運營管理chap004純英文

Chapter4ProcessAnalysisDesign&ProductionProcessdesignandproduct/servicedesignareinterrelated.Processandproduct/servicedesignmustsatisfycustomersProcessAnalysisTermsProcess:IsanypartofanorganizationthattakesinputsandtransformsthemintooutputsCycleTime:IstheaveragesuccessivetimebetweencompletionsofsuccessiveunitsUtilization:IstheratioofthetimethataresourceisactuallyactivatedrelativetothetimethatitisavailableforuseMechanicalmachine($12/hr*24hr*0.5)=$144/dayElectronicmachine($18/hr*24hr*0.5)=$216/dayProcessFlowcharting

Defined

ProcessflowchartingistheuseofadiagramtopresentthemajorelementsofaprocessThebasicelementscanincludetasksoroperations,flowsofmaterialsorcustomers,decisionpoints,andstorageareasorqueuesItisanidealmethodologybywhichtobeginanalyzingaprocessFlowchart

Symbols

TasksoroperationsExamples:Givinganadmissiontickettoacustomer,installingaengineinacar,etc.DecisionPointsExamples:Howmuchchangeshouldbegiventoacustomer,whichwrenchshouldbeused,etc.PurposeandExamples

Examples:Sheds,linesofpeoplewaitingforaservice,etc.Examples:Customersmovingtoaseat,mechanicgettingatool,etc.StorageareasorqueuesFlowsofmaterialsorcustomersFlowchart

Symbols

PurposeandExamples

Example:FlowchartofStudentGoingtoSchool

YesNoGoofoffGotoschooltoday?WalktoclassDrivetoschoolTypesofProcesses

Single-stageProcess

Stage1Stage1Stage2Stage3Multi-stageProcess

TypesofProcesses(Continued)Stage1Stage2BufferMulti-stageProcesswithBufferAbufferreferstoastorageareabetweenstageswheretheoutputofastageisplacedpriortobeingusedinadownstreamstageOtherProcessTerminologyBlockingOccurswhentheactivitiesinastagemuststopbecausethereisnoplacetodeposittheitemjustcompletedIfthereisnoroomforanemployeetoplaceaunitofworkdown,theemployeewillholdontoitnotabletocontinueworkingonthenextunitStarvingOccurswhentheactivitiesinastagemuststopbecausethereisnoworkIfanemployeeiswaitingataworkstationandnoworkiscomingtotheemployeetoprocess,theemployeewillremainidleuntilthenextunitofworkcomesOtherProcessTerminology(Continued)BottleneckOccurswhenthelimitedcapacityofaprocesscausesworktopileuporbecomeunevenlydistributedintheflowofaprocessIfanemployeeworkstooslowinamulti-stageprocess,workwillbegintopileupinfrontofthatemployee.Inthisiscasetheemployeerepresentsthelimitedcapacitycausingthebottleneck.PacingReferstothefixedtimingofthemovementofitemsthroughtheprocessOtherTypesofProcessesMake-to-orderOnlyactivatedinresponsetoanactualorderBothwork-in-processandfinishedgoodsinventorykepttoaminimumMake-to-stockProcessactivatedtomeetexpectedorforecastdemandCustomerordersareservedfromtargetstockinglevelMeasuringprocessperformanceProductivityisaratioofoutputtoinput.Dollarvalueofoutput/costofalltheinputsEfficiencyisaratiooftheactualoutputofaprocessrelativetosomestandards.Example:30box/mins(plan)36box/mins(actual),theefficiencyisimproved120percent(36/30).MeasuringprocessperformanceRuntimeisthetimerequiredtoproduceabatchofparts.Setuptimeisthetimerequiredtoprepareamachinetomakeaparticularitem.Operationtimeisthesumofthesetupandruntimeforabatchofpartsthatarerunonamachine.MeasuringprocessperformanceThroughputtimeincludesthetimethattheunitspendsactuallybeingworkedontogetherwiththetimespentwaitinginaqueue.Example:considerapacedassemblylinethathassixstations,andrunswithacycletimeof30seconds.Ifthestationarelocatedonerightafteranotherandevery30secondspartsmovefromonestationtothenext,thenthethroughputtimeisthreeminutes(30seconds*6stations/60secondsperminute).Thethroughputrateistheoutputratethattheprocessisexpectedtoproduceoveraperiodoftime.Thethroughputrateoftheassemblylineis120unitsperhour(60mins/hr*60seconds/mins/30seconds/unit).ProcessPerformanceMetricsOperationtime=Setuptime+

Runtime

Throughputtime=Averagetimeforaunitto

movethroughthesystemVelocity=Throughputtime

Value-addedtimeProcessPerformanceMetrics(Continued)Cycletime=Averagetimebetween

completionofunitsThroughputrate=1.

CycletimeEfficiency=Actualoutput

StandardOutputProcessPerformanceMetrics(Continued)Productivity=Output

InputUtilization=TimeActivated

TimeAvailableCycleTimeExampleSupposeyouhadtoproduce600unitsin80hourstomeetthedemandrequirementsofaproduct.Whatisthecycletimetomeetthisdemandrequirement?Answer:Thereare4,800minutes(60minutes/hourx80hours)in80hours.Sotheaveragetimebetweencompletionswouldhavetobe:Cycletime=4,800/600units=8minutes.

ProcessThroughputTimeReductionPerformactivitiesinparallelChangethesequenceofactivitiesReduceinterruptionsLittlelawItstatesamathematicalrelationshipbetweenthroughputrate,throughputtimeandtheamountofwork-in-processinventory.Little’sLawestimatesthetimethatanitemwillspendinwork-in-processinventory,whichcanbeusefulforcalculatingthetotalthroughputtimeforaprocess.Throughputtime=work-in-process/throughputrate=work-in-process*cycletimeExampleSupposeitisdecidedthat,whenthenewprocessisintroduced,theaveragenumberofcustomersintheprocessshouldbelimitedtoaroundtenandthemaximumtimeacustomerisintheprocessshouldbeonaveragefourminutes.Ifthetimetoassembleandsellasandwich(fromcustomerrequesttothecustomerleavingtheprocess)inthenewprocesshasreducedto1.2minutes,howmanystaffshouldbeserving?ProcesstypesManufacturingProjectprocessesJobbingprocessesBatchprocessesMassprocessesContinuousprocessesServiceoperationsProfessionalservicesServiceshopsMassservicesProjectprocessesarethosewhichdealwithdiscrete,usuallyhighlycustomizedproducts.Jobbingprocessesdealwithhighvarietyandlowvolumes.Itprocessmoreandusuallysmalleritemsthanprojectprocesses.Sharingresourceswithotheritems.Batchprocessesdonothavequitethedegreeofvarietyassociatedwithjobbing.Eachtimebatchprocessesproduceaproducttheyproducemorethanone.Massprocessesarethosewhichproducegoodsinhighvolumeandrelativelynarrowvariety.Continuousprocessesareonestepbeyondmassprocessesinsomuchastheyoperateatevenhighervolumeandoftenhaveevenlowvariety.Itisassociatedwithrelativelyinflexible,capital-intensivetechnologieswithhighlypredictableflow.Examples:Petrochemicalrefineries.Professi