Session 5 _ Reverse Engg & Rapid Prototyping

8/11/2019 Session 5 _ Reverse Engg & Rapid Prototyping

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1@M. S. Ramaiah School of Advanced Studies

Reverse Engineering

&

Rapid Prototyping

Session -5


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Session Objectives:

On completion of this session, the student would Know what is Reverse Engineering in CAD.

Understand the techniques used in Scanning, processing thedata and generating CAD models, their applications.

Know what is Rapid Prototyping, how it is integrated withthe CAD systems

Understand the techniques used in RP processes and theirapplications


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Challenges faced by Manufacturers today...

Reduce Manufacturing Cycle time

Increase Productivity

Reduce cost

Improve product quality Better customer service support

Flexible in accepting changes

CAD/CAM is the Major solution for Manysuch issues


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What is Reverse Engineering (RE)?

It is a process of generating engineering design datafrom existing components

CARE Computer Aided Reverse Engineering


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Need of Reverse EngineeringCAD models are often unavailable or unusable for parts

which must be duplicated or modified: CAD not used in original design.

Inadequate documentation on original design.

Original CAD model not sufficient to support modification ormanufacturing using modern methods.

Original supplier unable or unwilling to provide additionalparts.

Shop floor changes to original design.

To reproduce complex free form surface

Broken or obsolete Part

Aesthetics in design


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Application... Tool and Die making

Mould Making

Press tools

Aerospace and Automobile Industry

Jewelry and artistic work Or any where , where there is a need to produce free

form surfaces.


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7@M. S. Ramaiah School of Advanced Studies 7

The objective of reverse engineering is to increase the abilityto maintain a manufacturing capability at its peak rate byimproving documentation for logistically unsupportedequipment and systems

Reverse engineering should not be confused with systemmodernization, which involves technological upgrade of anentire system to eliminate many portions of a currentmanufacturing system

Reverse engineering is targeted at modernizing singularcomponents of a system to maintain or increase system

productivity

Objective of Reverse Engineering


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Typical Design Process

Manufacturing

Finished product

Idea

Concept

design

Detail design

CAD / CAM

CNC programme


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The Reverse Engineering Process

Manufacturing

Finished product

Idea

Concept

design

Detail design

CAD / CAM

CNC programme

Reverse

Engineering

Start

Start


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Reverse Engineering Process

Reverse engineering usually consists of four stages:

Data generation

Data evaluation

Design verification Design implementation

A reverse engineering process identifies and strengthensthe weak links in any system

New documentation support for equipment and improvedsystem maintenance are important byproducts of thereverse engineering processes


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Legality in RE

Patents protect the ideas behind the functioning of a product,

copyright protects only its look and shape. A warning sign to a competitor to discourage competition. If

there is merit in an idea, a competitor will do one of following:

Negotiate a license to use the idea

Claim that the idea is not novel and is an obvious step foranyone experienced in the particular field

Make a subtle change and claim that the changed product is notprotected by the patent

Ethical uses involved in RE

Do not reverse-engineer parts if the procurement contract of thecomponent prohibits reverse engineering.

Remember to perform reverse engineering using only data that

is part of the public domain.


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Reverse Engineering Methods

It is the process of gathering information about an undefined3D surface and digitizing it

Types of Scanning:

Contact Type Non-Contact Type

Scanning

The Physical part is scanned and the cloud point data with millions ofpoints is acquired.

The cloud point Data is converted into a Polyganized data set, of tinyfacets.

NURBS Surfaces are created and the geometry can be exported to anyCAD, CAM and RPT Software.


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Non-contact type 3D laser scanning

PICZA LPX 250 Laser Scanner

Converts scanned data intopolygon and NURBS surfaces

Exports in STL, DXF and IGESfile formats for industry standard3D CAD and solid modelingsoftware

Large scanning area -- up to406.4mm (16") high x 254mm(10") in diameter with a

resolution of 200 microns Dual modes -- offers both rotary

and plane scanning for optimumperformance


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Methodology of Reverse Engineering

A cloud of points taken from scanned datausing a digitizer such as a laser scanner,computed topography

Convert the point cloud to a polygonalmodel. The resultant mesh is cleaned up,smoothed, and sculpted to the required shapeand accuracy.

Draw/create curves on the mesh usingautomated tools such as feature detectiontools or dynamic templates


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Step 4: Create a restructured spring mesh usingtools

Step 5: Fit NURBS surfaces using surfacefitting/editing tools

Step 6: Export the resulting final NURBS surface

that satisfies accuracy and smoothnessrequirements to a CAD package for generatingtool paths for machining

Step 7: Manufacture and analyze the part for

physical, thermal, and electrical properties


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Typical RE Applications Creating data to refurbish/manufacture a part for which there is no

CAD data, or for which the data has become obsolete/lost

Creating 3D data from an individual, model or sculpture forcreating scaling, animation in games/movies, copying artwork

Documentation and/or measurement of cultural objects or artifactsin archaeology, paleontology and other scientific fields

Fitting clothing or footwear to individuals and determining theanthropometry of a population

Generating data to create dental or surgical prosthetics, tissue-engineered body parts, or for surgical planning

Documentation, measurement and reproduction of crime scenes,architectural and construction work

Inspection and/or Quality Control - Comparing a fabricated part toits CAD description or to a standard item


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Stages of RE Applications

Data Collection (Digitizing or Scanning)

Geometry Clean-up (Cleaning or Noise Removal) Data Collection

The process of gathering the requisite data (3D) from an object

Range: Mechanical (slow) - Radiation-based (fast, automated)

Output: Description of physical object in 3D space - point cloud

Point Cloud

Numerous data points of object in terms ofx, y, z coordinates

Typically correspond to point on the surface of object (external &internal view scanning) or inside of object (internal view)

The points on surface can be used to create surface poly-meshgeometric model and interior points for volumetric model


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Data Collection Specifications 3 Key Specs

Volume currently no issues, New RE software can stitch PCs

Accuracy - how precisely the measurements correspond todimensional standards; Resolution the smallest increment ofdistance or volume that the instrument can measure; different foraxis of measurement; other issues repeatability, linearity

Speed range from a few points per minute using manualtechnologies, to more than a million points per second; Thetradeoff for digitizers is time and accuracy

Data Collection Technologies

Contact - Mechanical Touch Probe Systems Non-contact - Laser based Systems

Structured light or Broadband source Systems

Seeing Inside - Internal Viewing Technologies

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Contact Type

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Non-Contact Type

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Mechanical Touch-probe Systems, CMMs Accurate over wide measurement volume, some devices most

affordable, operated manually or automatically in advanced

Usually an articulated arm that allows for multiple DOF ofmovement; position of each section of the arm is determined byencoders, glass scales or potentiometers mounted on joints

Other mechanical arrangements are gantry crane type CMMs

Can distort soft objects such as auto upholstery, and are too slowto digitize parts of human bodies, or may require much labor toscan complex curved surfaces.

Not affected by the color of a surface or if it is transparent orreflective, the way laser & other light-based systems may be.

Faster for simple surfaces & easier for hard to digitize areas of anobject such as narrow slots or pockets.

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Laser Line Systems

Use geometric triangulation to determine surface coordinates

A laser line is scanned on the target object and individualsensors image the line, (simultaneously from each side of line)

The rules of trigonometry are then applied to calculate theposition of the target surface at each point on the laser line

Technology is simple, fast, accurate and gives good resolution;but may affected by color of a surface, transparency, reflective

Although scanning lasers are rated below harmful threshold,reflections on curved surfaces can result harmful focused beam

Color video information can be gathered separately to combinewith surface measurement through laser scan

Color laser scanning: multiplexed arrangement of R G B lasersto simultaneously gather color and geometric data

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Laser-based Systems for long range tracking

Time of flight systems: measure how long it takes for light emittedby a laser to return to a sensor located near its source.

Optical radar systems: similar in operation, measure the return-time of a radio wave

Both don't usually require retro-reflectors on object and canoperate at very high rates to quickly capture entire object

Laser trackers: look for a signal in their field of view from a retro-reflector placed or held on the object

These methods offer good accuracy and capability of makingmeasurements from a long distance away from the subject

These offer a high precision over a large working volume and afrequent use is for aligning large pieces of machinery or verifyingas-built dimensions of large objects

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LED-based Tracking Systems

A probe with LED's is touched to the object to be digitized;Sensors images the LED's in their FOV; Trigonometry is thenused to calculate position of the probe on the surface of object

Encoding schemes ( high-speed modulation of light emitted byLED's) are used to simultaneously track the position of LED's.

Magnetic-based Tracking Systems

Instead of an LED probe, these systems use a small wire coil as atarget. Generally used for digitizing points not within LOS

Features

Have smaller working envelopes than laser-based systems, but

may not be quite as accurate. Gives good accuracy, moderatespeeds and not affected by surface quality or color.

Mainly used in human and other types of motion studies

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Structured-light or Broadband-source Systems

Project a pattern of lines (moire/fringes, structured-color light,polarized-light interferometry) on object to be digitized, whichgets distorted by the objects 3D nature.

Deviation from the original pattern is translated into a surfacemeasurement at each point in the FOV of the instrument.

Triangulation is used to calculate the surface data and nearly allsystems use CCD cameras for sensing.

Very fast and can digitize millions of points per second, dont usea laser. These strongly favored for digitizing human beings.

Somewhat less accurate than laser systems and does smallerscanning volumes. Takes considerable time and effort to scan.

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Seeing Inside - Internal Viewing Technologies

To verify a part with complicated internal features has beenmanufactured correctly, or to survey a fossils internal features

Destructive (CSS) applicable for quality control applications;Non-destructive (X-Ray CT) for valuable or irreplaceable object

X-ray Computed Tomography:beaming an X-ray from manydirections and calculating resulting interior point density;

Offer resolutions but require specialized knowledge to use

Cross-Sectional Scanning:based on a CNC milling machinecombined with optical data-gathering using a CCD camera

A part or other object is embedded in a contrasting color plasticmatrix material. The part and matrix combination is then shaved

by the miller and scanned layer by layer until data for the completeobject has been acquired.

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Data Collection RE Scanner & Digitizer Technology Comparison

Mechanical - Arm/Guided Probe

Accuracy: 0.001 inches, Speed: Manual, Color:Not Applicable

Strength: accuracy; low-cost instruments available; measures deepslots, pockets; not affected by color or transparency

Weakness: manual operation; slow for complex surfaces; can distort

soft objects Tracking - LED Based/Magnetic

Accuracy: 0.02 mm, Speed: 300 points/sec, Color:No

Strength: can digitize hidden points in some cases; can be used to

track motion of many points simultaneously; magnetic devices canmeasure outside line of sight; not affected by color, transparency orsurface quality

Weakness: requires targets or contacting probes; smaller volumes;lower accuracy; slow for complex surfaces

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Coordinate Measuring Machine Granite Base

Cross Bar Probe Mounting

Assembly

Computer Interface

Quality of CMMs

Resolution

Repeatability

Accuracy

Linearity

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DEA Gantry CMMpowered by Virtual DMISsoftware

It provides for the needs ofthe aerospace and

automotive industries withits ability to generateinspection points fromCAD imported part

surfaces

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Scanning Methods

Single 2D profile

Multiple 2D profiles

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Scanning Methods

Grids defined to suit part geometry

User defined stepover Data density automatically controlled

Scanning speed automatically controlled

Unmanned operation

Polygonal boundary

Radial

Y axis

Any angle

X axis

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Some of the Probe Mountings and scanning

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3-D Scanning

3-D Scanner

Dot cloud Model of surface

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Immersion MicroScribe G2XRomer STINGER Digitizer

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Limitations of Contact Type Scanning Probe itself Vibration, Humidity, Heat and other Environmental conditions

Accuracy

Non Contact Methods Machine Vision

Laser Probing

MRI ( For Non Metallic Objets )

ERI ( For For Metallic Objects )

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Scanner

Head

Standard

Tripod

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The Software in RE CopyCAD

HighRES, Inc.

PolyWorks

RevEng

RevWorks Alias|Wavefront

3D RESHAPER

Imageware

RapidForm

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2D and 3D scanning tools Male to Female Inversions

Differential Scaling

Generation of NC Programs Generation of Graphic exchangefiles

[ 2D and 3D DXF, IGES, PDES, STL ]

http://www.tenlinks.com/CAD/products/reverse_eng.htm

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Case Study: Duplication of existing tool withCARE

Tool

Scanned Data

Part

Surface Model

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Mockup of a Fuel Tankfor a sport Vehicle made

in wood and clay

Point Cloud Data

Final Output as a Surface File

given to Customer

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3DP

Rapid Prototyping & itsApplications

SLM LENSEBM

SLA

REPAIR

PROTOTYPESANALYSIS MODELS

TOOLING

ASSEMBLY

MOCKUP

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Rapid Prototyping

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Design Process Overview

Concept

Pre-lim Design Drawings

Testing

Analysis

Physical

Prototype

Iterate

Manufacturing

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Traditional Prototyping - Steps Engineering Drawings

Machine or prototype shop to produce part Part usually machined (Lathe, Mill etc.)

Problems:

Material incompatibility

Shop specialization (Cant perform task you need) Design limited by prototype tools available

Part too complex to produce (curved surfaces are very difficult)

Machine deficiencies (3 axis mill, Need for 5 axes)

Costs of traditional prototyping Skilled Craftsman ($60-70/Hour shop time)

Time to receive model from shop

Time to get model into the public domain

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NC Machining & Rapid Prototyping NC machining requires a skilled operator to set up machine and to specify

tools, speeds, and raw materials.

For this reason, many do not consider NC machining to be a true RapidPrototyping (RP) technique.

True RP should create a part from some model without any assistance.

NC Machining does have some benefits over trueRP NC Machining allows a wide range of materials for prototypes (true

RP techniques often prohibit material for function prototype)

NC Machining allows better accuracy than most true rapid

prototyping techniques (may be needed for fit prototypes) True RP techniques can produce a prototype of a part that is

impossible to manufacture. NC machining often revealsmanufacturing limits in a given design.

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Solid Freeform Manufacturing

Many restrict true Rapid Prototyping to the Solid Freeform

Manufacturing (SFM) procedures (i.e. RP=SFM) All the SFM procedures are based on some layering operation The CAD/CAM program takes the shape and models it as a series of

thin layers stacked upon one another The SFM process then forms the part a layer at a time, starting at

the bottom and working toward the top This can cause trouble with large overhangs-- one must somehow

support the overhang in order to form the next layer

Overhang

Support must be used

to form next layer

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Layer Formation Methods

Solid

Powder Bulk Liquid

Polymerization

Melting &

Solidification

1 ComponentSelective Laser

Sintering

Component& Binder

3D Printing &Gluing

Gluing SheetsLaminated

ObjectManufacturing

PolymerizationFoil

Polymerization

Liquid

Shape Melting

Fused DepositionModeling

Ballistic ParticleManufacturing

LightHeatThermalPolymer-

izationTwofrequencies

Beam Inter-ference

solid

Onefrequency

Lamps

Lasers

Solid Base CuringPhotosolid. Layer at a Time

Stereolithography

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RP Technologies: Introduction

Rapid prototyping processes are a relatively recentdevelopment.

The first machine was released onto the market in late1987.

The term Rapid prototyping is little outdated. A moreaccurate description would be layer manufacturingprocesses.

An alternative term is free-form fabricationprocesses.

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These processes work by building up a component layer by

layer, with one thin layer of material bonded to the previousthin layer.

There are several different processes. The main ones are: Stereolithography

Laser Sintering Fused Deposition Modeling - FDM

Solid Ground Curing

Laminated Object Manufacturing - LOM

In addition there are a number of newer processes, such as

ballistic particle manufacturing and three-dimensionalprinting, and so on

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RP processes are material addition processes where asin conventional manufacturing processes, the materialis removed to get the desired shape from a block ofmaterial.

RP processes are driven by instructions which arederived from three-dimensional computer-aideddesign (CAD) models. CAD technologies aretherefore an essential enabling system for rapid

prototyping.

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The processes use different physical principles, but essentiallythey work either by using lasers to cut, cure or sinter materialinto a layer, or involve ejecting material from a nozzle tocreate a layer.

Many different materials are used, depending upon theparticular process.

Materials include-

Thermopolymers Photopolymers

Other plastics

Paper

Wax Metallic powder, etc.

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The application of these processes

To supporting new product development activities.

To create models

Tooling

Prototypes In some cases to directly produce metal components.

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1st System - 1989 - (accuracy 200m)

Current State -(accuracy 1 m)

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Many rapid prototyping technologies actually producephysical models.

These models are then used to produce tooling using anindirect secondary process such as investment casting.

The resulting tool is then used to manufacture a component.

New processes are beginning to appear that allow the toolingto be manufactured directly from the computer model, thuseliminating the physical model production stage.

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Now RP technologies have potential applicationsspanning the complete product life cycle fromconcept generation, through preparation ofspecifications and detailed design, to manufacture.

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Benefits of RPThe manufacturing business objectives potentially

affected by rapid prototyping technologies are: Throughput time: for example, by helping to eliminate or

speed up bottleneck processes

Flexibility to support product development: for example, bybeing quickly able to develop models, prototypes and tooling

Unit costs: for example, by reducing the costs traditionallyassociated with customizing products

Delivery to schedule: for example, by exploiting timesavings to manufacture products faster to meet due date

promises

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Labor productivity: for example, by eliminating time-

consuming processes involved in making models andtooling

Flexibility to introduce new products: for example, bybeing able to quickly create new tooling for new products

Flexibility to customize products: for example, bydeveloping specific tooling for each customer

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Flexibility to change product specification: for example, by

being able to quickly modify or create new tooling inresponse to specification changes

Flexibility to change production volumes: for example, bybeing able to quickly create additional tooling in response

to increased demand.

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Data Transfer to RP Process

Typical Process of Data Transfer

Layered

Manufa

cturing

Techniq

ues(LMT).

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A 3D CAD system-a surface or solid modeler-is used forcreating the model.

The most common step that follows is faceting the model.

The current de facto data exchange standard for representingfaceted models is called STL.

This format requires significant redundancy and is restricted

to triangles. Normally, each vendor supplies the software tools for

verifying the correctness of the model, generate process-dependent data, and to perform the slicing of faceted models.

The format for representing the slices is proprietary

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Constraints On The Model

Correct Triangulation

In-correct Triangulation

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In a correct STL-file, each triangle has exactly oneneighbor along each edge, and triangles are onlyallowed to intersect at common edges and vertices.Under these conditions, it is possible to distinguishprecisely the inside from the outside of the model

The models can contain gaps due to missing facets,facets may intersect at incorrect locations, the sameedge may be shared by more than two facets, etc.These are not accepted.

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Errors in the model can interfere

with the building process. Forinstance, if a slice contains a gapwhen the internal structure of theslice is built, stray vectors might

be created. The possibility of this happeningis great, due to the fact, that thetool in this case is a laser beam of

small diameter. These strayvectors damage the resulting partand possibly other parts beingbuilt in the same platform.

Correct & Incorrect Slices

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RP T h i


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RP Techniques

Stereo-lithography- photopolymer cured by laser

Photosolidification Layer at a Time- photopolymer cured bylight

Solid Base Curing-photopolymer is cured by UV light

Fused Deposition Modeling - molten plastic is extruded &

solidifies Ballistic Particle Manufacturing- microparticles of moltenplastic

3D Printing Direct Shell Production Casting-powder w/binder

Selective Laser Sintering- fusible powder, fused by laser

Laminated Object Manufacturing- glued layers of sheets


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RP Processes: Stereolithography

Schematic of Stereolithography Apparatus (SLA)

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Stereo-lithography Apparatus(SLA)

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Stereolithography Overview

Laser is focused/shaped throughoptics. A computer controlled

mirror directs laser to appropriatespot on photopolymer surface.Polymer solidifies wherever laserhits it.

When cross sectionis complete, elevator

indexes to preparefor next layer.

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Initially, the elevator is located at a distance from the

surface of the liquid equal to the thickness of the first,bottom-most layer.

The laser beam will scan the surface following thecontours of the slice.

The interior of the contour is then hatched using a hatchpattern.

The liquid is a photopolymer that when exposed to the

ultra-violet (uv) laser beam solidifies or is cured. The elevator is moved downwards, and the subsequent

layers are produced analogously.

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Th l bi d h h Fi ll h i d f


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The layers bind to each other. Finally, the part is removed fromthe vat, and the liquid that is still trapped in the interior isusually cured in a special oven.

A second, HeNe-laser is used to ensure that the surface of theliquid is in the correct location. The sweeper breaks the surfacetension, ensures that a flat surface is obtained, and minimizesthe processing time of each layer.

Scanning time depends on-

The geometry of the contours

Hatch patterns

The speed of the laser

The recoating time (i.e.the time taken to place a layer ofphotopolymer over the last solidified layer).

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h lidifi i i
http://www.cs.hut.fi/~ado/rp/rp.foot.html


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Photosolidification Layer at a Time

1) Cross section shape is printed onto a glass mask2) Glass mask is positioned above photopolymer tank3) Another rigid glass plate constrains liquid photopolymer from

above4) UV lamp shines through mask onto photopolymer- light only

can pass through clear part, polymer solidifies there, polymerin masked areas remains liquid

5) Due to contact with glass plate, the cross linking capabilitiesof the photopolymer are preserved- bonds better w/ next layer

6) New coat of photopolymer is applied7) New mask is generated and positioned, and process repeats

8) 12-15 minute postcure is required

Much less warpage than SLA, but still uses photopolymerswhich are toxic.

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F d D i i M d li (FDM)


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Fused Deposition Modeling (FDM)

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F d D i i M d li


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Fused Deposition Modeling

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FDM L F i


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FDM Layer FormationFDM generated

cross section

Notice that the FDM filament cannotcross itself, as this would cause a highspot in the given layer

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In this process a plastic filament is unwound from a coil andsupplies material to an extrusion nozzle.

The nozzle is heated to melt the plastic and has a mechanism,which allows the flow of melted plastic to be turned on &off.

The nozzle is mounted to a mechanical platform, which canbe moved in both horizontal and vertical directions.

As the nozzle is moved over the table in the required geometry, it deposits a thin bead of extruded plastic to formeach layer.

The plastic hardens immediately after being squirted from thenozzle and bonds to the layer below.

Several materials are available for the process includinginvestment casting wax.

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STRATASYS Di i SST


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Build size:

Maximum size 203*203*305mm(8*8*12 inches)

Layer thickness:

0.245mm(0.010in) or 0.33mm(0.013in) of precisely deposited ABSand support material

STRATASYS - Dimension SST


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PEMP- AME2501FDM Applications: Functional Models


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FDM Applications: Functional Models

Key Characteristics (cont.)

Good MachinabilityMechanical Joining, Adhesive Bonding, and Welding ArePossibleSnap fit tests

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RP Application - Automotive

PEMP- AME2501Rapid Tooling - RP Patterns for Casting of Gear Box Casing


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Rapid Tooling - RP Patterns for Casting of Gear Box Casing

PEMP- AME2501Functional Design


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Functional Design

Toyota

Click to viewexamples

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Laminated Object Manufacturing (LOM)
http://../PT-10%20CAE%20material%20for%20review/PT-10%20CAE%20course%20notes%20PPTs/RP%20Models.ppshttp://../PT-10%20CAE%20material%20for%20review/PT-10%20CAE%20course%20notes%20PPTs/RP%20Models.ppshttp://../PT-10%20CAE%20material%20for%20review/PT-10%20CAE%20course%20notes%20PPTs/RP%20Models.pps


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Schematic of Laminated Object Manufacturing (LOM)

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Processes Involving Solid Sheets

Laminated Object Manufacture

The Sheet Material is supplied from the roll and it passes on the Part blockPlaced over the Platform. A laminating roller rolls over the Sheet material andthe Laser beam is Impinged over the sheet material and it is cutoff from the

Sheet and Are placed layer by Layer one over another.

85(c) M S Ramaiah School of Advanced Studies

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LOM: The Process


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LOM: The Process

Slice thickness depends onmaterial and ranges from0.002" to 0.02". Materialsin use are,

- butcher paper

- plastics

- ceramics

- composites



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Laminated Object


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Laminated Object

Manufacturing


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LOM Applications: Functional Models

Key Characteristics:

Large Size Form and fit

Design verification Joining to form even largermodels/prototypes

89(c) M S Ramaiah School ofAdvanced Studies

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Advantages of LOM:


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1. Materials

LOM uses varieties of thin sheet included paper, plastic and composites. The

sheets are coated with heat sensitive adhesive, which enable the sheet to bebonded layer by layer by hot compression to form the part.

2. Properties

The parts created by LOM system are durable structures, which have a wide varietyof applications. The parts created may be sanded, polished, coated and painted.

3. Post-curing

Since LOM parts use papers, there is no need for post-curing.

4. Cost

There is no need of special polymer or wax to build the part. Thus this reduce the

cost of buying these special polymer.5. Stress

Since the part is bonded layer by layer, there is no induced stress in the

parts.

Advantages of LOM:



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The parts are built surrounded by wax, eliminating the need forsupport structures .

Once a layer has been exposed to the uv-lamp, the un-curedareas-those areas filled with residual, liquid polymer-are replaced

by wax.

This is done by wiping away the residual polymer and applying a

layer of wax. The wax is hardened by a cold metal plate, and subsequently, thelayer is milled to the correct height.

The milling station also allows for layers to be removed, i.e.anundo operation is possible. The new layer of polymer is applied

when the workspace moves from the milling station back to theexposure chamber.

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Selective Laser Sintering
http://www.cs.hut.fi/~ado/rp/rp.foot.html


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Selective Laser Sintering

Schematic of Selective Laser Sintering

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Working Principle of SLS



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SLS Functional Models: Nylon-


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S S u ct o a ode s: Ny o

BasedAvailable Materials

DuraForm Polyamide

Nylons

Glass reinforced nylons

Key Part Characteristics

Good Toughness

High Use Temperature = 163 - 188C

(DTUL @ 0.45 MPa)

Good Solvent Resistance


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The 3D Printing Process


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The 3D Printing Process

3D Printing Process


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Laser Engineering Net Shape (LENS)


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L E i i N t Sh i


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Powder delivery nozzle

X-Y Motion

Focused laser beam

Laser Engineering Net Shaping


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The most advanced process in terms of achieved mechanical

properties of generated metallic parts among all commercialprocesses based on layered manufacturing build principle.

The process uses a high power laser focused onto a substrateto create a molten puddle on the substrate surface.

Metal powder is then injected into the melt pool to increaseits volume. Powder ejection head moves back and forth inaccording to geometry of the first layer.

After the first layer is completed, new layers are then builtupon it until the entire object represented in the three-

dimensional CAD model is reproduced. Employment of a substrate makes this process different from

another ones, considered in this work.

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This method can utilize wide range of metals and alloys(including super alloys) as a build material.

Relatively high cost of operation and of produced parts onthe on hand, and very high mechanical properties of

generated by this method objects on the other, do not allowto consider the method as a plain RP technique, or as ameans of visualization.

This technology became efficient only in case of functionalparts or tooling production.

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Comparison of some RP Processes

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Summary


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Summary

The Reverse Engineering concepts have been

discussed.

Various techniques, tools and applications of thereverse engineering have been presented.

An introduction to Rapid Prototyping has beenpresented.

Data transfer to RP and different RP techniques havebeen discussed.

Applications of RP have been discussed with casestudies

Documents

Session 5 _ Reverse Engg & Rapid Prototyping