Lecturer: 

Dr. Ahmad Zafari
zafari.a@unimelb.edu.au
Department of Mechanical Engineering, the University of Melbourne, Australia, Semester 2/2020

MCEN90020 Unit 2: Additive Manufacturing of Metals 2021

Subtractive, formative and additive Manufacturing

Subtractive manufacturing is a process by which 3D objects are

constructed by successively cutting material away from a solid block of
material.
 Manual cutting
 CNC
 Lathing
 Examples

1. It is hard or even impossible to create complicated shapes

2. Sometimes different parts are built separately and then
assembled by welding (each weld is a weak point)
3. High amount of waste materials
4. Tooling cost
 Formative manufacturing is a process through which a materials is shaped
using compressive, tensile, or shear stresses (or a combination of them). It is
normally used for metal or plastic forming. No material is added or subtracted,
and the workpiece is either deformed or displaced to the desired shape. Main
advantage of this method is mass production of identical parts at a low price per
unit.

Press Vacuum
Injection molding
forming

1. Time and cost needed to produce a mold.

2. Molds cannot be modified. For each new design, a new mold is required.
3. Simple designs, particularly for metal forming, are produced.
Additive Manufacturing (ISO/ASTM52900-15): a process of joining materials
to make parts from 3D model data, usually layer upon layer, as opposed to
subtractive manufacturing and formative methodologies. Synonyms: additive
fabrication, additive processes, additive techniques, additive layer
manufacturing, layer manufacturing, and freeform fabrication
Applications of 3D printing
Architecture (3D models)
Medical applications

educational material
 Medical implants

a titanium 3D-printed sternum and rib

cage, designed and manufactured by an
Australian company (CSIRO)
Titanium implant to
be used in a skull.
Aerospace applications
The old nozzle was made of
many parts that required assembly
and 25 welds (each one a
weakness point) and suffered from
coking (accumulation of carbon
deposits). The new nozzle has only
5 welds (instead of 25 welds
previously) greatly reducing the
potential fault/weakness points.
The designers added small built-in
cooling tubes inside the part to
prevent coking and optimized the
amount of material used in the part
to a minimum using strategically
placed supports. The result is a fuel
nozzle that is 25% lighter, and up to
5 times more durable. Fuel
efficiency was improved 15% and
Fuel Nozzle (by GE) emissions were drastically reduced,
by double digits.
Marin Engineering: Repairing

nozzle ring in turbocharger

Advantages of AM
 Manufacturing complicated shapes: almost any shape is printable if its CAD
model is produced
 Variety is free: If a part needs to be changed, the change can simply be
made on the original CAD file, and the new product can be printed right
away.
 Limited assembly is required: Moving parts such as hinges and bicycle
chains can be printed in metal directly into the product, which can
significantly reduce the part numbers.
 Tooling cost is low
 Manufacturing objects for individual customers
 Small amount of waste
Disadvantages of AM (in particular Metal AM)
 Size limitation: most metal AM powder bed machines making a part
limited to less than 400 millimetres per side, there are only a few
singular parts we can create in their entirety. And for small
components, machine size still limits us to perhaps only creating five
to ten at a time.
 Not suitable for mass production: slow build rates and high
production costs.
 Complicated process: there are many parameters which must be set
for each design to make it a success.
 Accuracy: the cost of AM is very high, and adding the costs of labour
and post-AM treatments makes the technology even more
expensive. Until AM can produce accurate parts with minimal need
for post-processing (e.g. heat treatments, machining), it will not be
economically viable for large-scale production.
 Bad surface finish
 Strong texture
 Materials: the alloys currently available are those designed for cast
or wrought products. We need materials particularly designed for AM
processes.
B. Blakey-Milner et al.,
Materials & Design
209 (2021) 110008.
AM processes
AM Processes

1. Stereolithography (SL/SLA)
2. Digital Light Processing (DLP)
3. Photopolymer Phase Change Inkjets (PolyJet)
4. Fused Deposition Modeling (FDM)
5. Selective Laser Sintering (SLS)
6. Selective Laser Melting (SLM)
7. Laser Metal Deposition (LMD)
8. Electron Beam Melting (EBM)
9. Wire and Arc Additive Manufacturing (WAAM)
10. Laminated Object Manufacturing (LOM)

http://3dprintingfromscratch.com/common/types‐of‐3d‐printers‐or‐3d‐printing‐
technologies‐overview/
 Standard classification of AM Processes
ISO/ASTM52900: there are seven different types of processes that an AM
system might implement to 3D print.
• Binder jetting: A process by which a liquid bonding agent is deposited onto a bed of powder. Can
be used with gypsum, sand, glass, metal, and several others.
• Direct energy deposition (DED): In which metal, as a powder or wire feedstock, is fed in front of an
energy source, such as an electron or laser beam, mounted on a multiaxis robotic arm. The material
is melted onto a substrate layer-by-layer. Used with metals such as titanium and cobalt-chrome.
• Material extrusion: A material is deposited from an extruder onto a substrate. Typically, a
thermoplastic filament is melted by a heating mechanism and extruded through a hot end.
However, the same process can be used with viscous materials such as concrete, clay, organic
tissue, or even food.
• Material jetting: Specialty printheads, such as piezoelectric printheads similar to those found in 2D
inkjet printers, spray a liquid material onto a substrate. Most often, this material is a photosensitive
plastic resin (also known as a photopolymer) that is then hardened with an ultraviolet (UV) light.
• Powder bed fusion: This is a process by which an energy source, such as a laser or electron beam,
is directed at a bed of powder to heat the individual particles until they melt together. Usually, this
technology is associated with metals such as titanium, as well as plastics such as nylon.
• Sheet lamination: In this process, sheets of material are fused together, with the desired shape
etched into each shape. The final object is then removed from the block of bound sheets. This rare
3D printing process is currently most not only often used with paper, but also with metal and plastics.
• Vat photopolymerization: A vat of photopolymer resin is exposed to an energy source, such as a
laser beam or digital light projector, which hardens the material layer-by-layer. This
process is usually associated with thermoset plastics.
Ref: Jing Zhang, Yeon-Gil Jung, Additive Manufacturing : Materials, Processes,
Quantifications and Applications, Cambridge, MA : Butterworth-Heinemann, 2018
Area Organisation Standard No. Title

ISO 17296-2-15 Additive manufacturing- General principles- Part 2: Overview of process categories and feedstock
ISO
Nomenclature and data

ISO 17296-4-14 Additive manufacturing-General principles- Part 4: Overview of data processing

ISO/ASTM Additive manufacturing- General principles- Terminology

formats

52900-15
ISO/ASTM Standard terminology for additive manufacturing- coordinate systems and test methodologies
ISO/ASTM
52921-13
ISO/ASTM Standard specification for additive manufacturing file format (AMF), Version 1.2
52915-16
VDI VDI 3405 Additive manufacturing processes, rapid prototyping- Basics, definitions, processes

Standard specification for additive manufacturing Titanium-6 Aluminum-4 Vanadium with powder bed
ASTM F2924-14 fusion
Standard specification for additive manufacturing Titanium-6 Aluminum-4 Vanadium ELI (extra low
ASTM F3001 interstitial) with powder bed fusion
Materials

ASTM
ASTM F3055-14a Standard specification for additive manufacturing Nickle alloy (UNS N07718) with powder bed fusion

ASTM F3056- Standard specification for additive manufacturing Nickle alloy (UNS N06625) with powder bed fusion
14e1
VDI 3405 Blatt Additive manufacturing processes, rapid prototyping – Laser beam melting of metallic parts- Material data
VDI sheet aluminnium alloy AlSi10Mg
2.1:2015-07
ISO 17296-3-14 Additive manufacturing- General principles- Part 3: Main characteristics and corresponding test methods
ISO

ASTM F2971-13 Standard practice for reporting data for test specimens prepared by additive manufacturing

ASTM F3049-14 Standard guide for characterizing properties of metal powders used for additive manufacturing
ASTM
Testing

ASTM F13122-14 Standard guid for evaluating mechanical properties of metal materials made via additive manufacturing
processes

ISO/ASTM Standard terminology for additive manufacturing- Coordinate systems and test methodologies
ISO/ASTM
52921-13
VDI 3405 Blatt 2 Additive manufacturing processes, rapid prototyping- Laser beam melting of metallic parts- Qualification,
VDI quality assurance and post processing
Stereolithography (SLA) 1. Low power, highly focused
ISO/ASTM52900: Vat photopolymerization
UV laser is used to trace out
successive cross-sections of
a 3D object in a vat of liquid
photosensitive polymer. As
the laser traces the layer, the
polymer solidifies (cures) and
the excess areas are left as
liquid.
2. A levelling blade (sweeper) is
moved across the surface to
smooth it before solidifying
the second layer.
3. The platform is lowered by a
distance equal to the layer
thickness and a subsequent
layer is formed on top of the
previous one.

Introduced in 1988 by 3D System, Inc based on

the work by inventor Charles Hull
 Digital Light Processing (DLP)
ISO/ASTM52900: Vat photopolymerization 1. Similar to SLA a
photoreactive polymer is
used
2. Light is projected at the
surface of the liquid
polymer, curing, and thus,
solidifying it. One layer at
a time is formed, unlike
the SLA that laser should
have moved at X and Y
directions to build one
solid layer.
3. The Z-axis moves by one
layer

created in 1987 by Larry Hornbeck of Texas

Instruments
SLA vs. DLP
 Both SLA and DLP use photoreactive polymers.
 SLA uses laser, while DLP uses light.
 SLA uses two motors, known as galvanometers or galvos, (one on
the X axis and one on the Y axis) to rapidly aim a laser beam across
the print area, solidifying resin as it goes along (Vector scan).
However, . Because the projector is a digital screen, the image of
each layer is composed of square pixels, resulting in a layer formed
from small rectangular bricks called voxels (Mask Projection).
 DLP is much faster than SLA
SLA vs. DLP
Photopolymer Phase Change Inkjets (PolyJet)
ISO/ASTM52900: Material jetting
1. 3D printer jets droplets of
liquid photosensitive
polymer and instantly
cures them by a UV laser.
This process continues
until one layer of the 3D
model is built.
2. Elevator is lowered by a
distance equal to the layer
thickness and a
subsequent layer is
formed on top of the
previous one.
3. The user easily removes
the support material by
hand, with water or in a
solution bath
Thermal Phase Change Inkjets
ISO/ASTM52900: Material jetting

1. Inkjet print-head jets

heated liquid plastic and
support material (wax)
2. The droplets cool down,
and thus, solidify
3. Plane milling head
removes excess
material to make the
thickness of the entire
layer uniform
4. Particles are vacuumed
5. The build platform is
lowered by one layer
thick
 Fused Deposition Modeling (FDM)/
Fused Filament Fabrication (FFF)
ISO/ASTM52900: Material extrusion
1. Thermoplastic is used
2. A wire of the thermoplastic
is fed into a temperature-
controlled FDM extrusion
head, where it is heated to
a semi-liquid state.
3. The head extrudes and
deposits a layer of the
material based on CAD
model by moving in X and
Y coordinates.
4. The build platform then
moves in Z direction for
depositing a second layer
5. Depending on the model a
supporting material is
used which can be
dissolved after printing is
Implemented at first time by Scott completed.
Crump, Stratasys Ltd. founder, in 1980s
Plaster-based 3D Printing (PP)
ISO/ASTM52900:Binder Jetting

1. A gypsum based powder

which is a form of plaster is
fed by a delivery system and
flattened by a roller to a fixed
thickness
2. A nozzle jet a binder into
the powder in the shape of
the cross section of the
object.
3. Once a layer is printed, the
build platform descends the
thickness of a single layer
and another layer of powder
is distributed by the roller.
Laminated Object Manufacturing (LOM)
ISO/ASTM52900: Sheet lamination
1. a feed mechanism advances
a sheet over a build platform
2. a heated roller applies
pressure to bond the sheet
to the layer below
3. a laser cuts the outline of
the part in each sheet layer.
4. Parts are produced by
stacking, bonding, and
cutting layers of adhesive-
coated sheet material on top
of the previous one.
5. After each cut is completed,
the platform lowers by a
depth equal to the sheet
thickness, and another
sheet is advanced on top of
the previously deposited
layers.
Developed by the California-based 6. The platform then rises
company Helisys Inc. slightly and the heated roller
applies pressure to bond the
new layer.
 Powder bed fusion methods

Selective Laser Sintering (SLS) 1. metallic powder is fed by a

delivery system and flattened by
a roller to a fixed thickness
(normally 30-90 µm)
2. The laser heats the powder to
the point that it can fuse
together, leading to the powder
sintering.
3. The working platform moves
downwards after each layer is
completed and the process
repeats until the whole 3D object
is produced.

This technique was developed by Carl

Deckard, a student of Texas University, and
his professor Joe Beaman in 1980s
Sintering in single- and two-component powders
 Selective Laser Melting (SLM)
ISO/ASTM52900:
Laser Powder bed fusion (L-PBF) 1. metallic powder is fed by a
delivery system and flattened by
a roller to a fixed thickness
(normally 30-90 µm)
2. The laser melts each layer of
powder based on a CAD
produced model
3. The working platform moves
downwards after each layer is
completed and the process
repeats until the whole 3D object
is produced.

The history of SLM started with German

research project held by group of
Fraunhofer Institute ILT in 1995.
AM250 SLM system
 Electron Beam Melting (EBM)
ISO/ASTM52900:
Electron Powder bed fusion (E-
PBF)

1. Work piece is placed in a high

vacuum chamber
2. The electron beam melts each
layer of powder based on a CAD
produced model
3. The working platform moves
downwards after each layer is
completed and the process
repeats until the whole 3D object
is produced.
https://www.youtube.com/watch?v=M_q
SnjKN7f8

https://www.youtube.com/watch?v=jqjD‐
FWMexo
It was originally coined by Arcam AB Inc. in the
beginning of this century.
Magnetic lens
C. Körner, International Materials Reviews 61 (2016) 361‐377. 
EBM: Future work
EBM facility is, in fact, a high voltage SEM. Hence all the
signals used for materials characterisation, are available in
EBM machines too  Live observation of melt pool formation,
solidification, phase transformation, etc.
Laser Metal Deposition (LMD)
ISO/ASTM52900: Direct energy deposition (DED)
It is used for :
• producing functional graded
materials (FGMs)
• Coating & repair purposes
• generating entire
components and joining
processes
Wire and Arc Additive Manufacturing (WAAM)
ISO/ASTM52900: Direct energy deposition-arc (DED-arc)
S. W. Williams et al.,
Mater. Sci. Technol.
32 (2016) 641-64
•A full circle means that the commercially available machines using the noted process are capable
of processing the noted material.
•A hollow circle means the process-material combination has been demonstrated in research or
pre-release commercial announcements, but machines are not yet shipping to customers.
•Circles shaded black represent direct processes, i.e., the printing process produces a part with the
desired final density and dimensions. Circles shaded blue are indirect processes, meaning that a
densification step such as sintering is needed to give the part its final density and dimensions. That
said, every AM process requires steps after printing.
Post AM: densification

Hot isostatic pressing (HIP)

New AM methods
World’s largest 3D printer
http://www.titomic.com/

Output size: 9 m × 3 m × 1.5 m

The cold spray process was originally developed in the mid-1980s at the Institute
of Theoretical and Applied Mechanics of the Russian Academy of Science in
Novosibirsk by A. Papyrin and colleagues.

Anatolii Papyrin, Cold spray technology, Elsevier, Amsterdam, 2007 (eBook is available)
Titomic kinetic fusion
The replicator

• Digital model is printed at once, rather than layer by layer.

• It is a lot faster than traditional 3D printing.
• No support structure is required.

https://www.firstpost.com/tech/science/groundbreaking‐new‐3d‐
printer‐the‐replicator‐uses‐light‐to‐print‐objects‐in‐resin‐6030351.html