·运筹管理 operations management ch09

Chapter9 ServiceOperationsPlanningandScheduling Overview IntroductionSchedulingQuasi ManufacturingServiceOperationsSchedulingCustomer as ParticipantServiceOperationsSchedulingCustomer as ProductServiceOperationsWrap Up WhatWorld ClassCompaniesDo Introduction Servicesareoperationswith IntangibleoutputsthatordinarilycannotbeinventoriedClosecustomercontactShortleadtimesHighlaborcostsrelativetocapitalcostsSubjectivelydeterminedquality Introduction Factsaboutservicebusinesses EnormousdiversityServicebusinessescanbeanysizeTwiceasmanynon retailservicebusinessesasretailTechnicaltrainingimportantduetosignificantdependenceoncomputers automationandtechnology Introduction OtherFactsaboutservicebusinesses ServiceworkerswellpaidrelativetomanufacturingNeedbetterplanning controlling andmanagementtostaycompetitive SomeoftheLargestServiceBusinesses Rankinthetop20USCorporations AT TWal MartCitigroupStateFarmSBCCommunicationsSear Roebuck Company SpectrumofServiceIndustries TransportationBankingRetailingHealthCareEntertainment InsuranceRealEstateCommunicationsUtilities andmore NoClearLineBetweenManufacturingandServiceFirms Everybusiness whethermanufacturingorservice hasamixofcustomerserviceaspectsandproductionaspectsinitsoperationsManufacturinghasmuchtolearnfromservicesthatexcelServiceshavemuchtolearnfrommanufacturersthatexcel ManufacturingandServiceJobs PercentageofUSJobs198819982008 ManufacturingJobs16 1 13 4 11 6 ServiceJobs66 270 873 9 Projected OperationsStrategies Positioningstrategiescontaintwoelements TypeofservicedesignStandardorcustomAmountofcustomercontactMixofphysicalgoodsandintangibleservicesTypeofproductionprocessQuasi manufacturingCustomer as participantCustomer as product TypesofServiceOperations Quasi manufacturingProductionoccursmuchasmanufacturingPhysicalgoodsdominantoverintangibleservicesCustomer as participantHighdegreeofcustomerinvolvementPhysicalgoodsmayormaynotbesignificantServiceeitherstandardorcustomCustomer as productServiceperformedoncustomer usuallycustom SchedulingChallengesinServices Planningandcontrollingday to dayactivitiesdifficultdueto ServicesproducedanddeliveredbypeoplePatternofdemandforservicesisnon uniform Non UniformDemand Cannotinventoryservicesinadvanceofhigh demandperiods sobusinessesusefollowingtactics PreemptiveactionstomakedemandmoreuniformOff peakincentives discounts telephone Appointmentschedules dentist Fixedschedules airline MakeoperationsmoreflexiblesoitiseasiertovarycapacityPart timepersonnel supermarket Subcontractors postalservice In housestandbyresources firedepartment Non UniformDemand Additionaltacticsusedbybusinesses AnticipatedemandandscheduleemployeesduringeachtimeperiodtomeetdemandAllowwaitinglinestoformThesetwotacticswillbecoveredingreaterdetail SchedulingQuasi ManufacturingServices Product FocusedOperationsResembleproduct focusedproductionlinesCustomerdemandisforecastandcapacitydecisionsmadejustasinmanufacturingHighvolumesofstandardizedproductsManagementfocusedoncontrollingproductioncosts productquality anddeliveryofphysicalgoodsExample McDonald sback roomoperation SchedulingQuasi ManufacturingServices Process FocusedOperationsManagedlikejobshopsinmanufacturingInput outputcontrolimportanttobalancecapacitybetweenoperationsGanttchartsusedtocoordinateflowsbetweendepartmentsSequenceofjobsconsidersequencingrules changeovercosts andflowtimes WorkShiftScheduling Threedifficultiesinschedulingservices DemandvariabilityServicetimevariabilityAvailabilityofpersonnelwhenneededManagersusetwotactics Usefull timeemployeesexclusivelyUsesomefull timeemployeesasbaseandfillinpeakdemandwithpart timeemployees Example SchedulingEmployees Theownerofahaircuttingshopwantstoconvertfromadrop insystemofcustomerarrivalstoanappointmentsystem Eachcustomerrequiresanaverageof30minutesofastylist stime Thestylistsareallfull timeemployeesandcanworkany4consecutivedaysperweekfrom10a m to7p m withanhouroffforlunch MondaythroughSaturday Onthenextslideare 1 averagenumberofdrop incustomerseachday and2 estimatednumberofcustomerappointmentseachday Example SchedulingEmployees Mon Tue Wed Thu Fri Sat TotalDrop ins403010203060190Appointments323232323232192a Howmanystylistsarerequiredtoservice32appointmentsinaday b Whatistheminimumnumberofstylistsrequiredperweek c Usetheworkshiftheuristicproceduretodevelopthestylists weeklyworkshiftschedules Example SchedulingEmployees NumberofStylistsRequiredperDayNumberofcustomersperdayNumberofworkhoursNumberofcustomersperdayperstylistservedperhourperstylist 32 8 2 2stylists Example SchedulingEmployees MinimumNumberofStylistsRequiredperWeek NumberofCustomersperWeekNumberofCustomersperStylistperWeek 192 8hr day 4days week 2cust hr stylist 192 64 3stylists Example SchedulingEmployees Stylists WeeklyWorkShiftSchedulesStylistMon Tue Wed Thu Fri Sat 122222222211113111100Note Pairofdaysboxedrepresentdaysoff SchedulingCustomer as ParticipantServices Mustprovidecustomereaseofuse accessfeatures lighting walkways etc LayoutsmustfocusonmerchandisingandattractivedisplayofproductsEmployeeperformancecrucialtocustomersatisfactionWaitinglinesusedextensivelytoleveldemand WaitingLinesinServiceOperations Waitinglinesformbecause Demandpatternsareirregularorrandom Servicetimesvaryamong customers Managerstrytostrikeabalancebetweenefficientlyutilizingresourcesandkeepingcustomersatisfactionhigh WaitingLineExamples ComputerprintingjobswaitingforprintingWorkerswaitingtopunchatimeclockCustomersinlineatadrive upwindowDriverswaitingtopayahighwaytollSkierswaitingforachairliftAirplaneswaitingtotakeoff WaitingLineAnalysis Assistsmanagersindetermining HowmanyserverstouseLikelihoodacustomerwillhavetowaitAveragetimeacustomerwillwaitAveragenumberofcustomerswaitingWaitinglinespaceneededPercentageoftimeallserversareidle WaitingLineTerminology Queue awaitinglineChannels numberofwaitinglinesinaqueuingsystemServicephases numberofstepsinserviceprocessArrivalrate l rateatwhichpersonsorthingsarrive inarrivalsperunitoftime Servicerate m ratethatarrivalsareserviced inarrivalsperunitoftime WaitingLineTerminology Queuediscipline rulethatdeterminestheorderinwhicharrivalsareservicedQueuelength numberofarrivalswaitingforserviceTimeinsystem anarrival swaitingtimeandservicetimeUtilization degreetowhichanypartoftheservicesystemisoccupiedbyanarrival QueuingSystemStructures SinglePhase SingleChannelSinglePhase Multichannel QueuingSystemStructures Multiphase SingleChannelMultiphase Multichannel DefinitionsofQueuingSystemVariables averagearrivalrate1 averagetimebetweenarrivals averageservicerateforeachserver1 averageservicetimen1 averagenumberofarrivalswaitingnS averagenumberofarrivalsinthesystemt1 averagetimearrivalswaittS averagetimearrivalsareinthesystemPn probabilityofexactlynarrivalsinthesystem Model1SinglechannelSinglephasePoissonarrival ratedistributionPoissonservice ratedistributionUnlimitedmaximumqueuelengthExamples Single booththeatreticketsalesSingle scannerairportsecuritystation QueuingModels Example QueuingModel1 JimBeampullsstockfromhiswarehouseshelvestofillcustomerorders Customerordersarriveatameanrateof20perhour ThearrivalrateisPoissondistributed EachorderreceivedbyJimrequiresanaverageoftwominutestopull TheservicerateisPoissondistributedalso Questionstofollow Example QueuingModel1 ServiceRateDistributionQuestionWhatisJim smeanservicerateperhour AnswerSinceJimcanprocessanorderinanaveragetimeof2minutes 2 60hr thenthemeanservicerate equals1 meanservicetime or60 2 30 hr Example QueuingModel1 AverageTimeintheSystemQuestionWhatistheaveragetimeanordermustwaitfromthetimeJimreceivestheorderuntilitisfinishedbeingprocessed i e itsturnaroundtime AnswerWith 20perhourand 30perhour theaveragetimeanorderwaitsinthesystemis tS 1 1 30 20 1 10houror6minutes Example QueuingModel1 AverageLengthofQueueQuestionWhatistheaveragenumberofordersJimhaswaitingtobeprocessed AnswerTheaveragenumberoforderswaitinginthequeueis n1 2 20 2 30 30 20 400 300 4 3or1 33orders Example QueuingModel1 UtilizationFactorQuestionWhatpercentageofthetimeisJimprocessingorders AnswerThepercentageoftimeJimisprocessingordersisequivalenttotheutilizationfactor Thus thepercentageoftimeheisprocessingordersis 20 30 2 3or66 67 QueuingModels Model2SinglechannelSinglephasePoissonarrival ratedistributionConstantservicerateUnlimitedmaximumqueuelengthExamples Single boothautomaticcarwashCoffeevendingmachine Example QueuingModel2 ThemechanicalponyridemachineattheentrancetoaverypopularJ Martstoreprovides2minutesofridingfor 50 Children accompaniedofcourse wantingtoridetheponyarriveaccordingtoaPoissondistributionwithameanrateof15perhour a Whatfractionofthetimeistheponyidle b Whatistheaveragenumberofchildrenwaitingtoridethepony c Whatistheaveragetimeachildwaitsforaride Example QueuingModel2 FractionofTimePonyisIdlel 15perhourm 60 2 30perhourUtilization l m 15 30 5Idlefraction 1 Utilization 1 5 5 Example QueuingModel2 AverageNumberofchildrenWaitingforaRideAverageTimeaChildWaitsforaRideor1minute QueuingModels Model3SinglechannelSinglephasePoissonarrival ratedistributionPoissonservice ratedistributionLimitedmaximumqueuelengthExamples AutorepairshopwithlimitedparkingspaceBankdrive thruwithlimitedwaitinglane QueuingModels Model4MultiplechannelSinglephasePoissonarrival ratedistributionPoissonservice ratedistributionUnlimitedmaximumqueuelengthExamples ExpresswayexitwithmultipletollboothsBankwithmultipletellerstations SchedulingCustomer as ProductServices WiderangeofcomplexityEveryfacetdesignedaroundthecustomerHighlytrained motivated andeffectiveworkforcecriticaltosuccessWaiting lineanalysiscanbehelpfulindeterminingstaffinglevelsInmorecomplexoperations simulationisahelpfultoolinschedulingresources ReasonsforSimulatingOperations Experimentationwiththerealsystemisimpossible impractical oruneconomical Systemissocomplexthatmathematicalformulascannotbedeveloped Valuesofthesystem svariablesarenotknownwithcertainty Problemunderconsiderationinvolvesthepassageoftimeandsimulationcouldbefaster ProceduresofComputerSimulation Definetheproblem Developandcomputer programamodelofproblem Identifythevariablesandparameters Specifythedecisionrules Gatherdataandspecifyvariablesandparameters Specifytime incrementingprocedures Specifysummarizingprocedures Processthesimulation Evaluatetheresultsofthesimulation Recommendacourseofaction SimulationExample WheneveraninternationalplanearrivesatLincolnairportthetwocustomsinspectorsondutysetupoperationstoprocessthepassengers Incomingpassengersmustfirsthavetheirpassportsandvisaschecked Thisishandledbyoneinspector Thetimerequiredtocheckapassenger spassportsandvisascanbedescribedbytheprobabilitydistributiononthenextslide SimulationExample TimeRequiredtoCheckaPassenger sPassportandVisaProbability20seconds 2040seconds 4060seconds 3080seconds 10 SimulationExample Afterhavingtheirpassportsandvisaschecked thepassengersnextproceedtothesecondcustomsofficialwhodoesbaggageinspections Passengersformasinglewaitinglinewiththeofficialinspectingbaggageonafirstcome firstservedbasis SimulationExample Thetimerequiredforbaggageinspectionhasthefollowingprobabilitydistribution TimeRequiredForBaggageInspectionProbabilityNoTime 251minute 602minutes 103minutes 05 SimulationExample RandomNumberMappingTimeRequiredtoCheckaPassenger sRandomPassportandVisaProbabilityNumbers20seconds 2000 1940seconds 4020 5960seconds 3060 8980seconds 1090 99 SimulationExample RandomNumberMappingTimeRequiredForRandomBaggageInspectionProbabilityNumbersNoTime 2500 241minute 6025 842minutes 1085 943minutes 0595 99 SimulationExample Next EventSimulationRecordsForeachpassengerthefollowinginformationmustberecorded WhenhisservicebeginsatthepassportcontrolinspectionThelengthoftimeforthisserviceWhenhisservicebeginsatthebaggageinspectionThelengthoftimeforthisservice SimulationExample TimeRelationshipsTimeapassengerbeginsservicebythepassportinspector Timethepreviouspassengerstartedpassportservice Timeofpreviouspassenger spassportservice SimulationExample TimeRelationshipsTimeapassengerbeginsservicebythebaggageinspector Ifpassengerdoesnotwaitforbaggageinspection Timepassengercompletesservicewiththepassportcontrolinspector Ifthepassengerdoeswaitforbaggageinspection Timepreviouspassengercompletesservicewiththebaggageinspector SimulationExample TimeRelationshipsTimeacustomercompletesserviceatthebaggageinspector Timecustomerbeginsservicewithbaggageinspector Timerequiredforbaggageinspection SimulationExample AcharteredplanefromabroadlandsatLincolnAirportwith80passengers Simulatetheprocessingofthefirst10passengersthroughcustoms SimulationExample SimulationWorksheet partial PassportControlBaggageInspectionsPass TimeRan Serv TimeTimeRan Serv TimeNum Beg Num TimeEndBeg Num TimeEnd10 00931 201 201 20130 001 2021 20631 002 202 20080 002 2032 2026 403 003 00601 004 0043 0016 203 204 00130 004 0053 2021 404 004 00681 005 00 SimulationExample SimulationWorksheet continued PassportControlBaggageInspectionsPass TimeRan Serv TimeTimeRan Serv TimeNum Beg Num TimeEndBeg Num TimeEnd64 0026 404 405 00401 006 0074 40701 005 406 00401 007 0085 4055 406 207 00271 008 0096 20721 007 208 00230 008 00107 20891 008 208 20641 009 20 SimulationExample ExplanationForexample passenger1beginsbeingservedbythepassportcontrolinspectorimmediately Hisservicetimeis1 20 80seconds atwhichtimehegoesimmediatelytothebaggageinspectorwhowaveshimthroughwithoutinspection SimulationExample ExplanationPassenger2beginsservicewithpassportinspector1 20minutes 80seconds