1. PRESENTATION ON RAPID
PROTOTYPING

2. What is Rapid prototyping?
• The first commercial rapid prototyping process was
brought on the market in 1987.
• Rapid prototyping is a technology which considerably speeds
up the product development, by allowing corrections in early
stages.
• It consists of various manufacturing processes by which
a solid physical model of part is made directly from 3D
CAD model data without any special tooling.
• It is also referred as computer automated manufacturing.
• Now a days, more than 30 different processes (not all
commercialized) with high accuracy and a large choice
of materials exist.

3. Why Rapid prototyping?
• Visualization.
• Complex shapes can be build.
• Decreases lead time.
• Facilitates concurrent engineering.
• No tooling.
• Testing and evaluating the design.
• First to market(product).
• Patentable details.

4. DIFFERENCE BETWEEN RAPID PROTOTYPING AND TRADITIONAL
FABRICATION
RP Traditional
1. RP processes are “additive”. Parts are built 1. Subtractive processes, as the name
up by adding, depositing, or solidifying in a implies, create objects by removing
horizontal layer-wise process. unwanted material from a large block
or sheet in the form of chips.
2. RP technologies are able to create one- 2. Part is made in assemblies.
piece part geometries.
3. Undercuts, overhangs, difficult shapes can 3. Useful for making simple shapes only.
me made.
4. No tooling required. 4. Tooling is always required
(jigs and fixtures).
5. Part can be fabricated in hours. 5. Take more time.
6. Rough surface finish. 6. Good surface finish.
7. Less human interaction. 7. More human interaction.
8. Non dangerous in nature 8. Dangerous in nature.
(dust free, noise free).

5. ADVANTAGES OF RAPID PROTOTYPING
• No planning of process sequences.
• No specific material for material handling.
• No transportation between machines.
• No need of jigs and fixtures.
• High accuracy.
• Tool for visualisation and product verification.
• CAD data files can be manufactured in hours.

7. SEQUENCE OF RAPID PROTOTYPING

8. SOLID MODELING AND TESSELATION
• Solid model is generated with the help of softwares (eg: pro
engineers, solidworks, etc).
• Surfaces of the CAD model are tessellated and STL file is
exported.
• Tessellation is piecewise approximation of surfaces of CAD
model by using series of triangles.
• STL file=An stl file is a standardized computer exchange file
which contains a 3d model, it entirely composed of triangular
faces, further the faces have assigned normals which
indicates their orientation (inside/outside).
• The name “STL” is taken from its extension .stl .

9. Solid model

10. Tessellated model

11. Slicing
• After selecting part orientation, the tessellated model is
sliced.
• The pre-processing software slices the stl model into a no of
layers from 0.01mm to 0.7mm thick, depending upon the
build technique.
• The program may also generate an auxiliary structure to
support the model during the build. Supports are useful for
delicate features such as overhangs, internal cavities.

12. slicing

14. GENERATION OF LASER SCANING PATHS
Deposition of Layers: various technologies for
layer deposition are used.
• Liquid based: Stereolithography
• Powder based: Selective Laser Sintering
• Solid based: Fused Deposition
Modeling, Laminated Object Manufacturing
etc.

15. Post processing/cleaning
• The final step is post-processing. This involves removing
the prototype from the machine and detaching any
supports.
• Some photosensitive materials need to be fully cured
before use.
• Prototypes may also require minor cleaning and surface
treatment.
• painting the model will improve its appearance and
durability.

17. METHODS OF RAPID PROTOTYPING
• Shape deposition manufacturing(SDM)
• Stereolithography(SLA)
• Solid base curing(SBC)
• Fused deposition modeling(FDM)
• Ballistic particle manufacturing (BPM)
• 3D Printing
• Selective layer sintering(SLS)
• Laminated object manufacturing(LOM)

18. Shape deposition manufacturing

19. Shape deposition manufacturing
• Shape Deposition Manufacturing (SDM) is developed at Carnegie
Mellon University in the early 1990's.
• Deposition of material(eg: welding).
• After deposition each layer is precisely shaped with a cnc milling
machine.
• Due to thermal deposition the internal residual stresses are build
up, due to contraction of internal gradients of previous layers on
the new layer, the internal stresses can lead to warpage, early
failure of the material.
• Shot peening is required to control the build up of stresses(small
round metal spheres are called “shot”)are projected at high velocity
against the surface of layer it imparts the compressive load on the
upper layer, this process is used to balance the stress.

20. SDM
• Special components can be embedded inside the structure.
• The filler material is removed to get the finished part.

21. STEREOLITHOGRAPHY(SLA)

22. STEREOLITHOGRAPHY
• Stereolithography started the rapid prototyping revolution.
The technique builds three-dimensional models from liquid
photosensitive polymers that solidify when exposed to
ultraviolet light.
• Elevator lowers hardened cross section below liquid surface.
• Laser prints the next cross section directly on top of previous.
• The self-adhesive property of the material causes each
succeeding layer to bond to the previous one and thus form a
complete, three-dimensional object out of many layers.
• Objects which have overhangs or under cuts must be
supported during the fabrication process by support
structure.

23. SOLID BASE CURING

25. SOLID BASE CURING
• Cross section shape is printed onto a glass mask
• Glass mask is positioned above photopolymer tank
• UV lamp shines through mask onto photopolymer light only
can pass through clear part, polymer solidifies
there, polymer in masked areas remains liquid
• All excess polymer is removed-part is again hit with UV light
• Melted wax is spread over workpiece filling all spaces
• Workpiece is precisely milled flat
• Glass is erased and re-masked, workpiece is placed slightly
below surface in photopolymer repeats
• After fabricating part, wax is melted and removed
• Note : No support or post cure needed

26. FUSED DEPOSITION MODELING
(FDM)

27. FDM
• FDM is the second most widely used rapid prototyping
technology, after stereolithography.
• A plastic filament is unwound from a coil and supplies
material to an extrusion nozzle.
• The nozzle is heated to melt the plastic and has a
mechanism which allows the flow of the melted plastic to be
turned on and off.
• The nozzle is mounted to an X-Y plotter type mechanism
which traces out the part contours, There is a second
extrusion nozzle for the support material (different from the
model material).
• Materials used mostly are ABS and PC(polycarbonate).

28. Ballistic particle manufacturing (BPM)

29. Ballistic particle manufacturing (BPM)
Employs a technology called Digital Microsynthesis
• Molten plastic is fed to a piezoelectric jetting mechanism, similar to
those on inkjet printers.
• A multi-axis controlled NC system shoots tiny droplets of material onto
the target, using the jetting mechanism.
• Small droplets freeze upon contact with the surface, forming the
surface particle by particle.
Process allows use of virtually any thermoplastic.

30. 3D PRINTING

31. 3D PRINTING
• The process starts by depositing a layer of powder object material at
the top of a fabrication chamber. To accomplish this, a measured
quantity of powder is first dispensed from a similar supply chamber by
moving a piston upward incrementally.
• A roller or scraper then distributes and compresses the powder at the
top of the fabrication chamber the jetting head subsequently deposit a
liquid adhesive (binder) in a two dimensional pattern onto the layer of
the powder. The binder bonds the powder particles together where it
has been deposited, solidifying it to form a layer of the object.
• Once a layer is completed, the fabrication piston moves down by one
layer thickness, and the process is repeated until the entire object is
formed within the powder bed. After completion, the object must be
removed from the chamber, and excess powder is brushed off.
• No external supports are required during fabrication since the powder
bed supports overhangs.

32. SELECTIVE LAYER SINTERING(SLS)

33. SELECTIVE LAYER SINTERING(SLS)
• SLS or Selective Laser Sintering is another process that begins
with raw material in a powdered state. Only instead of binding
with some extra solvent (as was done in 3-D Printing) powder
particles are sintered together, by heating with a laser until
adjacent particles sinter together.
• So process begins with a cartridge feeding system spreading a
thin layer of heat fusible (sinterable) powder into workspace
container. This layer of powder is heated to just below its
melting point.
• A carbon dioxide laser then traces the cross sectional shape.
Wherever the laser hits, enough extra heat is generated to sinter
the particles together. Upon completion of one layer, the
process can repeat.

34. LAMINATED OBJECT MANUFACTURING
(LOM)

35. LAMINATED OBJECT MANUFACTURING
• A solid physical model is made by stacking layers of sheet
stock, each an outline of the cross-sectional shape of a CAD
model that is sliced into layers.
• Starting material = sheet stock, such as
paper, plastic, cellulose.
• After cutting, excess material in the layer remains in place to
support the part during building.

36. REFRENCES
• Google.com
• http: / /paniit.iitd.ac.in/~ pmpandey
• RAPID PROTOTYPING - Principles and
Applications (2nd Edition) World Scientific
Publishing Co. Pte. Ltd.
• Manufacturing Processes and Engineering
Prof. J.S. Colton © GIT 2011