UNDER GUIDANCE OF1. MR ANKIT BAJPAI

Department of MECHANICAL Engg., DBIT, DEHRADUN

SUBMITTED BYSohan kumar

B. Tech(6 th sem)Mechanical Engg.

(2012-16)

DEV BHOOMI INSTITUTE OF TECHNOLOGY

DEHRADUN , UTTRAKHAND- 248007

.Introduction

.Need for prototyping

.Difference b/w Rapid prototyping and Traditional Fabrication

Basics of Rapid prototyping(RP)

.Rapid prototyping techniques

Material Used in RP

.Applications of RP

.Conclusion

Introduction

Rapid Prototyping Technology is a group

of manufacturing processes that enable

the direct physical realization of 3D

computer models.

This technology converts the 3D

computer data provided by a dedicated

file format directly to a physical model,

layer by layer with a high degree of

accuracy.

The presentation gives an overview on

existing major RP techniques and their

applications in engineering fields

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Fig 1: Flying sculpture called “the little shining man”

created using rapid prototyping technique.

RPT and Rapid Manufacturing (RM)

offers great potential for producing

models and parts.

By this reliability of product can be

increased, investment of time and money

is less risky.

RPT can automatically construct

physical models CAD data.

Rapid prototyping is an "additive"

process, combining layers of paper, wax,

or plastic to create a solid object.

In contrast, most machining processes

are "subtractive" processes that remove

material from a solid block.

Most prototypes require from one to

seventy-two hours.

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Fig 2: Rotors made using rapid prototyping techniques

08-10-2013 5Design & Manufacturing, NIT Silchar

08-10-2013 6Design & Manufacturing, NIT Silchar

The Basic Process

Create a CAD model of the design

# Object to be built is modelled using CAD software.

# Solid modellers like ProE yield better results.

# Existing CAD file may also be used

Convert the CAD model to STL (Standard Tessellation Language)

format

# STL format is the standard of rapid prototyping industry.

# This format represent 3D surface as an assembly of planar triangles and

describes only surface geometry. (without any representation of colour,

texture etc.)

Slice the STL file into thin cross-sectional layers

# Several programmes are available for this.

# STL models are sliced into a number of layers (.01mm to .7mm).

# Orientation size and location are adjusted using the software.

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department of mechanical,DBIT,DEHRADUN

Construct the model one layer atop another

# RP machine builds one layer at a time from polymers, paper, or powdered

metal.

# Fairly autonomous needing little human intervention.

Clean and finish the model

# Post processing step.

# Prototype may require minor cleaning and surface treatment.

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Rapid Prototyping Techniques

Most commercially available rapid prototyping machines use one

of the five techniques

Stereolithography (SL or SLA)

Laminated object manufacturing

Selective Laser Sintering

Fused deposition modeling

Solid Ground Curing

3D ink jet printing

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Fig 3: SL Machine

Stereolithography (SL or SLA) Builds 3D model from liquid photo sensitive polymers when exposed to UV rays.

Model is built upon a platform situated just below the surface of liquid epoxy or

acrylate resin.

A low power highly focused UV laser traces out the first layer, solidifying model

cross section.

An elevator incrementally lowers the platform into the liquid polymer.

Process is repeated until prototype is complete. Model is the placed in an UV oven for complete curing.

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Fig 4: Stereolithography

Laminated Object Manufacturing Layer of adhesive coated sheet materials are bonded to form a prototype.

Paper laminated with heat activated glue is rolled up on spools.

Heated roller applies pressure to bond the paper to the base.

Feeder/collector mechanism advances paper.

Laser cuts the outline of first layer.

Platform is lowered and fresh material is advanced.

Process is repeated and a roller bonds the layers.

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Fig 5: Laminated Object Manufacturing

Selective Laser Sintering Uses laser beam to selectively fuse powdered materials such as nylon,

elastomer or metal into a solid object.

Parts are built on a platform which sits below the surface in a bin of heat

fusible powder.

Laser traces the pattern of first layer, sintering it together.

Then platform is lowered, powder is reapplied and process is repeated.

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Fig 6: Selective Laser Sintering

Fused Deposition Modelling

Filaments of heated thermoplastics are extruded from a tip that moves in the

platform to form the first layer.

The platform is maintained at a lower temperature, so that the thermoplastic

quickly hardens.

After the platform lowers, the extrusion head deposits a second layer upon

the first.

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Fig 7: Fused Deposition Modelling

Solid Ground Curing (SGC)

Similar to stereolithography in that both use ultraviolet light to selectively

harden photosensitive polymers. Unlike SLA, SGC cures an entire layer at a

time.

First, photosensitive resin is sprayed on the build platform.

The machine develops a photo mask (like a stencil) of the layer to be built. This

photo mask is printed on a glass plate above the build platform using an

electrostatic process.

The mask is then exposed to UV light, which only passes through the

transparent portions of the mask to selectively harden the shape of the current

layer.

After the layer is cured, the machine vacuums up the excess liquid resin.

The top surface is milled flat, and then the process repeats to build the next

layer.

When the part is complete, it must be de-waxed by immersing it in a solvent

bath.

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Fig 8: Solid Ground Curing

12/02/2015

Dbit,dehradun

3-D Ink Jet Printing Parts are built upon a platform situated in a

bin full of powder material.

An ink-jet printing head selectively

deposits or "prints" a binder fluid to fuse

the powder together in the desired areas.

Unbound powder remains to support the

part.

The platform is lowered, more powder

added and levelled, and the process

repeated.

Finished parts can be infiltrated with wax,

glue, or other sealants to improve durability

and surface finish.

Typical layer thicknesses are on the order of

0.1 mm.

This process is very fast, and produces parts

with a slightly grainy surface.

There are also other different types of 3D

printing available in the market which gives

very good accuracy.16

Fig 9: 3-D Ink Jet Printing

Almost all materials can be manufactured through rapid prototyping operation, but polymer are the work piece most commonly used today,because they are less expensive.

.Poly carbonate

.ABS

.Metals

.Ceramics

and many mores

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Applications of Rapid Prototyping

Engineering

Made use in space stations and space shuttles.

Planning to install an RP machine in ISS for making spare parts.

Functional parts in F1 racing cars and fighter jets like F-18.

Medical Applications

Custom-fit, clear plastic aligners (braces) can be produced.

Used in hearing aids to make custom fit shells.

Arts and Archaeology

Selective Laser Sintering with marble powders can help to restore or duplicate

ancient statues.

Rapid Tooling

Tools are made by CNC-machining, electro-discharge machining, or by hand.

All are expensive and time consuming.

Manufacturers would like to incorporate rapid prototyping techniques to speed the

process.18

Conclusion

Modern CNC machines have high removal rates which helps in fast

machining.

For certain applications machining will continue to be a useful

manufacturing process.

One should regard RPT as one more option in the toolkit for

manufacturing parts.

Rapid prototyping will not make machining obsolete, but rather

complement it.

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References

en.wikipedia.org/wiki/Rapid_prototyping

www.protosystech.com/rapid-prototyping.h

P.M. Pandey, N.V Reddy, S. G. Dhande, ‘Slicing

procedure in layer manufacturing’, Rapid prototyping

journal 9(5), 2003, page 274 to 288.

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