Rapid prototyping

 Refers to processes and technology which can
produce physical models directly from the 3D
CAD model data.
 Variety of specialized equipment, software
and materials capable of using 3D CAD
design data input to directly fabricate
geometrically complex objects.
 Layered manufacturing
 STL (Standard Triangular Language) – Most
common and generally supported by all the
RP equipment

Arvind Deshpande(VJTI) 4/10/2012 2

 A CAD model is generated and converted to STL
format
 RP device processes the STL file by creating
sliced layers of the model. Resolution of model
depends on number of layers or layer thickness.
 First layer is created, the model is then lowered
by one layer thickness and process is repeated
until completion of the model
 The model and any supports are removed; the
surface of the model is then finished and
cleaned.


 Stereolithography
 Selective Laser Sintering
 3-D Printing
 Fused Deposition Modeling
 Laminated Object Manufacturing


 Most commonly used process for RP. First
commercialized process.
 Build shapes using light to selectively solidify photo
curable resins
 Uses support platform that is lowered into a reservoir
of liquid photo curable resin.
 A UV-laser “writes” on the surface tracing the outline
of the part, producing single layer of solidified resin.
Laser beam is guided across the surface by servo
controlled galvanometer mirrors.
 Initial layer is lowered incrementally by the height of
the next slice, the layer is recoated with resin and
another is traced on top of it.
 The process is repeated until entire part is made.


Materials – Liquid photo sensitive resins
Advantages
1. High accuracy
2. Medium range of materials
3. Large build size
Disadvantages
1. Expensive
2. Support structures needed
3. Limited to some of the photo curable
plastics only


 A layer of powdered material is spread out
and leveled in the plane
 CO2 laser selectively traces the layer to fuse
areas defined by geometry of the cross-
section along with fusing to the bottom layer
 The powder can be joined by melting or
surface bonding.
 After initial layer is formed, powder is
reapplied and laser processes the next layer


Materials – Plastics, waxes, low temp. melting
metal alloys, Nylon based materials
Advantages
1. Large range of materials
2. Good accuracy
3. Large build size
4. Has the highest strength of any RP models.
Disadvantages
1. High cost process
2. Poor surface finish
Generally used in applications such as direct
tooling applications for investment and die casting
applications.


 Similar to SLS but instead of laser beam, liquid binder
is applied to bond the powder particles.
 The printer spreads a layer of powder from the
feedbox to cover the surface of the build platform
and then prints binder solution on to the loose
powder, forming the first cross section of the part.
 Where the binder is printed, the powder’s particles
are glued together. When the cross section is
complete, the build platform is lowered slightly and a
new layer of powder is spread over its surface.
 The process is repeated until the whole model is
completed. The build platform is raised and loose
powder is vacuumed away revealing the completed
part.


 A plastic filament is unwound from a coil and
supplied material to an extrusion nozzle.
 The nozzle is heated to melt the plastic.
Nozzle can move in horizontal and vertical
direction.
 As the nozzle is moved over the table in the
required geometry, it deposits a thin bead of
extruded plastic to form each layer.
 The plastic hardens and bonds to the layer
below.


Materials – Wax, polycarbonate, polypropylene
and various polyesters.
Advantages
1. Good accuracy
2. Functional materials
3. Medium range of materials
Disadvantages
1. Support structures needed


 The paper foil comes off the material supply
roll and the laser cuts around the outline of
the layer.
 A heated roller moves over the top of the foil
to bond the layer to the rest of the object.
 Model has the properties of laminated wood.


Laminated Object manufacturing (LOM)


Material - Paper
Advantages
1. Good accuracy
2. Large build size
Disadvantages
1. Limited range of material
2. Support removal necessary
3. Poor material properties


 Similar to the SLA except uses a photo-mask
and a UV lamp to cure photoreactive resin
instead of UV-laser.
 Can build multiple parts simultaneously.
 Parts are encased in water-soluble wax
eliminating the need for supports


1. Check the feasibility of new design
concepts.
2. Conduct market tests/evaluation.
3. Assess the fit of complex mechanism.
4. Promote concurrent product development.
5. Make many exact copies simultaneously.
6. Make moulds for wax cores in castings.
7. Use as a master for silicon and epoxy
moulds.


 Must be a solid model.
 Converts solid model into a collection of
connected triangles.
 The size and number of triangles
determines the accuracy of the RP part.


Example Slices of a Solid Model


 Process where all surfaces are converted into
a collection of triangles.
 Curved surfaces can only be approximated by
triangles. It is controlled by two parameters:
ChordHeight and Angle Control.
 Angle Control is important when a surface
feature is bounded by a curve with very small
radii relative to its part size.
 Chordal Height specifies the maximum
distance between a facet edge and the precise
surface of the solid model.


SLA SGC SLS LOM FDM

System: 3-D Sys. Cubital DTM Helisys Stratasys

Typical slice: .010” .006” .006” .0037” .010”

.25 mm .15 .15 .0925 .25


Rapid prototyping

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