THE TECHNICAL PAPER PRESENTATION

ON

“ Rapid prototyping ”

Submitted by:

ANKIT SRIVASTAV

Rapid Prototyping

ACKNOWLEDGEMENT

We would like to thank from the depth of our heart to all the concerned faculty and

all our batchmates of OIST who have always been to our side in our happiness and

vain.Our parents which have always been the ultimate source of knowledge and

inspiration ready to help financially and emotionally without whose help our

presentation would have been merely a thrash .

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Rapid Prototyping

INDEX

Sr.No. Particular Page No.

1. Introduction 3

What is Prototyping

Rapid prototyping differs by

2. The principle Advantages 4

3. Need for Prototype 5

4. Development 6

5. Case Study for Rapid Prototyping 6

5. Basic Process 9

Stereolithography

LOM

3D Plotting

6. Conclusion 13

7. Bibliography 13

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Rapid Prototyping

An Introduction to Rapid Prototyping

The ability to rapidly produce accurate, tangible models of

products designed on a computer aided design system.

Rapid prototyping is a technology of producing a, 3

dimensional visual prototype or model direct from a CAD file. Rapid prototyping

is based on CAD computer aided design.

What is Rapid Prototyping?

The term "rapid prototyping" is a relatively new expression

for the generation of three-dimensional models manufactured without the need for

machining or tooling.

Production of models by machining has a number of limitations:-

1. Material removed during forming is difficult to reclaim.

2. Machining, in the form of drilling, turning, milling, spark erosion etc., is

limited by the shapes it can produce.

3. In the event of design change conventional tooling such as patterns, core

boxes, dies, jigs etc., become expensive to alter and, in many cases, may

require complete re-manufacture.

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Rapid Prototyping

Rapid prototyping differs by:-

Adding material layer by layer until the desired shape is

achieved, immediately reducing or avoiding the loss of material. The conventional

ways were very slow and costly requiring a lot of man power which also induced a

huge scope for human errors.

The principle advantages of using this technology are: -

1. Speed at which the solid model is generated.

2. The complexity of the model does not form any limitations to its production.

3. The early use of these models was to assist the designer in determining fit and

form. It also provided the sales team with a 3 dimensional object to show to a

prospective customer, this being far better than the traditional orthographic

drawing which many people find difficult to interpret.

4. Concept modeling

5. To make an object which is difficult to make by machining and tooling.

The Need for a Prototype

It is very difficult, and in many instances impossible, to

produce an article that will serve the purpose of use without making modifications

to the original shape or general design. This allows designers and manufacturers to

rapidly and inexpensively test the parts of the design that are most likely to have

problems, solve those problems, and then build the full design.

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Rapid Prototyping

Other uses for RP models are:-

Discussion piece.

Design and fit.

Assembly capabilities.

Suitability of mechanical properties.

Manufacturing process capabilities (forging,

casting, pressing, fabrication etc.)

Development

The first rapid prototyping system was developed on to the

US model in 1988 and gave the Engg. the opportunity to produce 3 dimensional

object from computer aided design (CAD) data.

The development of this technology has reach into many of traditional fields.

The Case for Rapid Prototyping

The prime concern of any management is to maintain and,

where possible, improve profitability. We are all aware that profits accrue when

income from sales exceed total cost and that profits can be increased by improved

sales or reduction in costs, or both.

Many technologies have been developed which have been

successful in reducing the labour content, which, in most cases is the major cost.

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Rapid Prototyping

Rapid prototyping is only some ten years old and is already

proving to be a very cost-effective way of producing models/patterns.

There are over 500 stereolithographic(SLA) machines installed world wide

(approximately 20 in the UK) to famous companies such as :-

Ford, General Motors, Rover, Rolls Royce, IBM, Boeing, BAe.

These companies have recognised the power of this

technology to boost their profits and competitiveness. Whilst most companies are,

understandably, reluctant to reveal the extent to which the technology contributes

to their profitability

Increasing Sales by:-

* Producing visual models for market research, publicity, packaging etc.,

* Getting to market sooner.

* Generating customer goodwill through improved quality.

* Expanding the product range.

* Reducing the cost and fear of failure.

* Visual Models

Consumer product manufacturers find value in having

tangible models of their proposed products to show to customers.

IBM used SLA to produce operating display units of its

ThinkPad tablet computer for the annual COMDEX show.

Coca-Cola used RP to design the nostalgic (coke

bottle) curves into a contemporary 20 ounce plastic Coke bottle.

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Rapid Prototyping

Getting to Market Sooner

"Six months of delay can reduce a product’s life cycle profits

by 33%".

The earlier a product appears, the better are its prospects for obtaining and

retaining a large share of the market… For each month cut from a product’s

development cycle a month can be added to its sales life, representing an extra

month of revenue and profit… It gains more customer loyalty due to the cost of

switching to another product… A third benefit is higher profit margins. If a new

product appears before there is competition, the company will enjoy more pricing

freedom, making higher profit margins

Generating Customer Goodwill through Improved Quality

The end result is an improved products and most importantly,

greater customer satisfaction. This has lead to many companies in the USA

producing a RP model with any quote.

Expanding Product Range

Today’s market place is characterised by more frequent

introductions of more product variants each having a life cycle than the previous

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Rapid Prototyping

one. In addition, lead-times demanded are shorter than ever before. Clearly, RP

makes a positive contribution here, by compressing development times, thus

making it possible to respond to the demands of the niche markets and to introduce

new products more frequently

Reducing the Cost and Fear of Failure

It takes a very confident person to allocate / sanction large

amounts of money and resources on tooling for a product that might not make it on

the market. This will inevitably make people cautious and restrict their design flair

to those tried and tested shapes and systems only. Where a relatively cheap model

can be produced quickly it reduces the fear that traditional methods attract

allowing the designer to be more adventurous.

Rapid Prototyping, the basic process

RP machines process CAD data by slicing the computer

model into layers, each layer being typically 0.1 - 0.25mm thick. The machine then

uses this data to construct the model layer by layer, each layer being bonded to the

previous until a solid object is formed. Due to this laminated method of

construction a stepped surface is developed on curved faces, the removal of which

is essential if maximum advantage of the process is to be realised

The lamination and the support structure is designed

by the software used to drive the process. This translates a conventional 3D CAD

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Rapid Prototyping

drawing into the STL format used by the Rapid Prototyping machines (see

Software)

Types

There are three major types of Rapid Prototyping. They are

1. Photopolymer (Stereolithography),

2. Laminated object modeling,

3. Fused Deposition Manufacture

As Rapid Prototyping technology develops, the number of methods which can

be used to produce prototypes increase, these are some of them.

1. Rapid Prototyping - Fused Deposition Manufacture (FDM)

Materials used include:-

ABS

Medical ABS

Investment casting wax

Elastomers similar to low and high density

Polyethylene

Polypropylene.

A thermo-polymer is extruded from a travelling head having a

single, fine nozzle. The head travels in the X axis while the table or platform

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Rapid Prototyping

travels in the Y axis and descends at predetermined increments in the Z axis. On

leaving the nozzle the thermo- polymer adheres and hardens to the previous layer.

2. SLA Process. ( Stereolithography )

SLA system builds shapes using light to selectively solidify liquid photocurable

resins.

Principle :

Laser SLA crates acrylic or epoxy parts directly from a vat of

liquid photocurable polymer by selectively solidifying the polymer with a

scanning laser beam.

Building -up Technique

1. Building - up parts on an elevator platform.

2. The platform is lowered into the vat by the distance of the layer thickness.

3. Guiding a laser beam using servo-controlled galvanometer mirror and drawing

a cross -sectional layer in the x-y plane to form a solid section.

4. The platform is then lowered into the vat and the next layer is drawn and

adhered to the previous layer.

5. These steps are repeated, layer-by-layer until the complete part is built up.

3. Rapid Prototyping - Laminated Object Manufacturing (LOM)

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Rapid Prototyping

As the name implies the process laminates thin sheets of film

(paper or plastic), the laser has only to cut/scan the periphery of each layer and

not the whole surface as in SLA.

The build material (paper with a thermo-setting resin glue on

its under side) is stretched from a supply roller across an anvil or platform to a

take- up roller on the other side. A heated roller passes over the paper bonding

it to the platform or previous layer. A laser, focused to penetrate through one

thickness of paper cuts the profile of that layer. The excess paper around and

inside the model is etched into small squares to facilitate its removal.

Meanwhile, this surplus material provides support for the developing model

during the build process. The process of gluing and cutting continuous layer by

layer until the model is complete.

To reduce the build time, double or even triple layers are cut

at one time which increases the size of the steps on curved surfaces and the

post processing necessary to smooth those surfaces.

Applications of LOM objects:

LOM objects are durable, multilayered structures which can be machined,

sanded, polished, coated and painted.

Used as precise patterns for secondary tooling processes such as rubber

moulding, sand casting and direct investment casting.

Used for limited testing.

Used as visual models.

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Rapid Prototyping

NASA have used LOM technology in their shuttle design.

Conclusion

Today’s market is customer market. R & D is the heart of any progressing,

developing industry because R&D can only word of new blood in industry, so that

no obsolance stage will covered in the life of industry.

R & D Engg. developing new shapes, size, design, type of various component for

the establishing machine or product but hurdle is to produce the part according to

design immediately for getting immediate solution to the problem which they want

to rid off.

Now the time has come where, the design egg. Just can imagine the new design,

reproduce on the paper and within the few minute the product will be ready with

this technology ( prototyping) because the time has come where this technology is

capable to give the product manufactured within few minutes if product details are

fed to computer as data.

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Rapid Prototyping

x

y

Z

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Plat form

Head nozzle

Rapid Prototyping

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Process Chamber

Fig. Fused deposition

Laser

Scanner Laser sinking

Elevation

Surface of resin

Platform

ResinVat

Support

Stereolithography

Rapid Prototyping

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Laminated Object Manufacturing (LOM)

Cross hatching by laser

Rapid Prototyping

Bibliography

1. “ R.P. Systems” Mech. Engg., April. 1991, PP 34-43 , wikimapia.

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