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

Deadline for manuscript submissions: closed (30 May 2018) | Viewed by 82629

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Prof. Dr. Mohamed Elbestawi

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Department of Mechanical Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada
Interests: metal additive manufacturing; machining science and technology; machine tools
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Additive Manufacturing (AM) methods have great potential for promoting transformative research in many fields across the vast spectrum of engineering and material science. Applications, such as tooling, production parts, biomedical devices and implants and aerospace components, all benefit from the flexibility that AM provides.

In this Special Issue of JMMP, current research results will be reported, which are focused on analytical and experimental work aimed at achieving the desired material properties and geometries of the final structure. This includes assessing the impact of process parameters and predicting optimized conditions. Submissions related to novel applications are also welcomed.

Contributions focused on metal additive manufacturing in any of the following topics are of particular interest:

Materials, processes and machines
Process monitoring, modeling and control
Functionally graded materials
Design for additive manufacturing
Advanced simulation and multi-scale modeling for metal additive manufacturing
Development of tailored materials for additive manufacturing

Prof. Mohamed Elbestawi
Guest Editor

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. Journal of Manufacturing and Materials Processing is an international peer-reviewed open access semimonthly 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 1800 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.

Published Papers (10 papers)

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Research

14 pages, 2523 KiB

Open AccessArticle

Processing Parameter DOE for 316L Using Directed Energy Deposition

by Federico M. Sciammarella and Benyamin Salehi Najafabadi

J. Manuf. Mater. Process. 2018, 2(3), 61; https://doi.org/10.3390/jmmp2030061 - 07 Sep 2018

Cited by 30 | Viewed by 5586

Abstract

The ability to produce consistent material properties across a single or series of platforms, particularly over time, is the major objective in metal additive manufacturing (MAM) research. If this can be achieved, it will result in widespread adoption of the technology for industry and place it into mainstream manufacturing. However, before this can happen, it is critical to develop an understanding of how processing parameters influence the thermal conditions which dictate the mechanical properties of MAM builds. Research work reported in the literature of MAM is generally based on a set of parameters and/or the review of a few parameter changes, and observing the effects that these changes (i.e., microstructure, mechanical properties) have. While these articles provide results with some insight, there lacks a standard approach that can be used to allow meaningful comparisons and conclusions to be made concerning the optimization of the processing variables. This study provides a template which can be used for making comparisons across DED platforms. The tests are performed with a design of experiments (DOE) philosophy directed to evaluate the effect of selected parameters on the measured properties of the DED builds. Specifically, a laser engineering net shaping system (LENS) is used to build multilayered 316L coupons and analyze how build parameters such as laser power, travel speed, and powder feed rate influence the thermal conditions that will define both microstructure and microhardness. A fundamental conclusion of this research is that it is possible to repeatedly obtain a consistent microstructure that contains a fine cellular substructure with a low level of porosity (less than 1.1%) and with microhardness that is equal to or better than wrought 316L. This is mainly achieved by maintaining an associated powder flow to travel speed ratio at the power level, ensuring an appropriate net heat input for the build process. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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17 pages, 5893 KiB

Open AccessArticle

Parametric Thermal FE Analysis on the Laser Power Input and Powder Effective Thermal Conductivity during Selective Laser Melting of SS304L

by Diego A De Moraes and Aleksander Czekanski

J. Manuf. Mater. Process. 2018, 2(3), 47; https://doi.org/10.3390/jmmp2030047 - 14 Jul 2018

Cited by 15 | Viewed by 4544

Abstract

A low-cost parametric finite element thermal model is proposed to study the impact of the initial powder condition, such as diameter and packing density, on effective thermal conductivity as well as the impact of the laser power input on the final temperature distributions during selective laser melting (SLM). Stainless steel 304L is the material used, since it is not yet commercially available in SLM equipment and our main goal was to show the capabilities of the finite element method in the evaluation of power input in the process. The results from our sensitivity analysis showed that packing density has a greater impact on the final temperature distributions compared with powder diameter variance. However, overall the thermal conductivity of the powder only showed significant effects below the melting point, otherwise the thermal conductivity no longer affected the temperature distributions. Among the three different power inputs analyzed, the temperature profile demonstrated that power inputs of 100 and 200 W are recommended when printing SS-304L rather than 400 W, which generates too high temperature in the powder bed, a non-favorable behavior that can induce high residual stresses and material evaporation. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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19 pages, 9433 KiB

Open AccessArticle

3D Printing Cellulose Hydrogels Using LASER Induced Thermal Gelation

by Tim Huber, Don Clucas, Mathieu Vilmay, Birte Pupkes, James Stuart, Simone Dimartino and Conan Fee

J. Manuf. Mater. Process. 2018, 2(3), 42; https://doi.org/10.3390/jmmp2030042 - 02 Jul 2018

Cited by 10 | Viewed by 4595

Abstract

A 3D printer was developed for the 3D printing of cellulose hydrogels using open source software and simple 3D printer hardware. Using a temperature-based sol-gel transition of cellulose dissolved in aqueous solutions of sodium hydroxide (NaOH) and urea, a three-dimensional gel can be created by moving a focused laser beam across a bath of the cellulose solution and lowering the print stage after every layer. A line width of 100–150 µm and layer thickness of 25 µm of the printed part could be achieved. No delamination between printed layers occurred and no additional support material was needed to create free hanging structures due to suspending the printed part in printing liquid. By adding cellulose powder to the solution, the gelation temperature, the gel strength and stiffness can be manipulated while maintaining a high internal porosity of the gel. A laser power of 100 mW was found to produce the highest quality print with an accurate representation of the previously designed part. Lower power settings (80 mW) produced insufficient gelation and as a result reduced print accuracy while higher power settings (120 mW) caused the gel to burn. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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16 pages, 7850 KiB

Open AccessArticle

Influence of Shot Peening on AlSi10Mg Parts Fabricated by Additive Manufacturing

by Ahmed H. Maamoun, Mohamed A. Elbestawi and Stephen C. Veldhuis

J. Manuf. Mater. Process. 2018, 2(3), 40; https://doi.org/10.3390/jmmp2030040 - 24 Jun 2018

Cited by 100 | Viewed by 13584

Abstract

The additive manufacturing (AM) of aluminum alloys promises to considerably enhance the performance of lightweight critical parts in various industrial applications. AlSi10Mg is one of the compatible Al alloys used in the selective laser melting of lightweight components. However, the surface defects obtained from the as-built parts affect their mechanical properties, and thus represent an obstacle to using them as final products. This study aims to improve the surface characteristics of the as-built AlSi10Mg parts using shot peening (SP). To achieve this goal, different SP intensities were applied to various surface textures of the as-built samples. The SP results showed a significant improvement in the as-built surface topography and a higher value of effective depth using 22.9 A intensity and Gp165 glass beads. The area near the shot-peened surface showed a significant microstructure refinement to a specific depth due to the dynamic precipitation of nanoscale Si particles. Surface hardening was also detected and high compressive residual stresses were generated due to severe plastic deformation. The surface characteristics obtained after SP could result in a significant improvement in the mechanical properties and fatigue strength, and thus promise performance enhancement for critical parts in various industrial applications. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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14 pages, 8550 KiB

Open AccessArticle

Porosity, Surface Quality, Microhardness and Microstructure of Selective Laser Melted 316L Stainless Steel Resulting from Finish Machining

by Yusuf Kaynak and Ozhan Kitay

J. Manuf. Mater. Process. 2018, 2(2), 36; https://doi.org/10.3390/jmmp2020036 - 05 Jun 2018

Cited by 51 | Viewed by 6307

Abstract

Among additive manufacturing (AM) techniques, Selective Laser Melting (SLM) is widely used to fabricate metal components, including biocompatible bone implants made of 316L stainless steel. However, an issue with the components manufactured using this technique is the surface quality, which is generally beyond the acceptable range. Thus, hybrid manufacturing, including AM and finish machining processes, are being developed and implemented in the industry. Machining processes, particularly finish machining, are needed to improve surface quality of additively manufactured components and performance. This study focuses on the finish machining process of additively manufactured 316L stainless steel parts. Finish machining tests were carried out under dry conditions for various cutting speeds and feed rates. The experimental study reveals that finish machining resulted in up to 88% lower surface roughness of SLMed 316L stainless steel; it also had a substantial effect on microstructure and microhardness of the additively manufactured components by creating smaller grains and strain-hardened layer on the surface and subsurface of the SLMed part. The finish machining process also significantly decreased the density of porosity on the surface and subsurface, compared to an as-built sample. The created strain harden layer with less porosity is expected to increases wear and fatigue resistance of these parts. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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21 pages, 9546 KiB

Open AccessArticle

Microstructural and Microhardness Evolution from Homogenization and Hot Isostatic Pressing on Selective Laser Melted Inconel 718: Structure, Texture, and Phases

by Raiyan Seede, Ahmad Mostafa, Vladimir Brailovski, Mohammad Jahazi and Mamoun Medraj

J. Manuf. Mater. Process. 2018, 2(2), 30; https://doi.org/10.3390/jmmp2020030 - 16 May 2018

Cited by 50 | Viewed by 6325

Abstract

In this work, the microstructure, texture, phases, and microhardness of 45° printed (with respect to the build direction) homogenized, and hot isostatically pressed (HIP) cylindrical IN718 specimens are investigated. Phase morphology, grain size, microhardness, and crystallographic texture at the bottom of each specimen differ from those of the top due to changes in cooling rate. High cooling rates during the printing process generated a columnar grain structure parallel to the building direction in the as-printed condition with a texture transition from (001) orientation at the bottom of the specimen to (111) orientation towards the specimen top based on EBSD analysis. A mixed columnar and equiaxed grain structure associated with about a 15% reduction in texture is achieved after homogenization treatment. HIP treatment caused significant grain coarsening, and engendered equiaxed grains with an average diameter of 154.8 µm. These treatments promoted the growth of δ-phase (Ni₃Nb) and MC-type brittle (Ti, Nb)C carbides at grain boundaries. Laves phase (Fe₂Nb) was also observed in the as-printed and homogenized specimens. Ostwald ripening of (Ti, Nb)C carbides caused excessive grain growth at the bottom of the HIPed IN718 specimens, while smaller grains were observed at their top. Microhardness in the as-fabricated specimens was 236.9 HV and increased in the homogenized specimens by 19.3% to 282.6 HV due to more even distribution of secondary precipitates, and the nucleation of smaller grains. A 36.1% reduction in microhardness to 180.5 HV was found in the HIPed condition due to

γ^{″}

phase dissolution and differences in grain morphology. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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24 pages, 11086 KiB

Open AccessFeature PaperArticle

The Static and Fatigue Behavior of AlSiMg Alloy Plain, Notched, and Diamond Lattice Specimens Fabricated by Laser Powder Bed Fusion

by Hugo Soul, Patrick Terriault and Vladimir Brailovski

J. Manuf. Mater. Process. 2018, 2(2), 25; https://doi.org/10.3390/jmmp2020025 - 20 Apr 2018

Cited by 9 | Viewed by 6249

Abstract

The fabrication of engineered lattice structures has recently gained momentum due to the development of novel additive manufacturing techniques. Interest in lattice structures resides not only in the possibility of obtaining efficient lightweight materials, but also in the functionality of pre-designed architectured structures for specific applications, such as biomimetic implants, chemical catalyzers, and heat transfer devices. The mechanical behaviour of lattice structures depends not only the composition of the base material, but also on the type and size of the unit cells, as well as on the material microstructure resulting from a specific fabrication procedure. The present work focuses on the static and fatigue behavior of diamond cell lattice structures fabricated from an AlSiMg alloy by laser powder bed fusion technology. In particular, the specimens were fabricated with three different orientations of lattice cells—[001], [011], [111]—and subjected to static tensile testing and force-controlled pull–pull fatigue testing up to 1 × 10⁷ cycles. In parallel, the mechanical behavior of dense tensile plain and notched specimens was also studied and compared to that of their lattice counterparts. Results showed a significant effect of the cell orientation on the fatigue lives: specimens oriented at [001] were ~30% more fatigue-resistant than specimens oriented at [011] and [111]. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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13 pages, 42667 KiB

Open AccessArticle

Additive Manufacturing of Overhang Structures Using Moisture-Cured Silicone with Support Material

by Mohan Muthusamy, Shahriar Safaee and Roland K. Chen

J. Manuf. Mater. Process. 2018, 2(2), 24; https://doi.org/10.3390/jmmp2020024 - 17 Apr 2018

Cited by 20 | Viewed by 6483

Abstract

Additive manufacturing (AM) of soft materials has a wide variety of applications, such as customized or wearable devices. Silicone is one popular material for these applications given its favorable material properties. However, AM of silicone parts with overhang structures remains challenging due to the soft nature of the material. Overhang structures are the areas where there is no underlying structure. Typically, a support material is used and built in the underlying space so that the overhang structures can be built upon it. Currently, there is no support structure that has been used for AM of silicone. The goal of this study is to develop an AM process to fabricate silicone parts with overhang structures. We first identified and confirmed poly-vinyl alcohol (PVA), a water-soluble material, as a suitable support material for silicone by evaluating the adhesion strength between silicone and PVA. Process parameters for the support material, including critical overhang angle and minimum infill density for the support material, are identified. However, overhang angle alone is not the only determining factor for support material. As silicone is a soft material, it deflects due to its own weight when the height of the overhang structure increases. A finite element model is developed to estimate the critical overhang height paired with different overhang angles to determine whether the use of support material is needed. Finally, parts with overhang structures are printed to demonstrate the capability of the developed process. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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11 pages, 9029 KiB

Open AccessArticle

Applications of Open Source GMAW-Based Metal 3-D Printing

by Yuenyong Nilsiam, Paul G. Sanders and Joshua M. Pearce

J. Manuf. Mater. Process. 2018, 2(1), 18; https://doi.org/10.3390/jmmp2010018 - 13 Mar 2018

Cited by 13 | Viewed by 16214

Abstract

The metal 3-D printing market is currently dominated by high-end applications, which make it inaccessible for small and medium enterprises, fab labs, and individual makers who are interested in the ability to prototype and additively manufacture final products in metal. Recent progress led to low-cost open-source metal 3-D printers using a gas metal arc welding (GMAW)-based print head. This reduced the cost of metal 3-D printers into the range of desktop prosumer polymer 3-D printers. Consequent research established good material properties of metal 3-D printed parts with readily-available weld filler wire, reusable substrates, thermal and stress properties, toolpath planning, bead-width control, mechanical properties, and support for overhangs. These previous works showed that GMAW-based metal 3-D printing has a good adhesion between layers and is not porous inside the printed parts, but they did not proceed far enough to demonstrate applications. In this study, the utility of the GMAW approach to 3-D printing is investigated using a low-cost open-source metal 3-D printer and a converted Computer Numerical Control router machine to make useful parts over a range of applications including: fixing an existing part by adding a 3-D metal feature, creating a product using the substrate as part of the component, 3-D printing in high resolution of useful objects, near net objects, and making an integrated product using a combination of steel and polymer 3-D printing. The results show that GMAW-based 3-D printing is capable of distributed manufacturing of useful products for a wide variety of applications for sustainable development. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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27 pages, 9691 KiB

Open AccessArticle

Characterization and Processing Behavior of Heated Aluminum-Polycarbonate Composite Build Plates for the FDM Additive Manufacturing Process

by Sherri L. Messimer, Albert E. Patterson, Nasiha Muna, Akshay P. Deshpande and Tais Rocha Pereira

J. Manuf. Mater. Process. 2018, 2(1), 12; https://doi.org/10.3390/jmmp2010012 - 16 Feb 2018

Cited by 33 | Viewed by 11755

Abstract

One of the most essential components of the fused deposition modeling (FDM) additive manufacturing (AM) process is the build plate, the surface upon which the part is constructed. These are typically made from aluminum or glass, but there are clear disadvantages to both and restrictions on which materials can be processed on them successfully. This study examined the suitability of heated aluminum-polycarbonate (AL-PC) composite print beds for FDM, looking particularly at the mechanical properties, thermal behavior, deformation behavior, bonding strength with deposited material, printing quality, and range of material usability. Theoretical examination and physical experiments were performed for each of these areas; the results were compared to similar experiments done using heated aluminum and aluminum-glass print beds. Ten distinct materials (ABS, PLA, PET, HIPS, PC, TPU, PVA, nylon, metal PLA, and carbon-fiber PLA) were tested for printing performance. The use of a heated AL-PC print bed was found to be a practical option for most of the materials, particularly ABS and TPU, which are often challenging to process using traditional print bed types. Generally, the results were found to be equivalent to or superior to tempered glass and superior to standard aluminum build plates in terms of printing capability. Full article

(This article belongs to the Special Issue Additive Manufacturing)

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