02.Stereolithography (NXPowerLite)

8/3/2019 02.Stereolithography (NXPowerLite)

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STEREOLITHOGRAPHY


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Other Names for Rapid Prototyping:1. ?

2. ?3. ?

4. ?


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Other Names for Rapid Prototyping:1. Additive fabrication

2. 3D printing3. Solid Free-Form Fabrication

4. Layered Manufacturing


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HISTORY:

Term stereolithography was coined in 1986 by Charles

(Chuck) W.HullStereolithography was defined as a method and apparatusfor making solid objects by successively printing thin layers

of ultraviolet curable material one layer on top of other

Hull described concentrated beam of UV light focused ontosurface of vat filled with liquid photopolymer

Light beam draws object onto surface of liquid layer by layer,causing polymerization or cross-linking to give a solid

Because of complexity of process, it must be computer-controlled

Company aiming to generalize & commercialize procedure

was founded immediately alongside invention


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First Stereolithography Machine invented by Chuck Hull
http://en.wikipedia.org/wiki/File:First_working_Stereolithography_system.jpg


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SLA

LIQUIDS v/s SOLIDS (incl. POWDERS)

FINE DETAIL,SURFACE FINISH

Optics Laser

XY Scanner

Photosensitive

Resin

ZLASER

low power initiator

*SAFE,UNMANNED

focussed to fine spot

*EFFECT LOCALISED


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RESINS

Continuous medium - no grain or structure of

own

Minimum feature size dictated by LASER

beam-width

Parts have clean,sharply-defined boundaries


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SL & RP

ROCESS PURELY ADDITIVE ADDITIVE& SUBTRACTIVE

SUPPORTS AUTOMATIC-as needed EVERY LAYER-regardless

LIQUIDS v/s SOLIDS (incl. POWDERS)

SUPPORTS

DIRECTION VERTICAL HORIZONTAL

OF SUPPORT/ 0.010 FULL AREA

ORIENTATION in contact / adhering

PARTS VISIBLE INVISIBLEREMOVAL EASY ----


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Flow chart of RP process model to

create a 3D objectTessellation/STL Format/De-facto Std. in RP

Boundary Surfaces of object are represented by

numerous tiny triangles (similar to FEM)

Generate supports in a separate CAD file (Reasons..?

Part & support must be sliced.The part is

mathematically sectioned by computer into series of

parallel horizontal planes ,like the floors of a tall

building.Layer thickness/intended building style / cure depth/

hatch spacing/line width compensation/shrinkage

compensation.

CAD Model

Translation

Supports

Slicing


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Parts + Support + Additional parts & supports are

merged for building concurrently on the sameplatform by merging their computer

representations (models).

Select Z Wait (sec) (pause after recoating to allow

any resin surface non-uniformities to undergo

fluid-dynamic relaxation.

Merge

Prepare

BuildResin polymerization begins & a physical

3-dimensional object is created.


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Stereolithography:

Additive Layer manufacturing process

Uses vat of liquid Photo-curable Polymer / resin & UV Laserto build parts one layer at time

On each layer, laser beam traces part cross-section patternon surface of the liquid resin

Exposure to laser light cures / solidifies pattern traced onresin & adheres it to layer below


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After pattern has been traced, elevator platform descendsby single layer thickness, typically 0.05 mm to 0.15 mm

Resin-filled blade sweeps across part cross section, re-coating it with fresh material

On new liquid surface, subsequent layer pattern is traced,adhering to the previous layer

Complete 3D part is formed

After building, parts are cleaned of excess resin byimmersion in a chemical bath & then cured in UV oven


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Stereolithography:

Requires use of support structures to attach part to elevator

platform & to prevent certain geometry from not onlydeflecting due to gravity, but to also accurately hold the 2-Dcross sections in place such that they resist lateral pressurefrom the re-coater blade

Supports are generated automatically during preparation of3-D models, although they may be manipulated manually

Supports must be removed from finished product manually


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ADVANTAGES

The machine can run unattended

Accuracy is good

Good detailed parts can be built Surface finish is good (compared to bending

operations)

Transparency of Parts

Dimensional stability on parts(?)


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ADVANTAGES

SLA Prototypes can be very beneficial as they arestrong enough to be machined and can be used asmaster patterns for

Injection molding

Thermoforming

Blow molding

Various metal casting processes


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FIG


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DISADVANTAGES High overall cost (?!)

Model requires support structures & separatesupports for overhanging sections

Parts can warp (shrink non-uniformly & curl due tophase change)

Resin handling problem

Toxic material & odor

Costly installation & maintenance cost

(LASER based) Requires post- curing

Materials-only Photo Polymers


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RP MACHINE COSTS:

SLA machine can cost from ~ $100,000 to $500,000

SLA resin costs ~ $300 to $800 per gallon


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LASER


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LASER

Laser: device capable of generating narrow uniform beamof concentrated high intensity light,made up almost

completely of single pure color

Precisely directed over small or large distances

(< millimeter to > thousands of km)

Vary greatly in size ;one type is as small as a grain of

sand,another as long as a football field

Beam Intensity(?) & diameter can be rigorouslycontrolled


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USE OF LASER IN INDUSTRY

In cutting, drilling, welding & annealing

operations. (Ex.Gear tooth

induction hardening)


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USE OF LASER IN MEDICINE

In Surgery for eyes

Treating brain tumors

Dermatology & other skin treatments Orthopaedics

Neurosurgery


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USE OF LASER IN GENERAL RESEARCH

Laser beams have been bounced of moon to

determine distance from earth to moon & to

check their movements in relation to each other Lasers used to detect slightest movements of

continents, or slight movement of crust that may

be a pre-cursor to earthquake


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NOTE:

MASER & LASER are acronyms

MASER stands for Microwave

Amplification by Stimulated Emission ofRadiation

LASER stands for Light Amplification by

Stimulated Emission of Radiation


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STEREOLITHOGRAPHYStereolithography, the first of the RP process and the most widely used rapid prototyping

technology is based on the instantaneous polymerization of the photo polymer resin onexposure to laser beam (ND:YVO4). Stereolithography builds prototypes directly from 3DCAD model layer by layer by tracing the cross-section of the layer on the surface of a vat(Vat-container holding the resin) of liquid photopolymer. Once a layer is completelytraced, the building platform is lowered by a distance equal to one layer thickness andthe next layer cross section is traced by the UV laser. The self-adhesive property of the

material causes the layers to bond to one another and eventually form a complete,three-dimensional object after many such layers are formed.


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StereoLithography Build

Process CAD Design (Pro-e, I-Deas, Catia) CAD Translator (STL) STL Verification Orient Support Prepare Build Post Process


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Principle of Stereolithography

How does SL work?

Laser Beam Cures LiquidResin Layer by Layer


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On layer-by-layerbasis, starting frombottom up, lasertraces outside of eachlayer profile (hatch),then fills in area in-between (fill)

COMPLETED WHEEL(ON RAISED PLATFORM)

LASER PATH(TIMED EXPOSURE)

LIQUIDBUILD MATERIAL

PART BUILDING

(SUBMERGED IN VAT)(WHEEL)


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# RP Technology Build Material

1 Stereolithography Photosensitive

Polymer


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http://en.wikipedia.org/wiki/File:Stereolithography_apparatus.jpg


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Specifications

SLA-7000 Laser: 354.7 nm Nd-YV04 Power at vat 800 mW

Recoating: Zephyr

Min. Layer Thickness: 0.004 in(?)

Max. part drawing speed: 140 - 525 ips

Spot size: 0.01 in - 0.03 in

Vertical resolution: 0.00004 in Build Envelope: 20 x 20 x 24 in


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SLA Applications:

FIT , FORM and FUNCTIONAL

For Conceptualization & Presentation:

Industrial Design

Tradeshows/Exhibits

Bid Packages

Marketing/Sales Presentations

Focus Studies

Package Design

Concept Models

Product Design

Design, Analysis, verification and testingDesign Verification/AnalysisDesign Iteration/OptimizationPhoto-Stress AnalysisFlow VisualizationHigh Impact

Tooling applications

ACES tooling for Injection Moulds

Investment casting patterns

Sand Casting

Spray Metal

Vacuum Casting


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SLA Applications: Tooling

SL patterns used as master

patterns to RTV mold limitedquantities of parts in urethane.

Mold:RTV and others

Qty:1-30 parts

Material(s):Urethanes

Rapid Prototype Tooling

Rapid Soft Tools using RTV


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Design verification and Assembly Mock-up


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Development of tooling using SL Prototype


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SLA Applications: Tooling

Direct ACES Injection Molding(Direct AIM) in ABS plastic

Quickly and inexpensively provides

true prototypes in actual productionmaterials

Mold:Direct AIM(ACES Injection Molding)

Qty:10-1,000Material:Thermoplastics

Rapid Bridge Tools with Direct AIM


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SLA Machine Models:

Viper

SLA 7000

Viper Pro


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Assignment:

You now know ~80% of Stereolithography

There are many videos available in Youtube

Download them, edit to make them succinct & present
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Thank [email protected]
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Documents

02.Stereolithography (NXPowerLite)