Additive manufacturing Processes PDF by (badebhau4@gmail.com)

Unit.5
Additive
Manufacturing
Processes
SPPUSemester VII – Mechanical Engineering
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ADVANCED MANUFACTURING PROCESS

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Bb
*Syllabus :
Introduction and principles, Development of additive manufacturing Technologies,
general additive manufacturing processes, powder based fusion process, extrusion
based system, sheet lamination process, direct write technologies.
Introduction :
Additive Manufacturing (AM) technology came about as a result of developments in a
variety of different technology sectors. Like with many manufacturing technologies,
improvements in computing power and reduction in mass storage costs paved the way for
processing the large amounts of data typical of modern 3D Computer-Aided Design (CAD) models
within reasonable time frames. Nowadays, we have become quite accustomed to having powerful
computers and other complex automated machines around us and sometimes it may be difficult for
us to imagine how the pioneers struggled to develop the first AM machines.
3D printing also known as additive manufacturing is any of various processes used to make
a three-dimensional object. In 3D printing, additive processes are used, in which successive layers
of material are laid down under computer control. These objects can be of almost any shape or
geometry, and are produced from a 3D model or other electronic data source. A 3D printer is a
type of industrial robot.
Additive Manufacturing refers to a process by which digital 3D design data is used to
build up a component in layers by depositing material. The term "3D printing" is increasingly used
as a synonym for Additive Manufacturing. However, the latter is more accurate in that it describes
a professional production technique which is clearly distinguished from conventional methods of
material removal. Instead of milling a work piece from solid block, for example, Additive
Manufacturing builds up components layer by layer using materials which are available in fine
powder form material. A range of different metals, plastics and composite materials may be used.
The technology has especially been applied in conjunction with Rapid Prototyping
(/industries markets /rapid prototyping) - the construction of illustrative and functional prototypes.
Additive Manufacturing is now being used increasingly in Series Production. It gives Original
Equipment Manufacturers (OEMs) in the most varied sectors of industry (/industries markets) the
opportunity to create a distinctive profile for themselves based on new customer benefits, cost-
saving potential and the ability to meet sustainability goals.
Additive Manufacturing ProcessesUnit-5.
Shri Swami Samarth
AMP
Digitally signed by Bade
Reason: I am the author
of this document

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 Functional Principle
The system starts by applying a thin layer of the powder material to the building platform. A
powerful laser beam then fuses the powder at exactly the point’s defined by the computer-
generated component design data. The platform is then lowered and another layer of powder is
applied. Once again the material is fused so as to bond with the layer below at the predefined
points. Depending on the material used, components can be manufactured using stereo lithography,
laser sintering or 3D printing.
 Development of Additive Manufacturing Technology
Like many other technologies, AM came about as a result of the invention of the computer.
AM takes full advantage of many of the important features of computer technology, both directly
(in the AM machines themselves) and indirectly (within the supporting technology), including:
*Processing power : Part data files can be very large and require a reasonable amount of
processing power to manipulate while setting up the machine and when slicing the data before
building. Earlier machines would have had difficulty handling large CAD data files.
*Graphics capability: AM machine operation does not require a big graphics engine except to
see the file while positioning within the virtual machine space. However, all machines benefit from
a good graphical user interface (GUI) that can make the machine easier to set up, operate, and
maintain.
*Machine control: AM technology requires precise positioning of equipment in a similar way to
a Computer Numerical Controlled (CNC) machining center, or even a high-end photocopy

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machine or laser printer. Such equipment requires controllers that take information from sensors
for determining status and actuators for positioning and other output functions. Computation is
generally required in order to determine the control requirements. Conducting these control tasks
even in real-time does not normally require significant amounts of processing power by today’s
standards. Dedicated functions like positioning of motors, lenses, etc. would normally require
individual controller modules. A computer would be used to oversee the communication to and
from these controllers and pass data related to the part build function.
*Networking: Nearly every computer these days has a method for communicating with other
computers around the world. Files for building would normally be designed on another computer
to that running the AM machine. Earlier systems would have required the files to be loaded from
disk or tape. Nowadays almost all files will be sent using an Ethernet connection, often via the
Internet.
*Integration: As is indicated by the variety of functions, the computer forms a central component
that ties different processes together. The purpose of the computer would be to communicate with
other parts of the system, to process data, and to send that data from one part of the system to the
other. Figure.1 shows how the above mentioned technologies are integrated to form an AM
machine.
Figure.1 General integration of an AM machine

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Without computers there would be no capability to display 3D graphic images. Without 3D
graphics, there would be no Computer-Aided Design. Without this ability to represent objects
digitally in 3D, we would have a limited desire to use machines to fabricate anything but the
simplest shapes. It is safe to say, therefore, that without the computers we have today, we would
not have seen Additive Manufacturing develop. Additive Manufacturing technology primarily
makes use of the output from mechanical engineering, 3D Solid Modeling CAD software. It is
important to understand that this is only a branch of a much larger set of CAD systems and,
therefore, not all CAD systems will produce output suitable for layer-based AM technology.
Currently, AM technology focuses on reproducing geometric form; and so the better CAD systems
to use are those that produce such forms in the most precise and effective way.
NC machining, therefore, only requires surface modeling software. All early CAM systems were
based on surface modeling CAD. AM technology was the first automated computer-aided
manufacturing process that truly required 3D solid modeling CAD. It was necessary to have a fully
enclosed surface to generate the driving coordinates for AM. This can be achieved using surface
modeling systems, but because surfaces are described by boundary curves it is often difficult to
precisely and seamlessly connect these together. Even if the gaps are imperceptible, the resulting
models may be difficult to build using AM. At the very least, any inaccuracies in the 3D model
would be passed on to the AM part that was constructed. Early AM applications often displayed
difficulties because of associated problems with surface modeling software.
Since it is important for AM systems to have accurate models that are fully enclosed, the preference
is for solid modeling CAD. Solid modeling CAD ensures that all models made have a volume and,
therefore, by definition are fully enclosed surfaces. While surface modeling can be used in part
construction, we can not always be sure that the final model is faithfully represented as a solid.
Such models are generally necessary for Computer-Aided Engineering (CAE) tools like Finite
Element Analysis (FEA), but are also very important for other CAM processes.
Additive Manufacturing Processes
The Powder Bed Fusion process includes the following commonly used printing
techniques: Direct metal laser sintering (DMLS), Electron beam melting (EBM), Selective heat
sintering (SHS), Selective laser melting (SLM) and Selective laser sintering (SLS).Powder bed
fusion (PBF) methods use either a laser or electron beam to melt and fuse material powder together.
Electron beam melting (EBM), methods require a vacuum but can be used with metals and alloys
in the creation of functional parts. All PBF processes involve the spreading of the powder material
over previous layers. There are different mechanisms to enable this, including a roller or a blade.
A hopper or a reservoir below of aside the bed provides fresh material supply. Direct metal laser
1. Powder Based Fusion Process

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sintering (DMLS) is the same as SLS, but with the use
of metals and not plastics. The process sinters the
powder, layer by layer. Selective Heat Sintering
differs from other processes by way of using a heated
thermal print head to fuse powder material together.
As before, layers are added with a roller in between
fusion of layers. A platform lowers the model
accordingly.
The technique fuses parts of the layer, and then
moves the working area downwards, adding another
layer of granules and repeating the process until the
piece has built up. This process uses the unfused
media to support overhangs and thin walls in the part
being produced, which reduces the need for temporary auxiliary supports for the piece. A laser is
typically used to sinter the media into a solid.
Fig. 2 Powder bed fusion process
* Powder Bed Fusion – Step by Step
1. A layer, typically 0.1mm thick of material is spread over the build platform.
2. A laser fuses the first layer or first cross section of the model.
part
Energy source (laser)
roller
Build chamberPowder chamber
powder
Inert gas

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3. A new layer of powder is spread across the previous layer using a roller.
4. Further layers or cross sections are fused and added.
5. The process repeats until the entire model is created. Loose, unfused powder is remains in
position but is removed during post processing.
In powder bed fusion, particles of material (e.g., plastic, metal) are selectively fused
together using a thermal energy source such as a laser. Once a layer is fused, a new one is created
by spreading powder over the top of the object and repeating the process. Unfused material is used
to support the object being produced, thus reducing the need for support systems.
Selective laser sintering (SLS) is the first among many similar processes like Direct Metal
Laser Sintering (DMLS), Selective Laser Melting (SLM) and laser cusing. SLS can be defined as
powder bed fusion process used to produce objects from powdered materials using one or more
lasers to selectively fuse or melt the particles at the surface, layer by layer, in an enclosed chamber.
SLM is an advanced form of the SLS process where, full melting of the powder bed particles takes
place by using one or more lasers.
Fig. Laser based powder bed fusion technology
Laser cusing is similar to SLM process where laser is used to fuse each powder bed layer
as per required cross section to build the complete part in the enclosed chamber. The term laser
cusing comes from letter ‘C’ (concept) and the word fusing. The special feature of laser cusing
machine is the stochastic exposure strategy based on the island principle. Each layer of the required
cross section is divided into number of segments called “islands”, which are selected stochastically
during scanning. This strategy ensures thermal equilibrium on the surface and reduces the
component stresses.
1.1 Laser based systems (DMLS/SLM/Laser cusing)
1. Build piston
2. Build platform
3. Powder dispenser
piston
4. Powder dispenser
platform
5. Metal powder supply
6. Recoater arm
7. Laser
8. Lenses
9. Laser beam
10. Sintered part
11. Powder bed
12. XY scanning mirror

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Most of these systems use one fiber laser of 200W to 1 KW capacity to selectively fuse the
powder bed layer. The build chamber is provided with inert atmosphere of argon gas for reactive
materials and nitrogen gas for non-reactive materials. Power of laser source, scan speed, hatch
distance between laser tracks and the thickness of powdered layer are the main processing
parameters of these processes. Layer thickness of 20-100 µm can be used depending on the
material. All of these processes can manufacture fully dense metallic parts from wide range of
metal alloys like titanium alloys, inconel alloys, cobalt chrome, aluminium alloys, stainless steels
and tool steels.
Most of the laser based PBF systems have low build rates of 5-20 cm 3
/hr and maximum
part size that can be produced (build volume) is limited to 250 x 250 x 325 mm 3
which increases
part cost and limits its use only for the small sized parts. So in recent years, the machine
manufactures and the research institutes are focusing on expanding the capabilities of their
machines by increasing the build rates and the build volumes. SLM solution from Germany has
launched SLM500 HL machine in 2012 which uses double beam technology to increase the build
rate up to 35 cm 3
/hr and has a build volume of 500 x 350 x 300 mm 3
.Two sets of lasers are used
in this machine, each set having two lasers (400W and 1000W). This means four lasers scan the
powder layer simultaneously.
EBM is another PBF based AM process in which electron beam is used to selectively fuse
powder bed layer in vacuum chamber. Electron beam melting (EBM) process is similar to the
SLM with the only difference being its energy source used to fuse powder bed layers: here an
electron beam is used instead of the laser . In EBM, a heated tungsten filament emits electrons at
high speed which are then controlled by two magnetic fields, focus coil and deflection coil as
shown in Fig.4a. Focus coil acts as a magnetic lens and focuses the beam into desired diameter up
to 0.1 mm whereas deflection coil deflects the focused beam at required point to scan the layer of
powder bed. When high speed electrons hit the powder bed, their kinetic energy gets converted
into thermal energy which melts the powder. Each powder bed layer is scanned in two stages, the
preheating stage and the melting stage. In preheating stage, a high current beam with a high
scanning speed is used to preheat the powder layer (up to 0.4 - 0.6 T m) in multiple passes. In
melting stage, a low current beam with a low scanning speed is used to melt the powder . When
scanning of one layer is completed, table is lowered, another powder layer is spread and the process
repeats till required component is formed. The entire EBM process takes place under high vacuum
of 10 -4 to 10 -5 mbar. The helium gas supply during the melting further reduces the vacuum
pressure which allows part cooling and provides beam stability . It also has multi-beam feature
which converts electron beam into several individual beams which can heat, sinter or melt powder
bed layer .
1.2 Electron beam melting (EBM)

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ARCAM EBM system uses high power electron beam of 3000 W capacity to melt powder bed
layers. Electron beam power, current, diameter of focus, powder pre-heat temperature and layer
thickness are main processing parameters of the EBM. Layer thickness of 50-200 µm is typically
used in this process . EBM systems can work with wide range of materials like titanium alloys
(Ti6Al4V, Ti6Al4V EI), cobalt chrome, Titanium aluminide, inconel (625 and 718), stainless
steels, tool steels, copper, aluminium alloys, beryllium etc.
Fig. Schematic of EBM process
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Fig. Steps in EBM process
* Materials Used
The Powder bed fusion process uses any powder based materials, but common metals and
polymers used are:
SHS: Nylon DMLS, SLS,
SLM: Stainless Steel, Titainium, Aluminium, Cobalt Chrome, Steel
EBM: titanum, Cobalt Chrome, ss, al and copper
* Advantages:
1. Relatively inexpensive
2. Suitable for visual models and prototypes
3. (SHS) Ability to integrate technology into small scale, office sized machine.
4. Powder acts as an integrated support structure.
5. Large range of material options.
Build plate heating
Powder spreading
Powder preheating scan
Powder melting scan
Build Table lowering
Repeat process till part completion

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* Disadvantages:
1. Relatively slow speed (SHS).
2. Lack of structural properties in materials.
3. Size limitations.
4. High power usage.
5. Finish is dependent on powder grain size.
 COMPARISON BETWEEN SLM AND EBM
As compared to the SLM system, the EBM has higher build rates (upto 80cm 3/hr because
of the high energy density and high scanning speeds) but inferior dimensional and surface finish
qualities.
In both the SLM/EBM process, because of rapid heating and cooling of the powder layer,
residual stresses are developed. In EBM, high build chamber temperature (typically 700- 900 0
C)
is maintained by preheating the powder bed layer. This preheating reduces the thermal gradient in
the powder bed and the scanned layer which reduces residual stresses in the part and eliminates
post heat treatment required. Preheating also holds powder particles together which can acts as
supports for overhanging structural members. So, supports required in the EBM are only for heat
conduction and not for structural support. This reduces the number of supports required and allows
manufacturing of more complex geometries. Powder preheating feature is available in very few
laser based systems where it is achieved by platform heating. In addition, entire EBM process
takes place under vacuum since, it is necessary for the quality of the electron beam. Vacuum
environment reduces thermal convection, thermal gradients and contamination and oxidation of
parts like titanium alloys . In SLM, part manufacturing takes place under argon gas environment
for reactive materials to avoid contamination and oxidation whereas non-reactive materials can be
processed under nitrogen environment. So it can be expected that EBM manufactured parts have
lower oxygen content than SLM manufactured parts .
In spite of having these advantages, EBM is not as popular as SLM because of its higher
machine cost, low accuracy and non-availability of large build up volumes. Characteristic features
of SLM and EBM are summarized in Table 1.
TABLE I. CHARACTERISTIC FEATURES OF SLM AND EBM
SLM EBM
Power source One or more fiber lasers of 200
to 1000 W
High power Electron beam
of 3000 W
Build chambcr environment Argon or Nitrogen Vacuum / He bleed
Method of powder preheating Platform heating Preheat scanning

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Powder preheating temperature (°
C) [3435]
100-200 700-900
Maximum available build volume
(mm)
500 x 350 x 300 350 x 38O(0xH)
Maximum build rate (cm /hr) 20-35 80
Layer thickness (pm) 20-100 50-200
Melt pool size (mm) 0.1-0.5 0.2-1.2
Surface finish [7] (Ra) 4-11 25-35
Geometric tolerance (mm) [12] ±0.05-0.1 ± 0.2
Minimum feature size(jim) [39] 40-200 100
Fuse deposition modelling (FDM) is a common material extrusion process and is
trademarked by the company Stratasys. Material is drawn through a nozzle, where it is heated and
is then deposited layer by layer. The nozzle can move horizontally and a platform moves up and
down vertically after each new layer is deposited. It is a commonly used technique used on many
inexpensive, domestic and hobby 3D printers.
The process has many factors that influence the final model quality but has great potential
and viability when these factors are controlled successfully. Whilst FDM is similar to all other 3D
printing processes, as it builds layer by layer, it varies in the fact that material is added through a
nozzle under constant pressure and in a continuous stream. This pressure must be kept steady and
at a constant speed to enable accurate results .Material layers can be bonded by temperature control
or through the use of chemical agents. Material is often added to the machine in spool form as
shown in the diagram.
2. Extrusion Based System

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* Material Extrusion – Step by Step
1. First layer is built as nozzle deposits material where required onto the cross sectional area
of first object slice.
2. The following layers are added on top of previous layers.
3. Layers are fused together upon deposition as the material is in a melted state.
Material Extrusion operates in a similar fashion to a hot glue gun; plastic filament is heated
to a malleable state and extruded through a nozzle. In order to create a part, a CAD model is sliced
into layers.
If the part has large overhangs, support material is required to prevent sagging and protect
part integrity. This support material is created either through thin, breakable trusses of the build
material or a second soluble material.
Advantages of the material extrusion process include use of readily available ABS plastic,
which can produce models with good structural properties, close to a final production model. In
low volume cases, this can be a more economical method than using injection moulding. However,
the process requires many factors to control in order to achieve a high quality finish. The nozzle
which deposits material will always have a radius, as it is not possible to make a perfectly square
nozzle and this will affect the final quality of the printed object. Accuracy and speed are low when
compared to other processes and the quality of the final model is limited to material nozzle
Material spool
Object/ model
Support material
Nozzle
Heated Element
Build Platform

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thickness .When using the process for components where a high tolerance must be achieved,
gravity and surface tension must be accounted for. Typical layer thickness varies from 0.178 mm
– 0.356 mm.
* Materials Used
The Material Extrusion process uses polyers and plastics.
Polymers: ABS, Nylon, PC, PC, AB
* Advantages:
1. Widespread and inexpensive process.
2. ABS plastic can be used, which has good structural properties and is easily accessible.
* Disadvantages:
1. The nozzle radius limits and reduces the final quality .
2. Accuracy and speed are low when compared to other processes and accuracy of the final
model is limited to material nozzle thickness.
3. Constant pressure of material is required in order to increase quality of finish.
Sheet lamination processes include ultrasonic additive manufacturing (UAM) and
laminated object manufacturing (LOM). The Ultrasonic Additive Manufacturing process uses
sheets or ribbons of metal, which are bound
together using ultrasonic welding.
The process does require additional CNC
machining and removal of the unbound metal,
often during the welding process. Laminated object
manufacturing (LOM) uses a similar layer by layer
approach but uses paper as material and adhesive
instead of welding. The LOM process uses a cross
hatching method during the printing process to
allow for easy removal post build. Laminated
objects are often used for aesthetic and visual
models and are not suitable for structural use.
UAM uses metals and includes aluminium, copper,
stainless steel and titanium. The process is low
3. Sheet Lamination Process

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temperature and allows for internal geometries to be created. The process can bond different
materials and requires relatively little energy, as the metal is not melted.
* Sheet Lamination – Step by Step
1. The material is positioned in place on the cutting bed.
2. The material is bonded in place, over the previous layer, using the adhesive.
3. The required shape is then cut from the layer, by laser or knife.
4. The next layer is added.
5. Steps two and three can be reversed and alternatively, the material can be cut before being
positioned and bonded.
6.Sheet is adhered to a substrate with a heated roller.
7. Laser traces desired dimensions of prototype.
8. Laser cross hatches non-part area to facilitate waste removal.
9. Platform with completed layer moves down out of the way.
10. Fresh sheet of material is rolled into position.
11. Platform downs into new position to receive next layer.
12. The process is repeated.

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Laminated object manufacturing (LOM) is one of the first additive manufacturing
techniques created and uses a variety of sheet material, namely paper. Benefits include the use of
A4 paper, which is readily available and inexpensive, as well as a relatively simple and inexpensive
setup, when compared to others.
The Ultrasonic Additive Manufacturing (UAM) process uses sheets of metal, which are
bound together using ultrasonic welding. The process does require additional CNC machining of
the unbound metal. Unlike LOM, the metal cannot be easily removed by hand and unwanted
material must be removed by machining. Material saving metallic tape of 0.150mm thick and
25mm wide does however, result in less material to cut off afterwards. Milling can happen after
each layer is added or after the entire process. Metals used include aluminium, copper, stainless
steel and titanium. The process is low temperature and allows for internal geometries to be created.
One key advantage is that the process can bond different materials and requires relatively little
energy as the metal is not melted, instead using a combination of ultrasonic frequency and pressure.
Overhangins can be built and main advantage of embedding electronics and wiring . Materials are
bonded and helped by plastic deformation of the metals. Plastic deformation allows more contact
between surface and backs up existing bonds .
Post processing requires the extraction of the part from the surrounding sheet material.
With LOM, cross hatching is used to make this process easier, but as paper is used, the process
does not require any specialist tools and is time efficient. Whilst the structural quality of parts is
limited, adding adhesive, paint and sanding can improve the appearance, as well as further
machining.
* Materials
Effectively any sheet material capable of being rolled. Paper, plastic and some sheet metals.
The most commonly used material is A4 paper.
* Advantages:
1. Benefits include speed, low cost, ease of material handling, but the strength and integrity
of models is reliant on the adhesive used .
2. Cutting can be very fast due to the cutting route only being that of the shape outline, not
the entire cross sectional area
3. Relatively large parts may be made.
4. Paper models have wood like characteristics, and may be worked and finished accordingly
* Disadvantages:
1. Finishes can vary depending on paper or plastic material but may require post processing
to achieve desired effect
2. Limited material use
3. Fusion processes require more research to further advance the process into a more
mainstream positioning.
4. Dimensional accuracy is slightly less

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Direct-write technologies are the most recent and novel approaches to the fabrication of
electronic and sensor devices, as well as integrated power sources, whose sizes range from the
meso- to the nanoscales. The term direct write refers to any technique or process capable of
depositing, dispensing, or processing different types of materials over various surfaces following
a preset pattern or layout. The ability to accomplish both pattern and material transfer processes
simultaneously represents a paradigm shift away from the traditional approach for device
manufacturing based on lithographic techniques. However, the fundamental concept of direct
writing is not new. Every piece of handwriting, for instance, is the result of a direct-write process
whereby ink or lead is transferred from a pen, or pencil onto paper in a pattern directed by our
hands. The immense power and potential of direct writing lies in its ability to transfer and/or
process any type of material over any surface with extreme precision resulting in a functional
structure or working device.
Direct-write technologies are a subset of the larger area of rapid prototyping and deal with
coatings or structures considered to be two-dimensional in nature. With the tremendous
breakthroughs in materials and the methods used to apply them, many of which are discussed in
this book, direct-write technologies are poised to be far-reaching and influential well into the
future. The industry's push toward these technologies and the pull from applications rapidly
changing circuits, designs, and commercial markets are documented for the first time here.
Although direct-write technologies are serial in nature, they are capable of generating patterns, of
high-quality electronic, sensor, and biological materials among others--at unparalleled speeds,
rendering these technologies capable of satisfying growing commercial demands.
4.1. Laser Direct-Write
From the earliest work on laser interactions with materials, direct-write processes have
been important and relevant techniques to modify, add, and subtract materials for a wide variety
of systems and for applications such as metal cutting and welding. In general, direct-write
processing refers to any technique that is able to create a pattern on a surface or volume in a serial
or “spot-by-spot” fashion. This is in contrast to lithography, stamping, directed self-assembly, or
other patterning approaches that require masks or pre-existing patterns. At first glance, one may
think that direct-write processes are slower or less important than these parallelized approaches.
However, direct-write allows for precise control of material properties with high resolution and
enables structures that are either impossible or impractical to make with traditional parallel
techniques. Furthermore, with continuing developments in laser technology providing a decrease
in cost and an increase in repetition rates, there is a plethora of applications for which laser direct-
write (LDW) methods are a fast and competitive way to produce novel structures and devices.
This issue of MRS Bulletin seeks to assess the current status and future opportunities of LDW
processes in the context of emerging applications.
4. Direct Write Technologies

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In LDW, the beam is typically focused or collimated to a small spot (in industrial
processes, this “small” spot can be several millimeters in diameter). Patterning is achieved by
either rastering the beam above a fixed surface or by moving the substrate or part within a fixed
beam. An important feature of LDW is that the desired patterns can be constructed in both two
and three dimensions on arbitrarily shaped surfaces, limited only by the degrees of freedom and
resolution of the motion-control apparatus. In this manner, LDW can be considered a “rapid
prototyping” tool, because designs and patterns can be changed and immediately applied without
the need to fabricate new masks or molds.
The key elements of any LDW system can be divided into three subsystems: (1) laser
source, (2) beam delivery system, and (3) substrate/target mounting system (Shown in Figure
1). At the heart of any LDW process is the laser source. Typical experiments and applications use
anywhere from ultrafast femtosecond-pulsed systems to continuous-wave systems employing
solid-state, gas, fiber, semiconductor, or other lasing media. In choosing an appropriate source,
one must consider the fundamental interactions of lasers with the material of interest. This requires
knowledge of the pulse duration, wavelength, divergence, and other spatial and temporal
characteristics that determine the energy absorption and the material response. In beam delivery,
there are a variety of ways to generate a laser spot, including fixed focusing objectives and mirrors,
galvanometric scanners, optical fibers, or even fluidic methods such as liquid-core wave- guides
or water jets. The choice depends on the application demands, for instance, the required working
distances, the focus spot size, or the energy required. The ultimate beam properties will be
determined by the combination of laser and beam delivery optics. Finally, the substrate mounting
is done in accordance with experimental or industrial requirements and can be manipulated in
multiple directions to achieve a desired result. Robotics and active feedback control, on either
the substrate or beam delivery optics, can add further design flexibility to the technique.
There is a vast range of LDW processes. For the purposes of this issue, we categorize them
into three main classes: 1.laser direct- write subtraction (LDW-), where material is removed by
ablation; 2.laser direct-write modification (LDWM), where material is modified to produce a
desired effect; and 3.laser direct-write addition (LDW+), where material is added by the laser.

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Figure 1. Schematic illustration of a laser direct-write system.
The basic components of an LDW system are (left to right) a substrate mounting system, a
beam delivery system, and a laser source. Motion control of either the beam delivery system or the
substrate mounting system is typically accomplished using computer-assisted design and
manufacturing (CAD/CAM) integrated with the laser source.
4.1.1. Laser Direct-Write Subtraction (LDW–)
LDW (-) is the most common type of laser direct-write. In general, this entails processes
that result in photochemical, photo thermal, or photo physical ablation on a substrate or target
surface, directly leading to the features of interest. Common processes include laser scribing, cut-
ting, drilling, or etching to produce relief structures or holes in materials in ambient or controlled
atmospheres. Industrial applications using this technique range from high-throughput steel
fabrication, to inkjet and fuel-injection nozzle fabrication, to high-resolution manufacturing and
texturing of stents or other implantable biomaterials. At a smaller scale, inexpensive bench top
laser cutting and en- graving systems can be purchased by the hobbyist or small company for
artistic and architectural renderings. More recent developments in LDW- include chemically
assisted techniques such as laser-drilling ceramics or biomaterials and laser-induced backside wet
etching (LIBWE) of glass. In fact, one may also consider laser cleaning to be a controlled LDW-
process. The fundamental interactions leading to material removal can be thermal or a thermal,
depending primarily on the material/environment characteristics and the pulse duration of the laser.

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These interactions have a direct effect on the quality of the resulting features. For instance, a heat-
affected zone (HAZ) tends to occur in the vicinity of thermally removed material. This region has
structures and properties that can differ from the bulk material and can exhibit additional surface
relief. Either of these effects may be beneficial or detrimental, depending on the application. In
contrast, a thermal and multiphoton absorption processes caused by ultrafast lasers can reduce the
formation of a HAZ and enable features smaller than the diffraction limit.
4.1.2. Laser Direct-Write Modification (LDWM)
In LDWM, the incident laser energy is usually not sufficient to cause ablative effects but
is sufficient to cause a permanent change in the material properties. Typically, these processes rely
on thermal modifications that cause a structural or chemical change in the material. A common
example of such processes is the rewritable compact disc, in which a diode laser induces a phase
transition between crystalline and amorphous material. In industrial applications, one may consider
laser cladding, where a surface layer different from the bulk material is produced through melting
and resolidification, or solid free-form fabrication (SFF) approaches such as selective laser
sintering (SLS), as important modifying processes that would fall under the umbrella of LDWM.
Many LDWM applications require a specific optical response in the material of interest beyond
simple thermal effects. Optically induced defects or changes in mechanical properties can lead to
many non-ablative material modifications. For instance, photoresists respond to light by breaking
or reforming bonds, leading to pattern formation in the material. Alternatively, LDW can cause
defects in photo- etchable glass ceramics or other optical materials through single- and multiphoton
mechanisms, enabling novel applications in optical storage, photonic devices, and microfluidics.
4.1.3. Laser Direct-Write Addition (LDW+)
LDW+ is perhaps the most recent of the laser direct-write processes. In this technique,
material is added to a substrate using various laser-induced processes. Many techniques are derived
from laser- induced forward transfer (LIFT), where a sacrificial substrate of solid metal is
positioned in close proximity to a second substrate to receive the removed material. The incident
laser is absorbed by the material of interest, causing local evaporation. This vapor is propelled
toward the waiting substrate, where it recondenses as an individual three-dimensional pixel, or
voxel, of solid material. Such an approach has found important use in circuit and mask repair and
other small-scale applications where one needs to deposit material locally to add value to an
existing structure. This general technique has significant advantages over other additive direct-
write processes, in that these laser approaches do not require contact between the depositing
material and a nozzle, and can enable a broad range of materials to be transferred. Variations on
the general LIFT principle allow liquids, inks, and multi- phase solutions to be patterned with

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computer-controlled accuracy for use in a variety of applications such as passive electronics or
sensors.
Alternatively, LDW+ techniques can rely on optical forces to push particles or clusters into
precise positions, or on chemical changes in liquids and gases to produce patterns. For instance,
laser-induced chemical vapor deposition, or multiphoton polymerization schemes of liquid
photoresists, can be used to fabricate three-dimensional stereographic patterns. Examples of this
have been demonstrated and show promise for many applications such as fabricating photonic
structures or biological scaffolding.
*Applications
In many cases, applications tend to drive the development of new technologies, and direct
writing is one such technology. The need for direct writing electronic and sensor materials is
founded in exciting and often revolutionary applications, numerous examples of which will be
given here. The specific applications presented individually in each chapter are representative of
some areas where direct-write technologies could have an impact. As successful applications are
commercialized demonstrating the inherent flexibility of direct-write techniques the potential for
using direct-write products in other areas grows. Part I is devoted to applications of direct-write
material deposition, in particular, applications to defense electronics, chemical and biological
sensors, industrial applications, and small-scale power-management applications. Other exciting
applications are on the horizon for use in medicine, tissue engineering, wireless and other
communications, optoelectronics, and semiconductors.
Directed Energy Deposition (DED) covers a range of terminology: ‘Laser engineered net
shaping, directed light fabrication, direct metal deposition, 3D laser cladding’ It is a more complex
printing process commonly used to repair or add additional material to existing components.
A typical DED machine consists of a nozzle mounted on a multi axis arm, which deposits
melted material onto the specified surface, where it solidifies. The process is similar in principle
to material extrusion, but the nozzle can move in multiple directions and is not fixed to a specific
axis. The material, which can be deposited from any angle due to 4 and 5 axis machines, is melted
upon deposition with a laser or electron beam. The process can be used with polymers, ceramics
but is typically used with metals, in the form of either powder or wire.
Typical applications include repairing and maintaining structural parts.
5.Directed Energy Deposition

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* Direct Energy Deposition – Step by Step
1. A4 or 5 axis arm with nozzle moves around a fixed object.
2. Material is deposited from the nozzle onto existing surfaces of the object.
3. Material is either provided in wire or powder form.
4. Material is melted using a laser, electron beam or plasma arc upon deposition.

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5. Further material is added layer by layer and solidifies, creating or repairing new material features
on the existing object.
The DED process uses material in wire or powder form. Wire is less accurate due to the
nature of a pre- formed shape but is more material efficient when compared to powder (Gibson et
al., 2010), as only required material is used. The method of material melting varies between a laser,
an electron beam or plasma arc, all within a controlled chamber where the atmosphere has reduced
oxygen levels. With 4 or 5 axis machines, the movement of the feed head will not change the flow
rate of material, compared to fixed, vertical deposition.
* Materials
The Electron Beam Melting process uses metals and not polymers or ceramics.
Metals: Cobalt Chrome, Titanium
* Advantages:
1. Ability to control the grain structure to a high degree, which lends the process to repair work of
high quality, functional parts.
2. A balance is needed between surface quality and speed, although with repair applications, speed
can often be sacrificed for a high accuracy and a pre- determined microstructure.
* Disadvantages:
1. Finishes can vary depending on paper or plastic material but may require post processing to
achieve desired effect.
2. Limited material use
3. Fusion processes require more research to further advance the process into a more mainstream
positioning
6. Material Jetting (Not in Syllabus)
Material jetting creates objects in a
similar method to a two dimensional ink
jet printer. Material is jetted onto a build
platform using either a continuous or Drop
on Demand (DOD) approach. Material is
jetted onto the build surface or platform,
where it solidifies and the model is built
layer by layer. Material is deposited from
a nozzle which moves horizontally across
the build platform. Machines vary in
complexity and in their methods of
controlling the deposition of material. The
material layers are then cured or hardened
using ultraviolet (UV) light. As material must be deposited in drops, the number of materials

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available to use is limited. Polymers and waxes are suitable and commonly used materials, due to
their viscous nature and ability to form drops.
* Material Jetting – Step by Step
1. The print head is positioned above build platform.
2. Droplets of material are deposited from the print head onto surface where required, using either
thermal or piezoelectric method.
3. Droplets of material solidify and make up the first layer.
4. Further layers are built up as before on top of the previous.
5. Layers are allowed to cool and harden or are cured by UV light. Post processing includes
removal of support material.
Drop on Demand (DOD) is used to dispense material onto the required surface. Droplets
are formed and positioned into the build surface, in order to build the object being printed, with
further droplets added in new layers until the entire object has been made. The nature of using
droplets, limits the number of materials available to use. Polymers and waxes are often used and
are suitable due to their viscous nature and ability to form drops. Viscosity is the main determinant

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in the process; there is a need to re-fill the reservoir quickly and this in turn affects print speed.
Unlike a continuous stream of material, droplets are dispensed only when needed, released by a
pressure change in the nozzle from thermal or piezoelectric actuators. Thermal actuators deposit
droplets at a very fast rate and use a thin film resistor to form the droplet. The piezoelectric method
is often considered better as it allows a wider range of materials to be used. The designs of a typical
DOD print head changes from one machine to another but according to Ottnad, typically include
a reservoir, sealing ring, Piezo elements and silicon plate with nozzle, held together with high
temperature glue.
* Materials
The material jetting process uses polymers and plastics.
Polymers: Polypropylene, HDPE, PS, PMMA, PC, ABS, HIPS, EDP
* Advantages:
1. The process benefits from a high accuracy of deposition of droplets and therefore low waste.
2. The process allows for multiple material parts and colours under one process.
* Disadvantages:
1.Support material is often required.
2. A high accuracy can be achieved but materials are limited and only polymers and waxes can be
used.
7. Binder Jetting (Not in syllabus)
The binder jetting process uses two
materials; a powder based material and a binder.
The binder acts as an adhesive between powder
layers. The binder is usually in liquid form and
the build material in powder form. A print head
moves horizontally along the x and y axes of the
machine and deposits alternating layers of the
build material and the binding material. After
each layer, the object being printed is lowered
on its build platform.
Due to the method of binding, the material
characteristics are not always suitable for
structural parts and despite the relative speed of
printing, additional post processing (see below)
can add significant time to the overall process.

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* Binder Jetting – Step by Step
1. Powder material is spread over the build platform using a roller.
2. The print head deposits the binder adhesive on top of the powder where required.
3. The build platform is lowered by the model’s layer thickness.
4. Another layer of powder is spread over the previous layer. The object is formed where the
powder is bound to the liquid.
5. Unbound powder remains in position surrounding the object.
6. The process is repeated until the entire object has been made.
The binder jetting process allows for colour printing and uses metal, polymers and
ceramic materials. The process is generally faster than others and can be further quickened by
increasing the number of print head holes that deposit material. The two material approach allows
for a large number of different binder-powder combinations and various mechanical properties of
the final model to be achieved by changing the ratio and individual properties of the two materials.
The process is therefore well suited for when the internal material structure needs to be of a specific
quality.

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* Materials
1. Metals: Stainless steel
2. Polymers: ABS, PA, PC
3. Ceramics: Glass
All three types of materials can be used with the binder jetting process.
* Advantages:
1. Parts can be made with a range of different colours.
2. Uses a range of materials: metal, polymers and ceramics.
3. The process is generally faster than others.
4. The two material method allows for a large number of different binder-powder combinations
and various mechanical properties.
* Disadvantages:
1. Not always suitable for structural parts, due to the use of binder material.
2. Additional post processing can add significant time to the overall process.
# Use and Benefits of AMP
Additive manufacturing offers consumers and professionals alike the ability to create,
customize and/or repair products, and in the process, redefine current production technology. It is
a means to create highly customized products, as well as produce large amounts of production
parts. Products are brought to market in days rather than months and designers save money by
using additive manufacturing instead of traditional manufacturing methods. In addition, the risk
factor is much lower and those involved can receive near-immediate feedback because prototypes
take less time to produce.
For those looking to do rapid prototyping, additive manufacturing is extremely beneficial.
The technology lends itself to efficiently create quick prototypes, allowing designers and
businesses to get their products more quickly. When done in a large printer, multiple parts can be
done at once in less time.
A variety of industries use additive manufacturing to fabricate end-use product, consumer
and otherwise, including aerospace, architecture, automotive, education, game and medical
industries. The technology is popular among design and architecture firms as well. Industries and
businesses that build products and prototypes, as well as short run and on demand manufacturing
of components benefit from the use of additive manufacturing.

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ADDITIVE MANUFACTURING : THE OPPORTUNITIES AND CHALLENGES
The main AM opportunities lie in the design flexibility and in mass customization,
industrial secrecy protection, process sustainability and rapid product development, while the
challenges are related to Intellectual Property protection, standards certification, mass production
applications, regulatory issues and - at the moment - limited scalability. Hybrid machine tools that
incorporate CNC and AM could represent the next step for the development of the industry.
# Materials Used in AM
Three types of materials can be used in additive manufacturing: polymers, ceramics and
metals. All seven individual AM processes, cover the use of these materials, although polymers
are most commonly used and some additive techniques lend themselves towards the use of certain
materials over others. Materials are often produced in powder form or in wire feedstock.
Other materials used include adhesive papers, paper, chocolate, and polymer/adhesive
sheets for LOM. It is essentially feasible to print any material in this layer by layer method, but
the final quality will be largely determined by the material. The processes above can also change
the microstructure of a material due to high temperatures and pressures, therefore material
characteristics may not always be completely similar post manufacture, when compared to other
manufacturing processes.
1.Polymers
Common plastics can be used in 3D printing, including ABS and PC. The common
structural polymers can also be used, as well as a number of waxes and epoxy based resins. Mixing
different polymer powders can create a wide range of structural and aesthetic materials. The
following polymers can be used:
1. ABS (Acrylonitrile butadiene styrene)
2. PLA (polylactide), including soft PLA
3. PC (polycarbonate) Polyamide (Nylon)
4. Nylon 12 (Tensile strength 45 Mpa)
5. Glass filled nylon (12.48 Mpa)
6. Epoxy resin
7. Wax
8. Photopolymer resins
2. Ceramics
Ceramic powders can be printed, including:
1. Silica/Glass
2. Porcelain
3. Silicon-Carbide

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3. Metals
Metals: A range of metals can be used, including a number of options suitable for structural and
integral component parts. Common metals used:
1.Steel,
2.TItanium,
3. Aluminium,
4. Cobalt Chrome Alloy.
# Advantages of AM
 Greater design ability. The technology allows assemblies to be printed in one process and
organic shapes to be easily produced. Traditional constraints of manufacture are reduced or
eliminated.
 Unlike many widely used manufacturing techniques such as injection moulding, no tooling is
required, which can be a barrier to production due to the high cost.
 Anywhere manufacture. Parts can be sent digitally and printed in homes or locations near to
consumers, reducing the requirement and dependence on transport.
 Compared to conventional techniques with more geometric limitations, additive
manufacturing can produce models quickly, in hours, not weeks.
 Fewer resources for machines and little skilled labour when compared to conventional model
making craftsmanship.
 Customisation - Particularly within the medical sector, where parts can be fully customised to
the patient and their individual requirements.
 Efficient material use due to the exact production of parts and no overproduction based on
estimated demand.
 Commercial advantage and increased competitiveness, in the form of reduced costs and risk,
as the development time from concept to manufacture is minimised.
 Material efficiency. Material required matches material used. Support material and powder can
often be recycled at source, back into the system.
 Environmental benefits. The emissions from transport are reduced because of the ability to
manufacture anywhere.
 With increasing numbers of machines, 3D printing is becoming more affordable, whereas
injection moulding machines remain relatively expensive and inaccessible.

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# Applications for Additive Manufacturing
technology
Initially seen as a process for concept modelling and rapid prototyping, AM has expanded
over the last five years or so to include applications in many areas of our lives. From prototyping
and tooling to direct part manufacturing in industrial sectors such as architectural, medical, dental,
aerospace, automotive, furniture and jewellery, new and innovative applications are constantly
being developed.
It can be said that AM belongs to the class of disruptive technologies, revolutionising the
way we think about design and manufacturing. From consumer goods produced in small batches
to large scale manufacture, the applications of AM are vast.The number of users of these
technologies has been growing constantly, from artists, designers and individuals to large
companies and enterprises using AM to manufacture a wide range of final products.
INDUSTRIES CURRENT APPLICATIONS POTENTIAL FUTURE APPLICATIONS
COMMERCIAL
AEROSPACE
AND
DEFENSE
 Concept modeling and prototyping
 Structural and non-structurat production
parts
 Low-volume replacement parts
 Embedding additwely manufactured
electronics directly on parts
 Complex engine parts
 Aircraft vring components
 Other structural aircraft components
SPACE
 Specialized parts for space exploration
 Structures using Ight-weight, Ngh-
strength materials
 On-demand parts/spares in space
 large structures directly created in
space, thus circumventing launch
vehicle size Imitations
Automotive
 Rapid prototyping and manufacturing of
end-use auto parts
 Parts and assemblies for antique cars
andracecars
 Quick production of parts or entire
 Sophisticated auto components
 Auto components designed through
crowdsourcing
Health Care
 Prostheses and implants
 Medical instruments and models
 Hearing aids and dental implants
 Developing organs for transplants
 Large-scale pharmaceutical
production
 Developing human tissues for
regenerative therapies
CONSUMER
PRODUCTS/
RETAIL
 Rapid prototyping
 Oeatmg and testing design iterations
 Customized jewelry and watches
 Umited product customization
 Co-designing and creating with
customers
 Customized living spaces
 Growing mass customization of
consumer products
Currently, metal AM is not a process suitable for the mass production of millions of
identical simple parts. However, as systems and technologies advance, and processing time is
reduced, the use of AM for producing large quantities of parts will become a viable option.

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The advantages of AM derive from its high flexibility due to the product being produced
directly from a CAD model without the need for tooling. This also allows the AM process to
produce almost any geometry that can be designed.
There are some applications, for example dental restorations, that really tap the full
potential of AM. In this highly individualized production process it is economically viable to use
AM technologies, speeding up the production time without inflating the costs per part.
Applications in aerospace, for example the fuel nozzles for the GE LEAP engine, highlight
the possibilities of AM in this demanding sector. Additive Manufacturing allowed engineers to
design a fuel nozzle which is 25% lighter and five times more durable than the previous part.
********** Thank You *************

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