The document discusses rapid prototyping, which uses additive manufacturing techniques to automatically create physical prototypes from 3D CAD models in a short period of time. It specifically describes stereolithography, fused deposition modeling, and selective laser sintering as common rapid prototyping methods that build parts layer by layer from materials like plastic or metal powder. Rapid prototyping allows faster design iteration and testing compared to traditional prototyping methods.

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CHAPTER 10
RAPID PROTOTYPING
MANUFACTURING TECHNOLOGY

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What is Rapid Prototyping?
• A CAD technique that allows “Automatic” creation of a
physical model or prototype from a 3-D model.
• A family of fabrication processes developed to make
engineering prototypes in minimum lead time based on a
CAD model of the item.
• Here material is added layer by layer to produce the part,
hence it is also termed as an additive process.
• The parts produced are not real prototypes as they are
made from materials whose properties are inferior to that
of the actual machine part

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What is Rapid Prototyping?
• Rapid Prototyping models can be used for testing
purposes.
• The materials used in Rapid Prototyping are limited and
dependent on the method chosen.
• Numerous plastics, ceramics, metals ranging from
stainless steel to titanium and wood like paper are some of
them.

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Why use Rapid Prototyping?
• Decreases lead time
• Traditional method is machining
• Can require significant lead-times – several weeks,
depending on part complexity and difficulty in ordering
materials
• Facilitates concurrent engineering
• Allows visualization of more ideas

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Why use Rapid Prototyping?
• Creating a prototype is an integral step in design
• A virtual prototype (a CAD model of the part) may not be
sufficient for the designer to visualize the part adequately
• Using RP to make the prototype, the designer can see and
feel the part and assess its merits and shortcomings

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Other names of Rapid Prototyping
• Layer manufacturing
• Direct CAD manufacturing
• Solid freeform fabrication
• Rapid prototyping and manufacturing (RPM)
• Additive Manufacturing

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Merits
• reduce prototype/production times from months to weeks/
days/hours
• a physical model is easier to sell to customers and
management
• Physical models are easier to check for errors
• avoids the high cost of prototype tooling, and allows
(more) design iterations
• prototypes costs can be lower than production types

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Demerits
• very expensive Investment/capital costs
• primary materials are specialized
• Low volume production
• Higher skill required for labour.

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STEREOLITHOGRAPHY (STL)
• RP process for fabricating a solid plastic part out of a
photosensitive liquid polymer using a directed laser beam
to solidify the polymer
• Part fabrication is accomplished as a series of layers - each
layer is added onto the previous layer to gradually build the
3-D geometry
• The first addition RP technology - introduced 1988 by 3D
Systems Inc. based on the work of Charles Hull
• More installations than any other RP method

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STEREOLITHOGRAPHY (STL)

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STEREOLITHOGRAPHY (STL)
• Stereolithography is the name of a process used to make
three-dimensional models from computer databases.
• Stereolithography uses a photochemical event to direct the
formation of points of plastic on the surface of an easily
solidified liquid.
• The computer directs a laser across the surface of a
polymerizable plastic converting the polymerizable material
point by point into a solid.

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STEREOLITHOGRAPHY (STL)
• This is done, in this particular experimental setup, on a
platform that is held a few millimeters under the surface of
the photo reactive liquid.
• After the laser has converted to solid plastic all the points in
one layer that are needed for the model, producing a two
dimensional lithograph of fixed z dimension, z, the platform
is dropped a small increment and a second layer is built on
top of the first.

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STEREOLITHOGRAPHY (STL)
• This process continues until each layer of the computer
graphic, or plan, is converted to solid plastic. When the
process is complete the model can be lifted from the plastic
vat as an exact replica of the computer graphic.
• Excess polymer is removed with alcohol and light sanding
is sometimes used to improve the appearance.

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STEREOLITHOGRAPHY (STL)
• One of the most important uses of stereolithography is in
making replicas of medical data, such as CT scans and
MRI scans, for surgical planning.
• Stereolithography generally is considered to provide the
greatest accuracy and best surface finish of any rapid
prototyping technology.

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FUSED DEPOSITION MODELING (FDM)
• RP process in which a long filament of wax or polymer is
extruded onto existing part surface from a work head to
complete each new layer
• Work head is controlled in the x-y plane during each layer
and then moves up by a distance equal to one layer in the
z-direction
• Extrudate is solidified and cold welded to the cooler part
surface in about 0.1 s
• Part is fabricated from the base up, using a layer-by-layer
procedure

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FUSED DEPOSITION MODELING (FDM)

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FUSED DEPOSITION MODELING (FDM)
• FDM starts with a 3D CAD model sliced into thin layers in
Z-axis. These sliced layers are used to drive an extrusion
head of FDM machine.
• The building material, in the form of a thin solid filament, is
fed from a spool to a movable head controlled by motors.
• Second filament is fed from an adjacent nozzle for support
material, it is used to give support for overhanged or
cantilever features.
• The filament reaches the liquifier head, melts it and then
gets extruded through a nozzle onto the part surface.

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FUSED DEPOSITION MODELING (FDM)
• After covering the whole cross section, the platform
descends by one layer thickness to lay down the next layer.
Process repeats itself until full 3D part is formed.
• The temperature of machine chamber is precisely
controlled below the melting point of the material so that
only little amount of heat is required to melt the filament
and on the other hand part need to be kept cool enough so
that the molten material solidifies upon contact.
• FDM is the second most widely used rapid prototyping
technology, after stereolithography.

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SELECTIVE LASER SINTERING (SLS)
• Moving laser beam sinters heat fusible powders in areas
corresponding to the CAD geometry model one layer at a
time to build the solid part
• After each layer is completed, a new layer of loose powders
is spread across the surface
• Layer by layer, the powders are gradually bonded by the
laser beam into a solid mass that forms the 3-D part
geometry
• In areas not sintered, the powders are loose and can be
poured out of completed part

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SELECTIVE LASER SINTERING (SLS)

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SELECTIVE LASER SINTERING (SLS)
• SLS process produces parts directly from 3D CAD model,
layer by layer similar wherein a resin powder is used.
• The CO2 Laser provides a concentrated heating beam
which is traced over the tightly compacted layer of fine
heat-fusible powder. The temperature in the entire chamber
is maintained little below the melting point of the powder.
• So laser slightly raises the temperature to cause sintering
that is, welding is carried out without melting.