Technical Seminar Rapid Pro to Typing Harish

8/6/2019 Technical Seminar Rapid Pro to Typing Harish

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RAPID PROTOTYPING


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Abstract

Rapid prototyping is the automatic construction of

physical objects using solid freeform fabrication. The firsttechniques for rapid prototyping became available in the late 1980s

and were used to produce models and prototype parts. Today, theyare used for a much wider range of applications and are even used

to manufacture production quality parts in relatively smallnumbers. Some sculptors use the technology to produce complex

shapes for fine arts exhibitions. Rapid prototyping takes virtual

designs from computer aided design (CAD) or animation modelingsoftware, transforms them into thin, virtual, horizontal cross-sections and then creates each cross-section in physical space, one

after the next until the model is finished. It is a WYSIWYG (WhatYou See Is What You Get) process where the virtual model and thephysical model correspond almost identically. This paper is a

presentation of application of nanotechnology in rapid prototyping.This paper has an emphasis on future applications of

nanotechnology in creation of models in rapid prototyping. Inresponse to these is a proposal to project wide scale applications of

nanotechnology in creative designing process.


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CONTENTS

CONTENTS PAGE NO

1. RAPID PROTOTYPING1

1.1. INTRODUCTION1

1.2. STEREOLITHOGRAPHY...... 21.3. SELECTIVE LASER SINTERING.3

1.4. FUSED DEPOSITION MODELLING...4

1.5. LAMINATED OBJECT MANUFACTURING...51.6. THREE DIMENSIONAL PRINTING.6

2. APPLICATIONS..7

3. FUNCTIONAL PARTS AND TOOLS FROM RAPIDPROTOTYPING.8

3.1. INTRODUCTION..83.2. INDIRECT OR SECONDARY PROCESSES.8

3.3.DIRECT FABRICATION PROCESS..83.4. INVESTMENT CASTINGS.8

3.5. INDIRECT OR SECONDARY PROCESSES THATUTILIZE RP GENERATED PATTERNS...9

3.6. DIRECTED FABRICATION OF INVESTMENTPATTERN9

3.7. SAND CASTING .9

4. MEDICAL APPLICATIONS OF RAPID PROTYPING.10

5. RAPID PROTYPING EQUIPMENTS..11

5.1. SLA-3500.11

5.2. SLA VIPER Si2.. 11


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INTRODUCTION

Rapid prototyping is the most common name given to ahost of related technologies that are used to fabricate physical

objects directly from CAD data source. These methods areunique in that they add and bond materials in layers to form

objects. The general also knows such systems names freeformfabrication (FFF), solid freeform fabrication (SFF) and layeredmanufacturing. Todays additive technologies offer advantages in

many applications compared to classical subtractive fabricationmethods such as milling or turning:

Objective can be formed with any geometric complexity

or intricacy with out the need for elaborate machine set up orfinal assembly; Rapid prototyping systems reduce theconstruction of complex objects to a Manageable,

straightforward, and relatively fast process. This has resulted intheir wide use by engineers as away to reduce time to market inmanufacturing, to better understand and communicate product

designs, and to make rapid tooling to manufacture those products.Surgeons, architects, and individuals from many other disciplines

also routinely use the technology.

Rapid prototyping isnt a solution to every part

fabrication problem.

After all, CNC technology is economical, widelyunderstood and available, offers wide material selection and

excellent accuracy. However, if the requirement involvesproducing a part or object of even moderately complex geometry,and doing so quickly - RP has the advantage. Its very easy to

look at extreme cases and make a determination of whichtechnology route to pursue, CNC or RP. For many other extreme

classes the selection crossover line is hazy, moves all the time,

and depends on a number of variably weighted, case dependantfactors. While the accuracy of prototyping isnt generally as

good as CNC, its adequate today for a wide range of exactingapplications.

At any rate, numerous secondary processes are availableto convert patterns made in a rapid prototyping process to final

materials or tools. The names of specific processes themselvesare also often used as synonyms for entire field. Among these is

stereo lithography (SLA for stereo lithography apparatus).Selective laser sintering (SLS), fused deposition modeling

(FDM), laminated object manufacturing (LOM), inkjets systems

and three dimensional printing (3DP). Each of these


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technologies- and many others has its singular strengths andweakness.

STEREOLITHOGRAPHY

Stereo lithography is the most widely used rapid

prototyping technology. Streolithography builds plastic parts or

objects a layer at a time by tracing a laser beam on the surface ofa vat of liquid photopolymer. This class of materials originally

develops for the printing and packaging industries, quicklysolidifies wherever the laser beam strikes the surface of the

liquid. Once one layer is completely traced, its lowered a smalldistance into the vat and a second layer is traced right on top ofthe first .the self adhesive property of the material causes the

layers to bond to one another and eventually from a complete,three dimensional object after many such layers are formed.

Some objects have overhangs or undercuts, which must

be supported during the fabrication process by support structures.These are either manually or automatically designed or fabricatedright along with the object. Upon completion process, the object

is elevated from the vat and the supports are cut off.

Stereo lithography generally is considered to provide the

greatest accuracy and best surface finish of any rapid prototypingtechnology. Over the years, a wide range of materials with

properties mimicking those of several engineering thermoplasticshas been developed. Limited selectively color changing materialsfor biomedical and other applications are available, and ceramic

materials are currently being developed .the technology is alsonotable for the large object sizes that are possible. On the

negative side, working with liquid materials can be messy andparts often require a post-curing operation in a separate oven-likeapparatus for complete cure and stability. Recently, inject

technology has been extended to operation with photopolymersresulting in systems that have both fast operation and good

accuracy.


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SELECTIVE LASER SINTERING

Thermoplastic powder is spread by a roller the surface ofa build cylinder .the piston in the cylinder moves down one

object layer thickness to accommodate the new layer of powder

.the powder deliver system is similar in function to the build

cylinder. Here, a piston moves upward incrementally to supply a

measured quantity of powder for each layer.

A laser beam is then traced over the surface of this

tightly compacted powder to selectively melt and bond it to form

a layer of the object. The fabrication chamber is maintained at a

temperature just below the melting point of the powder so that

heat form the laser needs only elevate the temperature slightly to

cause sintering. This greatly speeds up the process. The process

is the entire object is fabricated. After the object is fully formed,

the piston is raised to elevate it. Excess powder is simply brushed

away and final manual finishing may be carried out. No supports

are required with this method since overhangs and the solid

powder bed supports undercuts.

SLS offers the key advantage of making functional parts

in essentially final materials. However, the system is

mechanically more complex than stereo lithography and most

other technologies .a variety of thermoplastic materials such as

nylon and polystyrenes are available. Surface finishes and


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accuracy are not quite as good as with stereo lithography, but

material properties can be quite close to those of the intrinsic

materials .the method has also been extended to provide direct

fabrication of metal and ceramic objects and tolls. Since the

objects are sintered they are porous .it may be necessary to

infiltrate the part especially metals, with another material to

improve mechanical characteristics.

FUSED DEPOSITION MODELLING

FDM is the second most widely used prototyping

technology, after stereo lithography. A plastic filament is UN

from coil and supplies material to an extrusion 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 a mechanical stage, which can be moved in both horizontal

and vertical directions. As the nozzle is moved over the e table

required geometry, it deposits a thin bead of extruded plastic to

form each layer .the plastic hardness immediately after being

squirted from the nozzle and bonds to the layer bellow .the entire

system is contained within a chamber which is held at a

temperature just below the melting point of the plastic. Several

materials are available for the process including ABS and

investment casting wax. ABS offers good strength, and more

recently polycarbonate and polysuflone materials have beenintroduced which extended the capabilities of the further items of

strength and temperature range. Support structures are fabricated

for overhanging geometries and are later removed by breaking

them away from the object. Water solvable support material,

which can simpled be washed away is also available. The method

is office-friendly and quiet. FDM is fairly for small parts on the

order of a few cubic inches, or those that have tall, thin form-

factors it can very slow for parts with wide cross sections,


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however. The finish of parts produced with the method have been

greatly improved over the years, but arent quiet on a par with

stereo lithography. The closest competitor to the FDM process is

probably three-dimensional printing. However, FDM offers

greater strength and a wider range of materials than at least the

implements of 3DP from crop. Which are most closely

comparable.

LAMINATED OBJECT MANUFACTURING

Profile of object cross sections are paper or other web

material using a laser. The paper is unwound from a feed roll intothe stack and first bonded to the previous layer using a heated

roller, which melts a plastic coating on the bottom side of the

paper. The profiles are then traced by an optics system that is

mounted to an X-Y stage. After cutting of the layer is complete,

excess paper cut away to separate the layer from the web. Waste

paper is wound on take up roll. The method is self-supporting for

overhangs and under cuts. Areas of cross sections which are ton

be removed in the final object are heavily cross hatched with the

laser to facilities removal .it can be time consuming to remove

extra material for some geometries, however.

Variation on this method has been developed by many

companies and researched groups. For e.g. kiras paper

lamination technology (PLT) uses a knife to cut each layer

instead of a laser and applies adhesive to bond layers using the


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xerographic process. There also variations which seek to increase

speed and or material versatility by cutting edges of thick layers

diagonally to avoid stair stepping. In general, the finish, accuracy

and stability of paper objects are not as good as for materials

used with other RP methods. However, material costs are very

low; objectives have the look and feel of wood and can be

worked and finished in the same manner. This has fostered

applications such as patterns for sand castings. While there are

limitations on materials, work has been done with plastics,

composites, ceramics and metals. Some of these materials are

available on a limited commercial basis. The principal

commercial provider of LOM systems, Helisys ceased operation

in 2000. However there are several other companies with either

similar LOM technology or in yearly commercial stages. These

companies are addressing market segments ranging from concept

modeling to very objects for architectural applications.

THREE DIMENSIONAL PRINTING

Three-dimensional printing was developed at MIT. Its

often used as a direct manufacturing process as well as for rapid

prototyping. The process starts by depositing a layer of powder

objects 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. The roller then distributes and compresses the


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powder at the top of the fabrication chamber. Multi channel

jetting head subsequently deposits a liquid adhesives in a two

dimensional pattern onto the powder which becomes bonded in

the areas where the adhesive is deposited, to form a layer of the

objects.

Once a layer is completed, the fabrication piston moves

down by the thickness of a layer, and the process is repeated until

the entire objects is elevated and the extra powder brushed away

leaving a green objects. No external supports are required

during fabrication since the powder bed supports overhangs

Three-dimensional printing offers the advantages of speedy

fabrication and low materials cost. In fact, its probably the

fastest of all RP methods. Recently color output has also become

available. However there are limitations on resolution surface

finish part fragility and available materials. The closest

competitor to this process is probably fused depositing modeling.


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APPLICATIONS

RAPID PROTYPING IN FINE ARTS,ARCHITECTURE AND JEWELRY AND

INDUSTRIAL DESIGN

FINE ARTS

Today, layered fabrication is being used by an increasing

number of artists to build a wide variety of sculpture objects.

some of these works are realistic and representational while other

are abstract .the abstract objects can be the result of pure

imagination and artistic free will, or may be derived solely from

mathematics or computation. Some of the works created with

rapid prototyping may not have been possible to make any other

way.

JEWELRY DESIGN

Jewelry and the related arts have been particularly affected

.some system manufacturers, such as Meiko in Japan and solids

cape in the US, have concentrated on this application. There are

also service bureaus and university programs which emphasize

the design and manufacture of jewelry using rapid prototyping

system is most often used as a pattern for lost-wax or others types

of castings methods in jewelry manufacture. Direct manufacture

of jewelry is also a long-term possibility, however. While

precious materials are not yet possible for directed output, a few

artists are beginning to explore the use of the existing materials

of processes such as selective lasers sintering and stereo

lithography as final media.


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INDUSTRIAL DESIGN AND ARCHITECTURAL

MODELING

There is some interesting work going on in the industrial

design field, but it will require higher resolution and more

aesthetically pleasing output before rapid prototyping makes

substantial inroads. There is probably more interest in

architectural modeling at present where some complex post

modernist building forms, for example, those of the American

architect. Franck Ghery, are more faithfully and easily

represented than they could be using traditional model

construction methods.

FUNCTIONAL PARTS AND TOOLS FROM RAPID

PROTOTYPING

INTRODUCTIONParts made by rapid prototyping systems may be used

directly in many final applications today. This was not true just a

short a while ago and reflects grate strides in material researchthat have been spurred by instant market forces. Rapid

prototyping generated parts may well offered a direct solution tothe application problem with material requirements ranging fromceramics, to steel or titinaum. However, even the fastest RP

systems are still far too slow and limited in other ways: theysimply cant produce parts in a wide enough range of materials, at

a fast enough rate, to match the enormous spectrum of

requirements of industry. Convention processes such as moldingand casting are still the only means available to do that, but RP is

often or the starting point for making theses manufacturingprocesses faster, cheaper and better. Rapid prototyping is used in

two ways to accomplish this: molds may be directly fabricated byan RP system, or RP-generated parts can be used as patterns forfabricating a mould through so called indirect or secondary

processes.

INDIRECT OR SECONDARY PROCESSESAlthough the properties of RP material improve and

expand continuously a limit less array of applications means that


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there will always be a need to transfer parts formed a materialused in a RP process into yet another material. In addition, its

usually necessary to use very specific materials as the basis ofmost tool fabrication processes. Consequently numerous transfer

technologies have been developed typically a part made by the

RP systems is used as pattern or model in this processes. Whilemore than two dozen of them are in various stages of

development, just a few common and commercial importanttoday.

DIRECT FABRICATION PROCESSESSpecialized rapid proto typing processes have been

developed to meet specific applications and material requirementfor molding and castings. These may be forms of basic RP

processes, such as stereo lithography or selective laser sinteringor may be unique RP methods developed for a specificapplication. As in the case of indirect or secondary processes,

there are a large number of technologies begin explored but onlya few are commercially important today.

INVESTMENT CASTINGSNumerous RP technologies are appropriate for use as

investment castings patterns. These materials displacement-

casting methods are among the first industrial processes everdeveloped and are thousands of years old. The casting produce

can be exquisitely detailed and intricate. Bees wax was the firstmaterial used for patterns to produce stunningly detailed good

jewelry. More environmentally and socially conscious jewelry is

a significant application of rapid proto typing generated castingpatterns even today. There are numerous applications in industry

where parts are produced in a variety of metals with castingweighing up to several hundred pounds.

These processes typically involves thickly coating orinvesting a pattern which is made of a material that melts or

burns out easily with a material such as ceramic, which doesnt.

The pattern may be extended to provide a gate into which metalin a hot, liquid state poured. Passageways are also provided to

allow melted or burned pattern material and air to escape. Theinvested pattern is then fired in furnaces to burn out or melt the

pattern and fuse the ceramics into a strong hallow mold. Moltenmetal is then poured into the ceramic mould. After the metalcools and hardens the mould is broken away to reveal the final

object. Extra gate material is cut off and usually the parks willrequire substantially finish machining and clean up

INDIRECT OR SECONDARY PROCESSES THAT

UTILIZE RP GENERATED PATTERNS


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RP generated patterns can be obtained from fused

deposition modeling (FDM) in wax, selective laser sintering(SLS) in polystyrene or other plastics and inkjet technology in

wax like plastics. These materials may be melted or burned of the

investment very cleanly the patterns from these processes tend tobe small to medium in size and especially for inkjets, offer the

highest resolution and detailStereo lithography is also used to be produced patterns for

investment casting but the photo polymer materials used in thatprocess are more difficult to burn out than the materials used inother mentioned above and also have a tendency to expand and

crack the mould. To get around these problems, 3D systems haveproduced a special build style for this application with the trade

name quick cast. The RP generated patterns is built in hallow thinsections which tend to crumple during burn out rather than

expand and also results in a smaller mass of pattern materialremove the process has been developed over a number of years ina partner ship with large foundry companies and costumers.

A laminated object manufacturing (LOM) has also beenused for investment casting all though a more typical application

is for sand casting. The paper material used in the LOM processis said to some times be difficult to remove completely from the

mould although this is probably a strong function of theparticular geometry being produced

DIRECTED FABRICATION OF INVESTMENT

PATTERNSSoligen is a license of MITS 3D printing process and uses

it to produce investments directly with out patterns at all. Binderis deposited to bond a bed of ceramic powder in layer wise across

section to sequentially build up the investment. Extra powder isbrushed and vacuumed from the green part, which is fired to

consolidate it in a process similar to a convectional burned out.Soligen is vertically integrated to produce the final parts in itsown foundry

SAND CASTINGThe sand casting processes start by tightly compacting

fine, moist foundry sand in a box- like frame around the pattern

which is typically made of wood. The pattern is removed fromthe sand to leave a cavity into which the molten metal is poured.Once the metal cools and hardens its removed from the sand

which is then recycled as with investment casting it may benecessary to remove the extra material and perform finish

machining and cleanup.9


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MEDICAL APPLICATIONS OF RAPID

PROTYPING

Rapid prototyping is impacting medicine in several

important ways. Perhaps the most obvious application is as a

means to design, develop and manufacture medical devices and

instrumentation. This is simply an out growth of recognized

engineering applications of the technology. Any field where its

imperative to decrease product development time to while

simultaneously providing users with functional performance fed

back is an excellent prospect for rapid prototyping it there fore

follows that since human lives depend on the quality and ease of

use of numerous medical products there is a extra incentive to use

rapid prototyping in there development. E.g. of medical

instruments designed using the technology include reactors

scalpels surgical fasteners display system and many other

devices. Rapid prototyping technology is also being used to

fabricate drug dosage forms, which would be difficult if not

impossible to make any other way. Its possible to fabricate pills

with prcised and complex time release characteristics or that

dissolves almost instantly. Medication can be made more

effective and safer in this way, drug companies may be able to

realize stronger revenue streams from older compounds with

expired patience by providing them in novel and beneficialdosage forms.


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RAPID PROTYPING EQUIPMENTS

SLA VIPER Si2

Our latest addition to the lab the viper enables us toachieve small features with its dual laser spot capability: 0.003

inch and 0.01 inch laser spot sizes. The viper also embodies 3Dsystem latest machine design approaches to maximizeproductivity and useful ness installed new in the RPMI in

October 2001.

SLA-3500With its solid state laser, automatic resin dispensing system,

Zephyr recoated, smart sweep, large build envelope, and 0.002-

0.006 layer resolution, the SLA 3500 lets us do more and do itbetter we especially like its large build envelope of 14x14x16

inches for large parts. Installed new in the RPMI in august 1999

Technical Seminar Rapid Pro to Typing Harish

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