Chap04 01 Principle

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Introduction to

Rapid Prototyping

-A S Rao

Mechanical Engineering Department

MUMBAI-400019


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u

Principle

Popular RP Processes

Important Issues in RP

Conclusions


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Ways to Speed up Physical

Processes : AutomationHuman being is the bottleneck to speed.

1. Automation of processes

automats, SPMs, Transfer lines

Soft automation:

CNC, Robotics, AGVs, FMSs,

2. Automation of Process Planning

CAPP

28-Sep-06 3

RP


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Rapid Prototyping - Definition

Rapid Prototyping (RP) is an automatic process of manufacturing

objects (parts, prototypes, tools and even assemblies) directly from

their CAD models without any cutters, tools orfixtures specific to theobject geometry.

It is more

appropriate to call it

as La ered

Manufacturing or

3D Printing or3D

.

RP uses a divide-

28-Sep-06 5

-

manufacturingstrategy, viz., slicing.


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Principle Layered Manufacturing

RP is a Divide-and-Conquer based manufacturingstrategy.

Some examples of Divide and Conquer Technology :- FEM

-

- CSG(Cylinder,Cone etc)

Cutting the object into parallel slices and squaring the.

In RP, a complex 3D problem is broken down into several

.

Just as squaring the edges is responsible for totalau oma on, s a so respons e or s poor accuracy an

strength.


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Principle - Support Layered Manufacture is not new; even buildings are constructed that way.

However, it is labor-intensive and less automatic. This is because it does notemploy any automatic method of support generation.

Every RP process employs a support mechanism. It is required for Supporting overhanging features.

Means for securin isolated se ments or islands

Holds the part in place like a fixture

Help minimize distortion or curl.

Some processes have an inherent support mechanism. In others, an explicitsupport mechanism is to be incorporated. In most cases of explicit support,supports are built from a sacrificial material that is removed later.

Support is the place of poor finish.

Note: Identify the support mechanism used in various RP processes as we discussthem!


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FEATURES REQUIRING SUPPORT(issue5)


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Definition

Rapid Prototyping (RP) is an automatic process formanufacturing parts, prototypes, tools and even assemblies

,

tools or fixtures specific to the geometry of the object and withoutany human intervention anywhere in the process.

It is a CNC machine with an embedded CAPP system foradditive manufacturin .

As success in CAPP is evading subtractive manufacturing, all

.

It is a divide-and-con uer manufacturin strate .


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- Layered Manufacturing (LM)

- 3D Printin 3DP

- 3D Faxing

- o ree orm a r ca on- DeskTo Manufacturin DTM


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Steps in CNC Machining

Designer

CAD SOFTWARE

Cutter path file

Not a tightly

Integrated

system

NC MACHINE

Part/ Tool


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Designer

CAD SOFTWARE

STL file

Tightly

IntegratedSliced data

RP MACHINE

Parts/ Tools/ Assemblies


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Comparison of CNC and RP RP is also a CNC Machine:

As far as its construction is concerned, it is also a CNC machine - a 2.5axis machine. The onl difference is that it is an additive rocesspresently; this need not hold good in future since hybrid processes are

emerging. To meet the requirements of advanced slicing strategies, 3-6axis RP machines are under various stages of developments at various

arts of the world.

Total Automation:The idle time of a CNC machine is mainl due to the waitin for the NCprograms which are prepared by humans. The process of art-to-part isreally not fully automatic in CNC. Therefore, RP is increasinglybecoming an attractive alternative to CNC since it is more automaticthan the CNC machines albeit oor ualit .

Successful CAPP + CNC RP

Time Com ression:It is one of the time compression technologies as it cuts down product

development (more RP) and productionizing (more RT) cycle times.Therefore, it is an effective tool where time to market matters.


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It is possible to use any solid model or water-tight

sur ace mo e .

Tessellated model is referred due to its sim licit .Note that tessellated model does not meancompromise on accuracy. This is because anymanufacturin rocess has a limited accurac . Now-a-days, even STL-based CAM packages are available.

.

Triangular tessellation is preferred due to itsro us ness.


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Most popular format is Stereo-lithography (STL) format. This was

.

Other solid formats like VRML also are used. Advantage of

topology and (ii) storing additional details such as colorinformation.

In spite of its limitations, STL file still is the most popular due toits down-to-the-earth simplicity. There are packages for browsingand repairing STL files (Magics, Deskartes, SolidView etc.).

There are also unpopular attempts to use sliced contours informats such as HPGL format. Even scanned data from CT etc.

.


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Geometric Input STL File of a Cube

sol i d Aut oCADf acet nor mal 0. 0000000e+000 0. 0000000e+000 1. 0000000e+000

out er l oopver t ex . e+ . e+ . e+

ver t ex 1. 0000000e+001 1. 0000000e+001 1. 0000000e+001ver t ex 0. 0000000e+000 1. 0000000e+001 1. 0000000e+001

endl ooendf acet

f acet nor mal 1. 0000000e+000 0. 0000000e+000 0. 0000000e+000

out er l oopver t ex 1. 0000000e+001 0. 0000000e+000 0. 0000000e+000

ver t ex 1. 0000000e+001 1. 0000000e+001 0. 0000000e+000ver t ex 1. 0000000e+001 1. 0000000e+001 1. 0000000e+001

endl oop

endsol i d Aut oCAD


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Types of STL Files

1. ASCII format

- Human readable- Large file size

2. Binary format- Only machine readable

- Small file size. As small as a 5th in size.


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POPULAR RP PROCESSES

RP

PROCESS

DEVELOPED

BY

USED IN INDIA BY

LAMINATED OBJECT

MANUFACTURING (LOM)

HELISYS, USA

TOYODA, JAPAN

Intelmac (Pune), CMERI

(Durgapur,West Bengal)

FUSED DEPOSITION STRATASYS, USA IISc, IIT-B, IIT-K, Anna Univ.,

MODELING (FDM) MNREC (Allahabad),VJTI

STEREO LITHOGRAPHY

APPARARUS (SLA)

3D SYSTEMS,

USA

BARC, GTRE(DRDO)

(Bangalore),Imaginariumum a

PHOTOMASKING OR SOLID

GROUND CURING (SGC)

CUBITAL, ISRAEL Datar switchgears Ltd

(Nasik), IIT-K

SELECTIVE LASER SINTERING(SLS)

DTM, US CMTI (Bangalore),Imaginarium Mumbai

EOS, GERMANY ?

3D PRINTING Z-CORP ?

Objet ? Vectraform, Coimbatore

Chap04 01 Principle

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