9 Prezentacija SEMINAR 11-4-12

8/2/2019 9 Prezentacija SEMINAR 11-4-12

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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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MirrorSystem

LASER

Laminating Roller

Elevator Platform

Part boundaryExcess material cross-hatched for later removal

SupplyRoll

Take-UpRoll


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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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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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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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PowderBed

MirrorSystem

LASER

LoosePowder

Laser SelectivelySinters PowderLeveling

Roller



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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


Laminated Object Modeling


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?

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