Optimum bushing length in thermal drilling of galvanized steel using artificial neural network coupled with genetic algorithm
Optimalna dol`ina podpore ({ablone, vodila) pri termi~nem vrtanju galvaniziranega jekla z uporabo umetne nevronske mre`e in
genetskega algoritma
N. Rajesh J. Hynes, R. Kumar, J. A. J. Sujana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 813
Gelling polysaccharide as the electrolyte matrix in a dye-sensitized solar cell
@elirni polisaharid kot elektrolitna osnova v solarnih celicah, ob~utljivih na barvila
J. P. Bantang, D. Camacho . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 823
Development of a heat treatment for increasing the mechanical properties and stress corrosion resistance of 7000 Al alloys
Razvoj toplotne obdelave za izbolj{anje mehanskih lastnosti in napetostno korozijsko odpornost 7000 Al zlitin
M. Shakouri, M. Esmailian, S. Shabestari . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831
Corrosion resistance of as-plated and heat-treated electroless dublex Ni-P/Ni-B-W coatings
Korozijska odpornost platiranih in neelektri~no topolotno obdelanih dupleks Ni-P/Ni-B-W prevlek
B. Yüksel, G. Erdogan, F. E. Bastan, R. A. Yýldý . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837
Short-term creep of P91 heat-resistant steels at low stresses and an instantaneous-stress-change testing
Kratkotrajno lezenje toplotno odpornega jekla P91 pri nizkih napetostih in nenadni menjavi napetosti obremenjevanja
J. Zhe, S. Junjie, Z. Pengshuo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 843
Effect of severe plastic and heavy cold deformation on the structural and mechanical properties of commercially pure
titanium
U~inek plasti~nosti in deformacije pri podhlajevanju na strukturne in mehanske lastnosti ~istega komercialnega titana
J. Palán, P. [utta, T. Kubina, M. Dománková . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 849
Effect of yttrium and zirconium microalloying on the structure and properties of weld joints of a two-phase titanium alloy
U~inek mikrolegiranja itrija in cirkonija na strukturo in lastnosti na spoje zavrov dvofazne zlitine titana
A. Illarionov, A. Popov, S. Illarionova, D. Gadeev . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 855
Microstructure evolution and statistical analysis of Al/Cu friction-stir spot welds
Razvoj mikrostrukture in statisti~na analiza vrtilno-tornih to~kastih zvarov Al/Cu
M. P. Mubiayi, E. T. Akinlabi, M. E. Makhatha . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 861
Synthesis of PMMA/ZnO nanoparticles composite used for resin teeth
Sinteza PMMA/ZnO nanodelcev kompozitov za izdelavo zob iz umetnih smol
D. Popovi}, R. Bobovnik, S. Bolka, M. Vukadinovi}, V. Lazi}, R. Rudolf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 871
ERRATUM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 879
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
709–715
ADDITIVE MANUFACTURING: THE FUTURE OF
MANUFACTURING
DODAJALNA (3D) TEHNOLOGIJA: PRIHODNOST PROIZVAJANJA
Sheriff Adefemi Adekanye1, Rasheedat Modupe Mahamood1,2,
Esther Titilayo Akinlabi2, Moses Gbadebo Owolabi3
1University of Ilorin, Department of Mechanical Engineering, Nigeria
2University of Johannesburg, Department of Mechanical Engineering Science, South Africa
3Howard University, Department of Mechanical Engineering, Washington, USA
adekanyefm@gmail.com
Prejem rokopisa – received: 2016-08-26; sprejem za objavo – accepted for publication: 2017-03-16
doi:10.17222/mit.2016.261
Additive manufacturing is an advanced manufacturing method used to fabricate prototypes, tooling as well as functional
products. Additive manufacturing helps us produce complex parts as single-unit objects, which was not possible with the
traditional manufacturing methods. There are different types of additive-manufacturing technologies, including selective laser
melting, laser-metal-deposition process, fused deposition modeling and electron-beam melting. All these additive-manu-
facturing technologies produce three-dimensional (3D) objects by adding materials layer after layer. A 3D object is built directly
from a 3D computer-aided-design (CAD) model of the object. Additive manufacturing is a very promising method for the
aerospace industry, in particular because of its ability to reduce the buy-to-fly ratio. This technology is the technology of the
future because it is going to change the way products are designed and manufactured. In this research, various additive-manu-
facturing technologies are described in detail and some of the research works in this field are also presented. The future research
directions are also highlighted.
Keywords: additive manufacturing, fused deposition modelling, laser metal deposition, selective laser melting, selective laser
sintering
Dodajalni proizvodni proces je napredna tehnologija, ki se uporablja za izdelavo prototipov, orodij in funkcionalnih izdelkov. Z
naprednim proizvodnim procesom lahko izdelamo izdelke ali dele kompliciranih oblik, ki jih ni mo`no izdelati s tradicionalnimi
metodami proizvodnje. Obstajajo razli~ne vrste naprednih dodajalnih tehnologij, kot so na primer: selektivno lasersko
nataljevanje, proces laserskega nana{anja (depozicije) kovin, modeliranje z nana{anjem staljenih kapljic in taljenje z
elektronskim curkom. Vse te napredne dodajalne tehnologije omogo~ajo izdelavo tridimenzionalnih (3D) izdelkov z dodajanjem
materialov plast za plastjo. Tridimenzionalni produkt je izgrajen neposredno s pomo~jo 3D-ra~unalni{ko podprtega modeliranja
(angl. CAD). Napredna dodajalna proizvodnja je zelo obetavna proizvodna metoda, predvsem v letalski in vesoljski industriji,
{e posebej zaradi sposobnosti zmanj{evanja stro{kov izdelave (zmanj{anje razmerja med maso materiala, potrebnega za izdelavo
dolo~enega izdelka in njegovo dejansko maso).
Klju~ne besede: dodajalna proizvodnja, modeliranje z nana{anjem staljenih materialov, laserska depozicija kovin, selektivno
lasersko nataljevanje, selektivno lasersko sintranje
1 INTRODUCTION
The additive-manufacturing process is an advanced
manufacturing process that produces three-dimensional
(3D) objects directly from the 3D computer-aided-design
(CAD) digital information of the parts by adding ma-
terials layer by layer.1–3 This is different from the tradi-
tional manufacturing that involves material removal or an
energy-intensive process such as machining, casting and
forging. With additive manufacturing, a complex-shaped
product can be produced as a single object, which was
not possible in the past.
For the traditional manufacturing process, complex
parts have to be designed based on the ease of manufact-
uring the parts. Complex parts are usually broken down
into smaller parts because of the ease of manufacturing
those parts and the pieces are assembled at the later stage
through various joining processes. This practice does not
only involve labor-intensive processes but also results in
wastage of materials, in addition to the materials re-
moved during shaping and cutting operations; the excess
materials added for joining also contribute to material
wastage. The net weight of a product is also very large
because of the excess materials used during the
assembly. The additive-manufacturing technology, on the
other hand, can make a product directly from the 3D
CAD model of the product by just adding materials layer
by layer. Irrespective of the complexity, any part that can
be drawn using any computer-aided-design software can
be made and as a single-unit object. Additive-manu-
facturing technologies are classified into seven main
groups, namely: powder-bed fusion, directed energy
deposition, sheet lamination, material extrusion, binder
jetting, material jetting and vat photopolymerization.1 A
designer does not need to worry about the manufactur-
ability of a product; he/she is only concerned with the
functionality of the part being designed.
At the inception, the additive manufacturing process
was used to make prototypes because of the limitation in
Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715 709
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
UDK 620.183.183.4:621.039.337:316.422.44 ISSN 1580-2949
Review article/Pregledni ~lanek MTAEC9, 51(5)709(2017)
the choice of the materials that could be used on an
additive-manufacturing machine at that time.2–4 There are
a number of industries benefiting from this revolutionary
manufacturing technology,5 such as the aerospace, auto-
mobile and biomedical industries.6–9 In this study, some
of these additive-manufacturing technologies are re-
viewed with the aim of throwing light on these techno-
logies and describing their systems of operation as well
as their advantages, limitations and areas of applications.
The rest of the paper is organized as follows: section
2 of the paper presents the powder-bed-based process.
The extrusion-based process and sheet-lamination pro-
cess are presented in sections 3 and 4, respectively. Di-
rected-energy-deposition process is presented in section
5. Material development in additive manufacturing is
presented in section 6, while conclusions are presented
in section 7.
2 POWDER-BED-BASED PROCESS
This class of additive manufacturing technology uses
the energy from an electron beam or laser beam to fuse
or melt powder materials for the manufacturing of
parts.10,11 The additive-manufacturing technologies in
this class include direct metal laser sintering (DMLS),
electron-beam melting (EBM), selective heat sintering
(SHS), selective laser melting (SLM) and selective laser
sintering (SLS). Each of these technologies is described
in this section.
2.1 Direct metal laser sintering (DMLS)
A schematic diagram of direct laser sintering is
shown in Figure 1 below. This process manufactures
parts by compacting a metal powdered material with a
power source such as laser, without melting but by
binding the material together to create a solid structure
defined by the 3D CAD model of the part.12 The working
principle of this technology makes it capable of design-
ing and producing complex geometry of both internal
and external intricacies. In this process, to avoid the
collision of the recoater blade when moving, the building
and dispenser platforms are lowered by the layer
thickness. The powder metal needed to create a layer of
the material is supplied by the dispenser platform after it
has been ensured that the recoater stands in the right
position. The spreading of the metal powder from the
dispenser to the building platform is done by the re-
coater, moving from the right to the left position, and the
excess metal powder falls into the excess-powder
collector. The scan head moves the laser beam through
the two-dimensional (2D) cross-section, which is
switched on and off during the exposure of designated
areas. The powdered metals are generated, cured and
sintered by the solidified areas through the absorption of
energy.13 This process continues to create layer after
layer until the part is completed. Using this process,
parts have been successfully made from the materials
such as aluminium alloys – AlSi10Mg, stainless steel,
titanium alloys and cobalt chrome superalloy.13 Some of
the advantages of this additive-manufacturing process
are highlighted below.12,13
High speed: parts are produced easily within hours
since special tools are not required.
Complex geometry: this technology allows designs of
both internal and external features.
High quality: it creates parts with high accuracy and
detailed resolution.
It provides parts with better mechanical strength.
In spite of all these advantages, some of the limiting
factors are as follows: the process is expensive and
power intensive, the surface needs to be polished and the
metal support structure removed, and the thermal
post-processing is time consuming.14,15
2.2 Electron-beam melting
Figure 2 shows a schematic presentation of an
electron-beam process. Parts are developed by adding
material layer by layer, following the path described by
the 3D CAD data program.16 Electron beam is generated
within an electron-beam gun; the tungsten filament is
heated to an extremely high temperature so that it
releases electrons; the electrons are accelerated with an
electric field and then focused with electromagnetic
coils.17,18 The electron beam melts each layer of the
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
710 Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: Schematic diagram of the direct metal laser sintering
system14
Figure 2: Schematic drawing of an electron-beam additive-manu-
facturing machine18
metal powder to the desired geometry in a vacuum; the
process in the vacuum eliminates impurities and yields
high-strength properties of the material under
processing.16 The materials used for electron-beam
melting are mainly steel and titanium alloy. The
following advantages are characteristic of this
technology:17
• an increased efficiency of the raw-material use,
• the vacuum eliminates impurities and provides a
good thermal environment for a freeform fabrication,
• it significantly reduces the amount of finishing
operations,
• freedom in design – design for functionality,
• processing of high-melting-point and highly reactive
materials,
• decreased lead times for design and fabrication,
• a high degree of component customization.
Some of the disadvantages of the electron-beam
technology include the following:19
• It requires a vacuum, another system to the machine,
which must be maintained, leading to a high cost.
• It produces X-rays while in operation, which is
hazardous.
2.3 Selective laser sintering
Selective laser sintering is also a powder-bed-based
technology that involves the spreading of powder and the
subsequent compaction. A schematic diagram of the
selective laser sintering is shown in Figure 3. The set-up
is made up of a laser, an automatic powder-layering
apparatus, and a computer system for process control.20
Selective laser sintering uses a substrate for the part
fabrication, which is fixed onto the building platform and
leveled. The sealed building chamber containing oxygen
has a reduced amount of oxygen due to the protective
inert gas such as argon, which is fed into the chamber. A
thin layer of a loose powder is deposited on the substrate
by the layering mechanism. The laser beam scans the
powder-bed surface through the CAD program forming
layers of the material to be produced. The powder
spreading and laser-treatment process are repeated and
the parts are built layer by layer until completion.21–23
This technology allows a variety of materials, the most
common are: wax, paraffin, polymer-metal powders or
various types of steel alloys, polymers, nylon and carbo-
nates.24 The advantages of using selective laser sintering
include:
• parts can be created out of a wide selection of
materials,
• complex geometry is made easy as long as the
non-sintered powder can be removed easily,
• when printing overhanging, unsupported structures,
supports are not needed because the unused powder
provides the necessary support.
Disadvantages of selective laser sintering are:
• the equipment is very expensive,
• the most common problem of this technology is that
the fabricated parts are porous and the surface could
be rough, depending on the materials used,
• thermal distortion occurs on polymer parts and can
cause shrinking and warping of the fabricated parts.
2.4 Selective heat sintering
Figure 4 shows a schematic presentation of the
selective-heat-sintering process, which operates by selec-
tively fusing a thin layer of polymer powder through a
thermal print-head assembly. This assembly operates
bi-directionally and incorporates thermal print heads at
point A as shown in the diagram. The part labelled as B
is the powder-deposition mechanism, C is the layer
heater, D is the chamber for the material built up in an
internal build volume, E is the floor that is a vertically
movable building platform; at F, fresh powder is supplied
via scoops to the powder-deposition mechanism from the
powder containers.25 The heated building platform builds
up the parts, using the layer technology, with the roller
spreading across the plastic powders in layers. The
thermal print head of the apparatus forms a part in its full
cross-section with the already laid powder. The heat at
the building platform sinters the top layer of the powder;
once completed, the process is repeated until a complete
3D object is produced. The complex geometries pro-
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715 711
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Schematic presentation of selective heat sintering25
Figure 3: Schematic presentation of a selective-laser-sintering
apparatus21
the choice of the materials that could be used on an
additive-manufacturing machine at that time.2–4 There are
a number of industries benefiting from this revolutionary
manufacturing technology,5 such as the aerospace, auto-
mobile and biomedical industries.6–9 In this study, some
of these additive-manufacturing technologies are re-
viewed with the aim of throwing light on these techno-
logies and describing their systems of operation as well
as their advantages, limitations and areas of applications.
The rest of the paper is organized as follows: section
2 of the paper presents the powder-bed-based process.
The extrusion-based process and sheet-lamination pro-
cess are presented in sections 3 and 4, respectively. Di-
rected-energy-deposition process is presented in section
5. Material development in additive manufacturing is
presented in section 6, while conclusions are presented
in section 7.
2 POWDER-BED-BASED PROCESS
This class of additive manufacturing technology uses
the energy from an electron beam or laser beam to fuse
or melt powder materials for the manufacturing of
parts.10,11 The additive-manufacturing technologies in
this class include direct metal laser sintering (DMLS),
electron-beam melting (EBM), selective heat sintering
(SHS), selective laser melting (SLM) and selective laser
sintering (SLS). Each of these technologies is described
in this section.
2.1 Direct metal laser sintering (DMLS)
A schematic diagram of direct laser sintering is
shown in Figure 1 below. This process manufactures
parts by compacting a metal powdered material with a
power source such as laser, without melting but by
binding the material together to create a solid structure
defined by the 3D CAD model of the part.12 The working
principle of this technology makes it capable of design-
ing and producing complex geometry of both internal
and external intricacies. In this process, to avoid the
collision of the recoater blade when moving, the building
and dispenser platforms are lowered by the layer
thickness. The powder metal needed to create a layer of
the material is supplied by the dispenser platform after it
has been ensured that the recoater stands in the right
position. The spreading of the metal powder from the
dispenser to the building platform is done by the re-
coater, moving from the right to the left position, and the
excess metal powder falls into the excess-powder
collector. The scan head moves the laser beam through
the two-dimensional (2D) cross-section, which is
switched on and off during the exposure of designated
areas. The powdered metals are generated, cured and
sintered by the solidified areas through the absorption of
energy.13 This process continues to create layer after
layer until the part is completed. Using this process,
parts have been successfully made from the materials
such as aluminium alloys – AlSi10Mg, stainless steel,
titanium alloys and cobalt chrome superalloy.13 Some of
the advantages of this additive-manufacturing process
are highlighted below.12,13
High speed: parts are produced easily within hours
since special tools are not required.
Complex geometry: this technology allows designs of
both internal and external features.
High quality: it creates parts with high accuracy and
detailed resolution.
It provides parts with better mechanical strength.
In spite of all these advantages, some of the limiting
factors are as follows: the process is expensive and
power intensive, the surface needs to be polished and the
metal support structure removed, and the thermal
post-processing is time consuming.14,15
2.2 Electron-beam melting
Figure 2 shows a schematic presentation of an
electron-beam process. Parts are developed by adding
material layer by layer, following the path described by
the 3D CAD data program.16 Electron beam is generated
within an electron-beam gun; the tungsten filament is
heated to an extremely high temperature so that it
releases electrons; the electrons are accelerated with an
electric field and then focused with electromagnetic
coils.17,18 The electron beam melts each layer of the
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
710 Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 1: Schematic diagram of the direct metal laser sintering
system14
Figure 2: Schematic drawing of an electron-beam additive-manu-
facturing machine18
metal powder to the desired geometry in a vacuum; the
process in the vacuum eliminates impurities and yields
high-strength properties of the material under
processing.16 The materials used for electron-beam
melting are mainly steel and titanium alloy. The
following advantages are characteristic of this
technology:17
• an increased efficiency of the raw-material use,
• the vacuum eliminates impurities and provides a
good thermal environment for a freeform fabrication,
• it significantly reduces the amount of finishing
operations,
• freedom in design – design for functionality,
• processing of high-melting-point and highly reactive
materials,
• decreased lead times for design and fabrication,
• a high degree of component customization.
Some of the disadvantages of the electron-beam
technology include the following:19
• It requires a vacuum, another system to the machine,
which must be maintained, leading to a high cost.
• It produces X-rays while in operation, which is
hazardous.
2.3 Selective laser sintering
Selective laser sintering is also a powder-bed-based
technology that involves the spreading of powder and the
subsequent compaction. A schematic diagram of the
selective laser sintering is shown in Figure 3. The set-up
is made up of a laser, an automatic powder-layering
apparatus, and a computer system for process control.20
Selective laser sintering uses a substrate for the part
fabrication, which is fixed onto the building platform and
leveled. The sealed building chamber containing oxygen
has a reduced amount of oxygen due to the protective
inert gas such as argon, which is fed into the chamber. A
thin layer of a loose powder is deposited on the substrate
by the layering mechanism. The laser beam scans the
powder-bed surface through the CAD program forming
layers of the material to be produced. The powder
spreading and laser-treatment process are repeated and
the parts are built layer by layer until completion.21–23
This technology allows a variety of materials, the most
common are: wax, paraffin, polymer-metal powders or
various types of steel alloys, polymers, nylon and carbo-
nates.24 The advantages of using selective laser sintering
include:
• parts can be created out of a wide selection of
materials,
• complex geometry is made easy as long as the
non-sintered powder can be removed easily,
• when printing overhanging, unsupported structures,
supports are not needed because the unused powder
provides the necessary support.
Disadvantages of selective laser sintering are:
• the equipment is very expensive,
• the most common problem of this technology is that
the fabricated parts are porous and the surface could
be rough, depending on the materials used,
• thermal distortion occurs on polymer parts and can
cause shrinking and warping of the fabricated parts.
2.4 Selective heat sintering
Figure 4 shows a schematic presentation of the
selective-heat-sintering process, which operates by selec-
tively fusing a thin layer of polymer powder through a
thermal print-head assembly. This assembly operates
bi-directionally and incorporates thermal print heads at
point A as shown in the diagram. The part labelled as B
is the powder-deposition mechanism, C is the layer
heater, D is the chamber for the material built up in an
internal build volume, E is the floor that is a vertically
movable building platform; at F, fresh powder is supplied
via scoops to the powder-deposition mechanism from the
powder containers.25 The heated building platform builds
up the parts, using the layer technology, with the roller
spreading across the plastic powders in layers. The
thermal print head of the apparatus forms a part in its full
cross-section with the already laid powder. The heat at
the building platform sinters the top layer of the powder;
once completed, the process is repeated until a complete
3D object is produced. The complex geometries pro-
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715 711
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 4: Schematic presentation of selective heat sintering25
Figure 3: Schematic presentation of a selective-laser-sintering
apparatus21
duced are supported by the excess material surrounding
the object.26
This technology uses thermoplastic powder as its
working material. The benefits of this technology are as
follows: it allows inexpensive manufacturing and a good
concept evaluation; the thermal print heads are less
expensive and the overall cost is affordable.
2.5 Selective laser melting
Selective laser melting is similar to the selective-
laser-sintering process, with the main difference being
between full melting and fusing in selective laser sinter-
ing. The process begins with designing a 3D CAD
model; the model is broken down into parts to form a
number of finite layers. For each layer, the laser scan
path is calculated, defining both the boundary contour
and the form of the fill sequence called the raster pattern.
Layers are formed by spreading powder on the build
platform and then the laser melts the powder with the
scanning laser beam; the melted powder solidifies to
form a 3D solid component.27 A schematic diagram of
the process is shown in Figure 5.28
Different materials used with this technology include
steel, titanium, aluminium, cobalt-chromium and nickel
alloys. The benefits of using the selective-laser-melting
technology are as follows:
• it minimizes material wastage and saves costs,
• improved production-development cycle,
• it allows for complex geometry to be made,
• ideal process for a low-volume production,
• improved buy-to-fly ratio,
• functionally graded parts can be produced,
• it allows for fully customized parts that suit indi-
viduals.
The disadvantages of selective laser melting are as
follows:
• it is an expensive and a very slow process,
• tolerances and surface finishes are limited because of
the sticking of the unused powder on the surface of
the produced part.
3 EXTRUSION-BASED SYSTEM
An extrusion-based system uses material extrusion
where the material is heated to the molten state and then
extruded through a nozzle to form parts layer by layer.
The most common technology is fused deposition
modeling (FDM). A schematic diagram of the process is
shown in Figure 6.
Fused deposition modeling produces components by
depositing extruded material in layers through a nozzle.
Fused deposition modeling uses a 3D CAD program to
prepare and build a model; the material is heated to the
molten state and forced through the nozzle under
pressure to build up a component.29 The advantages of
fused deposition modeling are as follows:
• the technology supports complex geometries and
cavities,
• the technology produces high-grade parts,
• it is simple to use.
The limitations of fused deposition modeling are:
• limitation on the materials that can be used,
• limited size,
• the cost of the actual machine.
This technology uses different materials for compo-
nent fabrication, including acrylonitrile butadiene
styrene (ABS), polylactic acid (PLA), polycarbonate
(PC), polyamide (PA), polystyrene (PS), lignin, rubber,
nylon and others.29
4 SHEET-LAMINATION PROCESS
This is an additive-manufacturing technology, which
mainly uses metal sheets or paper for the manufacturing
process. This technology is characterized by a low cost
of production, high strength of the model, possibilities to
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
712 Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 6: Presentation of an extrusion-based system29Figure 5: Schematic presentation of selective laser melting28
control the range of speed of the process to create the
outcome desired. Apart from the benefits achieved when
using this technology, there are also limitations: the pro-
perties of the outcome product depends on the material
used and the process of fusing the material together
needs improved techniques.30
There are two variants of this process, namely: ultra-
sonic additive manufacturing (UAM) and laminated
object manufacturing (LOM). Ultrasonic additive manu-
facturing (UAM) uses metal as its working material and
employs the layer-by-layer techniques, whereby the
layers are welded together ultrasonically. This process
uses metals like aluminum, copper, stainless steel and
titanium alloy. Laminated object manufacturing (LOM)
incorporates the layer-by-layer lamination technique,
using sheets of paper as the working material and CO2
laser for cutting a sheet that has been joined together by
an adhesive to form layers of CAD-model parts. The
excess material that is not part of the component being
built is sliced into cubes, using a cross-hutch cutting
operation.31
5 DIRECTED ENERGY DEPOSITION
Directed energy deposition is a type of additive
manufacturing that uses the energy from a laser or elec-
tron beam to create a melt pool on the surface of the
substrate, where coaxial powder or wire is deposited,
following the path described by a CAD profile. An
example of this process is laser metal deposition, also
known as laser engineered net shaping (LENS), a pro-
cess with high material-utilization efficiency and cost
efficiency.32–41 The laser, or electron beam, leaves a solid
track of the melted powder. A schematic diagram of this
process is shown in Figure 7. The advantages of directed
energy deposition include the ability to carry out a
high-value repair on a part that was cost prohibitive in
the past; it can also be used to manufacture parts with
functionally graded materials or functionally graded
coatings.39–41 The materials that can be used for this tech-
nology include metals, alloys, ceramics and composites.
Other additive-manufacturing processes are material
jetting, binder jetting and the vat photopolymerization
process. These types of additive manufacturing use non-
metallic based materials and their applications are
limited. For further reading about these and other
additive-manufacturing processes, the reader can consult
references.42–52
A new 3D printing technology was developed and it
will help us create metallic, free-standing 3D structures.
This technology was developed by the researchers at
Harvard University.53 The existing direct ink writing 3D
printing technology is combined with laser annealing to
ensure accurate and stable free-standing 3D structures.
This technology is very useful in the applications where
free-standing 3D microstructures are required, e.g., in
sensors, electronics and also in biomedical applications.
6 MATERIAL DEVELOPMENT FOR ADDITIVE
MANUFACTURING
There is constant demand for light materials with
improved properties, especially in the automobile and
aerospace industries, with the aim of reducing the global
warming. The advent of additive manufacturing is the
beginning of a new dawn in the manufacturing indus-
tries. A number of restrictions were placed on material
development in the past because of thermodynamic
limitations as well as the difficulties in processing some
materials in the bulk form. With additive-manufacturing
technologies, new materials are now being developed
without any restriction. A number of complex metallic
alloys are now being developed and used for the fabri-
cation of important light-weight structures with im-
pressive properties, using the additive-manufacturing
process.54 Complex metallic alloys are intermetallic
compounds with unique thermal and transport properties
that cannot be found in any metal system.55
Complex metallic alloys are needed in a number of
applications because of their excellent properties, but
they cannot be used with the conventional manufacturing
processes because of their brittleness that makes them
difficult to process. These materials have low coeffi-
cients of friction, good corrosion resistance, good wear-
resistance properties and can now be processed using
additive manufacturing. New composite materials with
improved properties are introduced and used in additive-
manufacturing processes, with the functional-part pro-
duction now being commercialized.54 The traditional
manufacturing process presents a lot of challenges when
processing these materials because of the segregation of
constituent materials due to the thermodynamic proper-
ties of individual materials, but additive-manufacturing
technologies can be used to process these materials
without such problems.
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715 713
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 7: Schematic diagram of directed energy deposition41
duced are supported by the excess material surrounding
the object.26
This technology uses thermoplastic powder as its
working material. The benefits of this technology are as
follows: it allows inexpensive manufacturing and a good
concept evaluation; the thermal print heads are less
expensive and the overall cost is affordable.
2.5 Selective laser melting
Selective laser melting is similar to the selective-
laser-sintering process, with the main difference being
between full melting and fusing in selective laser sinter-
ing. The process begins with designing a 3D CAD
model; the model is broken down into parts to form a
number of finite layers. For each layer, the laser scan
path is calculated, defining both the boundary contour
and the form of the fill sequence called the raster pattern.
Layers are formed by spreading powder on the build
platform and then the laser melts the powder with the
scanning laser beam; the melted powder solidifies to
form a 3D solid component.27 A schematic diagram of
the process is shown in Figure 5.28
Different materials used with this technology include
steel, titanium, aluminium, cobalt-chromium and nickel
alloys. The benefits of using the selective-laser-melting
technology are as follows:
• it minimizes material wastage and saves costs,
• improved production-development cycle,
• it allows for complex geometry to be made,
• ideal process for a low-volume production,
• improved buy-to-fly ratio,
• functionally graded parts can be produced,
• it allows for fully customized parts that suit indi-
viduals.
The disadvantages of selective laser melting are as
follows:
• it is an expensive and a very slow process,
• tolerances and surface finishes are limited because of
the sticking of the unused powder on the surface of
the produced part.
3 EXTRUSION-BASED SYSTEM
An extrusion-based system uses material extrusion
where the material is heated to the molten state and then
extruded through a nozzle to form parts layer by layer.
The most common technology is fused deposition
modeling (FDM). A schematic diagram of the process is
shown in Figure 6.
Fused deposition modeling produces components by
depositing extruded material in layers through a nozzle.
Fused deposition modeling uses a 3D CAD program to
prepare and build a model; the material is heated to the
molten state and forced through the nozzle under
pressure to build up a component.29 The advantages of
fused deposition modeling are as follows:
• the technology supports complex geometries and
cavities,
• the technology produces high-grade parts,
• it is simple to use.
The limitations of fused deposition modeling are:
• limitation on the materials that can be used,
• limited size,
• the cost of the actual machine.
This technology uses different materials for compo-
nent fabrication, including acrylonitrile butadiene
styrene (ABS), polylactic acid (PLA), polycarbonate
(PC), polyamide (PA), polystyrene (PS), lignin, rubber,
nylon and others.29
4 SHEET-LAMINATION PROCESS
This is an additive-manufacturing technology, which
mainly uses metal sheets or paper for the manufacturing
process. This technology is characterized by a low cost
of production, high strength of the model, possibilities to
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
712 Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 6: Presentation of an extrusion-based system29Figure 5: Schematic presentation of selective laser melting28
control the range of speed of the process to create the
outcome desired. Apart from the benefits achieved when
using this technology, there are also limitations: the pro-
perties of the outcome product depends on the material
used and the process of fusing the material together
needs improved techniques.30
There are two variants of this process, namely: ultra-
sonic additive manufacturing (UAM) and laminated
object manufacturing (LOM). Ultrasonic additive manu-
facturing (UAM) uses metal as its working material and
employs the layer-by-layer techniques, whereby the
layers are welded together ultrasonically. This process
uses metals like aluminum, copper, stainless steel and
titanium alloy. Laminated object manufacturing (LOM)
incorporates the layer-by-layer lamination technique,
using sheets of paper as the working material and CO2
laser for cutting a sheet that has been joined together by
an adhesive to form layers of CAD-model parts. The
excess material that is not part of the component being
built is sliced into cubes, using a cross-hutch cutting
operation.31
5 DIRECTED ENERGY DEPOSITION
Directed energy deposition is a type of additive
manufacturing that uses the energy from a laser or elec-
tron beam to create a melt pool on the surface of the
substrate, where coaxial powder or wire is deposited,
following the path described by a CAD profile. An
example of this process is laser metal deposition, also
known as laser engineered net shaping (LENS), a pro-
cess with high material-utilization efficiency and cost
efficiency.32–41 The laser, or electron beam, leaves a solid
track of the melted powder. A schematic diagram of this
process is shown in Figure 7. The advantages of directed
energy deposition include the ability to carry out a
high-value repair on a part that was cost prohibitive in
the past; it can also be used to manufacture parts with
functionally graded materials or functionally graded
coatings.39–41 The materials that can be used for this tech-
nology include metals, alloys, ceramics and composites.
Other additive-manufacturing processes are material
jetting, binder jetting and the vat photopolymerization
process. These types of additive manufacturing use non-
metallic based materials and their applications are
limited. For further reading about these and other
additive-manufacturing processes, the reader can consult
references.42–52
A new 3D printing technology was developed and it
will help us create metallic, free-standing 3D structures.
This technology was developed by the researchers at
Harvard University.53 The existing direct ink writing 3D
printing technology is combined with laser annealing to
ensure accurate and stable free-standing 3D structures.
This technology is very useful in the applications where
free-standing 3D microstructures are required, e.g., in
sensors, electronics and also in biomedical applications.
6 MATERIAL DEVELOPMENT FOR ADDITIVE
MANUFACTURING
There is constant demand for light materials with
improved properties, especially in the automobile and
aerospace industries, with the aim of reducing the global
warming. The advent of additive manufacturing is the
beginning of a new dawn in the manufacturing indus-
tries. A number of restrictions were placed on material
development in the past because of thermodynamic
limitations as well as the difficulties in processing some
materials in the bulk form. With additive-manufacturing
technologies, new materials are now being developed
without any restriction. A number of complex metallic
alloys are now being developed and used for the fabri-
cation of important light-weight structures with im-
pressive properties, using the additive-manufacturing
process.54 Complex metallic alloys are intermetallic
compounds with unique thermal and transport properties
that cannot be found in any metal system.55
Complex metallic alloys are needed in a number of
applications because of their excellent properties, but
they cannot be used with the conventional manufacturing
processes because of their brittleness that makes them
difficult to process. These materials have low coeffi-
cients of friction, good corrosion resistance, good wear-
resistance properties and can now be processed using
additive manufacturing. New composite materials with
improved properties are introduced and used in additive-
manufacturing processes, with the functional-part pro-
duction now being commercialized.54 The traditional
manufacturing process presents a lot of challenges when
processing these materials because of the segregation of
constituent materials due to the thermodynamic proper-
ties of individual materials, but additive-manufacturing
technologies can be used to process these materials
without such problems.
S. A. ADEKANYE et al.: ADDITIVE MANUFACTURING: THE FUTURE OF MANUFACTURING
Materiali in tehnologije / Materials and technology 51 (2017) 5, 709–715 713
MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
Figure 7: Schematic diagram of directed energy deposition41
A number of new materials with improved properties
and performances are now being developed for the
additive-manufacturing technologies. These new mate-
rials include the high-temperature copper alloy, deve-
loped by NASA, with excellent properties such as
retention of high strength at elevated temperatures, used
in rocket engines. Other materials that present challenges
with the conventional manufacturing processes and are
now successfully processed using the additive-manu-
facturing technologies include titanium aluminide, used
in the fabrication of high-speed gas-turbine blades,
reactor-grade pure niobium and NiTi.
7 CONCLUSIONS
The concept of additive manufacturing has provided
solutions to most engineering problems, especially the
problems faced by product designers in the past when
products needed to be designed and redesigned because
of the limitations imposed by the available manu-
facturing process. Designers can now freely design parts
without having to worry about how they will be made.
This research paper presents a review on various
additive-manufacturing technologies. The aim of this
paper is to provide a clear description of this novel
manufacturing process – the additive-manufacturing
process. Each of the technologies is described in this
paper, including the materials suitable for use in each
technology, advantages, disadvantages. Application areas
and the new material development relating to the addi-
tive-manufacturing technologies are presented. In
summary, additive manufacturing is a reliable techno-
logy that can be used to manufacture prototypes, tooling
and functional parts, as it is less time consuming, allow-
ing an easy fabrication of a complex geometry, an easy
production of customized and personalized parts, with-
out any need for special tools, and low material wastage
that reduces the overall cost of the production. Im-
provements in the computing power and the reduction in
mass-storage costs paved the way for processing the
large amounts of data typical of modern 3D CAD models
within reasonable time frames.
A new 3D printing technology has recently been
developed at Harvard University. This new additive-
manufacturing technology combines the existing direct
ink writing 3D printing technology and the annealing
process. The innovation was born out of the necessity for
flexible and wearable electronic devices such as sensors
and in biomedical applications. The technology uses the
3D printing technology to create complex architectures,
while a printed structure is simultaneously annealed in
midair. This helps to increase the accuracy of the printed
material, also allowing the printed material to be created
in free air without the need for any support structure.
This technology has opened up possibilities of creating
microscopic metallic free-standing 3D structures without
an auxiliary support and in a single manufacturing run.
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MATERIALI IN TEHNOLOGIJE/MATERIALS AND TECHNOLOGY (1967–2017) – 50 LET/50 YEARS
A number of new materials with improved properties
and performances are now being developed for the
additive-manufacturing technologies. These new mate-
rials include the high-temperature copper alloy, deve-
loped by NASA, with excellent properties such as
retention of high strength at elevated temperatures, used
in rocket engines. Other materials that present challenges
with the conventional manufacturing processes and are
now successfully processed using the additive-manu-
facturing technologies include titanium aluminide, used
in the fabrication of high-speed gas-turbine blades,
reactor-grade pure niobium and NiTi.
7 CONCLUSIONS
The concept of additive manufacturing has provided
solutions to most engineering problems, especially the
problems faced by product designers in the past when
products needed to be designed and redesigned because
of the limitations imposed by the available manu-
facturing process. Designers can now freely design parts
without having to worry about how they will be made.
This research paper presents a review on various
additive-manufacturing technologies. The aim of this
paper is to provide a clear description of this novel
manufacturing process – the additive-manufacturing
process. Each of the technologies is described in this
paper, including the materials suitable for use in each
technology, advantages, disadvantages. Application areas
and the new material development relating to the addi-
tive-manufacturing technologies are presented. In
summary, additive manufacturing is a reliable techno-
logy that can be used to manufacture prototypes, tooling
and functional parts, as it is less time consuming, allow-
ing an easy fabrication of a complex geometry, an easy
production of customized and personalized parts, with-
out any need for special tools, and low material wastage
that reduces the overall cost of the production. Im-
provements in the computing power and the reduction in
mass-storage costs paved the way for processing the
large amounts of data typical of modern 3D CAD models
within reasonable time frames.
A new 3D printing technology has recently been
developed at Harvard University. This new additive-
manufacturing technology combines the existing direct
ink writing 3D printing technology and the annealing
process. The innovation was born out of the necessity for
flexible and wearable electronic devices such as sensors
and in biomedical applications. The technology uses the
3D printing technology to create complex architectures,
while a printed structure is simultaneously annealed in
midair. This helps to increase the accuracy of the printed
material, also allowing the printed material to be created
in free air without the need for any support structure.
This technology has opened up possibilities of creating
microscopic metallic free-standing 3D structures without
an auxiliary support and in a single manufacturing run.
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