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Rapid Prototyping (RP)
Introduction of RP
Generate a prototyping by Laying ManufacturingTechnology - composite material layer by layer
Build in one step - directly from model to
manufacturing
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Rapid Prototyping (RP)
Development of RP
First Phase : Manual (or Hard) Prototyping
Age-old practice for many centuries
Prototyping as a skilled craft is traditional and manual
and based on material of prototype Natural prototyping technique
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Development of RP
Second Phase : Soft (or Virtual) Prototyping
Mid 1970s
Increasing complexity
Can be stressed, simulated and tested with exactmechanical and other properties
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Rapid Prototyping (RP)
Development of RP
Third Phase : Rapid Prototyping
Mid 1980s
Hard prototype made in a very short turnaround time
(relies on CAD modelling) Prototype can be used for limited testing
prototype can consist in the manufacturing of theproducts
3 times complex as soft prototyping
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Rapid Prototyping (RP)
Fundamentals of RP
Building computer model
Model is building by CAD/CAM system
Model must be defined as enclosed volume or solid
Converting model into STL file format
STereoLithography (STL) file is a standard format todescribe CAD geometry used in RP system
STL file file approximates the surfaces of the model
by polygons
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Rapid Prototyping (RP)
Fundamentals of RP
Fabricating the model
Building model layer by layer
Forming a 3D model by solidification of liquid/powder
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Rapid Prototyping (RP)
Applications of RP
For design evaluation
Touch and holding a physical prototype
For function verification
e.g. assembly, kinematics performance, andaerodynamic performance
Models for further manufacturing processes
e.g. Vacuum casting, spray metal moulding,
investment casting, etc.
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Rapid Prototyping (RP)
Advantages and Disadvantages
No planning of process sequences
No specific equipment for handling materials
No transportation between machining
Features-based design and feature recognition areunnecessary
Defining a blank geometry is unnecessary
Defining different setups or complex sequences ofhandling material is unnecessary
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Rapid Prototyping (RP)
Advantages and Disadvantages
No need to consider jigs and fixtures
Designing and manufacturing moulds and dies
Specific materials are restricted
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Rapid Prototyping (RP)
Role of RP in Product Development Cycle
Product design
Increase part complexity and diversity with littleeffect on lead time and cost
Minimise time-consuming discussion and evaluationsof manufacturing possibilities
Tool design and manufacturing
Minimise design, manufacturing and verification of
tooling Reduce parts count and eliminate tool wear
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Rapid Prototyping (RP)
Role of RP in Product Development Cycle
Assembly and test
Reduce labour content of manufacturing (e.g.machining, casting, inspection and assembly, etc.)
Reduce material costs (e.g. handling, waste,transportation, spare and inventory, etc.)
Function testing
Avoid design misinterpretations, i.e. what you design
is what get)
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Rapid Prototyping (RP)
Due to the newness of the technology, thereare already so many words for RP used today:
RP( most commonly used) - Rapid Prototyping
RPTM(inc. new development trends) - Rapid
Prototyping, Tooling and Manufacture Direct CAD Manufacturing/Desktop
Manufacturing/Instant Manufacturing/CAD OrientedManufacturing = RP
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Rapid Prototyping (RP)
Layer Manufacturing/Material Addition
Manufacturing/Material Deposit Manufacturing/Material Increase Manufacturing/Solid FreedomManufacturing - Emphasis the unique characteristicof RP
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Rapid Prototyping (RP)
Classification of RP Systems
By the initial form of its material, RP systemscan be categorised into:
Liquid-based
Liquid-based material Curing Process Solid
(e.g. SLA, SGC, SOUP, etc.)
RP
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Rapid Prototyping (RP)
Classification of RP Systems
Solid-based
Encompass all forms of material in the solid form,such as in the form of wire, a roll, laminates and
pellets.(e.g. LOM and FDM, etc.)
Powder-based
Grain-like material
Joining/Binding
Solid(e.g. SLS and 3DP, etc.)
RP
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Rapid Prototyping (RP)
Features of RP Systems
The features of some commercially available RPsystems can be summarised into:
Process type - Stereo lithography, Laminating,Fused deposition modelling, Sintering of powder,Solid ground curing, etc.
Work space(mm) - depends on the models
Material - photopolymer resin, coated paper, ABS,wax, metal alloy, etc.
RP
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Rapid Prototyping (RP)
Features of RP Systems
Layer thickness(mm) - 0.05 - 0.3(SLA); 0.1 -1(LOM.); ~0.05(FDM); ~0.08(SLS); 0.01 -0.15(SGC)
Accuracy(mm) - 0.01- 0.2(SLA); 0.1 - 0.2(LOM);0.127 - 0.254(FDM); 0.03 - 0.38(SLS); 0.05 -0.5(SGC)
Manufacturer - 3D System, Stratasys, Helisys, DTM,
EOS, etc.
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Rapid Prototyping (RP)
Pre-Processing Tasks
Prepare geometric model in STL file format
Solid or surface CAD model to be built is nextconverted into format dubbed the .STL file format
because it is a standard input data to any RPprocess. STL originates from 3D Systems, whichpioneers the Stereolithography system in 1987. Theformat approximates the surfaces of the modelusing tiny triangles. Since 1990, almost all majorCAD/CAM vendor supply the CAD-STL interface.
RP
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Rapid Prototyping (RP)
Pre-Processing Tasks
Building up direction
The direction affects many key aspects of RPprocess, quality of the surface finish, build time,
amount of support structures needed, and amountof trapped volume. For experience, minimising theheight of the geometry will reduce the no. of layersrequired, thereby decreasing build time, but alsosacrifice part resolution or accuracy.
RP
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Pre-Processing Tasks
Trapped volume
It is the amount of liquid resin in the RP process(e.g. SLA) that was entrapped by the processed or
solidified region. Thus trapped volumes can exist inconcave regions that as containers. It may beeliminated by either building a part with a drain holeand fill the hole after solidification or modifying theorientation of the part.
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Pre-Processing Tasks
Part placement
In RP, the time spent building a prototype does notdepend on the no. of parts but on the total no. of
slices required. By closely packing multiple partsinto feasible volume, several parts can be built atthe same time.
RP
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Pre-Processing Tasks
Support structure
The support structure in RP process has thefollowing functions:
ensure the recoater blade will not strike the platformwhen the first layer is swept
improve uniformity of layer thickness
provide a simple means of removing the part from
the platform upon its completion
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Pre-Processing Tasks
Support structure
However, overdesign of support structures results inadded design and manufacturing time, as well as
finishing operations
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Rapid Prototyping (RP)
Post-Processing Tasks
Part removal and cleaning
After a part is built, drain excess liquid resin at theplatform and the part back into the vat. Next, the
part and the platform are placed in a cleaningapparatus with solvent (e.g. TPM). It will producelittle swelling distortion on a part. Once the part hasbeen thoroughly cleaned of excess resin, bothplatform and part are rinsed with water to remove
TPM film. The last step is to remove the part fromthe platform by flat-bladed knife.
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Post-Processing Tasks
Post curing
During some RP processes, such as SLA, the laserscans each layer along the boundary and hatching
lines only. This means that inside portions of thelayers may not be completely solidified. Thus thepart is post-cured to complete the polymerisationprocess by exploring with UV radiation in a speciallydesigned apparatus.
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Post-Processing Tasks
Part finishing
This process is to remove the supports by using adull edged blade or putty knife. Care must be taken
to avoid damaging a part that contains fragilesections. Once the supports have been removed,minor sanding is applied to eliminate residual tracesof the supports.
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Rapid Prototyping (RP)
Principle of Stereolithography Apparatus (SLA)
SLA was developed in 1986 by 3D Systems. Theprocess is based on the following principles:
Parts are built from a photo-curable liquid resin that
solidifies when sufficiently exposed to a laser beamwhich scans across the surface of the resin
The building is done layer by layer, each layer beingscanned by the optical scanning system and
controlled by an elevation mechanism which lowersat the completion of each layer
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Process of SLA
Step 1 - A liquid state photosensitive polymer thatsolidifies when exposed to a lighting source
Step 2 - A platform that can be elevated is located
just one layer of thickness below the surface
Step 3 - According to the cross section of the part(starting with bottom layer). The laser scansthe polymer layer above the platform to
solidify the polymer
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Process of SLA
Step 4 - The Platform is lowered into the polymerbath to the layer thickness
Step 5 - Repeat 3 and 4 until the top layer of the part
is generated
Step 6 - Post-curing and part finishing will then beperformed
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Applications of SLA
Models for conceptualisation,packaging and presentation
Prototypes for design, analysis, verification andfunctional testing
Masters for prototype tooling and low volume productiontooling
Patterns for investment casting, sand casting andmoulding
Tools for fixture and tooling design and productiontooling
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Principle of Selective Laser Sintering (SLS)
SLS was developed by DTM Corporation in 1992. The
process is based on the following principles:
Parts are built by sintering when a CO2 laser beam hit a
thin layer a powdered material. The interaction of thelaser beam with the powder raises the temperature,resulting in particle melting and bonding together
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Principle of Selective Laser Sintering (SLS)
The building of the part is done layer by layer. Eachlayer of the building process contains the cross sectionsof one or many parts. The next layer built directly on thetop of the sintered layer after an additional layer of
powder is deposited via a roller mechanism on the top ofthe previously formed layer
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Process of SLS
Step 1 - A part cylinder is located at the heightnecessary for a layer of powdered materialto be deposited on the cylinder to thedesired thickness. The powder is appliedfrom the feed cylinder by the levelling roller
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Process of SLS
Step 2 - The layer of powder is selectively raster-scanned and heated with a laser, causingparticles to adhere to each other. The laserscan forms the powder into the requiredcross section shape. Again this step startswith the bottom cross section
Step 3 - The part cylinder is lowered by the layer
thickness to permit a new layer of powder tobe deposited
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Process of SLS
Step 4 - The new layer is scanned, conforming it tothe shape of the next upper cross-sectionand adhering it to the previous layer
Step 5 - Repeat 3 and 4 until the top layer of the partis generated
Step 6 - Post-curing may be required for somematerial
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Applications of SLS
Concept models
Functional models and working prototypes
Wax casting pattern
Polycarbonate patterns. These build faster than waxpatterns and are ideally suited for design with thin wallsand fine features. These pattern are also durable andheat resistant
Metal Tools. Direct rapid prototype of tools of mouldsfor small or short production runs.
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Process of FDM
The process of FDM is relatively simple and fast but itsuse is limited to thermoplastic materials
Step 1 - The thermoplastic material in the form of
filament is heated to just above itssolidification temperature
Step 2 - The extrusion head is heated and movesaccording to the pattern of the cross section
of each layer of the part
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Process of FDM
Step 3 - The material is extruded on the foundationor previously built layer. As it is extruded, itis cooled and thus solidifies to form therequired pattern of part
Step 4 - Repeat 2 and 3 until the top layer of the partis generated
Step 5 - Part finishing may be required
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Applications of FDM
Models for conceptualisation and presentation
Prototypes for design, analysis and functionaltesting
Patterns and masters for tooling. Models can beused as patterns for investment casting, sand castingand moulding
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Principle of Laminated Object Manufacturing
(LOM)
LOM was developed by Helisys Inc. in 1991. The
process is based on the following principles:
Parts are built, layer by layer, by laminating and laser-trimming materials that are delivered in sheet form. Thesheets are laminated into block by a thermal adhesivecoating
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Process of LOM
The accuracy of the process of LOM is high. The mostpopular laminated material is paper sheet.
Step 1 - Sheet material is supplied from a continuous
roll form. Each sheet attached to the block,using heat and pressure to form a new layer
Step 2 - The platform is lowered by the thickness ofthe sheet whenever a sheet is attached to
the stack
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Process of LOM
Step 3 - After a layer is deposited, a CO2 laser istraced on the layer along the contourscorresponding to the current cross section
Step 4 - Areas of the layer outside the contours arecross-hatched by the laser (i.e. cut into smallpieces for removal afterwards)
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Process of LOM
Step 5 - After the part is built, the result is imbeddedwithin a block of supporting material. Thismaterial is then broken into chunks alongthe cross-hatching lines
Step 6 - The resulting part may then be coated witha sealant to keep out moisture
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Applications of LOM
Applicable for a wide range of product, equipmentfor aerospace or automotive, consumer products,and medical devices
Prototypes for design, analysis and functional
testing
Tools for production
Small volume of finished goods
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Principle of 3D Printing (3DP)
3DP was invented by MIT in 1994
Parts are created by a layered printing processand adhesive bonding, based on sliced crosssection data. A layer is created by adding another
layer of powder. The powder layer is selectivelyjoined, where the part is to be form, by ink-jetprinting of a blinder material
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Process of 3DP
The process of 3DP is more efficient and relativelycheaper than sintering types.
Step 1 - Platform is located at the height necessary
for a layer of ceramic powder to bedeposited
Step 2 - The layer of ceramic powder is selectivelyraster-scanned with a print head that
delivers a liquid binder, causing particles toadhere to each other
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Process of 3DP
Step 3 - The platform is lowered by the layerthickness to permit a new layer of powderto be deposited
Step 4 - The new layer is scanned, conforming it tothe shape of the next upper cross sectionand adhering it to the previous layer
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Process of 3DP
Step 5 - Repeat 3 and 4 until the top layer of the partis generated
Step 6 - A post-process heat treatment is applied to
solidify the part
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Applications of 3DP
CAD-Casting metal parts.A ceramic shell withintegral cores can be fabricated directly from the CADmodel
Direct metal parts. It is adaptable to a variety of
material systems, allowing the production ofmetallic/ceramic parts with novel composition
Prototypes with colours and elastic feature