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 la