Additive fabrication can be defined as an assortment of
techniques of making solid objects through the chronological delivery of
material and/or energy to specific points in the space for production of that
solid. Additive fabrication is also known as solid freeform fabrication,
layered manufacturing, rapid manufacturing, and rapid prototyping.

Techniques: Additive fabrication is carried
out using a number of techniques. Let some of them be studied in detail.

?Electron Beam Melting’: EBM (Electronic Beam
Melting) can be described as the ?rapid prototyping’ for metals. It is better
known as ?rapid manufacturing’ method. The parts are manufactured by having the
metal powder melted layer by layer through a beam of electron in high vacuum.
The parts produced acquire strength, solidity, and are void-free as well. The
electrons have a very high speed; around 5 to 8 times the light speed. The
bombardment of these electrons takes place on the work material’s surface. This
generates heat which is enough for melting the part’s surface and causing it to
vaporize locally. Vacuum is required for the operation of EBM. This means that
the size of work piece is directly proportional to vacuum used. This technique
works on composites, ceramics, non-metals, and as stated above, metals.

Fused Deposition Modeling: Fused Deposition
Modeling (FDM) can be described as a kind of rapid manufacturing (RP) or rapid
prototyping technology which is generally used in engineering design. S.Scott
Crump had founded this technology in 1980s. It caught the commercial market in
1990. Like most of the RP processes, the principle of working of FDM is the
?additive principle’. It states that the material has to be laid down in
layers. The metal wire or plastic filament is then unwound and material is
supplied through it to the extrusion nozzle that can turn off and on the flow.

The nozzle’ then is heated for melting the material. It
could be moved in vertical and horizontal directions with the help of a
mechanism which is numerically controlled. This numerical control is obtained
through ?Computer Aided Design’ software package. Like stereo lithography, the
building of the model takes place from layers. This happens because the
material starts hardening after getting extruded from nozzle.

Numerous materials are offered with diverse trade-offs
between temperature and strength. One can use the FDM technology with
polycaprolactone, polycarbonates, polyphenylsulfones, and Acrylonitrile
butadiene styrene (ABS). Temporary supports can be made by using a
?water-soluble’ material. These supports are needed when manufacturing is still
going on. The commercial applications include making prototypes of servo or
stepper motors.

?Selective Laser Sintering’: Selective Laser
Sintering can be defined as an additive type of rapid manufacturing wherein a
?high power laser’ (like carbon dioxide laser) is used for fusing tiny
particles of ceramic, metal, or plastic powders into mass representing the
desired three-dimensional object. In comparison to other methods of rapid
manufacturing, ?selective laser sintering’ has the capacity of producing parts
from several powder materials available. They include polymers (polystyrene and
nylon), metals (composites, alloy mixtures, titanium, steel), and not to
forget- green sand. This physical process could be liquid-phase sintering,
partial melting , or full melting. 

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Tags: bombardment, ceramics, composites, deposition, electron beam, electrons, engineering design, extrusion, fdm, filament, light speed, metal fabrication, nozzle, rapid manufacturing, rapid prototyping techniques, rapid prototyping technology, s scott crump, solid freeform fabrication, solidity, work materials

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