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Chapter 1 Introduction

1.1History:- The first attempt to create solid objects using photopolymers using a laser took place in the late 1960s at Battelle Memorial Institute. The experiment involved intersecting two laser beams of differing wave length in the middle of a vat of resin, attempting to polymerize (solidify) the material at the point of intersection. In the early 1970s, Formigraphic Engine Co. used the dual-laser approach in the first commercial laser-prototyping project, a process it called photochemical machining. In the late 1970s, Dynell Electronics Corp. was assigned a series of patents on solid photography. DEVELOPMENT OF SEREOLITHOGRAPHY- Hideo Kodama of the Nagoya Municipal Industrial Research Institute (Nagoya, Japan) was among the first to invent the single-beam laser curing approach, according to several sources. In October 1980, Kodama published a paper titled Three-Dimensional Data Display by Automatic Preparation of a Three-Dimensional Model that outlined his work in detail. His experiments consisted of projecting UV rays using a Toshiba mercury lamp and a photosensitive resin called Tevistar. In August 1982, Alan Herbert of 3M Graphic Technologies Sector Laboratory published a paper titled Solid Object Generation in the Journal of Applied Photographic Engineering. In this paper, Herbert described a system that directs an Argon Ion laser beam onto the surface of photopolymer by means of a mirror system attached to an x-y pen plotter device. With the system, Herbert was able to create several small, basic shapes. In August 1984, Charles Hull, co-founder and chief technical officer of 3D Systems (at that time, in Valencia, California), applied for a U.S. patent titled Apparatus for Production of Three-Dimensional Objects by Stereolithography, which was granted in March 1986. Osaka Prefectural Industrial Research Institute In 1984, Yoji Marutani of the Osaka Prefectural Industrial Research Institute

(OPIRI), also referred to as the Osaka Institute of Industrial Technology,

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developed and demonstrated a stereolithography process. Its not clear whether his work was connected with Kodamas early work, although theres a very good chance that Marutani at least studied Kodamas May 1980 patent application and his October 1980 and November 1981 technical papers. Its also possible that Marutani obtained a copy of Herberts 1982 paper, but its doubtful that Marutani knew about Hulls and Andres work in 1984.OPIRI was later commercialized.

1.2 Commercial History

Additive manufacturing first emerged in 1987 with stereo lithography (SL) from

3D Systems, a process that solidifies thin layers of ultraviolet (UV) light sensitive

liquid polymer using a laser.

In 1988,3D Systems and Ciba-Geigy partnered in SL materials development and

commercialized the first-generation SLAs. After 3D Systems commercialized SL

in the U.S., Japans NTT Data CMET and Sony/D-MEC commercialized versions of stereo lithography in 1988 and 1989, respectively. In 1990 Electro Optical

Systems (EOS) of Germany sold its first Stereo lithography system.

In 1991, three AM technologies were commercialized, including fused

deposition modeling (FDM) from Stratasys , solid ground curing (SGC) from

Cubital, and laminated object manufacturing (LOM) from Helisys. Selective laser

sintering (SLS) from DTM (now a part of 3D Systems) and the Soli form stereo

lithography system from Teijin Seiki became available in 1992. In 1993, Soligen

commercialized direct shell production casting (DSPC). Using an inkjet

mechanism, DSPC deposited liquid binder onto ceramic powder to form shells for

use in the investment-casting process. Massachusetts Institute of Technology

(MIT) invented and patented the process that Soligen used. 1994 was a year of

many new additive-manufacturing system introductions. Model Maker from

Solidscape (then called Sanders Prototype) became available, as did new systems

from Japanese and European companies. In 1996, Stratasys introduced the Genisys

machine, which used an extrusion process similar to FDM but based on technology

developed at IBMs Watson Research Center. In 1998, Beijing Yinhua Laser Rapid Prototypes Making & Mould Technology Co., Ltd. stepped up the promotion of its

products. In March 1999, 3D Systems introduced a faster and less expensive

version of Actua 2100 called Thermo Jet.

April 2000 was a month full of new

technology introductions. Objet Geometries of Israel announced Quadra, a 3D

inkjet printer that deposited and hardened photopolymer using 1,536 nozzles and a

UV light source. In early 2002, Stratasys introduced its Dimension product at a

price of $29,900. The Dimension machine, which deposits ABS plastic, is based on

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the former Prodigy product. In February 2003, Z Corp. introduced its ZPrinter 310

system. The product, then priced at $29,900, uses technology similar to the

companys other powder based 3D printers. At EuroMold 2004, EOS introduced the EOSINT P 385, a plastic material system capable of thinner layers than were

possible with its predecessor.

In April 2005, 3D Systems unveiled the Sinter station Pro, a large-frame laser

sintering machine with part breakout, powder handling, and recycling. In February

2006, 3D Systems announced its In Vision DP (dental professional) system that

includes an In Vision 3D printer and 3D scanner for the dental market. In January

2007, 3D Systems announced the V-Flash 3D printer. It uses film transfer and

flash-imaging technology. In January 2010, Stratasys and HP signed an agreement

for Stratasys to manufacture an exclusive line of HP-branded 3D printers. In March

2010, Stratasys extended its SMART supports capability to its entire line of

Dimension and Fortus machines, allowing for build time reductions of up to 14%

and reduction in support material by 40%.

1.3 Manufacturing Systems Four major types of manufacturing processes are typically considered-

1) Forming- It is probably one of the oldest form. In forming process something is smashed into desired shape. For example forging, rolling,

extrusion and drawing.

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2) Joining process- In joining process two substances are joined to produce desired shapes. Well known processes are like welding, soldering and

brazing.

3) Removal processes or subtractive machining- In this process metal is removed to get the desired shape. We start with a lump of material, cut it

away, cut it away .cut it away until the desired shape is obtained.

4) Additive manufacturing- In this process we start with some form of material and we keep adding to it layer by layer typically to create a desired shape.It

starts with a powder and laser cause them to bond together.

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Chapter 2

Most Prevalent Processes in AM

2.1 Stereolithography

Process-Thin layer of UV sensitive liquid polymers are solidified

through the use of laser.

Basic Principle- Stereolithography is a photopolymerisation

process, where under exposure of UV radiation small molecules

(monomers) in a resin form larger molecules. Three main photopolymer

system used in it are acrylate, epoxy resin and vinyl ether.

Figure 2.1 Stereolithography: (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.

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2.1.1Part Built Time

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 = delay time between layers to reposition the worktable

Once the Ti values have been determined for all layers, then the build

cycle time is:

where Tc = SLA build cycle time; and nl = number of layers used to

approximate the part

Time to build a part ranges from one hour for small parts of simple

geometry up to several dozen hours for complex parts.

Benefits-

No milling or masking steps needed. Can be highly accurate Only one material needed for build and support

Downsides-

Requires post curing of material Long term curing can lead to warping Can have brittle parts with a tacky surface Support structures are often needed Material is toxic and light sensitive

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2.2 Fused Deposition Modeling (FDM)

Process-

Heated thermoplastics are extruded through nozzles , extruded

material hardens as it cools.

Basic Principle-

Process starts with a 3D CAD model sliced into thin layers in Z-axis.

These sliced layers are used to drive an extrusion head of FDM machine.

The building material, in the form of a thin solid filament, is fed from a

spool to a movable head controlled by servomotors. Second filament is

fed from adjacent nozzle for support material, used to give support for

overhanged or cantilever features. The filament reaches the liquifier

head, melts it and then extruded through a nozzle onto the part surface.

After covering the whole cross section build platform descends by one

layer thickness to lay down the next layer. Process repeats itself until full

3D part is formed. The temperature of machine chamber is precisely

controlled below the melting point of the material so that only little

amount of heat is required to melt the filament and on the other hand

part need to be kept cool enough so that the molten material solidifies

upon contact.

Fig 2.2

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Benefits-

Can use standard engineering thermoplastics such as ABS.

Can use multiple materials (One for bulid, one for support)

Can produce water tight parts

Parts are hardened very quickly

Downsides-

Poor layer uniformity

Delamination of extruded layers can be problematic

Parts can have a rather coarse surface finish

2.3 3D Printing

Process- Molten/liquid plastics printed along with wax support structure.

Basic Principle-

3DP also known as 3D printing works on FDM principle as a layered

manufacturing process. 3DP offers prototypes with thermoplastic

Polyester material. A thin bead of molten plastic is extruded through the

computer controlled nozzle, which is deposited on a layer-by-layer basis

to construct a prototype directly from 3D CAD data. The technology is

commonly applied to initial conceptual design.

Fig 2.3

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Benefits-

Can be fast

Can do very fine details

Relatively clean/ office friendly

Downsides-

Can be expensive

Removal of wax

Support structure material necessary

2.4 Sintering

Process-

Lasers used to selectively sinter/fuse layers of powdered materials.

Basic Principle- SLS process produces parts directly from 3D CAD

model; layer by layer similar to SLA but rather than liquid resin powder

is used. The CO2 Laser provides a concentrated heating beam which is

traced over the tightly compacted layer of fine heat-fusible powder. The

temperature in the entire chamber is maintained little below the melting

point of the powder. So laser slightly raises the temperature to cause

sintering, means welding without melting. For next level, piston moves

down along with the formed object and powder is spread with a roller

for next layer. Process repeats until full object is formed.

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Fig 2.4

Benefits-

Can be very strong

Can use nylons, elastomers , metals (e.g. Ti and stainless steel)

Powder support material easy to remove

Can create hard/dense part

Downsides-

Powdery , rough, porous surface

Can be very expensive

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Chapter 3 Design Analysis and Comparisions

3.1 Stereolithographic design

Dimensional parameters:-

Each layer in SLA 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

RenShape SL 7560 -

Description

SL 7560 is durable SLA material that simulates ABS - like parts,

provides good combination of durability and rigidity.

Use of this material-

Suitable for Durable and rigid parts with having outstanding appearance

Excellent for RTV patterns and functional applications. Excellent side wall finish and fine features and good temperature performance.

Somos WaterClear 10120:

Description

Somos WaterClear 10120 is a high-speed liquid photo-polymer that

produces strong, rigid and durable parts with optical clarity.

Use of this material

This material is especially useful in applications requiring optical

clarity such as fluid flow analysis, stress analysis or transparent show

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models where internal features need to be displayed. Other application

where strong and durable products without the brittleness.

3.2 Fused Deposition Modeling Design

How the FDM process works

First, a part model is created in a STL file with AutoCad or another design program..

The model needs to be imported into Stratasys software, Insight. The software slices the .stl file into horizontal layers mathematically, generating the required supports.

Insight creates tool paths required for the extrusion head. The system draws cross-sectional layers one at a time in the X, Y, and Z coordinate by using a heated material extrusion process.

How the parts built

Import the .stl file of part model into Stratasys software, Insight, which slices the model into horizontal layers.

The supports are created if they are needed and the tool paths for the extrusion head are planned.

ABS material feeds into the temperature-controlled FDM extrusion head, where it is heated to a semi-liquid state.

The head extrudes and deposits the material in 0.254mm layers onto a fixtureless base, one layer at a time in X and Y coordinates first.

When the layer is finished, the head moves in Z direction to the next layer.

Each layer is extruded with precision, and the layers are bonded and solidified.

The designed object becomes a solid three-dimensional part.

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Material :-

Tough,Durable and accurate parts for functional testing.

When functionality is more important than surface finish.

Cost:-

The cost to create a part on FDM depends on the time and materials used

to create the part. Since FDM builds upon layers, complexity is less of

an issue on cost and rather it is the work to create mass that consumes

resources. Therefore, creating bigger parts becomes costly using FDM.

Small parts can be created for under $50, with larger parts costing more.

Time:-

Like cost, the time it takes to create a part using FDM depends on the

size of the part. Each layer created requires time to set before the next

layer can be placed on top and the process to continue. So it can be seen

that dimensionally longer parts with mass will take more time to create

rather than smaller, hollow parts. The range in tame it takes to create

these parts will vary from a couple of hours to multiple days.

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3.3 3D PRINTING

3DP also known as 3D printing, this Printer allows to try new design

iterations quickly and cheaply. The printer uses durable polyester

material. These concept models will provide considerable functional

strength and can be drilled, tapped, and sanded. These Polyester parts

are little flexible and can also be used for limited snap fitting features.

Materials:-

Use of this material:-

Durable parts for limited testing and it is suitable for parts where little

flexibility is needed.

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3.4 Sintering SLS system provides a wide variety of material choices enable us to

create functional prototypes, direct tooling, and patterns - even final

parts. Being able to use polymers, glass-filled nylon, metal and

composites give a lot of flexibility to quickly produce one or many

components without the typical delays associated with traditional

manufacturing methods.

Materials:-

Material Class - Thermoplastic

Use of this material

DuraForm PA material is ideal for parts with superior surface quality, fine details and functional features such as living hinges and snap fit

connections. Plus DuraForm PA material can be used for modeling and

testing surgical devices and can be sterilized with an autoclave.

DuraForm GF material's increased stiffness, heat resistance and mechanical integrity make it perfect material for extreme testing

conditions, e.g. DuraForm connector with snap fits, hinges and locking

cams recently withstood temperature up to 100C and an electrical

charge of 460 Amps.

Benefits

Durable parts without tooling

Heat and chemical resistant, Machinable, weldable and has excellent

surface quality High feature definition and detail, High durability and

stability

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3.5 Comparisions

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Brief about all the technologies-

SLA- Excellent surface finish suitable for presentation, master models

and light functional testing.

FDM- Good combination of strength and surface finish at affordable

price and lead time.

3DP- Suitable for general purpose parts for initial design stage with a

quick delivery

SLS- Range of materials available, soft like rubber to strong like metal.

SLS Nylon suitable for snap and living hinge features

CNC- Use when mechanical properties cannot be compromised with any

additive RP process.

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Chapter 4 4. AM Applications

4.1 Aerospace

The aerospace industry desires parts that are lightweight and

strong and sometimes electrically conductive. They are seeking

a standard set of AM materials, as well as a design manual for

the materials and processes, but neither are currently available.

Furthermore, they require material and process standards that

ensure part quality and consistency across machines and builds.

Turbine blades made by direct metal laser sintering (DMLS)

from EOS (a German manufacturer of laser sintering/melting

systems) have found their way onto test rigs. Morris Tech

believes that a variety of metal parts made by additive

manufacturing will initially make their way onto flying aircraft

in 2-3 years and will become common in 10 years.

4.2 Surgery and dental

The market for the production of dental products using AM is

on the verge of explosive growth. Already many dental labs are

using DMLS from EOS and other direct metal AM processes for

the production of copings for crowns and bridges. EOS has

reported that the dental business is currently its fastest growing

area of AM for production applications

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Fig 4.1

4.3 Automotive and Motorsports

The opportunity to use AM to manufacture parts for vehicles is

substantial. Production runs of high-end, specialty cars are

relatively small. Consequently, these products are candidates for

using AM for part production. Already, companies such as

Bentley and Rover have shown that it is feasible and have used

AM for small, complex parts. Likewise, the motorsports

industry (both cars and motorcycles) will benefit greatly from

improved helmet design brought about from AM. This includes

aftermarket products that are custom, semicustom,

and standard.

4.4 Cellular Design

The ability to put material only where it is desired could have

a profound impact on how parts are designed and

manufacturing. Cellular materials are examples of materials

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that are structured as repeated cells; their geometry enables a

high degree of optimization which provides the opportunity

for designers to control readily the distribution of material in a

part. These materials can achieve high stiffness or strength per

unit mass and can provide good energy absorption

characteristics and good thermal and acoustic insulation

properties

4.5 Regenerative turbines

The complexity of the modified blade profiles would normally

necessitate the use of expensive computer numerically

controlled machining with five-axis capability. With an impeller

less than 75mm in diameter with a maximum blade thickness of

1.3 mm, a rapid manufacturing technique enabled production of

complex blade profiles that are dimensionally accurate and

structurally robust enough for testing.

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Chapter 5 AM and Environment

They use excessive material as they are designed for processes such as

machining and molding. Moreover, they are made in geographically

disparate locations, often dictated by the location of tooling in low labor

cost economies. There are a number of clear, potential benefits to the

adoption of AM for part production, which could be driven by the

sustainability agenda. These include:

1). More efficient use of raw materials in powder/liquid form by

displacing machining which uses solid billets

2). Displacing of energy-inefficient manufacturing processes such as

casting and CNC machining with eradication of cutting fluids and chips

3). Ability to eliminate fixed asset tooling, allowing for manufacture at

any geographic location such as next to the customer, reducing

transportation costs within the supply chain and associated carbon

emissions

4). Lighter weight parts, which when used in transport products such as

aircraft increase fuel efficiency and reduce carbon emissions

5. Ability to manufacture optimally designed components that are in

themselves more efficient than conventionally manufactured

components by incorporating conformal cooling and heating channels,

gas flow paths, etc.

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CONCLUSION

Additive manufacturing (AM) technology has been researched

and developed for more than 20 years. Rather than removing

materials, AM processes make three-dimensional parts directly

from CAD models by adding materials layer by layer, offering

the beneficial ability to build parts with geometric and material

complexities that could not be produced by subtractive

manufacturing processes. Through intensive research over the

past two decades, significant progress has been made in the

development and commercialization of new and innovative

AM processes, as well as numerous practical applications in

aerospace, automotive, biomedical, energy and other fields.

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REFERENCES Jane Chu, Sarah Engelbrecht, Gregory Graf, David W. Rosen, (2010) "A

comparison of synthesis methods for cellular structures with application

to additive manufacturing", Rapid Prototyping Journal, Vol. 16 Iss: 4,

pp.275 283 Francis J. Quail, Thomas Scanlon and Matthew Strickland(2010)

Development of a regenerative pump impeller using rapid manufacturing techniques ,Rapid Prototyping Journal Volume 16 Number 5 2010 pp 337344

Tomaz Brajlih, Bogdan Valentan, Joze Balic, Igor Drstvensek, (2011) "Speed and accuracy evaluation of additive manufacturing machines",

Rapid Prototyping Journal, Vol. 17 Iss: 1, pp.64 75 http://wohlersassociates.com/terms.html http://additivemanufacturing.com/ http://www.ge.com/stories/additive-manufacturing http://www.docstoc.com/docs/71023917/ADDITIVE-

MANUFACTURING-AND-THE-ENVIRONMENT

http://www.arptech.com.au/slshelp.htm