Powder Based Additive Manufacturing Systems

DEPARTMENT OF INDUSTRIAL & PRODUCTION ENGINEERING www. jssstuniv.in
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ADDITIVE MANUFACTURING
(20IP653)
Module-3
Powder based AM systems
Course Instructor
Vijay Praveen P M
Assistant Professor
Department of I&P Engg.

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SYLLABUS
Powder based Additive manufacturing and 3d
printing systems:: Selective Laser Sintering –
Principles of SLS process – Process, advantages and
applications, Three-Dimensional Printing – Principle,
process, advantages and applications- Laser
Engineered Net Shaping (LENS), Electron Beam
Melting.
Multi Jet Modelling (MJM):Models and
specifications, Process, working principle,
Applications, Advantages and Disadvantages, Case
studies.

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3D SYSTEMS’ SELECTIVE LASER
SINTERING (SLS)

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3D SYSTEMS’ SELECTIVE LASER
SINTERING (SLS)
SLS involves the use of a high power laser (for example, a carbon dioxide laser)
to fuse small particles of plastic, metal, ceramic, or glass powders into a mass
that has a desired three-dimensional shape.

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Working principle:
● CAD data files are converted to STL files format are transferred to the
vanguard systems where they are sliced.
● A thin layer of heat fusible powder is deposited on the part building
chamber and Layer thickness is of bout nearly 0.1 mm thick;.
● The part building takes place inside an enclosed chamber filled with
nitrogen gas to minimize oxidation and degradation of the powdered
material;
● The powder in the building platform is maintained at an elevated
temperature just below the melting point and/or glass transition
temperature of the powdered material;
● Infrared heaters are used to maintain an elevated temperature around
the part being formed;
● A focused CO2 laser beam is moved on the bed in such a way that it
thermally fuses the material to form the slice cross-section;
● Surrounding powders remain loose and serve as support for subsequent
layers

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When the cross section is completely drawn an
additional layer of powder is deposited with a roller
mechanism on the top of previously scanned layer.
This prepares the next layer of scanning.
● This is repeated until each layer fuses to the
layer below until the part is completed.
● SLS parts may then require some post
processing or secondary finishing such as
sanding, lacquering and painting, depending upon
the application.

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Materials
Commercially-available materials used in SLS
are:
● polyamides (PA),
● polystyrenes (PS),
● thermoplastic elastomers (TPE), and
● polyaryletherketones (PAEK).
● Polycarbonate (PC)

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Advantages:
1. Parts possess high strength and stiffness
2. Good chemical resistance
3. Various finishing possibilities (e.g., metallization, stove
enameling, vibratory grinding, tub coloring, bonding, powder,
coating, flocking)
4. Complex parts with interior components can be built without
trapping the material inside and altering the surface from
support removal.
5. Fastest additive manufacturing process for printing functional,
durable, prototypes or end user parts
6. Wide variety of materials with characteristics of strength,
durability, and functionality
7. Due to the reliable mechanical properties, parts can often
substitute typical injection molding plastics.
Disadvantages:
Parts have porous surfaces; these can be sealed by several different
post-processing methods such as cyanoacrylate coatings or by hot
isostatic pressing.

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APPLICATIONS

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Laser Engineered Net Shaping (LENS)
Optomec Inc. was incorporated in 1992.
Since 1997, Optomec has focused on
commercializing a direct fabrication process,
the Laser Engineered Net Shaping (LENS)
process originally developed by Sandia
National Laboratories. Optomec delivered its
first commercial system to Ohio State
University.

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Principle
• (1) A high powered Nd :YAG(Yttrium Aluminum
Garnet) laser focused onto a metal substrate
creates a molten puddle on the substrate surface.
Powder is then injected into the molten puddle to
increase material volume.
• (2) A “printing” motion system moves a platform
horizontally and laterally as the laser beam traces
the cross-section of the part being produced.
After formation of a layer of the part, the
machine’s powder delivery nozzle moves upwards
prior to building next layer

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Process
The LENS process builds components in an additive manner from powdered
metals using a Nd :YAG laser to fuse powder to a solid as shown in Figure . It is
a freeform metal fabrication process in which a fully dense metal component
is formed.
1) A deposition head supplies metal powder to the focus of a high powered
Nd :YAG laser beam to be melted. This laser is typically directed by fiber
optics or precision angled mirrors.
(2) The laser is focused on a particular spot by a series of lenses, and a
motion system underneath the platform moves horizontally and laterally
as the laser beam traces the cross-section of the part being produced. The
fabrication process takes place in a low-pressure argon chamber for
oxygen-free operation in the melting zone, ensuring that good adhesion is
accomplished.
(3) When a layer is completed, the deposition head moves up and continues
with the next layer. The process is repeated layer by layer until the part is
completed. The entire process is usually enclosed to isolate the process
from the atmosphere. Generally the prototypes need additional finishing,
but are fully dense products with good grain formation

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Advantages
• (1) Superior material properties. The LENS process
is capable of producing fully dense metal parts
Metal parts produced can also include embedded
structures and superior material properties. The
microstructure produced is also relatively good.
• (2) Complex parts. Functional metal parts with
complex features bare the forte of the LENS
system.
• (3) Reduced post-processing requirements. Post-
processing is minimized, thus reducing cycle time.

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Disadvantages
• (1) Limited materials. The process is
currently narrowly focused to produce only
metal parts.
• (2) Large physical unit size. The unit requires
a relatively large area to house.
• (3) High power consumption. The laser
system requires very high wattage.

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Applications
The LENS technology can be used in the following
areas:
(1) Build mold and die inserts
(2) Producing titanium parts in racing industry
(3) Fabricate titanium components for biological
implants
(4) Produce functionally gradient structures

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Electron Beam Melting (EBM)
➢ Electron Beam Melting (EBM) is a 3D manufacturing process in which a
powdered metal is melted by a high-energy beam of electrons.
➢ An electron beam produces a stream of electrons that is guided by a
magnetic field, melting layer upon layer of powdered metal to create an
object matching the precise specifications defined by a CAD model.
Production takes place in a vacuum chamber to guard against oxidation
that can compromise highly reactive materials.
➢ Electron Beam Melting is similar to Selective Laser Melting (SLM), as they
both print from a powder from the 3D printer’s powder bed, but EBM uses
an electron beam instead of a laser.
➢ High speed electrons .5-.8 times the speed of light are bombarded on the
surface of the work material generating enough heat to melt the surface
of the part and cause the material to locally vaporize.
➢ EBM does require a vacuum, meaning that the workpiece is limited in size
to the vacuum used.
➢ The surface finish on the part is much better than that of other
manufacturing processes.
➢ EBM can be used on metals, non-metals, ceramics, and composites.

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• History of EBM Printing
• In 1993, Arcam collaborated with Chalmers
University of Technology in Gothenburg in
filing an application for a patent on the
principles of EBM. The process was
developed with the goal of creating 3D
objects by melting an electrically conductive
powder, layer by layer, with an electric beam.
In 1997, Arcam AB was founded and the
company has continued to develop EBM and
commercialize EBM printing.

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process

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3D Printing
This is a powder based 3D printing technique and uses a powder like
building material to be joined by liquid binder for 3D printing. In a
typical apparatus for binder jetting, there are two chambers where one
chamber is filled with powdered building material to feed into the other
chamber and the second chamber is used for realizing the 3D model.
The 3D model is built by gluing together the powdered building material
using the liquid binder.

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process
1. The machine spreads a layer of powder from the feed box to cover the
surface of the build piston. The printer then prints binder solution onto
the loose powder, forming the first cross-section.
(2) The powder is glued together at where the binder is printed. The
remaining powder remains loose and supports the layers that will be
printed above.
(3) When the cross-section is completed, the build piston is lowered, a
new layer of powder is spread over its surface, and the process is
repeated. The part grows layer by layer in the build piston until the part
is completed, completely surrounded and covered by loose powder.
Finally the build piston is raised and the loose powder is vacuumed,
revealing the complete part.
(4) Once a build is completed, the excess powder is vacuumed and the
parts are lifted from the bed. Once removed, parts can be finished in a
variety of ways to suit your needs. For a quick design review, parts can be
left raw or “green.” To quickly produce a more robust model, parts can
be dipped in wax. For a robust model that can be sanded, finished and
painted, the part can be infiltrated with a resin or urethane.

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materials
• The commonly used building materials for binder jetting
process are stainless steel, glass and some polymers like
Acrylonitrile Butadiene Styrene (ABS), Polyamide (PA) and
Polycarbonate (PC). With wide range of suitable building
materials and possibility of many binder and powder
combinations, a large range of models having many
possible colours and different mechanical properties can be
created using the binder jetting process. However, due to
use of binder liquid, the process is usually not suitable for
making structural parts. Still, Binder jetting can be
efficiently used for prototyping.

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Advantages:
➢ Relatively inexpensive
➢ Simple to operate
➢ Suitable for visual models and prototypes
➢ (SHS) Ability to integrate technology into small scale, office sized
machine
➢ Powder acts as an integrated support structure
➢ Large range of material options
Disadvantages:
➢ Relatively slow speed (SHS)
➢ Lack of structural properties in materials
➢ Size limitations
➢ High power usage
➢ Finish is dependent on powder grain size
➢ Limited functional parts. Relative to the SLS, parts built are much
weaker, thereby limiting the functional testing capabilities.
Applications:
➢ aerospace,
➢ energy/oil and gas,
➢ automotive,
➢ pump and tap industries

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Multi Jet Modelling (MJM) (PolyJet) in
3D Printing
• Material Jetting patented by Objet Ltd. in 1999
under the name of PolyJet (which merged with
Stratasys in 2012), combines Inkjet technology
and the use of photopolymers. Inkjet technology
is used by conventional 2D printers on paper
while photopolymers are materials that harden
when exposed to ultraviolet rays. This technology
has many benefits, including excellent resolution
(up to 0.016 mm), smooth surfaces (no staircase
effect unlike objects printed using FDM
technology) and a wide choice of materials and
colours for a relatively low cost and printing time.

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principle
➢ MJM builds models using a technique akin to ink-jet or phase-
change printing, applied in three dimensions.
➢ A print head comprising 352 jets oriented in a linear array
builds models in successive layers, each jet applying a special
thermopolymer material only where required.
➢ The MJM heads shuttles back and forth like a line printer (X-
axis), building a single layer of what will soon be a three-
dimensional concept model.
➢ If the part is wider than the print head, the platform
repositions (Y-axis) itself to continue building the layer. When
the layer is complete, the platform is distanced from the head
(Z-axis) and the head begins building the next layer. This
process is repeated until the entire concept model is
complete

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Advantages
1. Efficient and ease of use. MJM technology is an efficient and
economical way to create concept models. The large number of jets
from 352 heads allows fast and continuous material deposition at a
resolution of 300 dpi for maximum efficiency.
2. Cost-effective. MJM uses inexpensive thermopolymer material that
provides for cost-effective modeling.
3. Fast build time. As a natural consequence of MJM’s raster-based
design, the geometry of the model being built has little effect on the
building time.
4. Office-friendly process. As the system is clean, simple and
efficient, it does not require special facilities, thereby enabling it to
be used directly in an office environment.

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Dis advanatges
1.Small build volume. The machine has a comparatively small build
volume as compared to most other high-end rapid prototyping systems
(e.g., SLA-500), thus only small prototypes can be
fabricated.
2.Limited materials. Materials selection are restricted to 3D systems.
This limited range of material means that many functionally-based
concepts that are dependent on material characteristics cannot be
effectively tested with the prototypes.
3.Weak accuracy. The process lacks sufficient accuracy in building exact
prototypes when compared with the high-end RP systems.
Nevertheless, these prototypes are often good enough to be used as
visualization models or physical representations of the design.

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Models and Specifications
3D systems introduced its 3D printer, the
ThermoJet® in 1999, as a replacement for its
old model, ActuaTM 2100 that was launched
in 1996. Unlike other 3D Systems’ rapid
prototyping systems, ThermoJet® is intended
as a concept modeler. The purpose of a
concept modeler is mainly to generate a 3D
model in the fastest possible time for design
review.

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Case studies
1. Concept Modeler Speeds Handheld
Scanner
Development at Symbol Technology

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Important Question
1. Explain with a neat sketch SLS AM process and also state
its advantages, disadvantages and applications of it.
2.Explain with a neat sketch LENS AM process and also state
3. Explain with a neat sketch EBM AM process and also state
4. Explain with a neat sketch 3DP AM process and also state
5. Explain with a neat sketch MJM AM process and also state

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