Additive Fabrication, Rapid Prototyping, and Metal Fabrication
Additive Fabrication, Rapid Prototyping, and Metal Fabrication
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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