A7383 3D Printing UNIT-III : 3D printing techniques

3D PRINTING
(A7383)
Dr. M VISHNU VARDHAN
ASSOCIATE PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
VARDHAMAN COLLEGE OF ENGINEERING
HYDERABAD

UNIT-III
Extrusion-Based 3D
Printing Processes

UNIT III Course Syllabus
• Fused Deposition Modeling (FDM),
• Principles, Materials, Plotting and path control, Bio-Extrusion,
Process Benefits and Drawbacks, Applications of Extrusion-Based
Processes.
• Powder Bed Fusion 3D Printing Processes:
• Selective laser Sintering (SLS), Materials, Powder fusion
mechanism, SLS Metal and ceramic part creation,
• Electron Beam melting (EBM), Process Benefits and Drawbacks,
Applications of Powder Bed Fusion Processes.
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Fused Deposition Modeling
Contd….
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• Fused Deposition Modeling (FDM) was developed by Stratasys in Eden Prairie, Minnesota. In this process, a plastic
or wax material is extruded through a nozzle that traces the part's cross sectional geometry layer by layer.
Material type: Solid (Filaments)
Materials:
Thermoplastics such as ABS, Polycarbonate,
and Polyphenylsulfone; Elastomers
Max part size: 36.00 x 24.00 x 36.00 in.
Min feature size: 0.005 in.
Min layer thickness: 0.0050 in.
Tolerance: 0.0050 in.
Surface finish: Rough
Build speed: Slow
Applications:
Form/fit testing, Functional testing, Rapid
tooling patterns, Small detailed parts,
Presentation models, Patient and food
applications, High heat applications

VCE,HYB 5

• 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.
VCE,HYB 7
Contd….

• This pressure must be kept steady and at a constant speed to enable
accurate results (Gibson et al., 2010). 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.
VCE,HYB 8
Contd….

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.
VCE,HYB 9
Contd….

Contd….
• Technical Information
• 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 (Chua et al., 2010).
• Accuracy and speed are low when compared to other processes and the quality
of the final model is limited to material nozzle thickness (Krar et al., 2003).
VCE,HYB 10

Contd….
• When using the process for components where a high tolerance must be
achieved, gravity and surface tension must be accounted for (Gibson et al.,
2010). Typical layer thickness varies from 0.178 mm – 0.356 mm (Chua et al.,
2010).
• One method of post processing to improve the visual appearance of models
is through improving material transmissivity. Methods have been explored by
Ahn et all, include increasing temperature and the use of resin.
• Experiments using cyamo acrylate resin, often used to improve the strength
of parts, resulted in a 5% increase in transmissivity after 30 seconds and
sanding (Ahn, 2004).
• As with most heat related post processing processes, shrink- age is likely to
occur and must be taken into account if a high tolerance is required
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Contd….
Machine Area Layer Thickness Built Volume
Insstek MX3 1000 x 800 x 650
mm
Al, Cobalt, Copper and
Nickel alloys
520l
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Machine Example:
Materials
The Material Extrusion process uses polyers and plastics.
Polymers: ABS, Nylon, PC, PC, AB

Contd….
• Pros / Cons
• Advantages:
• Widespread and inexpensive process
• ABS plastic can be used, which has good structural properties and is easily accessible
• Disadvantages:
• The nozzle radius limits and reduces the final quality
• Accuracy and speed are low when compared to other processes and accuracy of the
final model is limited to material nozzle thickness
• Constant pressure of material is required in order to increase quality of finish
VCE,HYB 13

Powder Bed Fusion(PBF)3D Printing
Process
• 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
VCE,HYB 14

Powder Bed Fusion(PBF)
Definition
• Powder bed fusion is one of seven Additive
manufacturing techniques, in which either laser,
heat or electron beam is used to melt and fuse
the material together to form a three-dimensional
object.
Types of Powder bed fusion
• Both metal and plastic parts can be made using
this technique and it can be classified into the
following four groups by the energy source it uses
to melt the material.
• Laser Fused
• Electron Beam fused
• Fused with agent and energy
• Thermally fused
VCE,HYB 15

• Further, the Laser Fused technique can
be subdivided into Selective Laser
Sintering (SLS) where only plastic parts
can be printed and Direct Metal Laser
Sintering or it is sometimes called
Selective Laser Melting (SLM) where,
as the name suggests print metal.
(figure 2)
• EBM or Electron Beam Melting comes
under Electron beam fused where
metal powder is fused using electron
beam under high vacuum.
VCE,HYB 16
Figure 2. Powder bed fusion types

• HP’s Multi Jet Fusion (MJF) comes under
the third category where the powder bed
is heated uniformly at the start, where a
fusing agent is used to bond the powder
to create 3D geometrical parts.
• Danish company Blueprinter’s Selective
heat sintering (SHS) technology uses a
thermal print head for sintering
thermoplastic powder to create 3D parts
which come under the fourth category,
thermal powder bed fusion.
VCE,HYB 17

• How powder bed fusion works
• A schematic of a simple selective laser
sintering process is shown in figure 3
below to help describe the powder
bed fusion method.
• As shown in the above schematic,
Powder bed fusion printers have two
chambers, a Build chamber and a
powder chamber along with a coating
roller to move and spread the powder
material across the build chamber.
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Figure 3. Schematic of Selective Laser Sintering (Gibson,
Rosen, & Stucker, 2010)

• In some cases, the above setup is
inside a partial vacuum chamber and
filled with inert gas to protect the
molten material from corroding. Also,
some manufacturers have two powder
chambers on either side or the same
side of the build chamber and use
them as the excess overflow chamber
as shown in figure 4.
• Both powder and build chambers can
move up and down on linear z-axis
which is perpendicular to the top
horizontal plane.
• Figure 4. Powder bed fusion build chamber
(source: DMG MORI)
VCE,HYB 19

• Although each type of powder bed
fusion technique mentioned above
varies with the different technology it
uses to create the 3D parts, each
broadly follows some common steps in
the process to create the final part.
1. 3D CAD models are converted into
object cross-sections and saved as a .stl
file. (Find out what’s a .stl file and other
3D printing acronyms & abbreviations)
2. This stereolithographic file of the part
or parts is loaded and placed in the
correct orientation through the printer
user interface. VCE,HYB 20
Figure 5. multiple parts loading (source: DMG MORI)
This could be desktop based or printer
based software.
3. As the image below shows, the build
area can be filled with multiple parts to
increase productivity.

4. The powder chamber is filled with
powdered build material (material in
powder form) either manually or through
an automated process. This could be via a
build material cartridge or a hopper.
5. The coating roller then deposits a thin
layer of powder across the build platform.
The resolution of the parts is defined by
the thickness of the layer. Sometimes a
scrapper or a blade or a levelling roller is
used after the coating roller to ensure
uniform thickness of the material top layer.
VCE,HYB 21
Figure 6. Coating roller /blade (source:DMG
MORI)

6. Next, the energy source such as laser
or electron beam is used to melt the
deposited thin top layer of the metal
powder selectively as per digital 2D cross-
sectional data from the STL file.
7. When that layer has been scanned and
fused, the build platform is incrementally
lowered down by the resolution of the
bed z-axis. Simultaneously, the powder
chamber is raised by the same amount.
This defines the part resolution and
dictates the thickness of the powder
coating.
VCE,HYB 22
Figure 7. Powder_bed_fusion_ chambers
( source:google images)
8. The coating roller then deposits another thin
layer of powder across the build chamber or
platform on top of the fused section of a layer
thickness.

9. The energy source again scans and fuses
the layer. This layering and fusing process
continues until the 3D object is fully built.
10. At the end of the print operation, the
part will be buried inside the powder build
chamber. As shown below the powder will
be removed leaving the fused part
connected to the build plate. Although the
powder bed fusion doesn’t need part
support, the part still needs an anchor
point to build from, hence the part will be
built onto the built plate.
VCE,HYB 23
Figure 8. Cleaning and removing excess
powder (source:DMG MORI)

11. Parts are then removed from the
build plate by wire eroding or other
machining means. Hence it’s crucial that
the parts are designed and loaded in the
correct most suitable orientation to avoid
build errors and reduce waste and build
time.
12. Depending on the size of the
machine, the chambers can be either a
separate replaceable cartridge or built-in
hoppers.
12/06/2025 VCE,HYB 24
Figure 9. Parts build_DMLS (source:DMG
MORI)

Selective laser sintering (SLS-PBF)
VCE,HYB 25
• Selective Laser Sintering (SLS) was developed at the University of Texas in
Austin, by Carl Deckard and colleagues. The technology was patented in
1989 and was originally sold by DTM Corporation. DTM was acquired by 3D
Systems in 2001.
Material type: Powder (Polymer)
Materials:
Thermoplastics such as Nylon,
Polyamide, and Polystyrene;
Elastomers; Composites
Max part size: 22.00 x 22.00 x 30.00 in.
Min feature size: 0.005 in.
Min layer thickness: 0.0040 in.
Tolerance: 0.0100 in.
Surface finish: Average
Build speed: Fast
Applications:
Form/fit testing, Functional testing, Rapid
tooling patterns, Less detailed parts, Parts
with snap-fits & living hinges, High heat
applications

Selective laser sintering (SLS)
Contd…
VCE,HYB 26

Contd…
• 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 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.
VCE,HYB 27

Contd…
Selective Laser Sintering – 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.
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.
.
VCE,HYB 28

Contd…
• Selective laser sintering (SLS) machines are made up of three
components (Gibson et al., 2010): a heat source to fuse the material, a
method to control this heat source and a mechanism to add new layers of
material over the previous.
• The SLS process benefits from requiring no additional support structure,
as the powder material provides adequate model support throughout the
build process.
• The build platform is within a temperature controlled chamber, where
the temperature is usually a few degrees below that of the material melting
point, reducing the dependency of the laser to fuse layers together.
VCE,HYB 29

Contd…
• The chamber is often filled with nitrogen to maximize oxidation and end
quality of the model. Models require a cool down period to ensure a high
tolerance and quality of fusion.
• Some machines monitor the temperature layer by layer and adapt the power
and wattage of the laser respectively to improve quality.
VCE,HYB 30

Contd…
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Selective laser sintering (SLS) Products
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Electron Beam Melting (EBM) mechanism
VCE,HYB 33

Electron Beam Melting (EBM) 3D Printing Processes
• Electron Beam Melting (EBM) Layers are fused using an electron beam to
melt metal powders. Machine manufacturer Arcam used electromagnetic
coils to control the beam and a vacuum pressure (EBM Arcam , 2014).
• EBM provides models with very good strength properties due to an even
temperature distribution of during fusion (Chua et al., 2010). The high quality
and finish that the process allows for makes it suited to the manufacture of
high standard parts used in aeroplanes and medical applications.
• The process offers a number of benefits over traditional methods of implant
creation, including hip stem prosthesis (Agaruala, 1995). Compared to CNC
machining, using EBM with titanium and a layer thickness of 0.1mm, can
achieve better results, in an faster time and can reduce the cost by up to
35%.
VCE,HYB 34

Electron Beam Melting (EBM)
Contd….
• Post processing requirements include removing excess powder and further
cleaning and CNC work. One advantage and common aim of post processing
is to increase the density and therefore the structural strength of a part.
• Liquid phase sintering is a method of melting the metal powder or powder
combination in order to achieve homogenisation and a more continuous
microstructure throughout the material, however, shrinking during the process
must be accounted for.
• Hot isotactic pressing is another method to increase density; a vacuum sealed
chamber is used to exert high pressures and temperatures of the material.
• Although this is an effective technique to improve strength, the trade-off is a
longer and more expensive build time.
VCE,HYB 35

Contd….
Materials
• 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 (Materials
Arcam, 2014).
Machine Example:
VCE,HYB 36
Machine Area Layer Thickness Print Speed
3S Systems ProX 500 381 x 330 x 457 mm 0.08 - 0.15 mm 2 litres/hr

Contd….
• Advantages:
• Relatively inexpensive
• 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
VCE,HYB 37

Contd….
• Strengths
• Manufacturing speed. The electron beam can separate to heat the powder
in several places simultaneously, which significantly speeds up production.
On the other hand, a laser must scan the surface point by point.
• Pre-heating the power before it melts limits the deformations and thus
reduces the need for reinforcements and supports during manufacturing.
• Weaknesses
• Precision. At the powder level, the electron beam is a little wider than the laser
beam, which reduces the accuracy.
• The size of the parts that can be manufactured. Arcam’s largest build volume
(on the Q20 machine) represents a diameter of 350 mm for a height of 380
mm. On the other hand, laser machines (such as the X-Line of Concept Laser)
offer manufacturing volumes at least twice as high.
VCE,HYB 38

A7383 3D Printing UNIT-III : 3D printing techniques

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A7383 3D Printing UNIT-III : 3D printing techniques