Module1_1Additive manufacturing techniques - Copy - Copy.ppt

rapid menufactring

1. COURSE: RAPID MANUFACTURING
Mr. G. Praveen Kumar
Assistant Professor
Mechanical Engineering
Prepared by

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Additive Manufacturing
Introduction:Prototypingfundamentals:Needfortime
compressioninproductdevelopment,NeedforAdditive
Manufacturing,Historicaldevelopment,
FundamentalsofAdditiveManufacturing,AMProcessChain,
AdvantagesandLimitationsofAM,CommonlyusedTerms,
ClassificationofAMprocess,FundamentalAutomated
Processes:DistinctionbetweenAMandCNC,otherrelatedtechnologies.
MODULE -I: INTRODUCTION TO ADDITIVE MAUFACTURING TECHNIQUES

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ThetermRapidPrototyping(orRP)isusedtodescribeaprocessfor
rapidlycreatingasystemorpartrepresentationbeforefinalreleaseor
commercialization.
ArecentlyformedTechnicalCommitteewithinASTMInternational
agreedthatnewterminologyshouldbeadopted.Recentlyadopted
ASTMconsensusstandardsnowusethetermAdditiveManufacturing.
Thebasicprincipleofthistechnologyisthatamodel,initiallygenerated
usinga3DComputerAidedDesign(3DCAD)system,canbe
fabricateddirectlywithouttheneedforprocessplanning.
What is Additive Manufacturing?
Introduction

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Introduction
Prototype fundamentals
Aprototypeisthefirstororiginalexampleofsomethingthathasbeenor
willbecopiedordeveloped;itisamodelorpreliminaryversion;e.g.:A
prototypesupersonicaircraft.
or
Anapproximationofaproduct(orsystem)oritscomponentsinsome
formforadefinitepurposeinitsimplementation.
Definition of a Prototype

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TypesofPrototypeThegeneraldefinitionoftheprototypecontains
threeaspectsofinterests:
(1)Implementationoftheprototype;fromtheentireproductitself
toitssub-assembliesandcomponents,
(2)Formoftheprototype;fromavirtualprototypetoaphysical
prototype
(3)Degreeoftheapproximationoftheprototype;fromaveryrough
representationtoanexactreplicationoftheproduct.
Introduction

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Introduction

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Distinction between AM & CNC machining

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AdvantagesofAM
•Eliminationofdesignconstraints
•Allowpartstobeproducedwithcomplexgeometrywithnoadditionalcosts
relatedtocomplexity
•Buildspeed;reductionofleadtime
•Flexibilityindesign
•Noexpensivetoolingrequirements
•Dimensionalaccuracy
•Widerangeofmaterials(polymers,metals,ceramics)
•Wellsuitedtothemanufactureofhighvaluereplacementandrepairparts
•Greenmanufacturing,clean,minimalwaste

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The Eight Steps in Additive Manufacture
1.Conceptualization and CAD
2.Conversion to STL 3
3.Transfer and manipulation of STL file on AM machine
4.Machine setup
5.Build
6.Part removal and clean-up
7.Post-processing of part
8.Application

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Step 1: Conceptualization and CAD
• The generic AM process start with 3D CAD information.
• There may be a many of ways as to how the 3D source data can be
created.
• The model description could be generated by a computer.
• Most 3D CAD systems are solid modeling systems with some surface
modeling components.

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Step 2: Conversion to STL
•ThetermSTLwasderivedfromStereoLithograhy.
•STLisasimplewayofdescribingaCADmodelintermsofitsgeometryalone.
•Itworksbyremovinganyconstructiondata,modelinghistory,etc.,and
approximatingthesurfacesofthemodelwithaseriesoftriangularfacets.
•TheminimumsizeofthesetrianglescanbesetwithinmostCADsoftwareand
theobjectiveistoensurethemodelscreateddonotshowanyobvioustriangles
onthesurface.
•TheprocessofconvertingtoSTLisautomaticwithinmostCADsystems.
•STLfilerepairsoftwareisusedwhenthereareproblemswiththefile
generatedbytheCADsystemthatmaypreventthepartfrombeingbuilt
correctly.

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•Withcomplexgeometries,itmaybedifficulttodetectsuchproblemswhile
inspectingtheCADorthesubsequentlygeneratedSTLdata.
•Iftheerrorsaresmallthentheymayevengounnoticeduntilaftertheparthas
beenbuilt.
•STLisessentiallyasurfacedescription,thecorrespondingtrianglesinthefiles
mustbepointinginthecorrectdirection;(inotherwords,thesurfacenormalvector
associatedwiththetrianglemustindicatewhichsideofthetriangleisoutsidevs.
insidethepart).
•Whilemosterrorscanbedetectedandrectifiedautomatically,theremayalsobea
requirementformanualintervention.

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Step3:TransfertoAMMachineandSTLFileManipulation
•OncetheSTLfilehasbeencreated,itcanbesentdirectlytothetargetAM
machine.
•Ideally,itshouldbepossibletopressa“print”buttonandthemachineshould
build
•thepartstraightaway.
•Howevertheremaybeanumberofactionsrequiredpriortobuildingthepart.
•Thefirsttaskwouldbetoverifythatthepartiscorrect.
•AMsystemsoftwarenormallyhasavisualizationtoolthatallowstheusertoview
andmanipulatethepart

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•Theusermaywishtorepositionthepartorevenchangetheorientationtoallow
ittobebuiltataspecificlocationwithinthemachine.
•ItisquitecommontobuildmorethanonepartinanAMmachineatatime.
•Thismaybemultiplesofthesamepart(thusrequiringacopyfunction)or
completelydifferentSTLfiles.

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Step4:MachineSetup
•AllAMmachineswillhaveatleastsomesetupparametersthatarespecifictothat
machineorprocess.
•Somemachinesareonlydesignedtorunperhapsoneortwodifferentmaterialsand
withnovariationinlayerthicknessorotherbuildparameters.
•Inthemorecomplexcasestohavedefaultsettingsorsavefilesfrompreviously
definedsetupstohelpspeedupthemachinesetupprocessandtopreventmistakes.
•Normally,anincorrectsetupprocedurewillstillresultinapartbeingbuilt.

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Step 5: Build Setup
•ThefirstfewstagesoftheAMprocessaresemi-automatedtasksthatmay
requireconsiderablemanualcontrol,interaction,anddecisionmaking.
•Oncethesestepsarecompleted,theprocessswitchestothecomputer
controlledbuildingphase.
•AllAMmachineswillhaveasimilarsequenceoflayercontrol,usingaheight
adjustableplatform,materialdeposition,andlayercross-sectionformation.
•Allmachineswillrepeattheprocessuntileitherthebuildiscompleteorthereis
nosourcematerialremaining.

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Step 6: Removal and Cleanup
• The output from the AM machine should be ready for use.
• More often the parts still require a significant amount of manual finishing before
they are ready for use.
• The part must be either separated from a build platform on which the part was
produced or removed from excess build material surrounding the part.
• Some AM processes use additional material other than that used to make the part
itself (secondary support materials)

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Step 7: Post Process
• Post-processing refers to the (usually manual) stages of finishing the parts for
application purposes.
• This may involve abrasive finishing, like polishing and sandpapering, or
application of coatings.

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Step8:Application
•Followingpost-processing,partsarereadyforuse.
•Althoughpartsmaybemadefromsimilarmaterialstothoseavailablefromother
manufacturingprocesses(likemoldingandcasting),partsmaynotbehave
accordingtostandardmaterialspecifications.
•SomeAMprocessescreatepartswithsmallvoidsorbubblestrappedinsidethem,
whichcouldbethesourceforpartfailureundermechanicalstress.
•Someprocessesmaycausethematerialtodegradeduringbuildorformaterials
nottobond,link,orcrystallizeinanoptimumway

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Classification of AM processes

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