29513.2WorkingwithelectroniccomponentsElectronicsystemsSystemdiagrams wereintroducedinChapter 6asawayof showinghowsubsystemsareinterconnected, andshowingthesignals that flowbetweenthem. Wewill lookattheseideasinmore detail inthis section. The electronic systems relevant totheGCSEDesignandTechnologycourseconsistofoneormore inputs, a microcontroller as aprocesssubsystem, andoneormoreoutputs. Signals inelectronic systems areusuallyvoltagelevelsanditisuseful tounderstandthenature of thesesignals whenyouaredesigningsystems. Thetechniquesofconnectingsubsystems together inawaythat allows thesignalstopassproperlybetweenthemiscalledinterfacing. The simple electronic systemshownbelowisanexampleof howsubsystemscanbeinterfacedandmade tofunctioninawaythat canusefullyenhancethefunctionof aproduct. The systemdiagramshownis adesignfor abicyclesafetylampthatcouldincreasethevisibility of cyclists ontheroadat night. Thereisasinglepush-buttoninputandthreeultra-bright LEDoutputs. Themicrocontroller couldbeprogrammedtooperatethelampasfollows: lFirst pushof thebuttonturns onall threeLEDs. lSecondpushof thebuttonflashes all threeLEDs. lThirdpushturns off all LEDs. lThe cyclethenrepeats. At this point theflexibilityof themicrocontroller becomes evident, inthat it wouldbeasimplematter toreprogrammeit toaddenhancedfeaturestotheproduct. For example, a fourthpushof thebuttoncouldmaketheLEDs flashindependentlyinaneye-catchingpattern, anda fifthpushcouldchangetoadifferent patternor afaster flash, etc. Flowchart programsThe programfor a microcontroller is astep-by-stepset of instructionsthattellsthe microcontroller what todo. Theprogramshouldinitiallybewrittendownas a flowchart, whichis asimplewayof breakingdownthemicrocontrollertaskby showingthekey steps involved. At alater stageinthedesigndevelopmentthe flowchart may needtobeconvertedintoaspecificprogramminglanguage, dependingonthemicrocontroller used. It isbeyondthescopeofthis book todeal withindividual programminglanguagessowewill focusonusingflowcharts. Somemicrocontrollers canbeprogrammeddirectlyfromaflowchart, makingtheprogrammingstagesmuchsimpler. Amicrocontroller canperformonlyoneinstructionstepatatime, insequence. Whenthe programis run, eachinstructioniscarriedout extremelyquicklysothe user wouldnot normallynoticeanydelaybetweentheinstructions, unlessWAIT commands areinsertedintheflowchart todeliberatelyslowthingsdown. Constructinga flowchart helps thedesigner to'thinklikeamicrocontroller'. There are fivedifferent symbols usedfor drawingflowcharts: PushbuttonMicrocontrollerUltra-brightLEDUltra-brightLEDUltra-brightLEDFigure13.14AsystemdiagramforabicyclesafetylampNameStart/endArrowsInput/OutputProcessDecisionSymbolFigure13.15ThesymbolsusedinaflowchartKEYTERMSInterfacing:Themethodofconnectingsubsystemstogethertoallowsignalstopass.Programminglanguage:Thesetofinstructionsandrulesusedtowriteamicrocontrollerprogram.
296Chapter 13DesignengineeringKEYPOINTItisveryimportanttounderstandthedifferencebetweenasystemdiagramandaflowchart.lAsystemdiagramshowshowsubsystems(whicharephysical parts)arelinkedtogether,andthelinesonasystemdiagramshowthevoltagesignalsandthedirectioninwhichthesignalinformationflows.lAflowchartshowsasequenceofsteps(instructionsanddecisions)thatwill becarriedoutbythemicrocontrollerasitperformsitstaskwithinasystem.Thelinesandarrowsonaflowchartshowtheorderinwhichtheinstructionsareexecuted.Aprogramflowchartforthebicyclesafetylampintroducedintheprevioussectionisshownbelow.Studytheflowchartandnotethefollowingpoints:lTheprogramwill beginatthe'START'box.lTheinstructionswillbeexecutedoneafteranotheratveryhighspeed. Consequently, 'WAIT'instructionsareusedtocontrol thespeedthroughparticularsectionsoftheprogram. lThetwo'WAIT1s'instructionsareneededtogivetheusertimetoreleasethebuttonafterpressingit,beforetheprogramreachesthenext'Isthebuttonpressed'decision.lThereisnoENDboxbecause,afterthethirdpressofthebutton, thecyclerepeatsfromthestart.SensorsSensorscanbebroadlyclassifiedintotwotypes:lDigitalsensorsareusedfordetectingayes/nosituation,forexample: -Isthebuttonpressed?-Ismovementdetected?-Hastheproductfallenover?lAnaloguesensorsareusedwhenitisnecessarytomeasure'howbig'aquantityis,forexample:-Howbrightalightis. -Whatatemperatureis. Thedifferenttypesofsensorneedtobeinterfacedtotheappropriateanalogueinputordigitalinputonthemicrocontroller. Is buttonpressed? TurnonLEDs Wait 1s Is buttonpressed? TurnonLEDs Wait 0.5s Is buttonpressed? Turnoff LEDs Wait 1s Turnoff LEDs Wait 0.5s Start NNYYNYLEDs continouslyonLEDs flashLEDs off 1st press 2nd press 3rd press Figure 13.16 Flowchart programfor thebicyclesafetylamp KEYTERMSAnaloguesensor:Asensortomeasure'howbig'aphysicalquantityis.Digital sensor:Asensortodetectayes/nooron/offsituation.
29713.2WorkingwithelectroniccomponentslTimedelayswitches- t herearetwotypes, oneislikealatchingpush-to-makeswitch, whichstays closedfor aperiodof timebeforeautomaticallyopening. Theothertypeisprogrammedtoopen/closeat varioustimesthroughoutthe24-hourday. lAnother commonly usedtypeof switchismagneticreedswitches, whichclosewhena magnet is brought near tothem. Theseareoftenusedtosenseadoorbeingopenedina security system. Their benefit is that themagnet doesnotneedtotouchtheswitch, just be closetoit. Whena switchis usedas aninput sensor for amicrocontroller, itisconnectedwithanotherresistor inwhat is knownas avoltagedivider, asshowninthecircuitdiagrambelow. Notice that a digital input pinis usedonthemicrocontroller. The flowchart programneededfor themicrocontroller tomonitortheswitchmightlookasshownbelow. SwitchsensorsAll switches aredigital sensors, anddifferent switchesareavailabletodetectawidevarietyofthings. Aswitchcanbeclosed(on) or open(off). lTilt switches areclosedwhentheswitchisupright, andopenwheninverted. lPush-to-makeswitchesareclosedwhenthepush-buttonispressed. Amomentaryswitchopens whenthebuttonis released, andalatchingswitchstayscloseduntilthebuttonis pressedasecondtime. Figure 13.17 Various types of switchsensors Switch10kilohmresistor10k+5v0vDoMicrocontrollerFigure13.18ThemethodofconnectingaswitchsensortotheinputofamicrocontrollerIs input do high? Start NYRemainder of flowchart written here Figure 13.19 Readingthestateof aninput switch sensor LDR10k+5v0vAoMicrocontrollerFigure13.20AnLDRconnectedtoananalogueinput KEYTERMSVoltagedivider:Amethodofconnectinginputsensorstoproduceavoltagesignal.
298Chapter 13DesignengineeringLightsensorsAlight sensor isananaloguesensor-theactual light-sensingcomponentisalightdependentresistor(LDR), whichhasaresistancethatgetslowerasthelightlevelincreases. Toproduceananaloguevoltagesignal, theLDRisconnectedinavoltagedivider,as showninthecircuit diagrambelow. Noticethat ananalogueinputpinisusedonthemicrocontroller.Amultimetercanbeveryuseful tohelpfindfaultsinelectroniccircuits.Themultimeteris set toavoltagerangeandtheblack(common)probeisconnectedtothe0Vrail.Inthissensingcircuit, theredmultimeterprobeisconnectedtotheanalogueinputpin.ThemetershouldreadalowvoltagewhentheLDRisdark, andthevoltagewillrisetowards5Vaslightfalls ontheLDR. Thisanaloguevoltageisconvertedbythemicrocontrollertoanumberthatwill besomewherebetween0(intotal darkness)andamaximumvaluethatdependsonthemicrocontroller (themaximumvalue, inextremelybrightlight,islikelytobeeither255or1023, but checkthisfor themicrocontrollerthatyouuse). Aflowchart programtoreadandrespondtothelightlevelisshownbelow.This flowchart wouldfollowtheYESpathifthelightlevelishigh(abovenumber75)andtheNOpathif thelight level islow. Itisimportanttounderstandthatthesensorisnotcalibrated,sothenumber 75inthisflowchartdoesnothaveanyunits, itisjustanumberthatwouldbedeterminedexperimentallyduringtheiterativedesigningstages.Ifthesystemresponds'YES'at toolowalight level, thenthevalue75wouldbeincreaseduntilasuitablevalueisfound.TheLDRcaneasilybechangedforadifferentresistivecomponenttosenseotherphysicalquantities. Replacingit withathermistorwill produceatemperaturesensor.ReplacingtheLDRwithaforcesensitiveresistor(FSR)will produceaforce(oraweight)sensor,andsoon.Infra-redsensorsSeveral different typesof infra-red(IR)sensorsareavailableforvariousapplications,including:lIRsensorsthat detectthepresenceofawarmobject, e.g.ahandsensorforanautomatictap; thesehaveadigital output. lPassiveinfra-red(PIR) sensorsthatdetectamovingwarmobject,e.g.anintruderdetectorfor analarmsystem. lIRdistancesensorsthatmeasurethedistancetoanearbyobject;theseproduceananalogueoutput. lIRreceiversthat pickupdatasignalsfromanIRtransmitter,e.g.aTVremotecontrolsystem. Is light level >75? Read light level Start NYFigure 13.21Readingthelight level andmakingadecision Figure 13.22AnLDR, thermistor andFSRFigure13.23ArangeofIRsensorsKEYTERMSForcesensitiveresistor (FSR): Aforce-sensingcomponent. Light dependent resistor (LDR): Alight-sensingcomponent. Multimeter: Adevice usedtotakemeasurements andhelpfindfaults inelectronic circuits. Thermistor: Atemperature-sensingcomponent.
29913.2WorkingwithelectroniccomponentsOutput devicesOutputs consist of components toproducelight (for informationandillumination), ortoproduce soundor motion, etc. Manyoutputscanalsobedigital oranalogue, forexamplealight that is either onor off is digital, but thesamelight couldbeusedinananaloguewaybymakingit brighter or dimmer. Anelectricmotor canbevariedinspeed(analogue)orsimplyturnedonor off (digital). Manymicrocontrollershavebothdigital andanalogueoutputs. Make sure youselect theappropriateonesfor theoutput deviceyouintendtouse. Light emittingdiodesLight emittingdiodes (LEDs) areavailableinanenormousrangeof sizes, colours, brightnesses andshapes. Theyneedaresistor tobeplacedinserieswiththemtolimitthecurrent flowing, otherwisetheLEDwill burnout. Most small LEDs canbeconnected(throughtheresistor) directlytothedigital outputpinof a microcontroller. LEDs arepolarised, meaningtheyhaveapositivelead(anode)andanegative lead(cathode), andtheymust beconnectedthecorrectwayroundortheywillnot work. Thecircuit diagramshows howanLEDwouldbeconnectedtotheoutputpinofamicrocontroller. +5v 0v D1 Microcontroller LED330R330ohmresistor Figure 13.24 ConnectinganLEDtotheoutput pin of a microcontroller KEYPOINTTheseriesresistorforanLEDcanbecalculatedusingOhm'slaw:R=Vs VledIwhereVs isthepowersupplyvoltage,VledisthevoltagedropacrosstheLED,andIisthecurrent theLEDneedstolightup.ThevaluesforVs andI canbelookedupfor theLEDyouintendtouse.Example: For a5Vpowersupply, andaredLEDforwhichVs =2.0VandI =10mA:R=520.01R300ΩInpractice, a330Ωresistorwouldbeused.More powerful LEDs areusedwhenit is necessarytoprovideillumination, suchasina lamp. TheseLEDs requireahigher current andit wouldbenecessarytouseadriver toboost thecurrent. Drivers areexplainedlater inthissection. SpeakersandbuzzersThe differencebetweenaspeaker andabuzzer wasexplainedinChapter6. The speaker component inmost projects will beapiezo-electricsounder. These are small andcheapcomponents that cangeneratesurprisinglyloudtones, especially at higher frequencies. Apiezosounder wouldbeconnectedtotheoutput pinof a microcontroller as showninthediagram. Small buzzers may alsoworkconnecteddirectlytoanoutputpin, butloudersirenswouldneedtouseadriver, as explainedbelow. Piezosounder+5v0vD1MicrocontrollerFigure13.25ConnectingapiezosoundertoanoutputpinKEYTERMSAnode:Thepositiveconnectiononacomponent.Cathode:Thenegativeconnectiononacomponent.Driver:Acomponenttoboosttheoutputcurrent.Piezo-electricsounder:Aminiaturespeakerforproducingsoundsfromamicrocontroller.Polarised:Acomponentthatmustbeconnectedthecorrectwayroundinacircuit.
300Chapter 13DesignengineeringDCmotorsElectricmotorsaretheprimesourceofmotioninmechanicalsystems,andtheywerediscussedinChapter 6. DCmotorsarethemostcommontypeandtheirspeedanddirectioncanbothbecontrolledusingamicrocontroller. Adriverisalwaysnecessarytoprovidesufficient current tooperatethemotor. DriversSomeoutput devicesneedadriverbetweenthemicrocontrollerandtheoutputdevicetoboost thecurrent, otherwisetheoutputdevicewillnotworkproperly.Thedriver component iscalledaMOSFET. Ithasthreeleads,nameddrain(d),gate(g)andsource(s), andit isessential toconnectthesecorrectlyasshowninthefollowingcircuit.ThisexampleshowsaMOSFETdrivingaDCmotor, butthemotorcanbereplacedwithabuzzeroranLED(don'tforgettheseriesresistorwithanLED). Thediode(D)isincludedinthiscircuitasaprotectiondevicefortheMOSFET.Thediodeisneededonlyifanelectricmotorisused, asmotorsgeneratealotofelectrical'spikes'thatcandamagetheMOSFET.IfLEDsorbuzzersarebeingused,thediodecanbeomitted. +5v0vD1 Microcontroller MosfetgsdDMMotorFigure13.26UsingaMOSFETasadriverKEYPOINTMOSFETs areavailablewithdifferentcurrentratings.Twocommontypesareshowninthetablebelow. Table10.1MOSFETinformationMOSFETtypeZVN2106AIRF510Pinout DGSGDSMaximumdraincurrent0.45A4.0AChoosingtherightmicrocontrollerTherearemanymicrocontrollersavailable, andtherangeisconstantlychangingasnewtechnologiesaredeveloped. Eachmicrocontrollerhasbenefitsanddrawbacks.Thechoiceofmicrocontroller for aspecificapplicationwill dependon: lthetechnical requirementsof theapplication, suchasthenumberofinputs/outputsneededlhoweasyor challengingthemicrocontrolleristoprogrammelthechoiceof power supply(e.g. whichbatteriesyouintendtouse)ltherangeof dedicatedaccessoriesavailable, suchassensorsoroutputdevices,whichmaketheinterfacingmucheasier. KEYTERMSDiode: Acomponent that allows current toflowinone directiononly. MOSFET: Atypeof transistor usedas adriver.
302Chapter 13DesignengineeringSuccesswithmicrocontrollersUsingmicrocontrollersisgreatfunandyoushouldbeabletogetasimpleprojectrunningwithout muchtrouble- l ights, colours, soundsandsimplemovementshouldbequicklyachievableevenbybeginners. Moreadvancedprojectsrequireyoutogainsomeexperienceandtospendtimelearningsomemoreadvancedprogrammingskills.Donottrytorunbeforeyoucanwalk- r emember, aswithmanyaspectsofDesignandTechnology,youdonot needtolearneverythingatonce. Masterthebasicsanddrawupondeepertechnicalinformationasandwhenyouneedit. KEYPOINTTips for successwithmicrocontrollers: lStart everyproject withthemostbasicfunction,e.g.flashingasingleLED.Thismakessurethat themicrocontrollerisreceivingpowercorrectlyandthattheprogramisbeingsuccessfullydownloadedfromthecomputer.lAs youdevelopyour project, makeonlyonechangeatatime,andalwaystestthemicrocontroller after eachchange. Ifitstopsworking,undothechangeandgetitworkingagaininitspreviousstate. lThereis plentyof supportonlineandsomeonehasprobablyalreadydonethethingyouaretryingtodo, sosearchforanswerstoyourproblems-thisisallpartoftheiterativedesigningprocess. Remembertoacknowledgeall sourcesofhelp.ACTIVITY1Experiment withamicrocontroller. Ifyouhaveneverusedonebefore,chooseamicrocontroller that canbeconnectedusingcrocodileclips.UsingtheIDEsoftwareonaPC, start byprogrammingthemicrocontrollertoflashasingleLED.ThenflashafewLEDs inarepeatingpattern. Programmeittoplayasimpletuneorsoundeffect.Thentrydetectingwhenaninputbuttonhasbeenpressed.Thenuseanaloguecommandstosensethelight level fromalightsensorinputandrespondbyturningonLEDsormakingsounds asthelight level getsprogressivelydarker.2Designandbuildelectronicsystems,basedonamicrocontroller,toachievethefollowingfunctions: aAsystemtowarnifadoorhasbeenleftopenformorethan30seconds(retailstoresusesimilar devicesforsecurityreasons,towarnifthestockdeliverybackdoorhas beenleft open). Useamagneticreedswitchsensortodetectthedoorbeingopen. Theoutput devicewill beabuzzer.bAsystemtocontrol acoolingfansothatitrunsataspeeddependentontheroomtemperature- t hehottertheroom,thefasterthefan.Forthisapplication,useatemperaturesensorandalowvoltageelectricmotortodrivethefan.Rememberthat youwill needadriverbetweenthemicrocontrollerandthefan.3Searchfor onlinetutorialsforideastohelpyoudevelopyourprogrammingskillsandincreaseyour electronicsknowledge.
30313.3Sourcesandorigins13.3SourcesandoriginsLEARNINGOUTCOMESBy theendof this sectionyoushouldknowaboutandunderstand:➜thesources andorigins of systemcomponents➜considerationof theecological, social andethical issuesassociatedwithprocessingsystemcomponents➜thelifecycleof systemcomponentswhenusedinproducts➜recycling, reuseanddisposal of systemcomponents. Sourcesofsystemcomponentsandecological,socialandethical issuesSystemcomponents includeelectroniccomponentsandmechanical components. Thesecomponents aremanufacturedfromarangeof materialsusingarangeofprocesses, andthe manufacturemay takeplaceindifferent factories, perhapsindifferentcountries. Systemcomponents aremanufacturedonaglobal scale. Most electroniccomponentsarenowmanufacturedinAsia, withChina, Japan, IndiaandTaiwanbeingthebigplayers. TheUnitedStates leads theworldinmanufacturingmicrochips(integratedcircuits), andcertainotherhigh-value parts aremadeinEurope. Electronic components frequentlyrequirearangeof chemicalsandrawmaterialsthatareoftendifficult tosource, difficult touseandtoprocess, andoftentoxic. Also, extractingtheserawmaterials fromtheearthrequires energyanddepletesnatural resources, andrequiresenergyfor transportation. Companies that deal withsuchmaterialsneedtoinvestlargeamountsofmoney inequipment andstaff training, andtheywill beextremelyspecialisedmanufacturers. As such, they oftenproducecomponents onaverylargescaleatverylowunitcost. It is predictedthat, as thecomplexityof microchipsincreases, thenumberofcompanieswiththe technology tomanufacturethemwill droptoperhapsonlyfourcompaniesworldwide. Problems may thenarisebecauseof thedominationof thesecompaniesovertheindustry: lack of competitioncanleadtorisingpricesandalackof manufacturingcapacitycanleadto'chipfamine', whendemandfor certainmicrochipsexceedssupply. Thishappenedin2011whenthe damagecausedbytheJapaneseearthquakeandtsunami ledtoaworldshortageof computer memory chips anddisplayscreens. Fortunately, systemcomponents that aremanufacturedacrosstheglobearereadilyavailabletobuy fromUK-basedretailers, whichstockhugerangesof componentsandcanalsoprovide the technical dataneededtousethem. Infact, electroniccomponentshaveneverbeeneasier tobuy anduse. LifecycleofsystemcomponentsElectronic components areextremelyreliableinuse. Qualityassuranceandqualitycontrolduringmanufacturemeanthat it is almost unheard-of nowadaysfor anewcomponenttobefaulty. Provideda component is operatedwithinitsdesignratings, itisalsoveryrareforelectroniccomponents tofail duringuse. Thefaults that dooccur inelectronicproducts areoftenduetofailedsolder joints(perhapsduetophysical shocksuchas the product beingdropped) or other problemslikewateringress. The ratingof a component is themaximumvalueof aspecifiedquantitythe component canhandle. If this valueis exceeded, thecomponentwill be damaged, perhaps instantly, or thecomponent maycontinuetowork but its lifeexpectancywill bedrasticallyreduced. Sometimes, themanufacturer will statethat it is permissibletoexceedtheratingbriefly. KEYTERMSRating:Themaximumparameterthatacomponentcanreliablyhandle.Table13.2SomeexamplesofcomponentratingsComponentRatingResistorMaximumpower:0.25wattMicrocontrollerMaximumsupplyvoltage:5.5VBatteryMinimumtemperature:-15°CMotorMaximumspeed:12,000rpm
304Chapter 13DesignengineeringSomeelectroniccomponents, however, dosufferfromalimitedlifespan.Rechargeablebatteriesareoneexample; afterseveral hundredcharge-dischargecyclesthebattery'scapacityreducestothepointwhereitmaynotbeabletoholdenoughchargetousefullypower theproduct for alongperiod. Youmayhavenoticedsuchproblemswithyourmobilephoneor laptopbatteryasitages. Somesystemcomponentsaredeliberatelydisposable, suchasnon-rechargeablebatteries.Themanufacturer of aproductthatusesdisposablebatteriesshoulddemonstratearesponsibleattitudebybalancingtheenergyneedsoftheproductandtheuser'sneedstoreliablyusetheproduct, withtheenvironmentalimpactcausedbymanufacturinganddisposingof batteriesduringtheproduct'slife. Mechanical componentsgenerallyhaveshorterlifespansbecausemovingpartsalwaysinvolvesomedegreeof friction, whichcauseswear. Higher-qualitymechanicalcomponentswill useharder-wearingmaterialsthatlastlonger, andprovisionmaybemadeforservicingmechanical parts, suchasrenewinglubricationorchangingindividualpartsthatareknowntowear quickly. Inthesamewayasforelectroniccomponents,mechanicalcomponentsthatareoperatedwithintheir designratingsshouldhavealongandpredictablelifecycle.Recycling,reuseanddisposalTheprinciplesofobsolescenceandtheproblemscausedbyour'throwawaysociety'arecoveredinSection1.2.Thepointatwhichitisbetterfortheenvironmenttobuyanewproductratherthankeepusinganoldoneiscalledthebreakevenpoint. Thetypicalbreakevenpointforamobilephoneis7years, buttheaverageuserwillexchangetheirphoneforanewmodelafterjust11months.Electronicandmechanicalproductsmaycontainhundredsof differentcomponentsandawiderangeofrawmaterials,manyofwhichwillbetoxic.Someofthehazardousmaterialsusedinelectroniccomponentsincludelead,cadmium, mercury, sulphuricacidandradioactivesubstances. Ifproductsaredisposedofinnormalwastetheywill gostraighttolandfill,wheretheywilldecomposeandthehazardousmaterialswillleakintotheenvironment.Thismeanstheywillgetintothewatersystemandpotentiallycauseserioushealthproblemsforhumans.TheaverageUKcitizenwill disposeofover3tonnesofelectricalandelectronicproductsintheirlifetime. TheWEEEManisathought-provokingsculpturebasedattheEdenProjectinCornwall,constructedfromthetypical quantityofelectronicproductsanaveragepersonwillthrowawayintheirlifetime. TheWEEE(WasteElectricalandElectronicEquipment)directivenowrequiresall manufacturersandproducerstotakeresponsibilityfor whathappenstotheproductstheysellattheendoftheirlives.Inpractical terms, thismeansthatretailersofelectronicproductsmustnowprovideafreetake-backserviceforcustomerstohandintheunwantedproducttheyarereplacing. Theretailermustthendisposeoftheproductsatanapprovedtreatmentfacility.Youmayhavespottedinyour local supermarketthecollectionbinforoldbatteries-allbatteryretailersmustnowprovidethistake-backfacility.KEYTERMSObsolescence: Becomingoutdatedor nolonger wanted. WEEEdirective: Asustainability scheme toreducethe amount of wasteelectrical products sent tolandfill. Figure 13.28 Wasteprintedcircuit boardsreadytoberecycledFigure13.29TheWEEEMansculpture
30513.4Manipulatingandjoining13.4ManipulatingandjoiningLEARNINGOUTCOMESBy theendof this sectionyoushouldknowaboutandunderstand:➜Thespecialist manipulatingandjoiningtechniquesusedinDesignEngineeringWhendevelopingiterativedesigns, aDesignEngineer will needtoconsiderelectronicand/or mechanical systems toachieveadesiredfunction, but theywill alsoneedtoconsiderthe use of materials toprovidesupport, structural integrityor protectionforthesystem. Consequently, a workingknowledgeof polymers, metals, timbersandtextilesisrequiredtosuccessfully produceaDesignEngineeringsolution. Coreknowledgewill providestudentswitha broadunderstandingof what canbeachievedwiththesematerials. Asadesignisdeveloped, it will benecessarytolearnsomein-depthknowledgeinafewspecificareasofmaterial properties andhowtomanipulateandjointhemtoachieveadesiredoutcome. Forthis, the reader is encouragedto'dipin' toother sectionsof thisbooktoextractthepreciseinformationrequiredtodeveloptheir specificproject. PrintedcircuitboardmanufactureInanelectronic system, theprintedcircuit boardholdstheelectroniccomponentsandmakes the circuit connections betweenthem. Theboardismadefromaninsulatingmaterial(oftenglass-reinforcedplastic, GRP) andtheconnectionsareformedbycoppertracks, towhichthe components aresoldered. Ina school environment, printedcircuit boards(PCBs) areusuallymadebyoneoftwomethods: lPhoto-etchmethodlIsolationroutingPhoto-etchmethodThe PCBbegins as a sheet of GRPontowhichisbondedathinlaminateofcopperwithalayer of photosensitivefilmapplied. ThePCBartwork(thepatternof tracks)isprintedinblack ink ontoa transparent film. Duringprocessing, ultra-violet(UV) lightisshonethroughthe artwork filmontothePCBandthentheboardisdevelopedinachemical tank. Thisproduces animageof thetrackpatternonthesurfaceof thecopperlaminate. Theboardisthenimmersedintoanetchant whichchemicallyremovesall thecopperexceptintheareaswhere the track patternhas beenformed. At theendof theprocessthePCBisdrilledtoallowthe component wires tobeinsertedandthensoldered. School-madePCBsareusuallysingle-sided, havingtracks ononlyonesideof theboard.Step2: After developingStep2:AfteretchingUVLight Step 1: Exposure Photoresist Thincopper layer PCBartworkGRP board GRPboardGRPboardCoppertrackFigure 13.30 Photo-Etching
306Chapter 13DesignengineeringThephoto-etchmethodallowshighqualityPCBstobemade,butitdoesrequiretheuseofquitehazardouschemicalssosafetyprecautionshavetobetakenwhenusingthese.Therearealsoalargenumber of variableswhichcanaffecttheoutcomesuchasUVexposuretime, chemical temperature, developerandetchingtimes, ageofchemicalsetc,soitcanbedifficult toguaranteeagoodoutcomeatthefirstattempt, especiallyforaninexperienceduser. Thepre-sensitisedPCBsheetandthechemicalsarealsoquiteexpensive.PCBisolationroutingInthismethod(whichisalsoknownasPCBengraving),thePCBbeginsasasheetofGRPontowhichisbondedathinlaminateofcopper. ACNCengravingmachineisusedtoremovecopperfromtheboardtoleaveisolatedareaswhicharethentheconnectingtracksbetweencomponents. TheCNCmachineiscontrolledfromanoutputfilegeneratedbythePCBdesignsoftware.ThesamemachinewilloftenbeabletodrilltheholesinthePCBpads. Isolationroutinghassomeadvantagesoverthephoto-etchmethodinthatnounpleasantchemicalsareusedwhichmakestheprocesssomewhatsafer,andtherunningcostsarerelativelylow. Theprocessingtimeforasinglecircuitboardisquickerbytheroutingmethod.However,theinitial equipmentisexpensiveandaskilledtechnicianisneededtosetuptheCNCmachine,ensurethePCBisloadedinexactlytherightplaceandsecurelyclamped.Itisimportantthattheengravingtooliskeptsharpotherwisethecutedgesofthecopperwillbeburredandsolderingwill thenbeverydifficult. IncorrectinsertionofPCBortoolscanresultinexpensivedamagetotheCNCmachine.SolderingSolderingisof paramountimportanceinelectronicsystemsasitisthemainmethodusedtomakethephysical andelectrical connectionsbetweenelectroniccomponents.Poor soldering, or failureof asolderjointisbyfarthemostcommoncauseoffaultsinelectronicsystems. Solder istraditionallyanalloyof tinandleadbut, in2006, theRestrictionofHazardousSubstances(RoHS) directiveprohibitedtheuseofsignificantquantitiesofleadinconsumerproductsproducedintheEuropeanUnion. Thisresultedinmostsoldernowbeinglead-free, andmanyschoolswill alsouselead-freesolderas'goodpractice'.Lead-freesolderispredominantlymadefromtin, withsmall amountsofcopperand,possibly,silveradded.Solderingfor small scaleelectronicsconstructionwillbecarriedoutbyhandusingasolderingiron. Thehot endof thesolderingironiscalledthebitandthiswillbeshapeddowntoasmall sizeinordertodirecttheheattopreciselywhereitisneeded.Thesolderwill beintheformof athinwirewithacoreofflux, whichisacleaningchemicalneededtoensurethat thesolder bindseffectivelytobothpartsofthejoint.Solderingbyhandisaskillwhichcanbedevelopedanditmustbemasteredbeforeyoucanexpecttoproducereliableelectronicsystems. Poor solderjointscanoccurforanumberofreasons,including:lThejoint not beinghotenoughforthesoldertoflowcompletelyaroundthejointlDirt or oxidisationonthemetals, oradirtysolderingironbitlThejoint movingbeforethesoldersolidifieslNot feedinginfreshsolderwire-tryingtotransferhotsolderfromtheironontothejoint. Figure 13.31 PCBengraving
30713.4ManipulatingandjoiningAcareful visual inspectionmust bemadeafter everyjoint ismade. Examplesofgoodsolderingareshowninthephotograph. Badjointsmust becorrectedortheyarelikelytocause problems later onduringtesting. Insomecases, apoor jointcansimplybereheatedandfreshsolder applied. If thejoint alreadycontainstoomuchsolderthenthiswill needtobe removedwitha solder-sucker tool, or withde-solderingwick, beforefreshsolderisthenused. As withall manufacturing, it is better toget it right firsttime! AttachingtoarotarysystemIt is frequently necessaryfor onepart of arotatingsystemtotransferitsmotiontoanotherpart onthe sameaxis. Examples areexplainedbelow. Attachingawheel orageartoashaftDrive wheels needtobeattachedtotheir driveshaft sothat the rotationof theshaft is transferredtothewheel without slipping. For lowtorquesystemsusingplastic wheels this couldbeachievedbydrillingaholeinthe wheel whichis slightlysmaller thanthediameter of the metal shaft sothat thewheel is atight fit ontothe shaft, whichresults intherotationbeingtransferredthroughfriction. This methodwouldnot besatisfactoryinhigher-loadsystems wherea morepositivemethodof driveiscalledfor. The diagramillustrates twoother popular methodsof attachingwheels todriveshafts inschool projects. Bothmethods allowfor thewheel toberemoved. Thegrubscrewmethodis probablythesimplest andmost popular choice; noticethat asectionof theshaft needstobefiledflat sothat thegrubscrewhas asurfaceto'bite' on. AttachinganelectricmotortoadriveshaftElectric motors usually haveanoutput shaft whichisjust afewmillimetreslong. Insomeapplications, a pinionwill beattachedtothisshaft (possiblyusingthegrubscrewmethoddescribedabove). Inother applications it isnecessarytocouplethemotoroutputdirectlytoa drive shaft inorder totransfer therotationtoadifferent place. The diagramshows howadriveshaft coupler canbeusedtojointwodrive shafts end-to-end. Theshafts may beof different diameters. As it is very difficult topreciselyaligntwoshafts, especiallyif theyare quite long, flexiblecouplings are availablewhichallowfor slight misalignment. grubscrewwheelflatonshaftshaftFigure13.32DifferentwaysofattachingdrivewheelstoashaftGrubscrewsMotor BrasscouplerExtensionshaftGrubscrewslocateflatsectiononshaftsFigure13.33Extendingamotordriveshaft
308Chapter 13DesignengineeringLinkages,mountsandspecialcomponentsInaDesignEngineeringproject, mostofthecomponentswillbepurchasedreadytouse. However, it isquitecommon, especiallyinmechanicalsystems,forcertainpartstobeneededwhichcannotbeboughtandwhichneedtobedesignedandmanufacturedspeciallytoperformaparticularjob. Examplesincludealinkagetoconnectonepartofamechanismtoanother,oramotormountingbracket, or aholderforasensorinanelectronicsystem.Suchcomponentscanbemadeusingavarietyofmaterialsandworkshoptoolsandmachines, referringtoother sectionsinthisbook. Polymorph(seesection5.2)canbeauseful material for quicklymanufacturingspecial parts, especiallyinthedevelopmentstages.Onceit hasfullyhardened, polymorphcanbedrilledandmachinedtoacceptscrewsandother fasteners. Special componentscanalsobedesignedusing3DCADandthenproducedona3Dprinter toproduceaccurateanddurablepartswhichcanquicklybemodifiedandre-printedif necessary. FastenersandfixingsSection10.7of thisbookdescribesvarioustemporaryfastenerssuchasscrewsandnutsandbolts. ThesefastenersarefrequentlyusedinDesignEngineeringtoassemblemechanicalandelectroniccomponents. Inmechanical systems, screwfastenerscansometimesworklooseduetovibrationandcaremustbetakentopreventthisfromhappening.Figure 13.34Nyloc nuts Figure13.35ShakeproofwashersNylocnutscontainaringof nylonwhichgripsthescrewthreadsandpreventsthenutfromvibratingloose. Shakeproof washersareplacedunderaconventionalnutand,whenthenutis tightened, theteethonthewasherbiteintothenutandpreventitfromturningeasily.Threadlockisaliquidsubstancewhichisappliedtoascrewthreadbeforethescrewisinserted. Onceit dries, thethreadlockeffectivelygluesthethreadinplacepreventingitfromaccidentallyloosening. Threadlockedscrewscanstillbeloosenedifrequiredusingtools.
30913.5Structuralintegrity13.5Structural integrityLEARNINGOUTCOMESBy theendof this sectionyoushouldknowaboutandunderstand:➜howandwhy systemcomponentsneedtobereinforcedtowithstandforcesandstresses ➜processes that canbeusedtoensurethestructural integrityofaproduct.HowsystemcomponentscanbereinforcedtowithstandforcesThe individual parts of amechanical systemmust beheldfirmlyinplacewhilethemechanismis inmotionandwhileit is subject tovariousforcesandtorques. Astructureis a collectionof parts that worktogether toprovidesupport. Thepartsinastructurearecalledmembers. The support structurefor amechanical systemisoftencalledthechassis. Ifthechassisis not rigidenoughtowithstandtheloadswithout flexing, thereisariskthatgears, shafts, belts, etc., will moveout of alignment, whichcouldcauseproblemsandpossibledamage tothemechanical components. Achievingstructural rigidityisveryimportantinamechanical system. Astructural systemis saidtoberigidif it canwithstandforcesandstresseswithoutbendingor flexing. Thediagramshows athinbar of material supportedbetweentwoposts. Aforceappliedtothecentreof thebar will causeit tobend. Theamountitbendsdependson: lthe size of theforcelthe material thebar is madefromlthe distancebetweenthesupports lthe thickness of thebar lthe cross-sectional shapeof thebar. Force ForceFigure 13.36 Abar bendingunder loadRectangularbarRectangularboxsectionSolidroundTubularAngleI-sectionFigure13.37Examplesofmaterialcross-sectionsKEYTERMSChassis:Thesupportstructureforamechanicalsystem.Member:Theindividualcomponentsinastructure.Rigid:Theabilitytowithstandforceswithoutflexing.Structure:Acollectionofpartsthatprovidesupport.
310Chapter 13DesignengineeringPlacingthebar verticallyasshownintheseconddiagramwillreducethebendingbecausetheeffectivethicknesshasbeenincreased. Onewaythebar couldbemademorerigidisbymakingitthicker,butamoreefficientmethodis tochangethecross-sectional shape. Stocklengthsofmetalandplasticareavailableinarangeof different cross-sections. Someexamplesareshowninthediagrambelow.Theuseof hollowtubular or boxsectionmaterialsallowsdesignerstoachievealmostthesamerigidityasasolidmaterial withthesamedimensions, butwithreducedweightandreducedcost. Thisworksbecausewhenamaterial isbent, mostofthebendingforcesareconcentratedintheouter surfaces. Thismeansthatremovingmaterialfromthecentrehaslittleeffect ontherigidity. Havinglessmaterial inthemiddlesectionandmorematerialontheouter surfacesmakesfor amoreefficientandrigiddesign.Largesheetsof flat material aremademorerigidbyincludingfoldsandindentsinthematerial, asshowninthephotographs. Ribscanalsobeaddedtoincreaserigidity. Aribisathinsupportthatrunsatrightanglestothesurfaceof thesheet andthatisattachedtothesheet. Inplasticparts,ribsaremouldedat thepoint of manufacture. Formetal parts, ribsareoftenweldedorrivetedontothesheetduringassemblyof thesystem. Anexampleisplasticribsbeingusedtoreinforcetheplasticbaseof amonitor, asshowninthephoto. ACTIVITY1Findfiveexamplesof productsthatuseholloworangledcross-sectionpiecestoachieverigidity. Photographtheexamplesandannotatethephotostoexplainyourfindings.Youmayneedtolookcarefullytofindexamples;rememberthat,inmanyproducts,hollowtubes or boxsectionswill haveplasticendcapstofinishtheproductnicely-theseendcaps areacluethat thematerial ishollow!2Findandphotographfiveexamplesofproductsthatfeatureindentsorribstoachieverigidity. Youmayneedtolookinsideorunderneaththeproducts,asribsareoftenhiddenbecausetheyspoil theaestheticsofasmooth,flatsurface.KEYTERMSRib: Athinsupport addedtoincreaserigidity. Figure 13.38Corrugatedmetal sheet andametal panel withindents for rigidity Figure13.39Ribsmouldedintothebaseofamonitortoincreaserigidity
31113.5StructuralintegrityEnsuringthestructural integrityofaproductEvenif the individual components aremaderigid, acompletechassisstructurewill notberigidunless it has beendesignedproperly. Arectangular frameworkisnaturallyunstableandit cancollapsewhenasideways forceis applied. The only way tokeeparectangular frameworkrigidistomakethecornerjointsverystrong, for exampleby usinglargescrews, strongadhesiveor welds. Thisistheonlypracticalmethodinsomedesigns, but abetter approachistodesigntheframeusingtriangulation, whichis wheretheframeis composedof trianglesrather thanrectangles. Atriangular framecannot changeits shape- it isnaturallyrigidanddoesn'trelyonthestiffnessof the joints tokeepits shape. Addingadiagonal cross-memberacrossarectangularframecreates twotriangles andthis makes it becomeanaturallystableframework. If a designprevents afull cross-member beingused, thengussetplatescanbeusedtoachievea partial approachtotriangulationand, therefore, increasetherigidityof theframework. ForceFigure 13.40 Arectangular frameis naturallyunstableAdding a cross-member Corner-bracesGussetplatesFigure 13.41 Methods of triangulatingaframeworktoincreaseitsrigidityACTIVITY1 Findfive examples wherecross-members havebeenusedtoachievetriangulationinaframework. Photographandannotateyour findings. Lookforlarge-scaleframeworksintowers andbuildings, but alsofor smaller examplesaroundyourhouseorschool.2 Take five photographs of examples wheregusset platesorothermethodsofcornerreinforcement havebeenusedinproducts. KEYTERMSCross-member:Amemberaddedtoachievetriangulation.Gussetplate:Acornerreinforcementtoincreasestructuralrigidity.Triangulation:Achievingrigiditybyproducingtriangularstructures.
312Chapter 13Designengineering13.6MakingiterativemodelsLEARNINGOUTCOMESBytheendof thissectionyoushouldknowaboutandunderstand:➜theprocessesandtechniquesusedtoproduceearlymodelstosupportiterativedesigning. Other sectionsinthisbookexplainhowphysical andaestheticmodelscanbemadefromarangeof materials. Thischapterfocusesonmodelsusedtotestanddevelopmechanicalandelectronicsystems. Iterativedesigningreliesonmodelsbeingcreatedtotestideas,andtheresultsofthosetestsbeingusedtoimprovethedesign. Furthermodelsmaythenneedtobemade,untilthedesignachievesthedesiredoutcome. Models shouldbemadeonlybecausetheyareneededtoansweraquestionaboutadesign,or toprovidesomeparameters(numbers)orlimitationsforthedesign.Nevermakeamodeljust becauseyouthinkyouareexpectedto; beforemakinganymodelyoushouldknowexactlywhat it isyouaresettingouttoinvestigate. Also, thinkcarefullybeforebuildingamodel tofindout datathatyoucouldeasilylookupfromanexistingsource.Broadlyspeaking, modelscanbe: lphysical models, madeusingreal materialsandcomponentslcomputer-aidedmodels, suchas3Dcomputer-aideddesign(CAD)orelectroniccircuitsimulationusingcomputer-aidedengineering(CAE)lsoftwaremodels, whichtestflowchartprogramsforamicrocontrollerlmathematical models, whereareal situationisexplainedthroughamathematicalorscientificequationinordertomakepredictionsaboutthesituation.Remember that modelsareuseful forhelpingtosolvesmallproblemswithinalargerdesign.Whendesigningafunctioningsystem, themostusefulmodelsmaybetheonesthatexplore, for example, thedifferentwaysofattachingawheeltoadriveshaft,ortheoptimumnumber of LEDstousetoilluminateagivenarea. MakingmechanicalmodelsMechanical systemsarequitedifficulttodesignwithoutactuallybuildingandtestingthem.Forces, mechanical advantagesandgearratioscanbecalculated,butitisoftennotclearwhether asystemwill actuallyworkuntil itisbuilt. For example, whenusingelectricmotorsandgearboxesitisdifficulttopredicthowfastthemotor will turnwhenit isunderload. Someoftheuncertaintycanbereducedbytryingout different motors/gearboxes, andthisgivesabetterideawhetherthesystemislikelytobetoofast or whether it will producesufficienttorquetokeepitturningunderload.Somemotor/gearboxkitsallowyoutovarythegearratiobyusingdifferentcombinationsofgears,sothereareopportunitiesheretomodel variouscombinationsinordertodecideuponanoptimumratiofor agivenapplication. Whilesomemechanical componentswill bepurchased, partssuchaslinkages,levers,camsor chassiscomponentscanbedesignedonCADandthenlasercutoutofasuitablematerial.Themodellingstageisunlikelytoinvolvecuttingthesepartsoutofcardinthefirstinstance.This wouldallowyoutocheckthatthedimensionsarecorrect,includingfeaturessuchasbearingmountingholesizesandseparationofshaftstoensurethecorrectmeshingofgears. Correctionswouldthenbemadebeforecommittingtocutoutinthefinalmaterial.3Dprintingprovidesanalternativemethodofmodellingmechanicalcomponents,orevenof producingthefinal workpart. Duringthemodellingstagesthedesignermaystartto
31313.6Makingiterativemodelsexperiment withbought-incomponents suchasmotors/gearboxes/sensors etc. andthefixedsizesof thesepartswill begintodeterminecertaindimensionsof theoverall design. The final scaleof theprototypewill needtobekept under tight control duringtheiterationstagesbeforepresentationtostakeholders. Foamboard(seeChapter 11) is another useful sheet material for modellingmechanical components, andalsohas the advantageof beingeasytocut usingamodellingknife. Auseful methodfor testingthemovement of linkagesistomake a 2Dmodel out of foamboard(or card) andtousepaper fasteners as pivots. Suchmodels canbeusedtotest that the full rangeof requiredmotioncanbeachieved, andtoprove that parts don't collideor lock-up. Foamboardis easy tocut, soiterations of thesystemcanbequicklydevelopedandtested. CAE softwarehas someusefor modellingmechanical systemsbut, asmechanical systemstendtobe bespokedesigns for specificapplications, thebestresultsareoftenobtainedusing3DCADsoftware. It can, however, takealongtimeandalotof userskill todevelopvirtual mechanical systems usingthis software. MakingelectronicmodelsElectronic models areusuallyconstructedinorder to: lcheck that theinterfacingworks betweentheinput/outputdevicesandthemicrocontroller lcheck that theinput/output devices achievethedesiredeffectlcheck thefunctioningof theflowchart program. InSection10.2, it was explainedthat somemicrocontrollers aredesignedfor experimental work andthat thesetypes allowfor electrical connections tobequicklymade usingcrocodileclipleads. This meansthat input andoutput devices canveryeasilybe connected, disconnectedandswapped. For more advanceddesigns, whichrequirethe use of other components suchas resistors or driver ICs, abreadboardmaybeneeded. Abreadboard(or 'prototypingboard') consists of holes intowhichcomponent wires canbeinserted. Theholesare electrically joinedinrows of five, andwires sharingthesamerowwill beconnected. This allows electroniccircuits tobe quickly built without theneedfor anysoldering. Breadboards takealittlepracticetouse effectively, but theyarebyfar themost effectivemethodof modellingelectronic circuits. KEYTERMBreadboard:Aprototypingtoolforbuildingelectroniccircuits.Figure13.43AnelectronicsystemmodelledusingabreadboardFigure13.42Alinkagemechanismbeingmodelledinfoamboard
314Chapter 13DesignengineeringCAEsoftwareisavailablefor modellingelectroniccircuitsandthisisgenerallyveryeffectiveandcansavehoursof breadboardprototyping. Componentscanbequicklyconnectedanddisconnectedandthedesignercaneasilymodifyacomponent'svalue(e.g.theresistanceof aresistor) andobservetheeffect. Thisprovidesarapidmethodofoptimisingcomponentvalues bytrial anderror. Integratingthefull programmablefunctionalityofmicrocontrollersisaproblemforsomecircuit simulationsoftware. Certainsoftwarepackageswillsimulateonlyspecificmicrocontrollers, whileotherscan'tsimulateamicrocontrollerprogramatall.Itislikelythatthis functionalitywill improveasthesoftwaredevelops, butitisimportanttounderstandthelimitationsof CAEcircuit simulationforaparticulardesignsituation.MakingmicrocontrollersoftwaremodelsAveryimportant part of asuccessful functioningsystemindesignengineeringistheiterativedevelopment of themicrocontrollerprogram. Itisverytemptingtorushthisaspect,toleaveit totheend, or toassumethatthefirstversionisgoingtobesatisfactory.Themicrocontroller programiscrucial tothesuccessfuloperationofthewholesystem,however,andit must playacontinuingpartintheiterativedesignprocess.Themost obviousreasontoiterativelytestthemicrocontrollerprogramistoremovebugs- errors that causetheprogramtobehaveinanunexpectedorundesirableway.Somesoftwarepackagesfor programmingmicrocontrollersallowtheprogramtoberunandsimulatedbeforedownloadingittothemicrocontroller, andthiscanbeausefulwaytoironout obviousbugs. RunningtheprogramonaPCalsoallowssystemparameterstobemonitored; theprogramcanusuallyberunonestepatatime,givingyouachancetoidentifyexactlywhereaproblemisarising. Manyproductshaveauser interface(UI)thatisdirectlyinfluencedbythemicrocontroller,andapoor UI will maketheproductdifficultorevenimpossibletooperateproperly.Themicrocontroller program, therefore, candirectlyaffecttheergonomicsofaproduct.For example, refer backtothebicyclesafetylampinFigure13.14andFigure13.16.Eachpressof thepushbuttonchangestheoperatingmodeofthelamp.Itwasexplainedthatthe'WAIT1s' commandsareneededtopreventtheprogramskippingthroughthemodesbeforetheuser hasachancetoreleasethepushbutton. Ifthe'WAIT'intervalistoolong,however,theuser will havetopausebetweensuccessivepushesofthebutton,whichgivesanawkward(andannoying) operatingexperience. Therefore, thedurationofthe'WAIT'intervalisbestdeterminedbyiterativetrial-and-error, allowingrealoperatorstousetheprototypesystem,varyingthe'WAIT' interval andaskingfortheirfeedbackonwhichvaluegivesthebestoperatingexperience. Allowingreal userstotestamicrocontrollerprogramisessential,becausetheyarelikelytousetheproduct or systeminanintuitiveway, andyourfirstattemptsatwritingthesoftwaremaynot provideasuitableuserexperience. Iterativesoftwaretestingisalsoneededtofinetuneprogramparameters,ortocalibratethesystem. Onesuchexamplewouldbeinacoolingfansystem,whereprogramvaluesareiterativelyadjusteduntil thefanswitchesonatthedesiredtemperature.
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316Chapter 13DesignengineeringFor verydemanding, fullywaterproofsolutionsitwillprobablybenecessarytopurchaseawaterproof 'project case' andplacethesysteminsidethis. Remember,however,thatwhenever aholeisdrilledinthecaseforcables, switchesetc,thenthewaterproofnesscanbecompromised. Cablesshouldexitthrougha'cablegland'whichmaintainsthesealofthecase. Inadditiontowater, dirt ingresscanbeverydamaging, especiallytomechanicalsystems.Thelubricant usedinsomemechanismscanbeverystickyandcanpickupgritwhichthenacts as anabrasivewhichcancauseseriousweartomovingparts.Therefore,thechoiceoflubricant isimportant. For example, abikechainisfullyexposedtoroaddirt,socyclistsoftenusea'dry' lubricant onthechainratherthanconventionalgrease,asthedrylubricantdoesnot collect roaddirt likegreasewould. Whenbuyingmechanical components, itispossibletobuy'sealed'bearingswhicharepre-lubricatedandhavecoversontheirsidestokeepoutdirtandmoisture.Figure 13.46Waterproof seal onasportscameracaseFigure13.47WeatherproofboxwithcableglandsFigure 13.48Sealedandopenbearings
31713.7UsingdigitaldesigntoolsAestheticfinishesMuchis writtenelsewhereinthis bookabout howtoachieveaqualityfinishona range of materials, andhowtoprotect the materials fromenvironmental factors. Ina DesignEngineeringcontext, theaesthetic finishsometimes extends tolabelling: thereis frequentlyaneedtomount controls ona panel whichalsorequireslabelstoidentifythecontrols. Priorthoughtabout howtolabel thepanel canresult inahighqualitylabellingoutcome. Apooroutcomeresults when, at thelast minute, paper labelsaresimplystuckontothepanel! Various options exist for labellingprototypepanels. Sheetsof transferlettersareavailablewhichcanbeplaceddirectlyontothepanel; thesewouldrequireaclearlacquerfinishtoprotect themfrombeingscratchedoff. ACNCvinyl cutter canbeusedtocut out bespokelabelswhichcanthenbestuckontoanexistingpanel. By usinga laser cutter, acompletepanel canbecut out, includingholesandengravedlabelsinone go. Careful choiceof panel material for laser cuttingcanresultinsomeexcellent, professional-lookingpanels. Alsoavailablearea widerangeof 'engravinglaminates' whichareplasticsheetsavailableina wide rangeof finishes, includingaluminiumandwoodgraineffects. WhenengravedbyaCNCmachine(or a laser cutter), acontrastingcolour showsthrough, allowingcreativepaneldesigns tobeproduced. 13.7UsingdigitaldesigntoolsLEARNINGOUTCOMESBy theendof this sectionyoushouldknowaboutandunderstand:➜theuseof 2Dand3Ddigital technologyandtoolstopresent,model,designandmanufacturesolutions. RapidprototypingThroughtheiterativedesigningstages of adesignengineeringproject, itsometimesbecomes apparent that acustom-designedpart isneeded. Thisoftenoccursinamechanicalsystemwhena particular sizeor shapeof linkageisrequired, oraspecial bracketisneededtomount a motor or a sensor. Suchparts canbemanufacturedbyhandintheworkshopusingmachinetoolsandhandtools, but theadvent of rapidprototypinghasmeant that apartcanbedesignedusingCADsoftwareandthenproducedinamatter of minutesor hoursusingCAMmachinery. 3Dprinters are nowabletoproduceresilient andstrongcomplex-shapedpartsthat, inmanycases, canbeuseddirectlyinthefinal prototypesystem. Conventional machiningof thesamepart wouldrequireahighlevel ofskill andbetime-consuming(and, therefore, expensive). Rapidprototypinghasgivenbirthtotheprocessofiterative designing, wheredesigners cannowbuildfirst generationrapidprototypes, testandimprovethem, beforebuildingsecondgenerationprototypes, andsoon. Inadditiontotheactual rapidprototypedpart, thedesigner alsohasaCADmodel ofthepart that canthenbeassembledintotheCADmodel of theentiresystem. Figure13.49Simplelabellingonanaluminiumpanel
318Chapter 13DesignengineeringCAD,CAM,CAE,digitalmanufactureandinterpretationofplans,circuitdiagrams,PCBlayoutsDesignengineersalsomakeuseof otherdigital technologiesthatcanlinktovariousCAMmachinestoaidthemanufactureof systems. 2DCADsoftwarecanoutputcuttinginformationtoalasercutter,allowingsheetmaterialstobecut toaccuratedimensionsandintricateshapes. Thiscanbeusefulforcuttingoutfunctioningpartssuchasachassisforamechanicalsystem. Thechassismayneedtosupportvarious componentssuchasmotors, bearingsorpivots, anditiscrucialthattheseareallmountedinexactlytherightpositions. Producingpartsonalasercutterensuresaccuracyandrepeatability. Other industrial sheet material cuttingmachinesincludeplasmacutters,CNCroutersandvinyl cutters. All performasimilarjobbuteachoneissuitedtomachiningdifferentmaterialsanddifferent sheet sizes. CADsoftwarecanalsobeuseful forprintingoutfull-sizetemplatesthatcanbeusedtoassistthemanufactureof partsor helpensurethatpartsarealignedproperlywithinanassembly.Stickingatemplateontoasheetof material allowsthematerialtobecutoutanddrilledaccurately. Theelectronicsysteminmanyprototypesisbuiltonaprintedcircuitboard(PCB).APCBisacustom-designedboardwiththecomponentssolderedtocoppertracks,whichcompletethecircuit connections. MostCAEcircuitsimulationsoftwarewilllinktoPCBdesignsoftwaresothat afunctioningcircuitcanbedevelopedasarealPCBdesign.DesigningthePCBcopper trackpatterncanbequitetrickyasthecomponentsneedtobelaidout sothat thetracksdonotcrossovereachother. PCBdesignsoftwareusesanautoroutingfunctiontoachievethis. ThePCBsinmodernelectronicappliancessuchascomputersandmobilephonesaresocomplexthattheycouldnotpossiblybedesignedwithout theaidof PCBdesignsoftware. Figure 13.50APCBtrackpatternKEYTERMAutorouting: APCBdesignsoftwarefunctiontooptimisethe patternof tracks. OncethePCBdesigniscomplete, thesoftwarewillprintoutthetrackpatternartworkontoatranslucent film, whichisthenusedtoproducetheactualPCB.
31913.9Manufacturingmethodsandscalesofproduction13.9ManufacturingmethodsandscalesofproductionLEARNINGOUTCOMESBy theendof this sectionyoushouldknowaboutandunderstand:➜themethods usedfor manufacturingat differentscalesofproduction➜themanufacturingprocesses usedfor largerscalesofproduction.ScalesofproductionAproject's designbrief andinitial market researchwill determinehowmanyproductsneedtobe manufactured. Themethodof manufacturewill bedirectlyinfluencedbythescaleandspeedof productionrequired. Thedesignof theproductwill alsobeinfluencedbythemanufacturingscale, as products that wereoriginallyintendedtobemanufacturedonasmallscale are not likely tobesuitablefor mass productionunlesstheyaresignificantlyre-designed. One-off, bespokeproductionOne-off prototypes arequitecommonindesignengineering. Forexample, manyindustrialmanufacturingprocesses areuniquetoafactory, andadesignengineermaybeaskedtoproduce a bespokecontrol systemfor part of amanufacturingplant. Aone-off designis usuallyexpensivebecausethedesigner needstoreceivepaymentfortheir time spent developingtheprototypeastherewill notbeanyfutureproductsalestobringina long-termincome. Thedesigner mayspendsignificanttimeontheiterativedevelopment of theproduct until it functionstotheclient'ssatisfaction. Bespoke productionusuallyinvolves ahighdegreeof manufacturingskill, muchofwhichmay be carriedout manually, for exampleaPCBmaybesolderedbyhand. Insomecases, manufacturingmay becontractedout tospecialists, addingtothecosts. Rapidprototypingmay be useful for manufacturingbespokeparts, andsoftwareforthemicrocontrollerwillneedtobe writtenanddeveloped. BatchproductionFor a scale of productionthat is beyondafewitems, amanufacturerwill organisetheproductionina moreefficient way. Theexact manufacturingprocesswill dependonthe product andthemanufacturingfacilities. Generally, themanufacturerwill focusonproducinganentirebatchof productsinonego. Oncethebatchiscomplete, themanufacturer may thenswitchproductiontoanentirelydifferentproduct. The productionwill beorganisedtomakethemost efficientuseof themachineryavailableandthe skills of theworkers. Inthecaseof manufacturingasmall batchofasimplemechanical product, this might be: lDay 1: Theentirefactorymanufactureschassisparts. lDay 2: Thechassis areassembled. lDay 3: Thefinal components areadded. lDay 4: Product testing. lDay 5: Packaginganddispatch. Youshouldbeabletoseethat this approachrequireseverymemberofstafftobeskilledincarryingout all theprocesses, becauseeveryworker must bekeptbusyeveryday. Thismightbe the case ina smaller factory, but inalarger manufacturingplantstafftendtohaveskillsincertainareas sothemanufacturingwouldbeorganiseddifferently.
320Chapter 13DesignengineeringSTRETCHANDCHALLENGERe-organisethefive-daymanufactureofthemechanicalproductdescribedaboveforafactoryinwhichsomeworkersareskilledonlyatmanufacturing,someareskilledonlyatassembling, andothersareskilledattestingandpackaging.As theproduct complexityincreases, themanufacturerwillcontractoutthespecialisttasks.For example, it iscommonforaproductmanufacturertoleavethemouldingofplasticpartsandPCBmanufacturetospecialistcompanies. Batchproductiondescribesthewaythemanufacturerorganisestheproductionandthefact that atarget quantityisagreedbeforemanufacturingstarts.Thereisnolimitonbatchsize. Alarger, morecomplexproductmaybemanufacturedinabatchoften,whileasimplerproduct maybeproducedinabatchof10,000. MassproductionAs thenamesuggests, massproductioninvolvesthemanufactureofverylargenumbersof products. Suchmanufactureistypical forcommonlyusedcomponentssuchasscrews,connectors, batteries, etc. Massproducersareusuallyveryspecialistmanufacturersthathaveinvestedlargesumsinmachinerycapableofproducinglargevolumesofparts,withrepeatabilityandreliabilitybeingimportant. Oncetheproductionisunderwayitisoftenmost cost-effectivetoleavemachineryrunningcontinuously,withstaffworkingshiftstomonitor theprocess. Thesheerscaleofproductionandeconomiesofscalemeanthatmassproductionisthecheapestmethodofmanufacture. Leanmanufacturingandjust-in-timemethodsAmanufacturer that isproducingaproductbatchwillneedtoordermaterialsandcomponentsthat arespecifictothatproduct. Consequently, forproductiontostartondayone, themanufacturer reliesonreceivingdeliveryofthematerialsjustbeforemanufacturingstarts. Theywill not wanttotakedeliveryofmaterialstooearlybecausethiscausesproblemsstoringthem. Thematerialsareorderedtoarrivejustintimeformanufacturingtocommence. Just-in-time(JIT) manufacturingdependsonreliablesuppliersthatwilldeliverontime,becauseamisseddeliverywill holduptheentireproduction.Inpractice,theprocessworkssurprisinglywell aseverypartof thesupplychainrealisesthattheirreputationdependsonmeetingproductionpromises. Manufacturersareusuallykeentoshipouttheproductsassoonastheyarecompletedasthis clearsthefactoryreadyforthenextproductionruntocommence.ThewholeJITprocessis aimedat producingefficient'flow' throughthefactory. Thephraseleanmanufacturingreferstoamanagementstrategyofreducingwasteateverystageof theproductionprocess. JITisoneexampleofleanmanufacturing.Apartfromtheobviousaimsof reducingmaterial wastebyefficientcutting,thegeneralaiminleanmanufacturingistoremoveanyactivitythatdoesnotdirectlyaddvaluefromthecustomer'sviewpoint. Leanmanufacturingaimstoproducehigherqualityproductsatlowercost.ManufacturingprocessesusedforlargerscalesofproductionThemanufacturingmethodsusedtoproduceaprototypeinaschoolworkshopareusuallydifferent fromthoseusedatlargerscalesofproduction. KEYTERMSLeanmanufacturing: Amanufacturingstrategy toreducewaste.
322Chapter 13Designengineering610mm610mmTOPVIEW530mm90mm65mm80mmFRONTVIEWPRACTICEQUESTIONS:In-depthprinciplesofdesignandtechnologyTimbers1Thisfigureshowsasandwichboard, usedtoadvertiseoutsideshopsandcafés. Thesidesandlegsaremadefromahardwoodtimber.aMaterialsneedtobesourcedandprocessedinordertobeusedtomakeproducts. For onespecificmaterial fromthesandwichboard:- Statethesourceof thematerial. - Describehowitisprocessedintoaworkableform.- Discusshowtheselectionofthatmaterialisinfluencedbysocialandethical issues. 2Thisfigureshowsasidetable. Designersmakeprototypestoshowtheirdesignstokeystakeholders.Studyandusetheimagesandtechnical informationinthefigure.aProduceastep-by-stepplantoexplainthestagesthatyouwouldtakeifyouweremakingafinal prototypeofyourchosenproductinaschool workshop. Youmust includedetailsof: - specificmaterialsandcomponentsyouwouldusetomaketheprototype- theprocesses, techniquesorskillsyouwoulduse- toolsyouwoulduse, includingdigitaltechnologyasappropriate- howyouwouldensureaccuracywhenmakingtheprototype- howyouwouldfinishittopresentittostakeholders.
32313.9ManufacturingmethodsandscalesofproductionMetals3aChemical reactionis onemethodof extractingmetals. Nametwoother methods. bChemical reactionuses ablast furnace. Adiagramof ablast furnaceisshownbelow. Label theparts identifiedwitharrows. 4Thestructural integrityof metalscanbealteredbydifferent processes suchas annealing. Describethepurposeof annealingmetals1000˚C1500˚C1900˚C5Casehardeningis another treatment donetometals. Completethediagramof thecasehardeningprocessbelow. Stage 1: Heat metal until it glows red Paper andboards6Paper andboards areversatilemanufacturingmaterialsthatareusedforawidevariety of products. Discuss, usingrelevant examples, theenvironmental impactof usingpaper7Describetheembossingprocess. 8Acardboardleaflet holder is shownbelow. 3040 50100 aDrawthedevelopment(net)oftheleafletholderincludingall glueflaps.bUsingnotesandsketchesshowhowyouwouldcreatea90°foldinfoamboard.
324Chapter 13DesignengineeringaAretailer hasmadeanorderfor285bags. Completethetablesbelowtoshowthefinal material costingforthisorder. Polymers9Thisfigureshowsachild'ssit-ontoy. Thebodyismadefromathermopolymer. aNameasuitablethermopolymerthat couldbeusedforthemainbody. bGivetwopropertiesof thermopolymersthatmakethemsuitablefor toyslikethis. cNameasuitablemanufacturingprocessthatcouldbeusedforthemainbody.dExplainwhytheprocessnamedin(c)wouldbesuitable.eDiscusshowdigital technologieshaveprovidedopportunitiesfordesignersandmanufacturersofchildren'stoys. Fibresandfabrics10Theimagebelowshowsaschool bagmadefromaplainweavepolyamidefabric. Thebagincludesapolyester liningandanumberofcomponents. Materials andcomponents required. Quantityfor 1school bagQuantityfor285school bagsPolyamide fabric 1.0mmPolyester liningfabric 0.5mmPiping 1.0mmWebbing0.25mmStrap Adjuster 2Zip 22” 1Zip 10” 2MaterialsandcomponentsPriceperunit/mCostfor285schoolbagsPolyamidefabric£2.05Polyesterliningfabric£1.10Piping£0.18Webbing£0.20StrapAdjuster£0.05Zip22”£0.20Zip10”£0.09Total materialscostfor285schoolbags=bWhat isthetotal costof materialsfor1schoolbag?cExplainwhyaliningfabricisusedinsidetheschoolbag.dNamethescaleof productionthatwouldbeusedfortheschoolbags.
32513.9Manufacturingmethodsandscalesofproduction11aIdentify thetwill weavestructurefromtheimagesbelow. bDenimis acottontwill weavefabric. Explainthebenefitsanddrawbacksof usingacottontwill weavetomakedenimjeans. c Eco-Denimis acompanyspecialisingincreatingjeansthatarecarbonneutral. They wishtoaddalogotothebackpocket of theirnewlineofjeanstohelpbuildbrandawareness. dDescribeasuitabledecorativemethodtoaddalogodesigntothepocket. eDescribetheenvironmental impactsof cottonproduction.
326Chapter 13DesignengineeringDesignengineering12aExplainwhyelectronicproductsshouldnotbedisposedofinnormaldomesticwaste. bExplainwhyelectronicproductscanbedifficulttorecycle.cGiveoneexampleof howtheRoHSdirectivehaschangedthedesignof electronicproducts. dDescribeonewayinwhichtheWEEEdirectiveimpactsonretailersofelectronicproducts. 13aUsesketchesandnotestodescribethestagesinvolvedinproducingaprintedcircuitboardinschool. bIdentifywaysinwhichindustrial PCBassemblydiffersfromthemethodsusedinschool. 14Givethreereasonswhyadesignermaychoosetouseapulleyandbeltdriveratherthanspur gearstotransferrotarymotion.
328Chapter 14Non-examassessment: IterativeDesignChallengeCHAPTER14Non-examassessment:IterativeDesignChallengeLEARNINGOUTCOMESBytheendof thissectionyoushouldknowaboutandunderstand:➜thestructureandformatoftheNEA➜therequirementsofyourchronological portfolio➜therequirementsforthemarkscheme➜arangeof approachesforpresentingtheevidencefortheNEA.IntroductionTheIterativeDesignChallengeisthenon-examassessment(NEA)componentofyourGCSE, andit accountsfor 50percentofyourtotal GCSEmarks.Itgivesyoutheopportunitytodemonstratetheknowledge, understandingandskillsyouhavedevelopedthroughoutthecourseinorder tocreateafinal prototypeorgroupofprototypesthatreflectsareal-worlddesignconsideration. Whatisiterativedesign?Iterativedesignisawayof designingthatisbasedonacyclicprocessofprototyping,testing,analysingandrefiningadesignsolution: Explore-Create-Evaluate.Basedontheresultsof testing, themost recentiteration(orversion)ofadesignisrefinedtomorecloselymeettheneedsof theprimaryuserandthestakeholders. Theprocessfollowedmayappearunconventional, but beassuredthatitcloselymatcheswhathappensintherealworldandyour assessment ismoreconcernedwiththewiderprocessofdesignthanwiththepractical outcomesyouproduce. HowlongshouldIspendontheNEA?Althoughthereisnomaximumorminimumtimerequirement,asaguidelineyouwillhaveapproximatelyfortyhourstocompletethewholeIterativeDesignChallenge.Youshouldbewaryof spendingtoolongontheNEAasitcouldcauseyoutolosefocusandsoaffectthelevel of your work. WhencanIstart?Youwon't beabletostartyourchallengeuntil 1Juneintheyearbeforeyourfinalyear.ThisiswhenOCRreleasesthecontextualchallengesforyoutouseasastartingpoint.Thesewill beopen-ended, real-worldchallengesforyoutointerpretandrespondto.KEYPOINTContextual challenges are releasedby OCRon1June eachyear.
329WhatformatwilltheNEAtake?Examplecontextual challengeslPublic spaces - Thesensitivedesignof publicspacescanenhanceusers' experiencesandinteractions withthat space. Exploreaspaceinyour localitywiththeviewtoenhancingtheusers' experiences. lSecurity- T hetheft of people's possessionsisaprobleminmodernsociety. Exploretherole that designcanplayinsecuringpeople'sbelongings. lDining- Di ningcanbeawonderful social andcultural experiencethatnotonlyfocusesonthe eatingof food. Explorethewaysinwhichdesigncanenhancetheexperiencesforany of thestakeholders involved. As youcansee, thechallenges areopentointerpretationandarenotrestrictedtoaspecificmaterial or process. Theyoffer anauthenticstartingpoint for youtoexploreandtoconsiderinrelationtoyour subject interests andtheproblemsandopportunitiesthatyoucanidentifywithinthe context(s). It is important beforeyoustart thechallengethat youhaveexperiencedabroadrangeoflearningandpractical activities toprepareyoufor demonstratingyourabilitytoundertakeaniterative challenge. Youneedtobeconfident inyour decisionmakingwhendealingwitha givencontext andyoumust avoidhavingpre-conceivedideasof whatyoucoulddesignandmake. WhatformatwilltheNEAtake?Youshouldproduceachronological portfoliosupportedbyreal-timeevidencethatdemonstrates your completeresponsetothechallenge, alongwithafinalprototype(s). Achronological portfoliois aportfolioof evidencethat recordsthewholeprocessofdesigningas it happens. This includes exploringthecontext, analysingproductsandcomponents, communicatingwithstakeholders, andsketching, modellingandtestingyourdesigns. Itshouldoutline your designthinkingas it occurs inreal time. For example, insteadofpresentingallyour researchat thestart of your portfolioinasinglesection, youwouldpresentitthroughoutyour portfolio, as andwhenit happened. Youwouldpresentsketchingandmodellingastheyoccurred, insteadof inseparatesections headed'sketches' and'models'. Evidence of your final prototype(s) shouldbeclearlydocumentedinyourportfoliothroughthe use of photography andvideoas appropriate. For example, if akeyaspectofyourprototype(s) has a functionthat includes movement or sound, thenavideoofitinactionmust be presented. All portfolioevidencefor this assessment shouldbeeasytofollowandunderstand.Youcoulduse presentationsoftwaresuchas PowerPointtopresentyourportfolioasthisallowsinformationtobequicklyaddedtotheslidestorecordandpresentyourreal-timeevidenceas it happens. If a paper portfoliois submittedyoucanenhanceitbysupplyingaudio/videofiles separately. Whatever systemyouusethechronologymustbemadeclear. The majority of your visual evidencecanbecapturedusingastill digital image(suitablyannotated), whichcantheneasilybeinsertedintoyour PowerPointportfolio. Shortvideoclips, however, canbeusedtogreat effect whenconductingproductanalysis, userinterviews/feedback, model testing, andsoon. It is veryimportant that anyvideoclipsusedarerelevantandtothe point. They must alsobeinsertedintoyour portfoliocorrectlyforthemtoworkproperly. The file size of videos cancauseproblems whenopeningyour portfolio, somakesureyoucompress your videos beforeinsertingthemusingasuitableapponyourphoneorcomputer.
330Chapter 14Non-examassessment: IterativeDesignChallengeWhatwillIneedevidenceof?What youneedevidenceof will dependonthenatureofyourproject,butevidencemustberelevantandmayincludesomeof theexamplesshowninTable14.1.Table14.1Examplesof evidencethatcouldbeusedActions ExamplesVisits Tofashionshows, tradefairs,factories,workplaces,etc.InterviewsToestablishtheneedsofyourprimaryuserandotherstakeholdersObservationsTostudyusersintheirenvironment;foruserinteractionGatheringdataAnthropometrics, surveys, legislation,othermeasurementsProduct analysisDisassembly, use, inspiration,reverseengineeringWrittenreportsWrite-ups, analysisof research,testing,etc.CollaborativeworkTogenerateideaswithothers,peertesting,feedbackSketchingHanddrawn, digital, overphotosofmodels,etc.ModellingCADandphysical models, toscaleandfullsizeMaterialstestingDesirableproperties, sampleprocessesPrototypetestingFor viability, userfeedbackComponent testingUsingdestructiveandnon-destructivemethodsUser feedbackObservations, interviews, etc.Stakeholder feedbackEmails, videochats, etc. ManufacturingToexplorepotential processes,actual processesused,CAMFinal prototypeClear images, close-upviews,moving/workingparts,testinginsituVisualisationPhotoshop, imagemanipulation,etc.Remember that evidencealoneisnotenough. Youmustsummariseandanalysewhatyoufindandyoumust guideyourreader. Itmustbeclearwhatyouaredoing,whyyouaredoingit andhowit ishelpingyourproject. HowwillIbeassessed?Youwill beassessedonyourthinkingandonyourcreativeandpracticalskillsandabilitiesthroughthedesigningandmakingofaprototype(s). Therearefour AssessmentObjectivesinOCRGCSEDesignandTechnology,whicharedetailedinthetablebelow. AO1, AO2andAO3areassessedthroughtheNEA.(AO3isalsoassessedinthewrittenexam, alongwithall ofAO4.)TheAssessment ObjectivesrelatedirectlytotheiterativeprocessesofExplore,CreateandEvaluate, asshownbelow. Thosethreeprocessesarespreadacrossfivestrands,alsoshowninthetable. Your chronological portfoliowill bemarkedoutof100andthosemarksarespreadacrosstheiterativeprocesses.
332Chapter 14Non-examassessment: IterativeDesignChallenge4Designdevelopments-Whendevelopingyourdesigns,thefocusmustbeonnarrowingdownandimprovingyourideasthroughmoredetailediterationsthatgraduallyresolveyour stakeholderrequirements. Thequalityoftheseiterationsandhowwell theymeet thetechnical requirementsisimportantthroughoutthissection.5Developingafinal designsolution-Whendevelopingyourdesigns,youwillcarryoutadditional investigations, sketching, modellingandtesting, asappropriatetothedirectionof your thinking. It isimportantthatthisdevelopmentprocessandthethinkingbehinditisclearlydocumentedinyourportfolio. Itmustbeobvioushowyourdesignshaveprogressedtowardsyour final designsolution. Yourfinal designsolutionistheconclusiontoyourdevelopment prior tomakingafinal prototype(s); itmustpresentyourdesignasitwouldlookandfunctionif developedasasaleableproduct. 6Deliveringatechnical specification-Followingthepresentationofyourfinaldesignsolutionwill youwill needtodeliveratechnicalspecificationthatshowshowyourdesignmeetsyour stakeholderrequirements. Itwillincludespecificwrittenandgraphicalinformation(suchasworkingdrawings)thatissufficientforathirdpartytounderstandyour intentions. 7Producingafinal prototype-Aplanofhowtomakeyourfinalprototype(s)willberequiredfirst, thenevidenceof thespecialisttoolsandprocessesyouusedtomakeit.Clearphotosandvideosof thefinishedprototypewill beneededtoprovideevidenceofthelevelof skill involvedinitsrealisation. Themakingofyourfinalprototype(s)mustbecompletedatschool under thedirectsupervisionofyourteachers. Inordertomakeafinalprototype(s)intheschool workshop, itmaybenecessarytousedifferentmaterialsandprocessesthanyourdesignsolutionwouldbemanufacturedwith. Youmustplanforthesepossiblechangesinorder tomakeafinal prototype(s) thatbestpresentsyourintentionstoathirdparty.8Analysingthevalidityofthefinalprototype-Inordertomakeanappropriateevaluationof thefinal prototype(s), youwill needtoanalyseyourstakeholder'sopinions.Youwill alsoneedtoeffectivelytesttheprototypetodetermineitsstrengthsandweaknesses. Suggestionsformodificationsbasedonthistestingmustbepresented.This issimilar totheon-goingprocessreviewyouwillhavemadethroughoutthedevelopment of your designsolution, butwill bemoreconclusive.NEAmarkingcriteriaYour teacher will usethemarkingcriteriatoassessyourworkonceyouhavecompletedyourIterativeDesignChallenge. Eachcriterionhasfourmarkbandsthatgetprogressivelymoredifficult toachieve. Table 14.3 ExamplemarkingcriteriaMarkBand1(1- 5) MarkBand2(6-10)MarkBand3(11-15)MarkBand4(16-20)Quality of planningfor makingthe final prototype(s) Offers littleor nosupport tothe makingprocess. Generallysupportsthemanagement of themakingprocesswithsomerelevant requirementsidentifiedfromthetechnical specification. Goodlevel ofdetailandrelevance,coveringmostrequirementsidentifiedfromthetechnicalspecificationtomanagethemakingprocess.Comprehensiveandrelevant,coveringallrequirementsidentifiedfromthetechnicalspecificationtoeffectivelymanagethemakingprocess.Inthis section, wewill lookatwhatyoushouldbethinkingaboutandtheevidenceyoucouldprovidetoyour teachertoenablethemtoconfidentlyassessyouagainsteachofthemarkingcriteria. lTheWhat?sectionssuggestquestionsyoushouldaskyourselfasyouworkthroughthechallenge. lTheHow?sectionssuggestthepossibletechniquesandapproachesyoucoulduse.Thereis thenanexplanationof someofthetechniquesyoumayusetoprovideevidenceandhowthismight lookinyoure-portfolio.
333NEAmarkingcriteriaStrand1: Explore(A01)-20marksThe work beingassessedinthis strandwill beevidencedfromyourcompleteportfolio. Thisassessment focuses onall of theexplorationyouundertakeandtheneeds, opportunitiesandfacts that youuncover as part of theseinvestigations. MarkBand1MarkBand2MarkBand3MarkBand4Investigations of thecontext Superficial investigations identify fewor noproblems and/or opportunities for further consideration. Investigationsareof sufficient qualitytoidentifysomeproblemsand/or opportunitiesfor further consideration. Investigationsofferagoodlevel ofdetail andidentifyabreadthofproblemsandopportunitiesforfurtherconsideration.Comprehensiveinvestigationsidentifyabreadthofchallengingproblemsandopportunitiesforfurtherconsideration.What?Howwell haveyouexploredyour chosencontext?Haveyouusedavarietyofeffectivemethods toexplorethecontext? Haveyouidentifiedabroadrangeof problems?How?Moodboards, concept maps, observations, interviews, surveys. Howyoustart your initial investigationis veryimportant. Thecontextual challengesarestartingpoints for your owninvestigations. Amoodboardis a quick collectionof imagesandtext thatcanhelpyoustarttogetafeel for andunderstandingof your context. It isimportant toanalysetheimagesyoufindby explaininghowthey might identifyapotential problemor need. Theyareuseful intheearly stages of a project andcangiveyoufeedbackonpotential ideasbeforeyouhaveinvestedtoomuchtime. Theycanalsobeusedtostart identifyingpossiblestakeholders. Anypotential project ideas shouldbeclearlyhighlighted. Aconcept mapis another useful tool for exploringagivencontext. Itallowsyoutostartrecordingyour initial thoughts. Althoughmainlytextual, imagescanbeusedtoreinforcecertainkey areas. Start withacentral ideaor theme(thecontext), thenbranchoutintokeythemes/areas. Thesebranches canbeexpandedfurther asyouexplorethecontext. Usearange of different colours togrouptogether relatedideasandtohighlightpotential projectideas. Aconcept mapcanalsobeusedtobeginidentifyingpossiblestakeholders. Figure 14.1 An exampleof aquickconcept mapusedtobeginexploringthecontextofsecurity
334Chapter 14Non-examassessment: IterativeDesignChallengeObservingpeopleintheir natural environmentprovidesagoodsenseofthedifficultiestheyexperiencewithinareal-worldcontext. Studyingwhatpeopledo-ratherthanwhattheysaytheydo- providesamorerealisticoverviewoftheiractions. Observationmayinvolveshadowingapersonover aperiodof timeastheyprogressthroughvariousactivitiesrelatedtoyourchosencontext. Specificproblemsshouldbeclearlyhighlightedandlinkedtopotentialprojectideas.Interviewingpeoplewithinacontextisanotherusefultoolforestablishingneedsandidentifyingpotential projectideas. Interviewingbasicallyconsistsofaskingaseriesofquestionsdirectlytoanindividual. Youcouldaskhowtheyfeelwhenusingaparticularproduct, howeasyit istouse, whethertheyfindusingitenjoyableorfrustrating.Youranalysis of their responsesisimportantandwill guideyourthinking.Anypotentialideasforsuitabledesignbriefsshouldbeclearlyhighlighted. Questionnairesandsurveysaresimpleandeffectivewaystogatherinformationfromabroadrangeof people. Responseratescanvarydependingonthemethodsyouuse.Aprintedquestionnairegivenoutbyhandcouldbetime-consumingandthereareseveralonlinealternativesthat canbeusedtoquicklygenerateandsendoutsurveyquestions.Theseshouldbetargetedatgroupsofpeoplerelevanttothecontextbeinginvestigated.Surveys areauseful methodtoestablishtheparticulartraitsandvaluesoflargenumbersof users relativelyquickly. Onlinesurveyscanbesentaslinksandpostedonrelevantsocialnetworkingsites. Responsesshouldhighlightpotentialprojectideas.Winestoragesystemsurvey1. Areyoumaleorfemale?MaleFemale2. Howoldareyou?Under 2021-40Over 403. Howoftendoyoudrinkwine?OftenRegularlySometimesNever 4.Howmanywinebottlesdoyouhaveinyourhouse?1-34-67ormore5.Howoftendoyouhavefriendsroundfordrinks?OftenRegularlySometimesNever6.Wheredoyoustoreyourwinenow?7.Isitimportanttoseethewinelabels?YesNoFigure14.2Examplesof howyoucouldpresentinterviewandsurveyanalysisRESEARCHACTIVITY1 Observe a classmateperformingaspecific task. Recordthe stages involved. Canyouidentify the problems they experience? Present your findings as anannotatedphotostoryboard. 2 Write a survey usinga suitableonline survey tool.
335NEAmarkingcriteriaMarkBand1MarkBand2MarkBand3MarkBand4Design brief Limited relevance tothe context and little or noidentification of a primary user or other stakeholders. Somerelevancetothecontext andidentificationof aprimary user and/or other stakeholders. Mostlyhasrelevancetothecontext, offeringscopeforchallengeandidentificationof aprimaryuserandotherstakeholders. Clearandfullrelevancetothecontext,offeringscopeforchallengeandafocusedidentificationofaprimaryuserandotherstakeholders.What?Have youset yourself achallengingdesignbrief?Isit relevanttothechosencontextualchallenge? Haveyouidentifiedaprimaryuser andarangeof otherstakeholders?How?Writtenwork, contextual images, links tocontextual investigation, conceptmaps. Throughout your initial investigations intothecontext, youshouldhavehighlightedanypotential project ideas. Youmust nowset yourself asuitablychallengingdesignbrief, whichmust respondtothecontext andmust giveyoutheopportunitytodevelopasuitablycreative andinnovativedesignsolution. It shouldoffer significantscopeforchallengeandconsider whothestakeholders arewhocouldhaveaninterestinyourpotential outcome. Figure 14.3 Example of arangeof designbriefsKEYPOINTWhen writinga designbrief, youmust avoiddesignfixation- t his canhappenwhenyoufocus onaproduct rather thanona problem. For example, 'Designalunchbox' immediately locks youintoacertainwayof thinking, whereas 'Designamethodof transportingapackedlunchfromhometoschool' opens upseveral designpossibilities. CLASSROOMDISCUSSIONYouhavebeenaskedto'Designachair'.lInwhatways,mightthis'designanobject'focusencouragedesignfixation?lHowcouldthis'designanobject'berewordedintoa'problemtobetackled'inordertoavoidpotentialdesignfixation?Discussthesequestionsingroups.
336Chapter 14Non-examassessment: IterativeDesignChallengeMarkBand1MarkBand2MarkBand3MarkBand4Investigations of user andstakeholder needs andwants and the outliningof stakeholder requirements (non-technical specification) Superficial considerationof primary user's needs andwants, withlittleor noconsiderationof other stakeholders. Fewor norequirements havebeenidentifiedandtheseareoutlinedwithlimitedscope tosupport thefuture designprocess. Somerelevant considerationof primaryuser'sneedsandwants, andsomeconsiderationof other stakeholders. Somerequirementsareidentified, whichoffer somescopetosupport thedesignprocess. Informedconsiderationofprimaryuser'sneedsandwants,andthoseofotherstakeholders.Arangeofrequirementsisidentifiedwithagoodlevelofdetail,whichoffersscopetosupportthedesignprocess.Fullandobjectiveconsiderationofprimaryuser'sneedsandwants,andthoseofotherstakeholders.Arangeofcomprehensiverequirementsisidentified,whichoffersscopetosupportthedesignprocess.What?Haveyougatheredinformationfromyourprimaryuserandotherstakeholders?Haveyouanalysedandpresentedthisinformationclearly?Haveyousummarisedtheirrequirements(intheformof anon-technical specification)?How?Interviews, surveys, observations. Onceyouhaveset yourself asuitablychallengingdesignbrief,itmaynowbeappropriatetoconduct someinvestigationsintotheneedsandwantsofyourprimaryuserandotherimportant stakeholders. Theaimof theseinvestigationsistogenerateadetailedlistoftheirrequirements. Thetechniquesdescribedearlierinthissectioncanonceagainbeemployed,onlythistimewithmorefocus. Yourstakeholderrequirementsmightwellchangeasyourproject progressesandyoutestyourprototypes. Makesureanychangesarehighlightedasyoudevelopyour ideas. DesignbriefI will designalightweight, double-functionedproductthatwill transport youquicklyaroundplaces. It will beaimedat peoplewhotravel aroundonadailybasiswithheavyluggage. However, theproduct will beaverygoodideafortouriststoo. It will beusedbypeoplewhowill betravellingaroundalot andusepublictransport most days. It will bemostlysoldinairports. It will alsobesoldinall publictransportstationssuchas railwaystationsandbusstations. PrimaryuserThisisRichard(35).HelivesinthemiddleofLondonwithhisfamily.Heisaverysuccessfulbusinessmanwhoearns£160,000peryear.Thecompanyheworksforisverygood.Helikestospendalmostallofhisfreetimetravellingtonewplaces.Richardhasworkedforthesamecompanyformanyyearsandisgettingtiredofhavingtorusheverydaytowork.Hegetsatrainatacertaintimeeverydaywithhissuitcase.Buthissuitcaseishardtogetthroughpeopleandisheavy.Heisalwaysalmostlateforworkduetopeoplenotmovingoutofthewayforhissuitcase.Hisjobrequiresasuitcasebecausehehashisownlaptopandhastotakealotofpaperworkhomeeverynight,whichcanbeheavy.Hedecidednottouseabagtocarryhislaptopandpaperworkbecausehedidn'twanttoputsomuchstrainonhisshoulder.Sohethoughtasuitcasewouldbebetter.Thesuitcaseisbetterforhishealthbutisverydifficulttocartaroundeveryday,especiallyonpublictransportinLondon,whereit'sverybusy.Hishobbiesaretravelling,swimminganddrawing.TheneedPublic transport is usedby hundreds every single day. Aeroplanes are usedby many too. If you have luggage withyou, whether you'rea businessman/womanandneedasmall casefor work, or are goingonholiday, thenmostly everyone has had difficulty gettingplaces quickly if you'r e in a rushandyouhaveluggage. Suitcases can be verybigsoit canbeastruggle gettingthemthroughcrowds of people. They can alsodelay you…If you'reinan airport and are late, thenrunningwithyour suitcase can be a pain, especially if theairport is busy. Carryinga suitcasecanbevery heavy andverylarge. If the user is carryingother travel bags as well as the suitcase thenit canbe very inconvenient. There are different types of suitcases that can make things easier, suchas lightweight ones, but none has beenmade that canhelpyou get around a lot morequicklyandeasily. Figure 14.4 Exampleof adesignbrief withidentificationofstakeholders
337NEAmarkingcriteriaFigure 14.5 An exampleof stakeholder requirementsSTRETCHACTIVITYToy store Toys RUs wants tointroduceanewrangeof children'scycles. 1 List as many stakeholders as youcanthinkof. 2 Dothey fit intocategories that might behelpful?(Usestickynotessoeachstakeholdercanbe sortedintopossiblecategories.) 3 Indicate howimportant youthinkeachstakeholder's'stake' is. (Theirlevelsofinfluenceandinterest will vary.)MarkBand1MarkBand2MarkBand3MarkBand4Investigations of existing products anddesign practices Little or noinformationor sources of inspirationareidentifiedtooffer support to designiterations andthinking. Someinformationand/ or sourcesof inspirationareidentified, whichmaynot alwaysberelevant but dooffer someinfluenceondesigniterationsandthinking. Agoodamountofrelevantinformationandsourcesofinspirationareidentifiedtoinfluencedesigniterationsandthinkingwhenrequiredthroughoutthedesignprocess. Comprehensiveandrelevantinformationandsourcesofinspirationareidentifiedtoinfluenceondesigniterationsandthinkingwhenrequiredthroughoutthedesignprocess.What?Have youexaminedother products whiledesigning?Haveyoustudiedanyotherdesignpractices? Is it clear howtheyhaveinfluencedyour designthinking?How?Product analysis, usingarecogniseddesignprinciplesuchasproductdisassemblyormimicry. It canbe useful at thestart of aproject toquicklyexplorewhatsolutionsarealreadyavailable. Hands-onproduct analysiscanhelpyouunderstandwhycertainproductsperformbetter thanothers. Whendoneat thestart of theprocess, thiscanhelpyouevaluate
338Chapter 14Non-examassessment: IterativeDesignChallengecompetingproducts. Youshouldselectareasonablerangeofproductstoanalyseanddecideonaset of criteriaagainstwhichtojudgethem. Puteachproductthroughaseriesoftypical tasks. If yourecordhoweachproductperformsyouwillbeabletoevaluateeachinturn. Youcouldaskquestionssuchas'Howeasyisittouse?', 'Howreliableisit?','Howmuchdoes it cost?' If youcansummarisethesefindings, thiscanbeusedtogeneratealistofissuesor of desirablefunctionsthatyouwill needtoincludeinyourproduct.PRODUCT DESCRIPTION FUNCTION MATERIALS MANUFACTURINGERGONOMICSAESTHETICSCOSTOVERALLCONCLUSIONDesk tidy number 1 This is another desk tidy, it is designed to hold variety of stationary also note pads and sticky notes etc. It can hold more office desk items and it is easy to access these items. However, it is slightly obtrusive on the desk. It is made of plastic, made in many colours and is lightweight. It is injectionmoulded, requireda mouldand is not verycheapor cost efficient to make. It canholdalarger varietyof items, theyareeasier toget out. However, not easytoholdandmovearound. It looksmoreaestheticallypleasingandisnottooobtrusive. Thecostisveryreasonableforwhatitisandhowmuchitholdscomparedtootherproducts.Inconclusion,Ithinkthisisabetterproductasitcanholdmoreitems,itisnottooobtrusiveandcaneasilyaccessitems.Althoughtheproductisnotverycostefficientandcanbeexpensivetomanufactureandtransport.Bathroom tidy This is a bathroom tidy, it is designed to hold bathroom items like a face towel, toothpaste, toothbrushes. It holds fewitems and is not designed to hold much else. It does what it is supposed to but not a lot This is made of plastic in a similar way and more intricate so it takes more time and is more difficult. It will be made out of plastic and injectionmoulded, it will not be a cheapmouldandnot be very profitableat first for manufacturers. It cannot holdmanyitems, it is not easytoholdandcannot bemovedas it is screwedtothewall. It doesnotlookaestheticallypleasingandisobtrusiveinabathroomandlookstochildishandnotverymodern. Itcosts£9foroneofthesewhichisfairlyexpensiveandtoomuchforsuchasimpleproductthatonlyhasonepurpose. Inconclusion,Ithinkthisisaworseproductasitisnotveryappealing,obtrusiveandlookstackyinamodernbathroom.Itcannotbeeasilymoved.Desk tidy number 2 (rotational) This is another desk tidy, it is designed to hold a variety of stationary It is holds a lot of items and it can rotate to make items easily accessible. It is not too obtrusive on the desk but can be difficult to get items out. It is made out of plastic and has a mechanism. This is fairly lightweight, but heavier than my product. It uses a rotarymechanism, plastic, so it will more difficult and expensivetomanufacture. It is not easytoholdandmovearoundanddoesnot holdavarietyof items. It is alsoverydifficult toget small itemsout of thesmaller compartments. It is moreaestheticallypleasingthanmyproduct asit rotatesandlooksmoresleekandprofessional. Itcostsarouns£8whicchisrelativelycheapforwhatitdoesasthereisamechanism.Inconclusion,Ithinkthisisabetterproductasitcanrotateina360degerecircleandcaneasilyaccesstheproducts.Althoughthesmallercompartmentsaremoredifficulttogetitemsoutofastheyaretoosmall.Scissors holder This is a scissors holder, it is designed to hold many scissors that protects the blade with holes the same size in the peice of wood. It does what is suppose to, it protects the blades fromcutting people. It is not multifunctional. It is made out of wood and has a large number of holes drilled into it all the same depth. It is lightweight but can give you splinters. It is very easy andcheapto manufacture as it is just machinebasedjobto create these. It is not easytoholdor movearoundandcannot beusedfor other items. It is notveryaestheticallypleasingasit isjustablockof woodbut itdoes it jobandisnotobtrusive. Itisverycheapandeasytomanufactureandtransportsomakesahighprofit.Inconclusion,Ithinkthisisaworseproductasitcannotholdanythingbutscissorsandisnotaestheticallypleasing,itcanalsoharmtheuserbygivingthemsplinters.Cutlery tray This is a kitchen utensil tody, it is designed to cutlery and utensils found in the kitchen to help keep draws tidy and organised. It organises the kitchen cutlery and is not obtrusive and easy to move around. It is made out of wood, depending howfilled it gets it can get heavy and difficult to move. It is made by machinery andis easy to make as it is a simple mould. It is not veryeasytomovearoundandis not ergonomicallydesignedbut is not tooobtrusive. It is aestheticallypleasingaslongasthewoodisfinishedwell. It doesitsjob. Itisamoderatepriceforwhatitis,itlookappealingandiseasytomanufacture.Incolclusion,Ithinkthisisabetterproductasitisaestheticallypleasing,easytomanufacture,notverydifficulytotransportandcanbemultifunctional.ANALYSISOFOTHERSIMILARPRODUCTSThe stars mean howgood the product is compared to the desk tidy. Blue is the same, red is worse and green is better. The smiley faces showif the product is overall better (green) or worse (red). Figure 14.6 Anexampleof comparativeproduct analysisIt is alsouseful toseekoutsourcesof inspirationwhileyouaredesigning.Existingproductscanhelpinspireyour ownideasandprovideclarityinyourowndesignthinkingifanaspectof your designissimilar. Inspirationmayhoweveralsocomefromvisualsources,suchasnature, fromhistorical designmovementsorthinkingwhatmightexistfurtherinthefuture.
339NEAmarkingcriteriaFigure 14.7 An exampleof student workinspiredbyexistingproductsduringdevelopmentProduct disassemblycanbeusedtoget abetter understandingof howaproducthasbeendesignedandmanufactured. It is doneinthreestages: lTakingtheproduct apart. lRecordingthroughphotographs andsketcheshowthepartsgotogetherandhowtheyrelate toeachother. lEvaluatingthedisassembledproduct. There is moreondisassemblyinChapter 1. Mimicryis theprocess of copyingpre-existingsolutionstoproblems. Thiscouldbecopyingthe way things look, thewaythings act or thewaythingswork. Yourinspirationmaycomefroma widevariety of sourcematerials andshouldbebuiltintoyourdevelopment. STRETCHACTIVITYFind out what inspiredthefollowingproducts: lVelcrolTheShinkansenbullet trainlTheFastskinswimsuit.MarkBand1MarkBand2MarkBand3MarkBand4Exploration of materials andpossibletechnical requirements Superficial considerationof materials and/ or possible technical requirements. Somerelevant considerationof materialsandpossibletechnical requirements. Informedconsiderationof materialsandpossibletechnical requirementswhenrequiredthroughoutthedesignprocess.Fullandobjectiveconsiderationofmaterialsandpossibletechnicalrequirementswhenrequiredthroughoutthedesignprocess.What?Have youthought about materials andtheir workingpropertiesthroughoutthedesignprocess? Haveyoulookedat specifictechnical requirements(suchasfinishing, sustainability, flexibility, toughness, etc.)?
340Chapter 14Non-examassessment: IterativeDesignChallengeHow?Gatheringdata, materialstesting, componenttesting. As youdevelopideasandtestyourprototypes, youshouldexploresuitablematerialstofurther clarifyyour designthinkingandtoestablishanytechnicalrequirementsthatmayberequiredof your final prototype(s). Thiscouldincludespecificteststoestablishtheworkingpropertiesof potential materials. Itcouldalsoincludetestingofspecificcomponentsthatcouldbeincludedinthefinal prototype(s). Figure 14.8 Anexampleof materials testingduringdevelopmenttoestablishtechnicalrequirementssuchasflexibilityRESEARCHACTIVITYDesignandmakeatest rigcapableoftestingsamplesofdifferentmaterialsrelevanttoyourNEAactivity. Youmight test for toughness, durability,flexibility,resistancetotearing,etc.
341NEAmarkingcriteriaMarkBand1MarkBand2MarkBand3MarkBand4Technical specificationInaccurate, outlines basic details and/or is incomplete, makingit difficult for athirdparty tounderstand. Generallyaccurate, outlinesdetailsthat communicatesomerequirementstoathirdparty. Goodlevelsofaccuracy,outlinesdetailsthatcommunicatemostrequirementstoathirdparty. Highlevelsofaccuracy,outlinesdetailsthatclearlycommunicateallrequirementstoathirdparty.What?Have youprovidedspecifictechnical information?Areyour workingdrawingsaccurate?Haveyouspecifiedreal-worldmaterials? Doyouhaveacuttinglist?Haveyoudocumentedyourfinal design/prototype(s) features? How?Appropriateworkingorthographic, andexplodeddrawings, CADdrawings, partslist, features list. Before youmakeyour final prototype(s) youmust present atechnical specificationthatoutlines thedetails of your designsolutiontoathirdparty. Thesearethedetailsrequiredforif the designsolutionweremanufactured, NOTfor makingthefinal prototype(s). Relevant, accurate workingdrawingswill beyour priority. ThesecouldbedrawnusingasuitableCADsoftwarepackage. Figure 14.9 An exampleof asuitabletechnical specificationforabikelock/groundanchorconcept
342Chapter 14Non-examassessment: IterativeDesignChallengeIf your designsolutionhasaparticulardetail, featureorfunctionthatmayneedclaritytoexplainit toathirdparty, thenthisshouldalsobeexplained. Thismightinvolvetheuseofanexplodedview, detailsof anybought-incomponentsrequired,acircuitdiagramoracuttinglist, for example. Cuttinglistandbought-inmaterialsCuttinglist Number Nameof part NumberofSizes(mm)Material1Main frame2Length-800mmHeight-85upto170mmSheetaluminium(2mm)2Aluminiumspacers 2Height-19mmWidth-19mmLength-500mmSheetaluminium(2mm)3 Handles 2Length-1200mmWidth-19mmThickness-1mmThin-walled(1mm)Box-sectionsteel4 Bottomsupport panel that batterysits on1Length-400mmHeight-450mmSheetaluminium(2mm)5 Joiningcylinder that connects brushes toframe2Length-50mmDiameter-20mmAluminiumrod6 Ball ramp1Length-500mmWidth-400mm3mmacrylic7 Hooks that holdbasket inplaceonmainpanel 2Height-200mmWidth-2mmLength-50mmSheetaluminium(2mm)8 Battery cover 1Length-420mmWidth-3mm3mmacrylic9Aluminiumhooks that holdbasket onhandles 4Height-40mmWidth-50mmThickness-2mmSheetaluminium(2mm)Bought-inmaterialsNumber Nameof part NumberofSizes(mm)Material1 Door brush2Length-35mmWidth-2mmNylonbrush2 12v motor 1Length-90mmWidth-50mm3 Ball basket 1Length-Width-Height-GalvanisedsteelmeshFigure 14.10 Anexampleof acuttinglist for atennisball collector
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344Chapter 14Non-examassessment: IterativeDesignChallengeFigure 14.11Anexampleof collaborationtogenerateinitial ideasSTRETCHACTIVITYAs anexampleof anideationtask, takeasheetwith30roughlydrawncircles.Transformeachcircleintoarecognisableobject, suchasawheel,aball,aplanet,etc.Transformall30circles intwominutes. Youcandrawoutsideofthelines.Designisathree-dimensional subjectanditisessentialthatyoumodelyourideasphysicallyat theearliest opportunitysothatyoucantestthemintherealworld.Sketchmodelsarefull-sizeor scalemodelsthatcaptureyourideasastheyoccur.Theytendtousereadilyavailablematerialsdependingontheideayouhaveinmind. Youcouldusecard,paper,foam, binbags- whatever isathandandcanbemanipulatedquickly.Sketchmodelscanbeusedtomakeaquickevaluationofyouridea'sergonomics,aesthetics,functionalityandusability. Theycanbeusedtocommunicateyourideastoyourstakeholdersandtogaugetheir reactions.