameters. Through strategic placement of porous sections within samples, exact fracture location could be predicted. When mechanically loaded, these customised samples exhibited only ~2% reduction in yield strength compared to samples processed using single set parameters. As expected, microscopic analysis revealed that mechanical performance was closely tied to porosity variations in samples, with little or no variation in microstructure observed through parameter variation. The results indicate that there is potential to use SLM for customising mechanical performance over the cross-section of a component. Full article
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Open AccessArticle Additive Manufacturing: Reproducibility of Metallic Parts
Received: 20 December 2016 / Revised: 14 February 2017 / Accepted: 18 February 2017 / Published: 22 February 2017
Cited by 4 | PDF Full-text (1051 KB) | HTML Full-text | XML Full-text
Abstract
The present study deals with the properties of five different metals/alloys (Al-12Si, Cu-10Sn and 316L—face centered cubic structure, CoCrMo and commercially pure Ti (CP-Ti)—hexagonal closed packed structure) fabricated by selective laser melting. The room temperature tensile properties of Al-12Si samples show good consistency
[...] Read more.
The present study deals with the properties of five different metals/alloys (Al-12Si, Cu-10Sn and 316L—face centered cubic structure, CoCrMo and commercially pure Ti (CP-Ti)—hexagonal closed packed structure) fabricated by selective laser melting. The room temperature tensile properties of Al-12Si samples show good consistency in results within the experimental errors. Similar reproducible results were observed for sliding wear and corrosion experiments. The other metal/alloy systems also show repeatable tensile properties, with the tensile curves overlapping until the yield point. The curves may then follow the same path or show a marginal deviation (~10 MPa) until they reach the ultimate tensile strength and a negligible difference in ductility levels (of ~0.3%) is observed between the samples. The results show that selective laser melting is a reliable fabrication method to produce metallic materials with consistent and reproducible properties. Full article
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Open AccessFeature PaperArticle Emergence of Home Manufacturing in the Developed World: Return on Investment for Open-Source 3-D Printers
Received: 13 January 2017 / Revised: 30 January 2017 / Accepted: 6 February 2017 / Published: 9 February 2017
Cited by 11 | PDF Full-text (1212 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Through reduced 3-D printer cost, increased usability, and greater material selection, additive manufacturing has transitioned from business manufacturing to the average prosumer. This study serves as a representative model for the potential future of 3-D printing in the average American household by employing
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Through reduced 3-D printer cost, increased usability, and greater material selection, additive manufacturing has transitioned from business manufacturing to the average prosumer. This study serves as a representative model for the potential future of 3-D printing in the average American household by employing a printer operator who was relatively unfamiliar with 3-D printing and the 3-D design files of common items normally purchased by the average consumer. Twenty-six items were printed in thermoplastic and a cost analysis was performed through comparison to comparable, commercially available products at a low and high price range. When compared to the low-cost items, investment in a 3-D printer represented a return of investment of over 100% in five years. The simple payback time for the high-cost comparison was less than 6 months, and produced a 986% return. Thus, fully-assembled commercial open source 3-D printers can be highly profitable investments for American consumers. Finally, as a preliminary gauge of the effect that widespread prosumer use of 3-D printing might have on the economy, savings were calculated based on the items’ download rates from open repositories. Results indicate that printing these selected items have already saved prosumers over $4 million by substituting for purchases. Full article
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Review

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Open AccessReview Overhanging Features and the SLM/DMLS Residual Stresses Problem: Review and Future Research Need
Technologies 2017, 5(2), 15; https://doi.org/10.3390/technologies5020015
Received: 24 March 2017 / Revised: 7 April 2017 / Accepted: 10 April 2017 / Published: 12 April 2017
Cited by 8 | PDF Full-text (3679 KB) | HTML Full-text | XML Full-text
Abstract
A useful and increasingly common additive manufacturing (AM) process is the selective laser melting (SLM) or direct metal laser sintering (DMLS) process. SLM/DMLS can produce full-density metal parts from difficult materials, but it tends to suffer from severe residual stresses introduced during processing.
[...] Read more.
A useful and increasingly common additive manufacturing (AM) process is the selective laser melting (SLM) or direct metal laser sintering (DMLS) process. SLM/DMLS can produce full-density metal parts from difficult materials, but it tends to suffer from severe residual stresses introduced during processing. This limits the usefulness and applicability of the process, particularly in the fabrication of parts with delicate overhanging and protruding features. The purpose of this study was to examine the current insight and progress made toward understanding and eliminating the problem in overhanging and protruding structures. To accomplish this, a survey of the literature was undertaken, focusing on process modeling (general, heat transfer, stress and distortion and material models), direct process control (input and environmental control, hardware-in-the-loop monitoring, parameter optimization and post-processing), experiment development (methods for evaluation, optical and mechanical process monitoring, imaging and design-of-experiments), support structure optimization and overhang feature design; approximately 143 published works were examined. The major findings of this study were that a small minority of the literature on SLM/DMLS deals explicitly with the overhanging stress problem, but some fundamental work has been done on the problem. Implications, needs and potential future research directions are discussed in-depth in light of the present review. Full article
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