ENGG1960 Engineering Drawings Lecture Introduction 2014
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Transcript of ENGG1960 Engineering Drawings Lecture Introduction 2014
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EngineeringDrawings
AshortseriesoflecturesonEngineeringDrawingasPartofENGG1960IntroductiontoBiomedicalEngineering1ByPaulBriozzo
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WhatisanEngineeringDrawing?AnEngineeringDrawingisatechnical(notartistic)drawingwhichclearlydefinesandcommunicatesadesigntootherinterestedparties.
Otherpartiesmayhaveaninterestindesigncollaboration,procurement/purchasing,costing,manufacturing,qualitycontrol,marketing,handling/packaging.
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WhydoweneedtoknowaboutEngineeringDrawings?
Toallowourdesignstodevelopfromathoughtorconcepttoadesign/sketchonpaper.
Toenableustocommunicateourdesigns/sketchestocolleaguesforreview.
Toconvertoursketches/designsintolayoutdrawingswhichshowhowourideaslinkuptoexistinginfrastructures.
Toincludeourdesign/sketchesaspartofaproposalforclient/managementapprovalandreview.
ToprovideManufacturerswithworkingEngineeringDrawingsbasedfromouroriginaldesigns/sketches.
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ConsiderthefollowingdescriptionofaVBlock
MATERIAL:CASTIRON
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PictorialFreehand
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ExamplesofLayoutDrawings
CollapsibleCanoeOutriggerDesignProject,1998UndergraduateDesignProjectundertheLeadershipofA/Prof.HarryLipkin,GeorgiaTechUniversity
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LunarModuleLandingGearPlans,NASA,1969
ExamplesofLayoutDrawings
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ProposalDrawing
EngineeringdrawingbyHarryC.Shoaf (SpaceTaskGroupEngineeringDivision)oftheproposedlunarlandertobeusedwithanadvancedversionoftheMercuryspacecraft.(Shoaf,Drawing,Nov.15,1961.)
Surveyor1,1966LunarLander,1969
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EngineeringDrawing
DetailDrawing(FinishDrawing)ofConnectingRod,M.Jacek 1973
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TheHistoryofEngineeringDrawingFreeHandSketches LeonardoDaVinci 1500AD
Sforzamonument
Anatomicalstudyofthearmc1510
Rhombicuboctahedron
Designforaflyingmachinec1488
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GraphicalProjectionsProjections
Axonometric/Isometric Orthographic
Oblique
ParallelProjectionPerspective
Orthogonal
1st Angle 2nd Angle 3rd Angle 4th Angle
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Perspective
Staircase twopointperspective Cube twopointperspective
Cube onepointperspective Cube twopointperspective Cube twopointperspective
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MethodandRulesofProjections
Selectaviewfromthemostadvantageousposition. Observeoverallstructurefirst. Note:parallelism,proportionsandalignment.
Method
RulesofProjection Objectviewedfrom. Parallellinesremainparallel. Proportionsremainunchanged. Circlesarealwaysellipseswiththemajoraxisofellipse
perpendiculartothepolaraxisofcircle. Transformationof90 angles.
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ParallelProjection
Axonometric/Isometric Orthographic
Oblique
ParallelProjection
Orthogonal
1st Angle 2nd Angle 3rd Angle 4th Angle
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ObliqueProjection
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Cavalierviewsarenotpreferred.Theyshowlineswhichrepresentthedepthoftheobjectasbeingdisproportionallylong.Eventhoughtheyareparalleltoeachother,depthlinesappeartodivergeawayfromeachother.
CabinetviewsarepreferredoverCavalier.Theissueofdepthdisproportionalityanddivergenceissomewhateliminatedbyhalvingthedepthdimension.
ObliqueProjectionCavalierandCabinetProjections
Cavalier Cabinet
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ObliqueProjection4BasicRules
1.Placetheobjectsothattheviewwiththemostdetailisparalleltothepictureplane.
2.Placetheobjectsothatthelongestdimensionrunshorizontallyacrossthesheet.
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ObliqueProjection4BasicRules
3.Insomecasesthepreviousrulesconflict,andwhenthisisso,Rule1haspreferenceastheadvantagegainedbyhavingtheirregularfacewithoutdistortionisgreaterthanthatgainedbyobservingRule2.
4.Decisionsaboutviewinganobjectinobliqueprojectionshouldaimtoshowtheobjectsothatitsshapeismostclearlypresentedandisconducivetoshowingitsdimensions.
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AxonometricProjection
ProjectionlinesareperpendiculartoProjectionPlane. PrincipalaxesinclinedtoProjectionPlane. Isometric(EqualScaling) Dimetric Trimetric
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IsometricDimetric
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Orthographic
Orthogonal
1st Angle 2nd Angle 3rd Angle 4th Angle
OrthogonalProjection
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3rd AngleProjection
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1st AngleProjection
Emok26th ofJune2008
DihedralAngles 1st AngleEmphasised
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FreeHandPictorialSketching
DesignHandbook:EngineeringDrawingandSketchingMITOpenCourseware
DesignHandbook:EngineeringDrawingandSketchingMITOpenCourseware
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Whydoweneedtodothiswhenweallhavecamerasonourmobilephonesandcansketchonourtablets?
NotesomeofthefeaturesanddifferencesbetweentheSolidWorks renderingandthephoto
ShadowsFocus
Lackofparallellinesaddsdistortion
Hiddenfeatures
ReflectionScratches/stains/blemishes
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ConstructionofFreehandPictorialSketchingTheThing
SuitableDrawingSize
LineDrawingonly(NoShading)
LineQuality
ThreeFacesVisible(Thefaceswhichshowmostdetail)
Linesthatareparallelontheobjectshouldbeparallelonthesketch
Proportionsoffeatureswithintheobjectmustremainthesame
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Sketchingaboundingboxforanellipse
Boxdefinestheperimeterofthecylinder
Definetwoaxismidwayandparalleltoeachsideofthebox
Minoraxis(orPolaraxis)oftheellipsegoesthroughtheintersectionofthetwoaxisandisparalleltotheedgeofthebox
MinoraxisdoesNOTgothroughthecornersofthebox
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Sketchinganellipse
Sketchellipsenotingthatminorandmajoraxisdefineouterlimitsoftheellipse
Definemajoraxisoftheellipsegoingthroughtheintersectionpointandat90 totheminoraxis
EllipsecurvesdoNOTnecessarilyblendattheintersectionpoints
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Projectinganellipse
Removeallconstructionlines
Projecttheellipseforwardtothecorrectdistancealongtheboss
Tracetheellipseinthenewpositionanderasethehiddenarcsfromtheoriginalellipse