1、WANGHUI U of G1Operations SchedulingOperations SchedulingOperations ManagementChapter 102Capacity Planning,Aggregate Scheduling,Master Capacity Planning,Aggregate Scheduling,Master Schedule,and Short-Term SchedulingSchedule,and Short-Term SchedulingCapacity Planning 生产能力规划生产能力规划 1.Facility size 2.Eq
2、uipment procurementAggregate Scheduling 综合计划综合计划 1.Facility utilization 2.Personnel needs 3.SubcontractingMaster Schedule 主生产计划主生产计划 1.MRP 2.Disaggregation of master planLong-termIntermediate-termShort-termIntermediate-termShort-term Scheduling 短期排程短期排程 1.Work center loading 2.Job sequencingWANG HUI
3、 U of G3Chapter 10 CONTENTSGlobal Company Profile:Delta Air LinesGlobal Company Profile:Delta Air LinesThe Strategic Importance of Short-Term The Strategic Importance of Short-Term SchedulingSchedulingScheduling IssuesScheduling IssuesForward and Backward SchedulingForward and Backward SchedulingSch
4、eduling CriteriaScheduling CriteriaLoading Jobs Loading Jobs Gantt ChartsGantt ChartsAssignment Method Assignment Method CONTENTSSequencing JobsSequencing JobsPriority Rules for Dispatching JobsPriority Rules for Dispatching JobsSequencing N Jobs on Two Machines:Sequencing N Jobs on Two Machines:Joh
5、nsons RuleJohnsons RuleLimitations of Rule-Based Dispatching Systems Limitations of Rule-Based Dispatching Systems Theory of ConstraintsTheory of ConstraintsScheduling ServicesScheduling ServicesWANGHUI U of G4？How are we start the jobs?1001501209012011585112180Guiding Problems&Case？How can we get t
6、he best sequence?Guiding Problems&CaseWANGHUI U of G6As we know,scheduling Airplanes When Weather is the enemy.Throughout the ordeals of tornadoes,ice storms,and snowstorms,airlines across the globe struggle to cope with delays,cancellations,and furious passengers.Close to 10%of Delta airlines fligh
7、ts are disrupted in a typical year,half because of weather,the cost is$440 million in lost revenue,overtime pay,and food and lodging vouchers.Here is what Delta officials had to do when a bad weather happened.Now Delta is ready to take the sting out of the scheduling nightmares that come from weathe
8、r-related problems.It opened a$33 million high-tech nerve center adjacent to its major hub at the airport.From computers to telecommunications systems to deicers,Delta s new operations Control Center more quickly notifies customers of schedule changes,routes flights,and gets jets into the air.Delta
9、figures its new scheduling efforts will save$35 million a year.It also finds competitive advantage with its flexibility for last-minute adjustments to demand and weather disruptions.WANGHUI U of G7WANG HUI U of G8The strategic importance of short-term schedulingBy scheduling effectively,companies us
10、e assets more effectively and create greater capacity per dollar invested,which,in turn,lowers cost.This added capacity and related flexibility provides faster delivery and,therefore,better customer service.Good scheduling is a competitive advantage because it contributes to dependable delivery.WANG
11、HUI U of G9Scheduling Issues-Schedule&Job SequencingScheduling deals with the timing of operations.A schedule is a timetable for performing activities,utilizing resources,or allocating facilities.Sequencing(priority sequencing)is the process of determining which job to start first on some machine or
12、 in some work center.Priority rules are the rules used in obtaining a job sequence.Scheduling Decisions examplesScheduling Decisions examplesOrganizationOrganizationManagers Must Schedule the FollowingManagers Must Schedule the FollowingArnold Palmer Arnold Palmer HospitalHospitalOperating room useO
13、perating room usePatient admissionsPatient admissionsNursing,security,maintenance staffsNursing,security,maintenance staffsOutpatient treatmentsOutpatient treatmentsUniversity of University of MissouriMissouriClassrooms and audiovisual equipmentClassrooms and audiovisual equipmentStudent and instruc
14、tor schedulesStudent and instructor schedulesGraduate and undergraduate coursesGraduate and undergraduate coursesLockheed Martin Lockheed Martin factoryfactoryProduction of goodsProduction of goodsPurchases of materialsPurchases of materialsWorkersWorkersHard Rock CafeHard Rock CafeChef,waiters,bart
15、endersChef,waiters,bartendersDelivery of fresh foodsDelivery of fresh foodsEntertainersEntertainersOpening of dining areasOpening of dining areasDelta Air LinesDelta Air LinesMaintenance of aircraftMaintenance of aircraftDeparture timetablesDeparture timetablesFlight crews,catering,gate,ticketing pe
16、rsonnelFlight crews,catering,gate,ticketing personnelScheduling FlowScheduling FlowWANG HUI U of G12Scheduling Issues-Work Center DefinedA work center is an area in a business in which productive resources are organized and work is completed.May be a single machine,a group of machines,or an area whe
17、re a particular type of work is done.WANGHUI U of G13WANGHUI U of G14Scheduling IssuesScheduling IssuesForward scheduling-the system takes an order and then schedules each operation that must be completed forward in time.It can tell the earliest date that an order can be over.It work well in firms w
18、hose suppliers are usually behind in meeting schedules.Backward scheduling(Example:MRP)-starts from some date in the future and schedules the required operations in reverse sequence.It can tell when an order must be started in order to be done by specific date.WANGHUI U of G15StartStart Due DateB BE
19、 EForward SchedulingStartStart Due DateB BE EBackward SchedulingWANGHUI U of G16Typical Scheduling CriteriaCriteria Allocating orders,equipment,and personnel.Determining the sequence of order performance.Initiating performance of the scheduled work.(Dispatching of orders)Shop-floor control.Loading J
20、obsLoading JobsAssign jobs so that costs,idle time,Assign jobs so that costs,idle time,or completion time are minimizedor completion time are minimizedTwo forms of loadingTwo forms of loadingGantt ChartsGantt ChartsAssigning specific jobs to work centersAssigning specific jobs to work centersGantt C
21、hartsGantt Charts Load chart shows the loading and idle times of departments,machines,or facilities Displays relative workloads over time Schedule chart monitors jobs in process All Gantt charts need to be updated frequently to account for changesGantt Load Chart ExampleGantt Load Chart ExampleDayMo
22、ndayTuesdayWednesday ThursdayFridayWork CenterMetalworksMechanicalElectronicsPaintingJob 349Job 349Job 349Job 408Job 408Job 408ProcessingProcessingUnscheduledUnscheduledCenter not availableCenter not availableJob 350Job 349Job 295Gantt Schedule Chart ExampleGantt Schedule Chart ExampleJobDay 1Day 2D
23、ay 3Day 4Day 5Day 6Day 7Day 8ABCNowNowMaintenanceStart of an Start of an activityactivityEnd of an End of an activityactivityScheduled Scheduled activity time activity time allowedallowedActual work Actual work progressprogressNonproduction Nonproduction timetimePoint in time Point in time when char
24、t is when chart is reviewedreviewedWANGHUI U of G21Work-Center Scheduling ObjectivesMeet due datesMinimize lead timeMinimize setup time or costMinimize work-in-process inventoryMaximize machine utilization WANGHUI U of G22Sequencing JobsSequencing Jobs-Priority Rules for Job Sequencing 1.First-come,
25、first-served(FCFS)-order are run in the order they arrive in the department.2.Shortest operating time(SOT)-run the job with the shortest completion time first,next shortest second,and so on.3.Earliest due date first(EDD)-run the job with the earliest due date first,next earliest second,and so on.WAN
26、GHUI U of G23Priority Rules for Job Sequencing4.Earliest start date first(due date-lead time)-run the job with the earliest start date first5.Least slack time remaining(STR)first-is calculated as the time remaining before the due date minus the processing time remaining.Orders with the shortest STR
27、are run first.WANGHUI U of G24Priority Rules for Job Sequencing(Continued)6.STR/OP(slack time remaining per operation)-orders with the shortest STR/OP are run first7、Smallest critical ratio(CR)first-CR=(due date-current date)/(number of days remaining)8、Smallest queue ratio(QR)first-QR=(slack time r
28、emaining in schedule)/(planned remaining queue time)WANGHUI U of G25Priority Rules for Job Sequencing(Continued)9.Last come,first served(LCFS)-as orders arrive they are placed on the top of the stack；the operator usually picks up the order on top to run first.10.Random order or whim-select whichever
29、 job they feel like running.WANGHUI U of G26Example of Job Sequencing:First-Come First-ServedJobs(in orderProcessingDue DateFlow Timeof arrival)Time(days)(days hence)(days)A454B71011C3614D1415Answer:FCFS ScheduleJobs(in orderProcessingDue Dateof arrival)Time(days)(days hence)A45B710C36D14Suppose you
30、 have the four jobs to the right arrive for processing on one machine.What is the FCFS schedule?Do all the jobs get done on time?No,Jobs B,C,and D are going to be late.Total Flow Time=44Mean Flow Time=11Average lateness=5WANGHUI U of G27Example of Job Sequencing:Shortest Operating TimeJobs(in orderP
31、rocessingDue Dateof arrival)Time(days)(days hence)A45B710C36D14Answer:Shortest Operating Time ScheduleJobs(in orderProcessingDue DateFlow Timeof arrival)Time(days)(days hence)(days)D141C364A458B71015Suppose you have the four jobs to the right arrive for processing on one machine.What is the SOT sche
32、dule?Do all the jobs get done on time?No,Jobs A and B are going to be late.Total Flow Time=28Mean Flow Time=7Average lateness=2WANGHUI U of G28Example of Job Sequencing:Last-Come First-ServedJobs(in orderProcessingDue Dateof arrival)Time(days)(days hence)A45B710C36D14Answer:Last-Come First-Served Sc
33、heduleJobs(in orderProcessingDue DateFlow Timeof arrival)Time(days)(days hence)(days)D141C364B71011A4515No,Jobs B and A are going to be late.Suppose you have the four jobs to the right arrive for processing on one machine.What is the LCFS schedule?Do all the jobs get done on time?Total Flow Time=31Mean Flow Time=7.75Average lateness=2.75WANGHUI U of G29Example of Job Sequencing:Earliest Due Date F
