prototype , type of 3D printer and MFG.pptx

1. Rapid prototyping technology

2. Lecture contents
Challenges encountered in RPT processes
Overview of RPT processes
Applications of RPT processes
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Definition of rapid prototyping
Classification of RPT processes
Selection criteria of RPT processes
Steps of RPT process

3. Definition of rapid prototyping
Rapid prototyping (RP) is a family of technologies used to fabricate engineering
prototypes of parts in minimum possible lead time based on a computer-aided
design (CAD) model of the item.
The traditional method of fabricating a prototype part is machining, which can
require significant lead times—up to several weeks, sometimes longer, depending
on part complexity.
As the RP technologies have being used to produce parts, not just prototypes, a
more general term has emerged: Additive manufacturing (AM). All of these
technologies work by adding layers of material

4. Steps of RPT process
Rapid
prototyping
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2
3
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5
Geometric modeling
Convert the CAD model to STL format
Slicing the model into thin layers
Construct the model layer by layer
Clean and finish the model

5. Classification of RPT processes
RPT Processes
Subtractive Additive
(Desktop milling) (Based on the starting material)
Liquid-based solid-based powder-based
▪ Stereolithography
process
▪ Selective laser
sintering
▪ 3D printing
▪ Laminated object
manufacturing
▪ Fused deposition
modeling

6. Stereo lithography (SL) process
Stereolithography (SL) is a process for fabricating a solid plastic part out of a
photosensitive liquid polymer using a directed laser beam to solidify the polymer.
How it works?
⮚ The platform is positioned vertically near the
surface of the liquid photopolymer.
⮚ the laser beam is directed through a curing path
to form the base (bottom layer) of the part.
⮚ When the initial layer is completed, the platform
is lowered by a distance equal to the layer
thickness, and a second layer is formed on top of
the first by the laser, and so on.

7. Stereolithography (SL) process
Advantages Limitations
1. Round the clock operation. The
SL can be used continuously and
unattended round the clock.
2. Build volumes. The different SL
machines have build volumes
ranging from small to large.
3. Good accuracy. The SL has good
accuracy.
4. Surface finish. The SL can obtain
one of the best surface finishes
amongst RP technologies.
5. Wide range of materials.
1. Requires support structures.
Structures that have overhangs and
undercuts must have supports.
2. Requires post-processing. Post
processing includes removal of
supports and other unwanted
materials.
3. Requires post-curing. Post-curing
may be needed to cure the object
completely and ensure the
integrity of the structure.

8. Fused deposition modeling (FDM)
It is an RP process in which a filament of wax and/or thermoplastic polymer is
extruded onto the existing part surface from a work head to complete each new layer.
How it works?
⮚ a solid filament with typical diameter of 1.25
mm is fed from a spool into the work head.
⮚ The material is heated above it's melting point
by 1 ̊C.
⮚ The molten material is extruded out from a fine
nozzle and deposited on a platform to form a
thin layer of the part.
⮚ The platform is then lowered and a next layer is
deposited on the surface of the previous layer.

9. Fused deposition modeling (FDM)
Advantages Limitations
1. Fabrication of functional parts. It
is able to fabricate fully functional
parts that have 85% of the strength
of the actual molded part.
2. Minimal wastage. only those
material needed to build the part
and its support are needed.
3. Ease of support removal. support
structures can be easily broken off
or simply washed away
4. Ease of material change.
1. Restricted accuracy.
2. Slow process. Building speed is
restricted by the extrusion rate of
the material. As the build material
used are plastics and their
viscosities are high, the process
cannot be easily speeded up.
3. Unpredictable shrinkage.
shrinkages and distortions caused
to the model built are a common
occurrence and are usually
difficult to predict

10. Laminated object manufacturing (LOM)
It produces a solid physical model by stacking layers of sheet stock that are each cut
to an outline corresponding to the cross-sectional shape of a CAD model that has
been sliced into layers.
How it works?
⮚ The build material (paper) is stretched from a
supply roll across a platform to a take-up roll on
the other side.
⮚ A heated roller passes over the paper bonding it
to the platform or previous layer.
⮚ A laser beam is focused to cut the profile of each
layer.
⮚ The process of gluing and cutting continuous
layer by layer until the model is complete.

11. Laminated object manufacturing (LOM)
Advantages Limitations
1. Wide variety of materials. In
principle, any material in sheet
form can be used in the LOM.
2. Fast build time. The laser scans
only the periphery. Therefore,
parts with thick sections are
produced just as quickly as those
with thin sections.
3. High precision.
4. Support structure. There is no
need for additional support
structure.
1. Precise power adjustment. The
power of the laser used for cutting
needs to be precisely controlled so
that the laser cuts only the current
layer of lamination and not
penetrate into the previously cut
layers.
2. Fabrication of thin walls.
3. Removal of supports. The most
labor-intensive part of the LOM is
to separate the part from the
laminated block.

12. Selective laser sintering (SLS)
(SLS) uses a moving laser beam to fuse powders in areas corresponding to the CAD
geometric model one layer at a time to build the solid part.

13. Selective laser sintering
Advantages Limitations
1. Good part stability.
2. Wide range of processing materials.
nylon, polycarbonates, metals and
ceramics are available.
3. No part supports required.
4. Little post-processing required. The
finishing of the part is reasonably
fine and requires only minimal
particle blasting and sanding
5. No post-curing required. The
completed laser sintered part is
generally solid enough
1. Large physical size of the unit.
The system requires a relatively
large space to house it.
2. High power consumption.
3. Poor surface finish. The as-
produced parts tend to have poorer
surface finish due to the relatively
large particle sizes of the powders
used.

14. Three dimensional printing (3DP)
This technology (3DP) builds the part using an inkjet printer to eject adhesive bonding
material onto successive layers of powders. The binder is deposited in areas
corresponding to the cross sections of the solid part, as determined by slicing the CAD
geometric model into layers.
How it works?
⮚ A layer of powder is spread on the existing part-
in-process.
⮚ An ink-jet printing head moves across the
surface, ejecting droplets of binder on those
regions that are to become the solid part.
⮚ When the printing of the current layer is
completed, the piston lowers the platform for the
next layer.

15. Three dimensional printing (3D printing)
Advantages Limitations
1. High speed. Each layer is printed
in seconds, reducing the
prototyping time of a hand-held
part to 1 to 2 hours.
2. Versatile. Parts are currently used
for the automotive, packaging,
education, footwear, medical,
aerospace and telecommunications
industries.
3. Simple to operate.
4. No wastage of materials.
1. Limited functional parts. parts
built are much weaker, thereby
limiting the functional testing
capabilities.
2. Limited materials.
3. Poor surface finish. Parts built by
3D printing have a relatively
poorer surface finish and post
processing is frequently required.

16. Applications of RPT processes
RPT processes are applied in four main areas including:
Engineering
Design
Engineering
analysis
Tooling
Parts
production

17. Selection criteria of RPT processes
Selection criteria of
RPT processes
Product process Environment Other issues
Speed
Variety
Max. part size
Surface finish
production cost
Price
Reliability
Maturity level
Loc. Of Tech.
Flexibility
Ease of use
Hazards
Recycling
Skills & Training
Product quality
improvement
Lead time
improvement
Cost
improvement

18. Challenges encountered in RPT processes
Limited Part
accuracy
Limited
variety of
materials
Low
Mechanical
performance
of fabricated
parts
There are some problems in RPT technologies that need to be solved to widen
the applicability of the technology for wide range of materials and products: