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INTREPID SEMINAR @ Karlovac
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Rapid Prototyping and Scanning
Seminar
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Product Development
First Day- morning session
Introduction
Rapid Prototyping
Coffee break
ScanningLunch
Afternoon session
Establishing Process Capability
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Product Development
Second Day- morning session
Introduction
Decision Tools
Design Structure Matrix
System dynamics
Coffee break
Innovation
LunchAfternoon session
New Technologies
Summary
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Challenges Ahead
Consumer products from months to weeks to
market
Large products from years to months New materials designed
Integration of Human and Technical
resources
More knowledgeable/informed workforce
Conversion of information to knowledge Environmental compatibility
Reconfigurable Enterprises
Innovative Processes
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The Need for Speed in the Product Development Process
More competitors = more pressure to develop new
and improved products.
Shorter model life = fewer number of units to
recover development costs.
To be profitable, costs must be low. It is much more
difficult now to pass on costs to the consumer.
New design tools must focus on speeding up theproduct development process and reducing costs
(read that as getting it right the first time).
Global Manufacturing Environment:
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RP Product
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RP Product
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RP Product
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RAPID PROTOTYPING
1. Introduction to Rapid Prototyping2. Basics of Rapid Prototyping
3. Rapid Prototyping Technics4. Applications of Prototyping
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RAPID PROTOTYPING Techniques for constructing objects from a
3-dimensional computer models in a seriesof layers without requiring moulds, jigs ormachining
Selective placement of solid material in aplane. Solidifying a liquid
Fusing solid particles Cutting and stacking
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Applications:Visualization modelsToolingDirect fabrication of objectsUnique materials, composites, and geometries.
Major advantage over conventional machining is the reduction of lead time of the order
of weeks to a much shorter hours or at most days!
RAPID PROTOTYPING
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Why is Rapid Prototyping Important?
Product designers want to have a physicalmodel of a new part or product design
rather than just a computer model or line
drawing 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 partadequately
Using RP to make the prototype, the designer can see
and feel the part and assess its merits and shortcomings
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RP Two Basic Categories:
1. Material removal RP - machining, using adedicated CNC machine that is available to the
design department on short notice Starting material is often wax Easy to machine
Can be melted and re-solidified
The CNC machines are often small - called desktop machining
2. Material addition RP - adds layers of material oneat a time to build the solid part from bottom to
top
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Starting Materials in Material Addition RP
1. Liquid monomers that are cured layer by layer into solid polymers
2. Powders that are aggregated and bonded layer by layer
3. Solid sheets that are laminated to create the solid part
Additional Methods
In addition to starting material, the various materialaddition RP technologies use different methods of
building and adding layers to create the solid part
There is a correlation between starting material and part buildingtechniques
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More About Rapid Prototyping
Alternative names for RP:
Layer manufacturing
Direct CAD manufacturing
Solid freeform fabrication
Rapid prototyping and manufacturing (RPM)
RP technologies are being used increasingly
to make production parts and production
tooling, not just prototypes
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Classification of RP Technologies
There are various ways to classify the RP
techniques that have currently beendeveloped
The RP classification used here is based on
the form of the starting material:
1. Liquid-based
2. Solid-based3. Powder-based
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Liquid-Based Rapid Prototyping Systems
Starting material is a liquid
About a dozen RP technologies are in thiscategory
Includes the following processes:
Stereo lithography
Solid ground curing
Droplet deposition manufacturing
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Stereo lithography (STL or SLA)
RP process for fabricating a solid plastic part out of aphotosensitive 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 buildthe 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
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StereolithographyMirrorSystem
LASER
Base
Elevator Platform
Liquid Photopolymer
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Stereo lithography: (1) at the start of the process, in which the initial layer is
added to the platform; and (2) after several layers have been added so that
the part geometry gradually takes form.
Stereo lithography
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Stereolithography
2.0.a
Laser used to selectively cure layer of liquid photopolymer. Acrylate resin
Epoxy
Curing by ultraviolet wavelengths. He-Cd or solid state laser.
Elevator moves downward by one layer thickness, allowingliquid photopolymer to form a new layer over the part.
After build is completed, must be post processed: Supports removed.
Post-cured to develop full strength.
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SLA Advantages
Good accuracy and surface finish
Good speed, especially if multiple parts are
made in a single build
Well-characterized and accepted technology
(oldest RP process)
Almost no waste
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SLA Disadvantages
Resins are skin irritants Requires support structures for some part
geometries
High material cost (Appx. 140 per liter)
Limited choice of materials
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A part produced by stereo lithography (photo courtesy of 3DSystems, Inc.).
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Facts about STL/SLA
Each layer is 0.076 mm to 0.50 mm (0.003
in to 0.020 in.) thick Thinner layers provide better resolution and more
intricate shapes; but processing time is longer
Starting materials are liquid monomers
Polymerization occurs on exposure to UV
light produced by laser scanning beam Scanning speeds ~ 500 to 2500 mm/s
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Part Build Time in STL/SLA
Time to complete a single layer :
where Ti= time to complete layer i; Ai= area of layer i; v=average scanning speed of the laser beam at the surface; D=
diameter of the spot size, assumed circular; and Td= delaytime between layers to reposition the worktable
Ti= Ai
vD+T
d
P B ild Ti i STL/SLA
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Part Build Time in STL/SLA
- continuedOnce the Ti values have been determined for
all layers, then the build cycle time is:
where Tc= STL build cycle time; and nl= number of layers usedto approximate the part
Time to build a part ranges from one hour for small parts ofsimple geometry up to several dozen hours for complex parts
=
=
in
i
ic TT1
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Solid Ground Curing (SGC)
Like stereo lithography, SGC works by curing aphotosensitive polymer layer by layer to create a
solid model based on CAD geometric data
Instead of using a scanning laser beam to cure agiven layer, the entire layer is exposed to a UV
source through a mask above the liquid polymer
Hardening takes 2 to 3 s for each layer
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SGC steps for each
layer: (1) mask
preparation, (2)
applying liquidphotopolymer
layer,(3) mask
positioning and
exposure of layer,(4) uncured polymer
removed from
surface, (5) wax
filling, (6) millingfor flatness and
thickness.
Solid Ground Curing
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Facts about SGC
Sequence for each layer takes about 90 seconds
Time to produce a part by SGC is claimed to be
about eight times faster than other RP systems
The solid cubic form created in SGC consists ofsolid polymer and wax
The wax provides support for fragile andoverhanging features of the part duringfabrication, but can be melted away later to leave
the free-standing part
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Droplet Deposition Manufacturing (DDM)
Starting material is melted and small droplets areshot by a nozzle onto previously formed layer
Droplets cold weld to surface to form a new layer
Deposition for each layer controlled by a movingx-y nozzle whose path is based on a cross section
of a CAD geometric model that is sliced into
layers Work materials include wax and thermoplastics
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Solid-Based Rapid Prototyping Systems
Starting material is a solid Solid-based RP systems include the
following processes:
Laminated object manufacturing
Fused deposition modeling
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Laminated Object Manufacturing
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Laminated Object Manufacturing (LOM)
Solid physical model made by stacking layers of sheet stock,each an outline of the cross-sectional shape of a CADmodel that is sliced into layers, uses paper (or other film)
sheets coated with thermal adhesive to build up parts. Starting sheet stock includes paper, plastic, cellulose,
metals, or fiber-reinforced materials, each new sheetbonded to part with heat and pressure.
The sheet is usually supplied with adhesive backing asrolls that are spooled between two reels
After cutting, excess material in the layer remains in place
to support the part during building
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Laminated Object Manufacturing
MirrorSystem
LASER
Laminating Roller
Elevator Platform
Part boundaryExcess material cross-hatched for later removal
SupplyRoll
Take-UpRoll
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Laminated object manufacturing.
Laminated Object Manufacturing
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LOM Advantages
Subtractive method allows large volumesto be built rapidly
Supported building
Surface quality and accuracy
Materials
Dry forming vs. liquids or loose powders Only as good as tape casting technology
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LOM Disadvantages
Manual cleanup requires skill, time
Waste
Majority of the material consumed by LOM doesnot contribute to the part itself
Safety Laser cutting produces smoke and/or fumes -
venting may be required
Laminar structure Parts are formed from alternating layers of material
and adhesive. Physical properties (strength, modulus)
inhomogeneous and anisotropic
Delamination and warping
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Fused Deposition Modeling
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Fused Deposition Modeling
ThermoplasticFilament
ExtruderHead
ElevatorPlatformSupplyRoll
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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 thex-y plane during
each layer and then moves up by a distance equal
to one layer in thez-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
F d D i i M d li
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Fused Deposition Modeling
Parts built up with thermoplastic
polymer (usually ABS) or wax.
Material supplied on flexible filament.
Material heated to 0.5o C above
solidification temperature, extruded ontopart where it quickly cools.
No post-processing of model other thanremoval of thin-wall support structures.
FDM Advantages
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FDM Advantages
Safety Inert, non-toxic solids.
No fumes, solvents; office environment.
Reliability Low cost
Ability to create hollow parts (no trapped liquid)
Materials ABS is tough, functional material. Wax is important as patterns for investment castings.
Possibility for multiple materials.
Metals and ceramics possible using powder processingtechniques.
FDM Di d t
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FDM Disadvantages
Poor surface finish due to thicklayers
Supports are required Slow build speed (10X slower
than other RP processes)
P d B d RP S t
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Powder-Based RP Systems
Starting material is a powder
Powder-based RP systems include thefollowing: Selective laser sintering
Three dimensional printing
S l ti L Si t i
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Selective Laser Sintering
S l i L Si i
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Selective Laser Sintering
PowderBed
MirrorSystem
LASER
LoosePowder
Laser SelectivelySinters PowderLeveling
Roller
Selective Laser Sintering
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Selective Laser Sintering
Developed at University of Texas, commercializedby DTM corporation.
Uses powder as bulk material (thermoplasticpolymer, wax, metal, or ceramic).
Layer of powder spread over the top of the part,
leveled. Laser used to fuse or sinter layer onto part.
No support structure is needed, as unfused powder
supports the part. Finished part is embedded within a cake of loosepowder.
Selective Laser Sintering (SLS)
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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 bondedby the laser beam into a solid mass that forms the
3-D part geometry
In areas not sintered, the powders are loose andcan be poured out of completed part
SLS Materials
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SLS Materials
Polycarbonate
Polystyrene Nylon
Glass-filled nylon Coated metal powder
Elastomer
SLS Advantages
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SLS Advantages
Wide choice of materials
Direct functional parts Tooling
Supported build
Good for complex parts
Speed
SLS Disadvantages
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SLS Disadvantages
Surface finish
Retains granular texture of original particles
Porosity, strength Many materials not fully dense
Shrinkage, curling
Process complexity Many operational variables: laser power, speed, supply
material temperature
Concerns about nitrogen leaks, lack of O2
High cost ($400,000+)
Three Dimensional Printing (3DP)
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Three Dimensional Printing (3DP)
Part is built layer-by-layer using an ink-jet printer to
eject adhesive bonding material onto successive
layers of powders Binder is deposited in areas corresponding to the
cross sections of part, as determined by slicing the
CAD geometric model into layers The binder holds the powders together to form the
solid part, while the un-bonded powders remain
loose to be removed later To further strengthen the part, a sintering step can
be applied to bond the individual powders
Th Di i l P i i
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Three dimensional printing: (1) powder layer is deposited, (2) ink-jet
printing of areas that will become the part, and (3) piston is lowered
for next layer (key: v = motion).
Three Dimensional Printing
RP Applications
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RP Applications
Applications of rapid prototyping can beclassified into three categories:1. Design
2. Engineering analysis and planning3. Tooling and manufacturing
Design Applications
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Design Applications
Designers are able to confirm their design
by building a real physical model in
minimum time using RP
Design benefits of RP:
Reduced lead times to produce prototypes Improved ability to visualize part geometry
Early detection of design errors
Increased capability to compute mass properties
Engineering Analysis and Planning
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Engineering Analysis and Planning
Existence of part allows certain engineering
analysis and planning activities to be
accomplished that would be more difficultwithout the physical entity
Comparison of different shapes and styles to determine
aesthetic appeal
Wind tunnel testing of streamline shapes
Stress analysis of physical model
Fabrication of pre-production parts for process planning
and tool design
Tooling Applications
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Tooling Applications
Called rapid tool making (RTM) when RPis used to fabricate production tooling
Two approaches for tool-making:
1. Indirect RTM method
2. Direct RTM method
Indirect RTM Method
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Indirect RTM Method
Pattern is created by RP and the pattern is
used to fabricate the tool
Examples: Patterns for sand casting and investment casting
Electrodes for EDM
Direct RTM Method
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Direct RTM Method
RP is used to make the tool itself
Example: 3DP to create a die of metal powders followed by
sintering and infiltration to complete the die
Manufacturing Applications
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a u actu g pp cat o s
Small batches of plastic parts that could not
be economically molded by injection
molding because of the high mold cost
Parts with intricate internal geometries that
could not be made using conventionaltechnologies without assembly
One-of-a-kind parts such as bone
replacements that must be made to correct
size for each user
Problems with Rapid Prototyping
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p yp g
Part accuracy: Staircase appearance for a sloping part surface due to
layering
Shrinkage and distortion of RP parts
Limited variety of materials in RP Mechanical performance of the fabricated parts is
limited by the materials that must be used in the RP
process
1980s Design Tools
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g
Computer-Aided Design (CAD)
2-dimensional representation of 3-dimensional parts.
Used more for design documentation than for design.
Finite Element Analysis (FEA)
No link to CAD, analyst creates model from scratch. Mostly 2-D linear analysis on PCs, more complex problems
limited to mainframe computers.
Used more for design verification than for design development.
1990s Design Tools
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Rapid Prototyping
Physical 3-D models for visualization
Functional prototypes for some parts Tooling patterns for some processes
Solid Modeling
3-dimensional representations.
2-dimensional drawings created from solid model for documentation.
Links to FEA, tool design, CNC manufacturing, and rapid prototyping. Finite Element Analysis
Better hardware, software: complex analysis possible with PCs.
Links to solid modeling and 2-D CAD programs reduce modeling time.
Some programs have optimization capabilities.
Rapid Prototyping as a way to capture potential
realisation problems
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realisation problems
Cost of engineering changes increase by an
order of magnitude as the design moves intothe next stage of development:
$1$10
$100
$1.000
$10.000
$100.000
$1.000.000
ConceptualDesign
Detail Design Prototype Tooling Production Field Service
Steps to Prepare Control Instructions
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1. Geometric modeling - model the component on a
CAD system to define its enclosed volume
2. Tessellation of the geometric model - the CADmodel is converted into a computerized format
that approximates its surfaces by facets (triangles
or polygons)
3. Slicing of the model into layers - computerized
model is sliced into closely-spaced parallel
horizontal layers
Solid Model to Layers
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Conversion of a solid model of an object into layers (only onelayer is shown).
Solid Model to Layers
Steps Common to RP Processes
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p
Construct solid model on CAD system.
Translate to surface representation: .stl file (common format read by RP
software.)
Generate 2-D slices with path definitions. (RP machine-specific software.)
Add support structures where needed to support the model during fabrication
Build object.
Post processing.
STL File Format
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STL File Format
(3.00, -1.00, 1.00)
Triangle size demonstration
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a g e s e de o st at o
Triangles: 38,000File Size: 1.9 MB
Triangle size demonstration
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g
Triangles: 195,000File Size: 19.5 MB
Rapid Prototyping Center Equipment
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Stereolithography
Fused Deposition Modeling
Laminated Object Modeling
Selective Laser Sintering
Advantages of Rapid Prototyping
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No tooling/forms/fixtures
Complex geometries
Shapes that cannot be cast
Internal cooling channels, etc.
Unattended operation
Waste-less fabrication
Rapid: days rather than weeks!
Disadvantages of Rapid Prototyping
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Reduced accuracy
RP ~ 50-100 m (0.002-0.004 in.)
Good-to-fair surface finish
Inefficient bulk fabrication
Build envelope size limits
Limited material choices
Concept Modelers
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Solidscape
3DS Thermojet
Stratasys Genisys Z Corporation Z406
Concept Modelers
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Low cost LAN devices, three dimensionalprinters.
Low noise, office environment. Easy to use, no specialized skills.
Lower resolution, higher speed, low cost per
part. Weak materials, used for visual models only.
Generally used by designers as a rough
draft before sending to more expensive rapidprototyping equipment.
Current Uses of Rapid Prototyping
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Functional or Ergonomic Models
Visual Aids for Engineering and Toolmaking
Fit and Assembly Evaluations
Patterns for Prototype Tooling and Metal Casting
Direct Tooling Inserts...
Quoting and Proposals...
Source: 2001 Wohlers Report
22.3%
27.3%
18.2%
19.7%
3.7%
5.0%
which is the best RP system?
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Answer: it depends
Many different suppliers worldwide,
all have a niche.
Two real categories
Rapid Prototyping equipment
Concept Modelers
Selection depends on users needs.
END
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THANK YOU
Questions?