EngineeringDrawings

AshortseriesoflecturesonEngineeringDrawingasPartofENGG1960IntroductiontoBiomedicalEngineering1ByPaulBriozzo

WhatisanEngineeringDrawing?AnEngineeringDrawingisatechnical(notartistic)drawingwhichclearlydefinesandcommunicatesadesigntootherinterestedparties.

Otherpartiesmayhaveaninterestindesigncollaboration,procurement/purchasing,costing,manufacturing,qualitycontrol,marketing,handling/packaging.

WhydoweneedtoknowaboutEngineeringDrawings?

Toallowourdesignstodevelopfromathoughtorconcepttoadesign/sketchonpaper.

Toenableustocommunicateourdesigns/sketchestocolleaguesforreview.

Toconvertoursketches/designsintolayoutdrawingswhichshowhowourideaslinkuptoexistinginfrastructures.

Toincludeourdesign/sketchesaspartofaproposalforclient/managementapprovalandreview.

ToprovideManufacturerswithworkingEngineeringDrawingsbasedfromouroriginaldesigns/sketches.

ConsiderthefollowingdescriptionofaVBlock

MATERIAL:CASTIRON

PictorialFreehand

ExamplesofLayoutDrawings

CollapsibleCanoeOutriggerDesignProject,1998UndergraduateDesignProjectundertheLeadershipofA/Prof.HarryLipkin,GeorgiaTechUniversity

LunarModuleLandingGearPlans,NASA,1969

ExamplesofLayoutDrawings

ProposalDrawing

EngineeringdrawingbyHarryC.Shoaf (SpaceTaskGroupEngineeringDivision)oftheproposedlunarlandertobeusedwithanadvancedversionoftheMercuryspacecraft.(Shoaf,Drawing,Nov.15,1961.)

Surveyor1,1966LunarLander,1969

EngineeringDrawing

DetailDrawing(FinishDrawing)ofConnectingRod,M.Jacek 1973

TheHistoryofEngineeringDrawingFreeHandSketches LeonardoDaVinci 1500AD

Sforzamonument

Anatomicalstudyofthearmc1510

Rhombicuboctahedron

Designforaflyingmachinec1488

GraphicalProjectionsProjections

Axonometric/Isometric Orthographic

Oblique

ParallelProjectionPerspective

Orthogonal

1st Angle 2nd Angle 3rd Angle 4th Angle

Perspective

Staircase twopointperspective Cube twopointperspective

Cube onepointperspective Cube twopointperspective Cube twopointperspective

MethodandRulesofProjections

Selectaviewfromthemostadvantageousposition. Observeoverallstructurefirst. Note:parallelism,proportionsandalignment.

Method

RulesofProjection Objectviewedfrom. Parallellinesremainparallel. Proportionsremainunchanged. Circlesarealwaysellipseswiththemajoraxisofellipse

perpendiculartothepolaraxisofcircle. Transformationof90 angles.

ParallelProjection

Axonometric/Isometric Orthographic

Oblique

ParallelProjection

Orthogonal

1st Angle 2nd Angle 3rd Angle 4th Angle

ObliqueProjection

Cavalierviewsarenotpreferred.Theyshowlineswhichrepresentthedepthoftheobjectasbeingdisproportionallylong.Eventhoughtheyareparalleltoeachother,depthlinesappeartodivergeawayfromeachother.

CabinetviewsarepreferredoverCavalier.Theissueofdepthdisproportionalityanddivergenceissomewhateliminatedbyhalvingthedepthdimension.

ObliqueProjectionCavalierandCabinetProjections

Cavalier Cabinet

ObliqueProjection4BasicRules

1.Placetheobjectsothattheviewwiththemostdetailisparalleltothepictureplane.

2.Placetheobjectsothatthelongestdimensionrunshorizontallyacrossthesheet.

ObliqueProjection4BasicRules

3.Insomecasesthepreviousrulesconflict,andwhenthisisso,Rule1haspreferenceastheadvantagegainedbyhavingtheirregularfacewithoutdistortionisgreaterthanthatgainedbyobservingRule2.

4.Decisionsaboutviewinganobjectinobliqueprojectionshouldaimtoshowtheobjectsothatitsshapeismostclearlypresentedandisconducivetoshowingitsdimensions.

AxonometricProjection

ProjectionlinesareperpendiculartoProjectionPlane. PrincipalaxesinclinedtoProjectionPlane. Isometric(EqualScaling) Dimetric Trimetric

IsometricDimetric

Orthographic

Orthogonal

1st Angle 2nd Angle 3rd Angle 4th Angle

OrthogonalProjection

3rd AngleProjection

1st AngleProjection

Emok26th ofJune2008

DihedralAngles 1st AngleEmphasised

FreeHandPictorialSketching

DesignHandbook:EngineeringDrawingandSketchingMITOpenCourseware

DesignHandbook:EngineeringDrawingandSketchingMITOpenCourseware

Whydoweneedtodothiswhenweallhavecamerasonourmobilephonesandcansketchonourtablets?

NotesomeofthefeaturesanddifferencesbetweentheSolidWorks renderingandthephoto

ShadowsFocus

Lackofparallellinesaddsdistortion

Hiddenfeatures

ReflectionScratches/stains/blemishes

ConstructionofFreehandPictorialSketchingTheThing

SuitableDrawingSize

LineDrawingonly(NoShading)

LineQuality

ThreeFacesVisible(Thefaceswhichshowmostdetail)

Linesthatareparallelontheobjectshouldbeparallelonthesketch

Proportionsoffeatureswithintheobjectmustremainthesame

Sketchingaboundingboxforanellipse

Boxdefinestheperimeterofthecylinder

Definetwoaxismidwayandparalleltoeachsideofthebox

Minoraxis(orPolaraxis)oftheellipsegoesthroughtheintersectionofthetwoaxisandisparalleltotheedgeofthebox

MinoraxisdoesNOTgothroughthecornersofthebox

Sketchinganellipse

Sketchellipsenotingthatminorandmajoraxisdefineouterlimitsoftheellipse

Definemajoraxisoftheellipsegoingthroughtheintersectionpointandat90 totheminoraxis

EllipsecurvesdoNOTnecessarilyblendattheintersectionpoints

Projectinganellipse

Removeallconstructionlines

Projecttheellipseforwardtothecorrectdistancealongtheboss

Tracetheellipseinthenewpositionanderasethehiddenarcsfromtheoriginalellipse