Rapid Prototyping Technology

-Mitesh Parmar 1220037

Table of content Introduction Basic Operation RP Techniques Applications References

Introduction Group of manufacturing

processes that enable the direct physical realization of 3D computer models.

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.

By this reliability of product can be increased, investment of time and money is less risky.

RPT can automatically construct physical models by CAD data.

Rapid prototyping is an "additive" process, combining layers of paper, wax, or plastic to create a solid object.

Most prototypes require from one to seventy-two hours.

Basic Operation Create a CAD model of the design Object to be built is modelled using CAD software. Solid modellers like Pro E yield better results. Existing CAD file may also be used

Convert the CAD model to STL (Standard Tessellation Language) format

Standard format of rapid prototyping industry. 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.

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.

RP TechniquesMost 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

Stereolithography 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.

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.

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.

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.

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.

Solid Ground Curing (SGC) 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.

Solid Ground Curing (SGC)

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.

3-D Ink Jet Printing 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.

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.

3-D Ink Jet Printing

ApplicationsEngineering 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.Arts and Archaeology Selective Laser Sintering with marble powders

can help to restore or duplicate ancient statues.

ApplicationsMedical Applications Custom-fit, clear plastic aligners (braces) can be

produced. Used in hearing aids to make custom fit shells. 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.

References en.wikipedia.org/wiki/Rapid prototyping www.protosystech.com/rapid-

prototyping.htm www.jharper.demon.co.uk/rptc01.htm 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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