Brief overview on additive manufacturing of thermoplastics, material extrusion (FDM) technology.

1. ADDITIVE MANUFACTURING OF THERMOPLASTICS
The world of manufacturing is now looking forward to a ‘paradigm shift’, from traditional
subtractive manufacturing to growing additive manufacturing technology. Though additive
manufacturing has been there for decades of years, unparalleled activities are happening in this
field in recent couple of years from amateur hobbyist level to high end manufacturing, mainly
due to the facts that several patents associated with this technology is about to be expired in
near future and secondly it really can make the big next step in the arena of manufacturing
technology as several news unfold in the industry.
ADDITIVE LAYER MANUFACTURING
In additive layer manufacturing 3D objects are synthesised by computer controlled addition of
2D layers of finer thickness as little as 0.05 mm; it is opposed to material subtractive nature of
conventional machining processes.
Fig. 1 Illustration of AM
WHAT IS THE BIG STEP?
It is able to create models of mind-boggling geometrical complexity at very little waste, without
involving any tooling/ tooling costs, which will also drastically reduce the lead time. Owing to
this benefits it’s been used exclusively in rapid prototyping applications for decades where
prototypes are available overnight.
Ford says: “3D printing can deliver prototypes in a matter of hours, enables designers and
engineers to quickly test and refine new designs and innovations – sometimes hundreds of
times.”
WHAT IS THE DIFFERENCE BETWEEN ALM, AM AND 3D PRINTING?
Generally, AM qualifies any process that does not operate by subtractive manufacturing (where
the material is removed to attain the desired shape), it is the process of joining materials to
build objects from 3D model data, usually layer after layer.
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. Indeed, all the

2. ALM processes are "additive" but not all of them look like "printing". The term 3D printing
has its origin sense, in reference to a process that deposits a binder material onto a powder bed
with inkjet printer heads layer by layer.
“Additive Layer Manufacturing (ALM)” or simply “additive manufacturing (AM)”, are terms
that encompass many others such as 3D Printing, Rapid Prototyping, Rapid Manufacturing,
Direct Digital Manufacturing or Layered Manufacturing.
ASTM and global technical standards use the official term additive manufacturing which gives
no room for ambiguity, making the meaning exact.
ADDITIVE MANUFACTURING TECHINQUES
Common to AM technologies is the use of a computer, 3D modelling software (Computer
Aided Design or CAD), machine equipment and layering material. Once a CAD sketch is
produced, the AM equipment reads in data from the CAD file and lays downs or
adds successive layers of liquid, powder, filament, sheet material or other, in a layer-upon-
layer fashion to fabricate a 3D object.
Fig. 2 Additive Manufacturing Categories
ISO/ASTM52900-15 defines seven categories of AM processes within its meaning, covering
all classes of materials: Powder Bed Fusion, Material Extrusion, Material Jetting, Binder
Jetting, Sheet Lamination, Vat Photo-polymerization and Directed Energy Deposition.
WHERE DOES IT STANDS NOW?
The technology has especially been applied in conjunction with Rapid Prototyping - the
construction of illustrative and functional prototypes. Additive Manufacturing is now being
used increasingly in series production particularly for customised tools and fixtures, consumer
products, art, entertainment and construction.
THERMOPLASTICS IN ADDITIVE MANUFACTURING
Additive manufacturing processes are gradually increasing in their practical application, and
engineers are starting to figure out where, when and how they could be the most useful. Rather
than looking to completely replace all conventional manufacturing techniques, additive
manufacturing is being used selectively on projects where it can offer a real advantage.

3. WHY THERMOPLASTICS?
The beauty of thermoplastics is that it get moldable at elevated temperatures and solidifies upon
cooling. These are amongst the cheapest materials that can be used in additive manufacturing
and are the typical content for commercial 3D printers being sold for home use (metals are
limited to industrial machines). While the other category of plastics, thermosets are difficult
for 3D printing applications, as it can’t be softened upon heating.
THERMOPLASTICS ADDITIVE MANUFACTURING- VARIOUS
TECHNIQUES
Major AM technologies in thermoplastics are; 1. Stereo-lithography, 2. Selective Layer
Sintering, 3. Fusion Deposition Modelling
1. Stereo-lithography (SLA): SLA works with photopolymer resins, which react with the laser
and cure to form a solid in a very precise way to produce very accurate parts. This is the first
invented AM technology, used extensively for rapid prototyping applications, also in master
pattern synthesis for injection molding and casting. It is limited with material flexibility as it
specifically requires photopolymers with considerable photo-degradation resistance, acrylic
derived plastics are commonly used.
2. Selective Laser Sintering (SLS): It uses a high power laser to fuse small particles
of plastic, metal, ceramic, or glass powders into a mass that has a desired three-dimensional
shape. The laser selectively fuses powdered material by scanning cross-sections generated from
a 3-D digital description of the part (from a CAD file or scan data) on the surface of a powder
bed. The greatest advantage is that it is having wider material spectrum, ranging from plastics
to metals. The machine requires greater amount of engineering as well as high end safety
features as it involves energy radiations, which makes it the costliest. Polyamides (Nylon) are
the commonly used thermoplastics in SLS.
FUSED DEPOSITION MODELLING AS THE MOST POPULAR AM
TECHNOLOGY
The term, Fused Deposition Modelling and its abbreviation to FDM are trademarked
by Stratasys Inc. The exactly equivalent term, Fused Filament Fabrication (FFF), was coined
by the members of the RepRap (open source DIY in 3D printing) project to give a phrase that
would be legally unconstrained in its use. It is also sometimes called Plastic Jet Printing (PJP).
It is currently the most commonly used AM technique.
A plastic filament or metal wire is unwound from a coil and supplies material to an extrusion
nozzle which can turn the flow on and off. There is typically a worm-drive that pushes the
filament into the nozzle at a controlled rate. It can create models with moderate amount of
details.
The great attraction about FDM is that it is time efficient process and simplest design are
possible for the machine on comparison with other AM processes, which makes it the cheapest
also, hobbyist’s desktop printer even starts from $200. Industrial FDM printers cost between
$10,000 and $400,000, high end Stratasys Fortus 900MC set back at $750,000.

4. Fig. 3 Illustration of FDM technology
Fig. 4 RepRap Pro Ormerod-3D-Printer-
Kit
MATERIALS:
It uses real engineering grade thermoplastics, parts built are stronger, durable and widely used
for functional testing applications. Parts can be built directly into ABS, polycarbonate, nylon
and various other materials. PLA and ABS plastic are the most common materials used in this
process.
Almost all printers can print ABS (extruder temperature, 190°C) and PLA plastic (160°C).
Most printers are capable of printing nylon (220°C not as strong as ABS but can be cheaper),
some can print PVC, though very rarely, PEEK (limited in market, very expensive) are also
used. The all metal hot-end printers can usually do HMPE (300°C), also there are variety of
PLA blends (mixed with wood, ceramics, metals, carbon fiber, etc.). These filaments are
available in various colors.
APPLICATIONS/ INDUSTRIAL VERTICALS ASSOCIATED WITH FDM:
Case study- BMW and Stratasys: BMW uses FDM technology to build hand-tools for vehicle
assembly and testing. In addition to financial advantages, the technology helps in getting
improved ergonomics to the tool. One of the tool built by Stratasys, reduced the weight of the
device by 72%, also it resulted in improved functionality, as the company managed to print
parts with complex shapes. In one such instance, specific tool was created for attaching bumper
supports, featuring a convoluted tube that bends around obstructions and places fixturing
magnets exactly where needed. Various applications includes,
a) Prototypes: It is produced for form / fit and functional testing in standard materials across
aerospace, automotive, energy sectors.
b) Rapid tooling parts/ Manufacturing tools: Customised tools, jigs and fixtures used in
automotive OEMs (Ford, BMW, and Opel) as well as in other sectors, which drastically reduce
tooling cost and lead time associated with conventional processes.

5. c) Small series parts: Precise, detailed parts are made in low volume for art, entertainment and
learning purposes (3D printed models of human organs).
Fig. 5 Batman- 3d printed
Fig. 6 Architecture model created by
FDM
d) Customized parts: Certain applications (Medical) demand personalised features which will
be uneconomical to go for molding, customised ancillary tools in medical field, mass
customization is expected to be a reality.
OUR VISION:
We, the Vimana Engineering Solutions, Bangalore, are a team of vibrant young engineers
totally engaged in taking up the baton of 3D printing revolution to our nation, there by leading
with the global wave.
We are looking forward to support creative verticals in 3d printing and introduce the power of
ALM to artists and creators. We are as well developing testing specimens to evaluate the
characteristics of ALM products and develop a bench mark.
We welcome, research organisations to get in touch with us who are working on similar lines
for us to mutually support each other and add value to the manufacturing perspective of ALM.