Rapid prototyping technology

Presented by:ANIL VARGHESE MANGALAN

DESIGN AND MANUFACTURINGDEPT OF MECHANICAL ENGG

NIT SILCHAR

RAPID PROTOTYPING TECHNOLOGY

2Design & Manufacturing, NIT Silchar

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

Fig 1: Flying sculpture called “the little shining man” created using rapid prototyping technique.

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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.

Fig 2: Rotors made using rapid prototyping techniques

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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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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 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

Fig 3: SL Machine08-10-2013


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.

Fig 4: Stereolithography08-10-2013


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.

Fig 5: Laminated Object Manufacturing08-10-2013


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.

Fig 6: Selective Laser Sintering08-10-2013


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.

Fig 7: Fused Deposition Modelling08-10-2013


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

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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.

Fig 9: 3-D Ink Jet Printing

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Applications of Rapid PrototypingEngineering 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. 08-10-2013


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.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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http://www.jharper.demon.co.uk/rptc01.htm


THANK YOU

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