Lecture notes- 7 Engineering graphics PDF

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ECOR1010 Lecture7 EngineeringGraphics‐ 3

EngineeringGraphics • Engineeringgraphicshasevolved intosixmajorareas,whichoverlap: – DescriptiveGeometry(Engineering Drawing,asshownpreviously) – GraphicalMathematics – Nomography – EmpiricalEquations – TechnicalIllustration • inmanuals,etc.usedtocommunicate anidea,notnecessarilytechnicallyexact.

– EngineeringComputerGraphics:CAD 2

GraphicalMathematics We may wish to find the intersection of all the possible positions a robot arm can have and a space in which it will operate.

www.maplesoft.com/applications/view.aspx?SID=6850&view=html

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Nomographs •



• Widelyusedinengineering,industry,and thenaturalandphysicalsciences

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Nomographexample: ExpectedFlowsinariver(Willitflood?):

B A

A. Itrains5inchesin6hours,theaverageintensityis0.83 in/h;thepointonthechartfallsclosesttothecurvefor 22,000cuft/s:yellow"FloodCaution"zone B. Itrainsfor4hoursatanintensityof1.5in/h(foratotalof 6.0in).Itisexpectedtherainwillcontinueforanother houratthesamerate,aflowlevelof~23,500ft3/scanbe 5 expected:floodingishighlylikely!

ParallelResistorNomograph • Thisnomographdetermines theequivalentresistanceof twoparallelresistors • e.g.,theequivalent resistanceofa50anda 75resistorinparallelis 30

RT

1

 1 1  R1 R2

R 1(  )

R T ()

R 2(  ) 6

GraphicalMathematics • Solvingalgebraicequations usinggraphicaltechniques withoutprojection • Example:Equivalent Resistance • Theequivalentresistanceof a50 anda75 resistor inparallel(30)

RT



1 1 1  R1 R 2 7

EmpiricalEquations •



 • Example:findanempirical equationtodescribehow differentpartsofarobot heatupfromambient conditionsduringthe courseofperforminga continuouscyclictask

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InfraredCameras

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EmpiricalEquations • Infra‐RedThermogram (start)

• Infra‐RedThermogram (end)

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EmpiricalEquations Averagetemperatureat measurementspotson lowerarm











Room temperature

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EmpiricalEquations Averagetemperatureat measurementspotson lowerarm

Thesedataaremodeledempirically with: T  Tss  (Tss  To ) et /   30.6  (30.6  23.6) e t /83 Average Temperature (oC)

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Steady-State region 30 28 26

Transient region

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Room temperature

0

200

400

600

800

1000

Time (min)

Thiscanbejustanequationthatfitsthe data,withnophysicsbehindit,ifthegoal isanequationforinterpolation…

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Wheredotheseequationscome from? • Threeplaces: 1. Anyequationthatreproducesthedatainan ‘acceptable’waycanbeused,IFthegoalisto haveanequationforinterpolation. •

Thisiscalled“

”.

2. Atheoretically‐basedequationthatisderived fromsomephysicalinsight. •

thiscanbeusedforinterpolationandextrapolation, withinlimits.

3. Or,acombinationoftheabove 13

Wheredidweget: T  Tss  (Tss  To ) e  t /



 30.6  (30.6  23.6) e t /83 Assume that the rate the temperature changes with time is proportional to how far the piece is from i ts final steady-state temperatur e: dT  TSS  T dt The proportionality constant we will call: 1 /  , where  is some 'time constant' that depends on the material properties. Hence, dT 1  (TSS  T ) dt  We can now integrate this expres sion over the limits of the test, and determine the parameters for this model equation "empirically" by finding the values that make the equation 'fit' the data. We will learn how this is done when we study 14 regression later.

EmpiricalEquations •

•

Integrated optical/robotic measurement system Applicationto rapidprototyping

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EmpiricalEquations Rawimage

Wireframe

Reconstructedsection Renderedsolidmodel

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IntroductiontoCAD

EvolutionofDrafting

A drafting room in the 1950s

in 2013

ComputerAidedDrafting(CAD) • Replacedthedraftingtable • Creatingelectronicdrawings • Canbeusedtocreatepictorialperspective, isometric,oblique,andorthographicdrawings aswellaselectrical,pneumatic,hydraulic,and controlsystemschematics • ExamplesincludeIntelliCAD andAutoCAD

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WhydoweneedCAD? • CADisaneffectivewaytocommunicateyourideas anddesigns – Usedtoproduceworkingdrawings

• Manufacturingisbecomingmoreintegrated,more global • Systemsarebecomingmorecomplex • Workingdrawingsareneededinalldisciplines – Electrical,civil,mechanical,aerospace,manufacturing, architecture

WhydoweneedCAD? • 1960s– LockheedSR‐71 – Supersonicreconnaissanceaircraft – 30,000hand‐draftedworkingdrawings! • Designchangesrequiredalotoftime • Filingandrecordkeepingwerechallenging

WhydoweneedCAD? • 2007– AirbusA380 – Modern,500+passengercommercialaircraft – Designedandmanufacturedinseveralcountries • Approximately500suppliers

– 1globaldatabase • Databasewithsolidmodels andCADdrawings • Automaticallyupdated

ComputerAidedDrafting • CADiscrucialinthedetailed designstage • Computeraideddraftingenables modificationstobemadewith ease • Comparethiswithhanddrafting

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AWordOnCAD • CADprogramsareveryusefultoolsbecause mostofthemautomaticallyfollowthe conventionsdiscussed • However,thedesignerisstillresponsiblefor ensuringtheintegrityofthedrawing – CADprogramsmakemistakes,andsometimesthe defaultoptionsarenotthemostefficientwayto conveytheinformation

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CADAdvantages • • • • • • •

Increasedaccuracy Increasedspeed Easyrevision Betterdesignanalysis Betterpresentation Librariesofdrawingaids Improvedfiling 25

WhendoweuseCAD? • Whenyouwanttoclearlycommunicateaconceptual design • Whenyouwanttomachineapart • Whensomeoneelseismanufacturingormachining partsforyou – Wanttogetexactlywhatyouhadinmind – Technologistsandmachinistsneedtobeableto understandandinterpretthedesign

EngineeringComputerGraphics • Themajorareasofcomputergraphicsare: – CAD:Computer‐AidedDesign • Usedtosolvedesignproblems,analyzedesigndata,storeand disseminatedesigninformation

– CADD:Computer‐AidedDesignDrafting • Usingcomputerstogenerateengineeringdrawingsandtechnical documents

– CAD/CAM:Computer‐AidedDesign/Computer‐Aided Manufacturing • Acomputerbasedsystemusedtodesignaproduct,devisethe productionsteps,electronicallytransferthedatatocontrolthe manufacturingequipment

– CIM:Computer‐IntegratedManufacturing • Acomputerbasedsystemthatcoordinatesandoperatesallstagesof manufacturingfromdesigntofinishedproduct 27

SolidModeling(Visualization) • Usingasolidmodeler,an    • Showshowpartsfittogether

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SolidModeling • Thesoftwarecreates3Dvirtualobjects • Thevirtualobjectsappearasaxonometric projections • Themodelscanbevirtuallymanipulated,just likeaphysicalobject • ExampleproductsincludePro/ENGINEER and SolidEdge

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CarletonGeoSurvIIUAVProject

CUBCLProject

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CADinECOR1010 • CADisoneofthemanytoolsthatyou’relearningthis semester – Lab2,lab3,andthedesignproject

• Won’tbecomeanexpertin4months,sodon’tworry – You’lllearnwhatthetoolsareandwheretofindthem – Willdevelopabasethatyoucanbuildoninfutureyears – WillhavemanyopportunitiestousetheseskillsatCarletonandin yourcareersasengineers

CADSoftware:IntelliCAD • IntelliCADcanbeusedforreportsketches,but itisreallymeantfortechnicaldrawing • YoushouldalreadybefamiliarwithIntelliCAD (Lab2) – ThelayoutoftheIntelliCADenvironment – Basicdrawing– lines,circles,etc. – Gridandsnapfeatures – Importingblocks – Creatingtext 33

DesignandCAD • AsaresultofCAD,thedesignprocesshas becomemuchfaster • Althoughrevolutionary,CADhasnottaken overeveryaspectofdrawing • Freehandsketchingisstillimportant

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Freehand Sketching • Freehandsketch:drawingcreatedwithoutthe useofastraightedgeorotheraids • Usedintheearlystagesofdesign – Ideassketchedonanapkinornotepad

• OutperformsCADwhenafastsketchisneeded • Notintendedtobeusedasatechnicaldrawing formanufacturingapart

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Visualization • Beingabletovisualizein3Diskey • Thoughtexperiment: – Closeyoureyesandpictureanyobjectfloatingin mid‐air…Nowrotatetheobjectinyourmind… Imaginelookingatitfromeveryangleand direction

• Thisabilityiscrucialwhencreatinggraphical representationsofrealobjects 36

Sketching • Sketchingisfreehand drawing withouttheuseofinstrumentssuch asastraightedge,compass,or drawingtemplates • Sketchingisakeymeansof engineeringcommunication • Sketchesareusedtodevelopideas andmakedecisionsabouthowto solveaproblem • Manynewprojectsandproducts beginassketchesmadeontheback ofanenvelope,oronanapkinina restaurant,hockeygame,airplane... 37

Sketching • Sketchingisusedwhen“on‐ site”problemsareencountered • Theseare“back‐of‐the‐ envelope”solutions • Theabilitytocommunicateby anymeansisagreatasset • Sketchingisthebestwayto communicateengineeringideas • Sketchingskillsmustbeused on‐the‐jobtoexplainideas, delegateworkassignments,or togethelp

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HandSketchingTips • Useonestrokewhendrawingaline– don’tlift penciloffpaper • Forlonglines,keepyoureyesfocusedon wherethelineisgoingtoend • Useconstructionlines– veryfaintlinesthat outlineanobject • Forcircles,useasquareconstructionsquare andthendrawtheinscribingcircle 39

SketchingExample

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OrthographicSketching

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ObliqueSketching

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AxonometricSketching

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IsometricSketching

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IsometricSketchPaper

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ReadingAssignment • YoushouldhavereadChapters12to14 already. • FornextlectureReadChapters15&16.

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Workingdrawingprinciples The drawing must be a well-thought-out plan to get you from start to finish. Think of the drawing as a road map. Do you correctly identify all the detours and details? Will the user, or a crew of users, have to stop and ask for directions?

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