Chapter2WorkStudyIntroductiontoWorkStudyUnit1MethodStudyUnit2TimestudyUnit3TimeMeasurementMethodsUnit4WorkSamplingIntroductiontoWorkStudyUnit1MethodsStudyTheDefinitionandContentofMethodsStudy

StepsofMethodsStudy

TheClassificationsofMethodsStudyPrinciplesofMotionEconomy

1.TheDefinitionandContentofMethodsStudy

Wecandefinemethodstudyasthesystematicrecordingandcriticalexaminationofwaysofdoingthingsinordertomakeimprovements.FromtheFigure2-1,wecanseethatthemaincontentsofthemethodstudyincludeprocessanalysis,operationanalysisandmotionanalysis.2.StepsofMethodsStudy

Selecting—theworktobestudied&boundariestobedefined.Recording—therelevantfactsaboutthejobtoberecorded.Examininganddeveloping—thewaythejobtobeperformed.SixquestioningtechniquesAnalysiswith“ECRS”principles3.ClassificationsofMethodsStudyTherearethreemainclassesofmethodsstudy:processanalysisoperationanalysismotionanalysis.ProcessAnalysisProcessanalysisisoneofthemaincontentsofmethodsstudy,bywhichresearcherscancompletelyobserveandrecordthewholeproductionprocessesandcarryoutintegratedanalysisfromamacroscopicviewpoint.ProcessAnalysisActivitysymbolsExplainExampleOperationIndicatesthemainstepsinaprocess,methodorprocedure.Usuallythepart,materialorproductconcernedismodifiedorchangedduringtheoperation.Drivenail,drillholeandtypeletter,etcTransportIndicatesthemovementofworkers,materialsorequipmentfromplacetoplace.Movematerialbytruck,elevatororcarrying

InspectionIndicatesaninspectionforqualityand/oracheckforquantity.Examinematerialforqualityorquantity

TemporarystorageordelayIndicatesadelayinthesequenceofevents:forexample,workwaitingbetweenconsecutiveoperations,oranyobjectlaidasidetemporarilywithoutrecorduntilrequired.Materialintruckoronflooratbenchwaitingtobeprocessed,EmployeewaitingforelevatorStorageIndicatesacontrolledstorageinwhichmaterialisreceivedintoofissuedfromastoreundersomeformofauthorization,ofanitemisretainedforreferencepurposes.Bulkstorageofrawmaterial,finishedproductinwarehouseProcessAnalysisProcessAnalysisFlowDiagramAdiagramormodel,substantiallytoscale,showsthelocationofspecificactivitiescarriedoutandtheroutesfollowedbyworkers,materialsorequipmentintheirexecution.Intheflowdiagram,layoutofworkareaandmovementsarerecorded,andtheexcessivedistances,convolutedroutesandnon-value-addedactivitiesareindicated.Thentherearrangementofworkareacanbedonetoreducethetravelingdistancesandnon-value-addedactivities.ProcessAnalysisStringDiagramThestringdiagramisascaleplanormodelonwhichathreadisusedtotraceandmeasurethepathofworker,materialorequipmentduringaspecifiedsequenceofevents．Inthestringdiagram,thedistancesmovedbyworkers,materialorequipmentarerecorded,andheexcessivedistances,convolutedroutesareindicated．Thentherearrangementofworkareacanbedonetoreducethetravelingdistance．ProcessAnalysisManagementTransactionAnalysisWiththedeepeningoftheapplicationinindustrialengineeringmethods,theprocessanalysiscanalsobeusedinthedailyworkontheaffairsofbusiness,managementaspectstoimproveproductionefficiency,reducecost,calledmanagementtransactionanalysis,andusingmanagementtransactionflowdiagramasanalyticaltoolsforrecordingandanalysis．Withthemanagementtransactionanalysiscanmaketheprocessofmanagementscientific,managementworkstandardandautomation．ProcessAnalysisManagementTransactionAnalysisOperationAnalysisPrimaryDemandofOperationAnalysisMan-machineOperationAnalysisGangprocessanalysisTwo-handProcessAnalysisOperationAnalysisPrimaryDemandofOperationAnalysis(1)Reducingthequantitiesofoperationstothelowest,arrangingtheprocesseswithreasonablesequenceandmakingeveryoperationeasiestbyusingtheprinciplesofECRS.(2)Exertingthefunctionoftwohands,balancingtheburthenoftwohandsandavoidingholdingaworkpieceforalongtimeandmakinguseoftoolstotheutmostextent.OperationAnalysisPrimaryDemandofOperationAnalysis(3)Lettingthemachinesdothemostwork.(4)Reducingtheoperationalcyclesandfrequencies,decreasingthetransportationandtransfertimesofmaterialsandcuttingdownthedistanceoftransportationandmoving,makingthemovingandtransportationeasily.OperationAnalysisPrimaryDemandofOperationAnalysis(5)Eliminatingtheunreasonablespaceandgivingtheworkerenoughworkspace.(6)Eliminatingtheunreasonableidlenesstimeandrealizingthesynchronizationworkofthemachineandoperator.OperationAnalysisMan-machineOperationAnalysisTheman-machineoperationanalysisisusedtoinvestigate,analyzetherelationshipofworkerandmachineintheoperationcycle.Thesefactscanleadtoafullerutilizationofbothworkerandmachinetime,andabetterbalanceoftheworkcycle.OperationAnalysisMan-machineOperationAnalysisMan-machineoperationanalysisusesthemanandmachinecharttoshowtheexacttimerelationshipbetweentheworkingcycleoftheoperatorandtheoperatingcycleofthemachine.Sothroughanalyzingthechartwecangetnewmethodstoreducetheidletimeofworkerandmachineandtoenhancetheefficiencyoftheman-machinesystem.Example2:Oneworkeroperatestwosemi-automaticlathes,theprocess:loadingmaterial0.5min;turning1min;returningmaterial0.25min,twomachinesprocessingthesameparts,automaticallyturningandstopping,thetimeofpeoplecomingfromonemachinetoanotherneeds6seconds．Trytodrawaprogramchartofthebestutilizationofthisman-machine．OperationAnalysisMan-machineOperationAnalysisThechartiscomposedoftwoparts.Onepartcanbecalledthecharttitlesuchasman-machineprocesschartandotherinformationincludingpartnumber,drawingnumber,operationdescription,presentorproposedmethod,dateandnameoftheresearcherinthetopofthechart.Andtheotherpartcanbedividedintotwosides.Theleftsideshowstheoperationsandtimefortheworkerandtherightshowstheworkingtimeandtheidletimeofthemachineormachines.OperationAnalysisGangprocessanalysisIntheworkplace,there’realwaystwoormorethantwoworkersoperatingwithonemachineorjob,andthenthisoperationiscalledgangprocessanalysis.Thegangprocesschartshowstheexactrelationshipbetweentheidleandoperatingcycleofthemachineandtheidleandoperatingtimepercycleoftheworkerswhoservesthatmachine.Thischartpresentsthepossibilitiesforimprovementbyreducingbothidleoperatorandmachinetime.OperationAnalysisTwo-handProcessAnalysisIntheworkplace,workers’twohandsfinishmanyconcretemotions.Recordingandstudyingthesemotionsoftwohandsarecalledtwo-handprocessanalysis.Thetwo-handprocesschartisaprocesschartinwhichthemotionsofaworker’shands(orlimbs)arerecordedinanoperatingcycletoshowtheexactrelationshipbetweentwohands’movement.Thepurposeofthetwo-handprocesschartistopresentagivenoperationinsufficientdetailthattheoperationcanbeanalyzedandimproved.Figure2-5

Two-HandOperationChart(Updated)MotionAnalysisMotionanalysisregardsoneactivityastargettoanalyzethemotionindetails.Themainprincipleofmotionanalysisistoanalyze,compareandresearchthemotionsoftheoperator’shands,eyesandtheotherpartofbody,andthentoeliminatetheotiosemotions,rearrangethenecessaryandeffectivemotionstoastandardsetofmotionswithreasonabletoolsandlayout.MotionAnalysisThrebligsF．B.Gilbreth,thecreatorofmotionstudy,dividedtheoperationsofmaninto17smallestunits—threbligs(Table2-3).MotionAnalysisClassPivotBodymembermoved1KnuckleFingers2WristHandandfingers3ElbowForearm,handandfingers4ShoulderUpperarm,forearm,handandfingers5TrunkTorso,upperarm,forearm,handandfingers4.PrinciplesofMotionEconomy

IPrinciplesrelatedtotheuseofhumanbodyIIPrinciplesrelatedtothearrangementofworkplaceⅢPrinciplesrelatedtotoolsandequipment

Unit2Timestudy

Whatistimestudy?ThemethodsofdeterminingtimestandardsThesignificanceandpurposesoftimestudyRequirementsoftimestudyToolsoftimestudyProcessofTimeStudyWhatistimestudy

TimestudyisoneoftheworkmeasurementtechniquesTimestudyisastructuredprocessofdirectlyobservingandmeasuringhumanworkinordertoestablishthetimerequiredforcompletionoftheworkbyaqualifiedworkerwhenworkingatadefinedlevelofperformanceThemethodsofdeterminingtimestandardsEstimateshistoricalrecordsworkmeasurementproceduresThesignificanceoftimestudyAccuratelyestablishedtimestandardshelpincreasetheefficiencyoftheequipmentandtheoperatingpersonnelSoundstandardswillmeanthedifferencebetweenthesuccessorfailureofabusinessPurposesoftimestudy

Todeterminethetimestandardsandcontrollaborcosts.Tosetupthestandardtimesandtakethemasthebaseofpayroll.Todecidetheworkscheduleandworkplan.Todeterminethestandardcostandtakeitastheevidenceofstandardbudget.Todeterminetheutilizationefficiencyofmachinesandtosolvetheproblemsonbalanceofproductionlines.RequirementsoftimestudyTheoperatorshouldbethoroughlyacquaintedwiththenewtechniquebeforetheoperationisstudiedthemethodmustbestandardizedatallpointswhereitistobeused,beforethestudybeginsResearchersoftimestudyshouldtellallrelatedpeoplethatthejobistobestudied……ToolsoftimestudyStopwatchADecimalMinuteWatchAnElectronicStopwatchAComputer-assistedElectronicStopwatchToolsoftimestudyVideotapeCamerasTimeStudyBoardTimeStudyFormsProcessofTimeStudy

SelectingtheoperatorAnalyzingthejobBreakingitdownintoelementsRecordingtheelapsedelementalvaluesPerformanceratingtheoperatorAssigningappropriateallowancesThestandardtimeDefinition:thetimerequiredforafullyqualified,trainedoperator,workingatastandardpaceandexertingaverageeffortThestandardtimeiscalculatedbythefollowingequations:NT=OT×R/100ST=NT+NT×Allowance=NT×(1+Allowance)

Unit3

TimeMeasurementMethods

DirectTimeStudyamethodofusingtimemeasurementtodeterminethestandardtime.Whenrecordingthewatchreadings,noteonlythenecessarydigitsandomitthedecimalpoint,thusgivingasmuchtimeaspossibletoobservingtheperformanceoftheoperatorTwotechniquesusedforrecordingtheelementaltimes1.Thecontinuoustimingmethod

PresentsacompleterecordoftheentireobservationperiodBebetteradaptedtomeasuringandrecordingveryshortelementsMoreclericalworkisinvolvedTwotechniquesusedforrecordingtheelementaltimes2.ThesnapbacktechniqueNoclericaltimeisneededDelaysarenotrecordedEncouragestheremovalofindividualelementsfromtheoperationComparisonofTwoMethodsSometimestudyresearchersusebothmethods,believingthatstudiesofpredominantlylongelementsaremoreadaptedtosnapbackreadings,whileshort-cyclestudiesarebettersuitedtothecontinuousmethodCyclesinStudyDetermininghowmanycyclestostudytoarriveatanequitablestandardisasubjectthathascausedconsiderablediscussionTheactivityofthejobanditscycletimedirectlyinfluencesthenumberofcyclesthatcanbestudiedfromaneconomicstandpointCyclesinStudyAmoreaccuratenumbercanbeestablishedusingstatisticmethods．Sincetimestudyisasamplingprocedure,theobservationscanbeassumedtobedistributednormallyaboutanunknownpopulationmeanwithanunknownvariance．Usingthefollowingequationcancalculatethenumberofcycleswhenthemeanerrorequalsto±5%andreliabilityequalsto95%accordingtotheprincipleofstatistics:PerformanceRatingThebasicprincipleofperformanceratingistoadjustthemeanobservedtime(OT)foreachelementperformedduringthestudytothenormaltime(NT)thatwouldberequiredbythequalifiedoperatortoperformthesameworkAddingAllowancesNooperatorcanmaintainastandardpaceeveryminuteoftheworkingday.AllowancesmustbeaddedtothestandardtimeTheallowanceistypicallygivenasafractionofnormaltimeandisusedasamultiplierequalto1+allowanceST=NT+NT×Allowance=NT×(1+Allowance)ST=NT/(1-Allowance)Anexampletocomputethe

standardtimeInaunit,theobservedtimeis0.8min.,R=110,allowance=5%NT=OT×R/100=0.8×110/100=0.88min.ST=NT×(1+Allowance)=0.88×(1+5%)=0.924min.IntroductiontoPredeterminedTimeSystemsFrankB.Gilbrethistheinventorofmotionstudy.HeclassifiedthebasicmotionsintowhathecalledTherbligsthatisthebaseofpredeterminedtimesystems.Since1945,therehasbeenagrowinginterestintheuseofthebasicmotiontimeasamethodestablishingratesquicklyandaccuratelywithoutusingthedirecttimestudy.TheCharacteristicsofPredeterminedTimeSystemsDeterminethestandardtimeinadvanceandobjectivelyinworkmeasurementswithouttheperformancerating.Recordtheoperationalwaysindetailsandobtaintheelapsedtimeofeachbasicmotion.Determinethestandardtimebeforetheworkbeingdonewithoutusingthestopwatch.Whentheoperationalwaysupdate,thestandardtimevaluesmustbealtered.However,thebaseofsettingupthestandardtime,predeterminedtimesystems,remainthesame.Itisthebestwaytobalancetheproductionlineswithpredeterminedtimesystems.TheMethodofWorkFactorsThemethodofworkfactorsisthebasiconeofpredeterminedtimesystems.Itdeterminesworktimebasedonthemotionfeaturesandconditionsthroughthespecifiedtimevaluesinadvance.Fourvariablesinflectingmotiontimewhenmotion,whichportionofbodyisworkingthemotiondistancethegravitationorresistanceovercomewhenmotionadjustmentbyhumanbeings(includingstop,guidanceofdirection,speciallycareof,anddirectionchange)MethodsTimeMeasurement

(MTM)Definition:

Aprocedurewhichanalyzesanymanualoperationormethodintothebasicmotionsrequiredtoperformit,andassignseachmotionapre-determinedtimestandardwhichisdeterminedbythenatureofthemotionandtheconditionsunderwhichitismadeTheSystemof

MethodsTimeMeasurementInMTM,MTM-1isthebasicmethod.MTM-1dataaretheresultofframe-by-frameanalysesofmotion-picturefilmsofdiversifiedareasofwork.ThedatatakenfromthevariousfilmsareratedbytheWestinghousetechniques,tabulated,andanalyzedtodeterminethedegreeofdifficultycausedbyvariablecharacteristics.MTM-1,MTM-2,MTM-3,MTM-C,MTM-V,MTM-M,MTM-TE,andsoforthconstitutedthesystemofMTMModularArrangementofPredeterminedMotionTimeStandard(MOD)MODisthelatestdevelopmentofpredeterminedtimesystems.MODclassifiesoperationalmotionsintoupperlimbbasicmotionsandothermotions.UsingMODneitherneedsmeasuringtimenortheperformancerate.ModularArrangementofPredeterminedMotionTimeStandard(MOD)ApplicationsofMODThereisacompany,whichproducesthevariousbushings.Theinternaldiameterofthebushingsmustbecontrolledtomeethigheraccuracy.Therefore,theproducedbushingsmustbemeasuredbythepluggauge(Figure2-9).Therearefourupdatingmeasurementmethods(Figure2-10).TrytodeterminetheoperationtimeofmeasuringtheinternaldiameterofthebushingsbyMOD.Unit4WorkSamplingWorksamplingisalsocalledtheinstantobservationmethod.Itgetstherequiredresultsthroughobservinginstantly,systematicanalysisanddealingwiththeobservationdatatotheoperatorduringalongerperiod.Stopwatchtimestudy

Thereare18minutesvacancyand42minutesworking.Workratio=worktime/totalobservationtime=42/60=70%Vacancyratio=vacancytime/totalobservationtime=18/60=30%TheResultofObservationRecordApplicationsofworksamplingWorksamplingcanbeusedinthefollowingtwosituations:WorkimprovementSetuptimestandardStandardTime=(Totalobservationtime×workratio×averageperformanceindex)/Totalobservationtime+allowanceAverageperformanceindex（%）=thenormaltimespentbytheproduct/thepracticaltimespentbytheproductAccuracyandObservationsBasedonthetheoryofprobability,thephenomenadisposedbyworksamplingsubmittothenormaldistributionapproximatelyasshowninFigure2-15.AccuracyandObservationsBasedontheprinciplesofstatistics,thestandarddeviationofthebinomialdistributionequalsthefollowingequationunderthecertainconditions:AccuracyandObservationsSamplingPurposesandtheStandardsoftheAbsoluteAccuracyTheSamplingPurposesTheStandardsoftheAbsoluteAccuracySurveyofbreakdown±(3.6-4.5)%Workimprovement±(2.4-3.5)%Decisionofthetimeratios±(1.2-1.4)%Settingupthestandardtime±(1.6-2.4)%AccuracyandObservationsForexample,thereisaworkgroup,whichhas10workers,theconfidencesetsupto95%,therelativeaccuracyis5%,theworkratiois70%,20observationsareplannedeveryday,askforhowmanydaysarerequiredtodoobservation.

TheactualobservationsK=n/X=686/10=68.6≈69obseroationsTheobservationdays=69/20≈4daysTheMethodofWorkSamplingStep1PlanningthesurveypurposesandscopeStep2ClassificationofthesurveyitemsStep3DecisionofobservedmethodsStep4DesignofthesurveytableStep5ExplanationofsurveypurposesTheMethodofWorkSamplingStep6Pre-observationanddecisionoftheobservedtimesStep7FormalobservationsStep8Datadisposal(1)Removingtheabnormaldata(2)VerifyingobservationsandaccuracyStep9MakingconclusionsTheMethodofWorkSamplingTheRandomlySampling[Example1]Theworksamplingisdoneontheshopfloorofthefactory.5daysareobservedand20observationsarecarriedouteveryday.Theworkingtimeonthejobisafull8-hourday(onehourrestfrom12:00to13:00).Askfortheobservedtimetableeveryday.TheMethodofWorkSamplingTheRandomlySampling[Example1]1.Arrangingrandomnumbersintwo-digitalfigures.Forthissample,thereare15selections,therandomfigureslistshowsasfollows:21,94,62,35,06,64,96,40,85,77,88,63,52,27,752.Remainthefiguresthatarelessthan50andtheresiduessubtract50.Weget:21,44,12,35,06,14,46,40,35,27,38,13,02,27,25TheMethodofWorkSamplingTheRandomlySampling[Example1]3.Removethefiguresthatmorethan30.Weget:21,12,06,14,27,13,02,27,254.Determinetheobservedtimetableonthefirstday.Atfirst,wewanttodecidethefirsttimetableofobservationonthefirstday.Thefirstnumberis21.Becauseoftheworkingtimeisat8:00,thefirsttimetableofobservationisat8:21.Thenwewanttodecidetheintervalsofobservation.Theinterval=(theworkingtime-thefirsttimetableofobservation)/theobservations=(480-21)/20≈23TheMethodofWorkSamplingTheRandomlySampling[Example1]Inthisway,wecangetthetimetableofobservationonthesecondday8:21+0:23=8:44Thetimetableofobservationonthethirdday8:44+0:23=9:075.Decidethetimetableofobservationonthesecondday.Atfirst,wewanttodecidethefirsttimetableofobservationonthesecondday.Thesecondnumberis12.Becauseoftheworkingtimeisat8:00,thefirsttimetableofobservationisat8:12.Basedontheintervalof23,wecangetthesecondtimetableofobservationis8:35,thethirdtimetableofobservationis8:58,andsoon.TheMethodofWorkSamplingTheRandomlySampling[Example1]6.Decidethetimetablesofobservationonthethirddaythroughthefifthday.Thecalculationmethodisthesame.ThecalculatedresultsareshownintheTable2-12.TheMethodofWorkSamplingTheLayeredSampling[Example2]Table2-13istheworkingscheduleofoneshiftontheshopflooratafactory.Trytodecidetheobservationsandtimet