15 - 1© 2011 Pearson Education, Inc. publishing as Prentice Hall15Short-TermSchedulingPowerPoint presentation to accompany...
15 - 2© 2011 Pearson Education, Inc. publishing as Prentice HallOutline Global Company Profile:Delta Air Lines The Impor...
15 - 3© 2011 Pearson Education, Inc. publishing as Prentice HallOutline – Continued Scheduling Process-FocusedFacilities...
15 - 4© 2011 Pearson Education, Inc. publishing as Prentice HallOutline – Continued Sequencing Jobs Priority Rules for D...
15 - 5© 2011 Pearson Education, Inc. publishing as Prentice HallOutline – Continued Scheduling Repetitive Facilities Sch...
15 - 6© 2011 Pearson Education, Inc. publishing as Prentice HallLearning ObjectivesWhen you complete this chapter youshoul...
15 - 7© 2011 Pearson Education, Inc. publishing as Prentice HallLearning ObjectivesWhen you complete this chapter youshoul...
15 - 8© 2011 Pearson Education, Inc. publishing as Prentice HallDelta Airlines About 10% of Delta’s flights aredisrupted ...
15 - 9© 2011 Pearson Education, Inc. publishing as Prentice HallShort-Term SchedulingShort-term schedules translatecapacit...
15 - 10© 2011 Pearson Education, Inc. publishing as Prentice HallImportance of Short-TermScheduling Effective and efficie...
15 - 11© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Issues Scheduling deals with the timing ofope...
15 - 12© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling DecisionsOrganization Managers Must Schedule t...
15 - 13© 2011 Pearson Education, Inc. publishing as Prentice HallFigure 15.1SchedulingFlow
15 - 14© 2011 Pearson Education, Inc. publishing as Prentice HallForward and BackwardScheduling Forward scheduling starts...
15 - 15© 2011 Pearson Education, Inc. publishing as Prentice HallForward and BackwardScheduling Backward scheduling begin...
15 - 16© 2011 Pearson Education, Inc. publishing as Prentice HallForward and BackwardScheduling Backward scheduling begin...
15 - 17© 2011 Pearson Education, Inc. publishing as Prentice HallDifferent Processes/Different ApproachesProcess-focusedfa...
15 - 18© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Criteria1. Minimize completion time2. Maximize...
15 - 19© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Process-Focused Facilities Schedule incoming ...
15 - 20© 2011 Pearson Education, Inc. publishing as Prentice HallPlanning and Control Files1. An item master file contains...
15 - 21© 2011 Pearson Education, Inc. publishing as Prentice HallLoading Jobs Assign jobs so that costs, idletime, or com...
15 - 22© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output Control Identifies overloading andunderload...
15 - 23© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output ControlExampleWeek Ending 6/6 6/13 6/20 6/27...
15 - 24© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output ControlExampleWork Center DNC Milling (in st...
15 - 25© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output ControlExampleOptions available to operation...
15 - 26© 2011 Pearson Education, Inc. publishing as Prentice HallGantt Charts Load chart shows the loading andidle times ...
15 - 27© 2011 Pearson Education, Inc. publishing as Prentice HallGantt Load Chart ExampleFigure 15.3DayMonday Tuesday Wedn...
15 - 28© 2011 Pearson Education, Inc. publishing as Prentice HallGantt Schedule ChartExampleFigure 15.4JobDay1Day2Day3Day4...
15 - 29© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method A special class of linearprogramming m...
15 - 30© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method Build a table of costs or timeassociat...
15 - 31© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method1. Create zero opportunity costs byrepea...
15 - 32© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method3. Subtract the smallest number notcover...
15 - 33© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment ExampleA B CJobR-34 $11 $14 $ 6S-66 $ 8 $10 $1...
15 - 34© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment ExampleStep 2 - LinesA B CJobR-34 $ 5 $ 6 $ 0S...
15 - 35© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment ExampleBecause three lines areneeded, the solu...
15 - 36© 2011 Pearson Education, Inc. publishing as Prentice HallStep 4 - AssignmentsA B CJobR-34 $ 3 $ 4 $ 0S-66 $ 0 $ 0 ...
15 - 37© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing Jobs Specifies the order in which jobsshould ...
15 - 38© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobJob Work(Processing) Time(Days)Job D...
15 - 39© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlow...
15 - 40© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlow...
15 - 41© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleSPT: Sequence B-D-A-C-EJobSequenceJob W...
15 - 42© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlow...
15 - 43© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleEDD: Sequence B-A-D-C-EJobSequenceJob W...
15 - 44© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlow...
15 - 45© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleLPT: Sequence E-C-A-D-BJobSequenceJob W...
15 - 46© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlow...
15 - 47© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleRuleAverageCompletionTime (Days)Utiliza...
15 - 48© 2011 Pearson Education, Inc. publishing as Prentice HallComparison ofSequencing Rules No one sequencing rule exc...
15 - 49© 2011 Pearson Education, Inc. publishing as Prentice HallCritical Ratio (CR) An index number found by dividing th...
15 - 50© 2011 Pearson Education, Inc. publishing as Prentice HallCritical Ratio ExampleJobDueDateWorkdaysRemaining Critica...
15 - 51© 2011 Pearson Education, Inc. publishing as Prentice HallCritical Ratio Technique1. Helps determine the status of ...
15 - 52© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing N Jobs on TwoMachines: Johnson’s Rule Works w...
15 - 53© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule1. List all jobs and times for each workcen...
15 - 54© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule ExampleJobWork Center 1(drill press)Work C...
15 - 55© 2011 Pearson Education, Inc. publishing as Prentice HallJobWork Center 1(drill press)Work Center 2(lathe)A 5 2B 3...
15 - 56© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule ExampleTime 0 3 10 20 28 33B ACDEWC1WC2B A...
15 - 57© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule ExampleTime 0 3 10 20 28 33Time 0 1 3 5 7...
15 - 58© 2011 Pearson Education, Inc. publishing as Prentice HallLimitations of Rule-BasedDispatching Systems1. Scheduling...
15 - 59© 2011 Pearson Education, Inc. publishing as Prentice HallFinite Capacity Scheduling Overcomes disadvantages of ru...
15 - 60© 2011 Pearson Education, Inc. publishing as Prentice HallFinite Capacity SchedulingMRP Data• Masterschedule• BOM• ...
15 - 61© 2011 Pearson Education, Inc. publishing as Prentice HallFinite Capacity Scheduling
15 - 62© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling RepetitiveFacilities Level material use can h...
15 - 63© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling RepetitiveFacilities Advantages include:1. Lo...
15 - 64© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling ServicesService systems differ from manufactur...
15 - 65© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Services Hospitals have complex schedulingsys...
15 - 66© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Services Airlines must meet complex FAA andun...
15 - 67© 2011 Pearson Education, Inc. publishing as Prentice HallDemand Management Appointment or reservationsystems FCF...
15 - 68© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Service EmployeesWith Cyclical Scheduling Obj...
15 - 69© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling Example1. Determine the staffing requ...
15 - 70© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 71© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 72© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 73© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 74© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 75© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 76© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 77© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 ...
15 - 78© 2011 Pearson Education, Inc. publishing as Prentice HallAll rights reserved. No part of this publication may be r...
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Heizer om10 ch15

  1. 1. 15 - 1© 2011 Pearson Education, Inc. publishing as Prentice Hall15Short-TermSchedulingPowerPoint presentation to accompanyHeizer and RenderOperations Management, 10ePrinciples of Operations Management, 8ePowerPoint slides by Jeff Heyl
  2. 2. 15 - 2© 2011 Pearson Education, Inc. publishing as Prentice HallOutline Global Company Profile:Delta Air Lines The Importance of Short-TermScheduling Scheduling Issues Forward and Backward Scheduling Scheduling Criteria
  3. 3. 15 - 3© 2011 Pearson Education, Inc. publishing as Prentice HallOutline – Continued Scheduling Process-FocusedFacilities Loading Jobs Input-Output Control Gantt Charts Assignment Method
  4. 4. 15 - 4© 2011 Pearson Education, Inc. publishing as Prentice HallOutline – Continued Sequencing Jobs Priority Rules for Dispatching Jobs Critical Ratio Sequencing N Jobs on TwoMachines: Johnson’s Rule Limitations of Rule-BasedDispatching Systems Finite Capacity Scheduling (FCS)
  5. 5. 15 - 5© 2011 Pearson Education, Inc. publishing as Prentice HallOutline – Continued Scheduling Repetitive Facilities Scheduling Services Scheduling Service Employees withCyclical Scheduling
  6. 6. 15 - 6© 2011 Pearson Education, Inc. publishing as Prentice HallLearning ObjectivesWhen you complete this chapter youshould be able to:1. Explain the relationship between short-term scheduling, capacity planning,aggregate planning, and a masterschedule2. Draw Gantt loading and schedulingcharts3. Apply the assignment method forloading jobs
  7. 7. 15 - 7© 2011 Pearson Education, Inc. publishing as Prentice HallLearning ObjectivesWhen you complete this chapter youshould be able to:4. Name and describe each of the prioritysequencing rules5. Use Johnson’s rule6. Define finite capacity scheduling7. Use the cyclical scheduling technique
  8. 8. 15 - 8© 2011 Pearson Education, Inc. publishing as Prentice HallDelta Airlines About 10% of Delta’s flights aredisrupted per year, half because ofweather Cost is $440 million in lost revenue,overtime pay, food and lodgingvouchers The $33 million Operations ControlCenter adjusts to changes and keepsflights flowing Saves Delta $35 million per year
  9. 9. 15 - 9© 2011 Pearson Education, Inc. publishing as Prentice HallShort-Term SchedulingShort-term schedules translatecapacity decisions, aggregateplanning, and master schedulesinto job sequences and specificassignments of personnel,materials, and machinery
  10. 10. 15 - 10© 2011 Pearson Education, Inc. publishing as Prentice HallImportance of Short-TermScheduling Effective and efficient schedulingcan be a competitive advantage Faster movement of goods through afacility means better use of assetsand lower costs Additional capacity resulting fromfaster throughput improves customerservice through faster delivery Good schedules result in moredependable deliveries
  11. 11. 15 - 11© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Issues Scheduling deals with the timing ofoperations The task is the allocation andprioritization of demand Significant issues are The type of scheduling, forward orbackward The criteria for priorities
  12. 12. 15 - 12© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling DecisionsOrganization Managers Must Schedule the FollowingArnold PalmerHospitalOperating room usePatient admissionsNursing, security, maintenance staffsOutpatient treatmentsUniversity ofMissouriClassrooms and audiovisual equipmentStudent and instructor schedulesGraduate and undergraduate coursesLockheed MartinfactoryProduction of goodsPurchases of materialsWorkersHard Rock Cafe Chef, waiters, bartendersDelivery of fresh foodsEntertainersOpening of dining areasDelta Air Lines Maintenance of aircraftDeparture timetablesFlight crews, catering, gate, ticketing personnelTable 15.1
  13. 13. 15 - 13© 2011 Pearson Education, Inc. publishing as Prentice HallFigure 15.1SchedulingFlow
  14. 14. 15 - 14© 2011 Pearson Education, Inc. publishing as Prentice HallForward and BackwardScheduling Forward scheduling starts as soonas the requirements are known Produces a feasible schedulethough it may not meet due dates Frequently results inbuildup of work-in-process inventoryDueDateNow
  15. 15. 15 - 15© 2011 Pearson Education, Inc. publishing as Prentice HallForward and BackwardScheduling Backward scheduling begins withthe due date and schedules the finaloperation first Schedule is produced by workingbackwards though the processes Resources may notbe available toaccomplish thescheduleDueDateNow
  16. 16. 15 - 16© 2011 Pearson Education, Inc. publishing as Prentice HallForward and BackwardScheduling Backward scheduling begins withthe due date and schedules the finaloperation first Schedule is produced by workingbackwards though the processes Resources may notbe available toaccomplish thescheduleDueDateNow
  17. 17. 15 - 17© 2011 Pearson Education, Inc. publishing as Prentice HallDifferent Processes/Different ApproachesProcess-focusedfacilitiesForward-looking schedulesMRP due datesFinite capacity schedulingWork cells Forward-looking schedulesMRP due datesDetailed schedule done using work cellpriority rulesRepetitive facilities Forward-looking schedule with abalanced linePull techniques for schedulingProduct-focusedfacilitiesForward-looking schedule with stabledemand and fixed capacityCapacity, set-up, and run times knownCapacity limited by long-term capitalinvestmentTable 15.2
  18. 18. 15 - 18© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Criteria1. Minimize completion time2. Maximize utilization of facilities3. Minimize work-in-process (WIP)inventory4. Minimize customer waiting timeOptimize the use of resources sothat production objectives are met
  19. 19. 15 - 19© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Process-Focused Facilities Schedule incoming orders withoutviolating capacity constraints Check availability of tools and materialsbefore releasing an order Establish due dates for each job andcheck progress Check work in progress Provide feedback Provide work efficiency statistics andmonitor times
  20. 20. 15 - 20© 2011 Pearson Education, Inc. publishing as Prentice HallPlanning and Control Files1. An item master file contains information abouteach component2. A routing file indicates each component’s flowthrough the shop3. A work-center master file contains informationabout the work centerPlanning FilesControl FilesTrack the actual progress made againstthe plan
  21. 21. 15 - 21© 2011 Pearson Education, Inc. publishing as Prentice HallLoading Jobs Assign jobs so that costs, idletime, or completion time areminimized Two forms of loading Capacity oriented Assigning specific jobs to workcenters
  22. 22. 15 - 22© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output Control Identifies overloading andunderloading conditions Prompts managerial action toresolve scheduling problems Can be maintained using ConWIPcards that control the schedulingof batches
  23. 23. 15 - 23© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output ControlExampleWeek Ending 6/6 6/13 6/20 6/27 7/4 7/11Planned Input 280 280 280 280 280Actual Input 270 250 280 285 280Cumulative Deviation –10 –40 –40 –35Planned Output 320 320 320 320Actual Output 270 270 270 270Cumulative Deviation –50 –100 –150 –200Cumulative Change inBacklog0 –20 –10 +5Figure 15.2Work Center DNC Milling (in standard hours)
  24. 24. 15 - 24© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output ControlExampleWork Center DNC Milling (in standard hours)Week Ending 6/6 6/13 6/20 6/27 7/4 7/11Planned Input 280 280 280 280 280Actual Input 270 250 280 285 280Cumulative Deviation –10 –40 –40 –35Planned Output 320 320 320 320Actual Output 270 270 270 270Cumulative Deviation –50 –100 –150 –200Cumulative Change inBacklog0 –20 –10 +5Explanation:270 input,270 output implies0 changeExplanation:250 input,270 output implies–20 changeFigure 15.2
  25. 25. 15 - 25© 2011 Pearson Education, Inc. publishing as Prentice HallInput-Output ControlExampleOptions available to operationspersonnel include:1. Correcting performances2. Increasing capacity3. Increasing or reducing input tothe work center
  26. 26. 15 - 26© 2011 Pearson Education, Inc. publishing as Prentice HallGantt Charts Load chart shows the loading andidle times of departments,machines, or facilities Displays relative workloads overtime Schedule chart monitors jobs inprocess All Gantt charts need to be updatedfrequently to account for changes
  27. 27. 15 - 27© 2011 Pearson Education, Inc. publishing as Prentice HallGantt Load Chart ExampleFigure 15.3DayMonday Tuesday Wednesday Thursday FridayWorkCenterMetalworksMechanicalElectronicsPaintingJob 349Job 349Job 349Job 408Job 408Job 408Processing Unscheduled Center not availableJob 350Job 349Job 295
  28. 28. 15 - 28© 2011 Pearson Education, Inc. publishing as Prentice HallGantt Schedule ChartExampleFigure 15.4JobDay1Day2Day3Day4Day5Day6Day7Day8ABCNowMaintenanceStart of anactivityEnd of anactivityScheduledactivity timeallowedActual workprogressNonproductiontimePoint in timewhen chart isreviewed
  29. 29. 15 - 29© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method A special class of linearprogramming models that assignstasks or jobs to resources Objective is to minimize cost ortime Only one job (or worker) isassigned to one machine (orproject)
  30. 30. 15 - 30© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method Build a table of costs or timeassociated with particularassignmentsTypesetterJob A B CR-34 $11 $14 $ 6S-66 $ 8 $10 $11T-50 $ 9 $12 $ 7
  31. 31. 15 - 31© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method1. Create zero opportunity costs byrepeatedly subtracting the lowest costsfrom each row and column2. Draw the minimum number of verticaland horizontal lines necessary to coverall the zeros in the table. If the numberof lines equals either the number ofrows or the number of columns,proceed to step 4. Otherwise proceed tostep 3.
  32. 32. 15 - 32© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment Method3. Subtract the smallest number notcovered by a line from all otheruncovered numbers. Add the samenumber to any number at theintersection of two lines. Return tostep 2.4. Optimal assignments are at zerolocations in the table. Select one, drawlines through the row and columninvolved, and continue to the nextassignment.
  33. 33. 15 - 33© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment ExampleA B CJobR-34 $11 $14 $ 6S-66 $ 8 $10 $11T-50 $ 9 $12 $ 7TypesetterA B CJobR-34 $ 5 $ 8 $ 0S-66 $ 0 $ 2 $ 3T-50 $ 2 $ 5 $ 0TypesetterStep 1a - RowsA B CJobR-34 $ 5 $ 6 $ 0S-66 $ 0 $ 0 $ 3T-50 $ 2 $ 3 $ 0TypesetterStep 1b - Columns
  34. 34. 15 - 34© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment ExampleStep 2 - LinesA B CJobR-34 $ 5 $ 6 $ 0S-66 $ 0 $ 0 $ 3T-50 $ 2 $ 3 $ 0TypesetterBecause only two linesare needed to cover allthe zeros, the solutionis not optimalStep 3 - SubtractionA B CJobR-34 $ 3 $ 4 $ 0S-66 $ 0 $ 0 $ 5T-50 $ 0 $ 1 $ 0TypesetterThe smallest uncoverednumber is 2 so this issubtracted from all otheruncovered numbers andadded to numbers at theintersection of lines
  35. 35. 15 - 35© 2011 Pearson Education, Inc. publishing as Prentice HallAssignment ExampleBecause three lines areneeded, the solution isoptimal andassignments can bemadeStep 2 - LinesA B CJobR-34 $ 3 $ 4 $ 0S-66 $ 0 $ 0 $ 5T-50 $ 0 $ 1 $ 0TypesetterStart by assigning R-34 toworker C as this is the onlypossible assignment forworker C.Step 4 - AssignmentsA B CJobR-34 $ 3 $ 4 $ 0S-66 $ 0 $ 0 $ 5T-50 $ 0 $ 1 $ 0TypesetterJob T-50 mustgo to worker A as worker Cis already assigned. Thisleaves S-66 for worker B.
  36. 36. 15 - 36© 2011 Pearson Education, Inc. publishing as Prentice HallStep 4 - AssignmentsA B CJobR-34 $ 3 $ 4 $ 0S-66 $ 0 $ 0 $ 5T-50 $ 0 $ 1 $ 0TypesetterAssignment ExampleFrom the original cost tableMinimum cost = $6 + $10 + $9 = $25A B CJobR-34 $11 $14 $ 6S-66 $ 8 $10 $11T-50 $ 9 $12 $ 7Typesetter
  37. 37. 15 - 37© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing Jobs Specifies the order in which jobsshould be performed at work centers Priority rules are used to dispatch orsequence jobs FCFS: First come, first served SPT: Shortest processing time EDD: Earliest due date LPT: Longest processing time
  38. 38. 15 - 38© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobJob Work(Processing) Time(Days)Job DueDate(Days)A 6 8B 2 6C 8 18D 3 15E 9 23Apply the four popular sequencing rulesto these five jobs
  39. 39. 15 - 39© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessA 6 6 8 0B 2 8 6 2C 8 16 18 0D 3 19 15 4E 9 28 23 528 77 11FCFS: Sequence A-B-C-D-E
  40. 40. 15 - 40© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessA 6 6 8 0B 2 8 6 2C 8 16 18 0D 3 19 15 4E 9 28 23 528 77 11FCFS: Sequence A-B-C-D-EAverage completion time = = 77/5 = 15.4 daysSum of total flow timeNumber of jobsUtilization metric = = 28/77 = 36.4%Total job work timeSum of total flow timeAverage number ofjobs in the system = = 77/28 = 2.75 jobsSum of total flow timeTotal job work timeAverage job lateness = = 11/5 = 2.2 daysTotal late daysNumber of jobs
  41. 41. 15 - 41© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleSPT: Sequence B-D-A-C-EJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessB 2 2 6 0D 3 5 15 0A 6 11 8 3C 8 19 18 1E 9 28 23 528 65 9
  42. 42. 15 - 42© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessB 2 2 6 0D 3 5 15 0A 6 11 8 3C 8 19 18 1E 9 28 23 528 65 9SPT: Sequence B-D-A-C-EAverage completion time = = 65/5 = 13 daysSum of total flow timeNumber of jobsUtilization metric = = 28/65 = 43.1%Total job work timeSum of total flow timeAverage number ofjobs in the system = = 65/28 = 2.32 jobsSum of total flow timeTotal job work timeAverage job lateness = = 9/5 = 1.8 daysTotal late daysNumber of jobs
  43. 43. 15 - 43© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleEDD: Sequence B-A-D-C-EJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessB 2 2 6 0A 6 8 8 0D 3 11 15 0C 8 19 18 1E 9 28 23 528 68 6
  44. 44. 15 - 44© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessB 2 2 6 0A 6 8 8 0D 3 11 15 0C 8 19 18 1E 9 28 23 528 68 6EDD: Sequence B-A-D-C-EAverage completion time = = 68/5 = 13.6 daysSum of total flow timeNumber of jobsUtilization metric = = 28/68 = 41.2%Total job work timeSum of total flow timeAverage number ofjobs in the system = = 68/28 = 2.43 jobsSum of total flow timeTotal job work timeAverage job lateness = = 6/5 = 1.2 daysTotal late daysNumber of jobs
  45. 45. 15 - 45© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleLPT: Sequence E-C-A-D-BJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessE 9 9 23 0C 8 17 18 0A 6 23 8 15D 3 26 15 11B 2 28 6 2228 103 48
  46. 46. 15 - 46© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleJobSequenceJob Work(Processing)TimeFlowTimeJob DueDateJobLatenessE 9 9 23 0C 8 17 18 0A 6 23 8 15D 3 26 15 11B 2 28 6 2228 103 48LPT: Sequence E-C-A-D-BAverage completion time = = 103/5 = 20.6 daysSum of total flow timeNumber of jobsUtilization metric = = 28/103 = 27.2%Total job work timeSum of total flow timeAverage number ofjobs in the system = = 103/28 = 3.68 jobsSum of total flow timeTotal job work timeAverage job lateness = = 48/5 = 9.6 daysTotal late daysNumber of jobs
  47. 47. 15 - 47© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing ExampleRuleAverageCompletionTime (Days)UtilizationMetric (%)Average Numberof Jobs inSystemAverageLateness(Days)FCFS 15.4 36.4 2.75 2.2SPT 13.0 43.1 2.32 1.8EDD 13.6 41.2 2.43 1.2LPT 20.6 27.2 3.68 9.6Summary of Rules
  48. 48. 15 - 48© 2011 Pearson Education, Inc. publishing as Prentice HallComparison ofSequencing Rules No one sequencing rule excels on all criteria SPT does well on minimizing flow time andnumber of jobs in the system But SPT moves long jobs tothe end which may resultin dissatisfied customers FCFS does not do especiallywell (or poorly) on anycriteria but is perceivedas fair by customers EDD minimizes maximum lateness
  49. 49. 15 - 49© 2011 Pearson Education, Inc. publishing as Prentice HallCritical Ratio (CR) An index number found by dividing thetime remaining until the due date by thework time remaining on the job Jobs with low critical ratios arescheduled ahead of jobs with highercritical ratios Performs well on average job latenesscriteriaCR = =Due date - Today’s dateWork (lead) time remainingTime remainingWorkdays remaining
  50. 50. 15 - 50© 2011 Pearson Education, Inc. publishing as Prentice HallCritical Ratio ExampleJobDueDateWorkdaysRemaining Critical RatioPriorityOrderA 30 4 (30 - 25)/4 = 1.25 3B 28 5 (28 - 25)/5 = .60 1C 27 2 (27 - 25)/2 = 1.00 2Currently Day 25With CR < 1, Job B is late. Job C is just on scheduleand Job A has some slack time.
  51. 51. 15 - 51© 2011 Pearson Education, Inc. publishing as Prentice HallCritical Ratio Technique1. Helps determine the status of specificjobs2. Establishes relative priorities amongjobs on a common basis3. Relates both stock and make-to-orderjobs on a common basis4. Adjusts priorities automatically forchanges in both demand and jobprogress5. Dynamically tracks job progress
  52. 52. 15 - 52© 2011 Pearson Education, Inc. publishing as Prentice HallSequencing N Jobs on TwoMachines: Johnson’s Rule Works with two or more jobs thatpass through the same twomachines or work centers Minimizes total production time andidle time
  53. 53. 15 - 53© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule1. List all jobs and times for each workcenter2. Choose the job with the shortest activitytime. If that time is in the first work center,schedule the job first. If it is in the secondwork center, schedule the job last.3. Once a job is scheduled, it is eliminatedfrom the list4. Repeat steps 2 and 3 working toward thecenter of the sequence
  54. 54. 15 - 54© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule ExampleJobWork Center 1(drill press)Work Center 2(lathe)A 5 2B 3 6C 8 4D 10 7E 7 12
  55. 55. 15 - 55© 2011 Pearson Education, Inc. publishing as Prentice HallJobWork Center 1(drill press)Work Center 2(lathe)A 5 2B 3 6C 8 4D 10 7E 7 12B E D C AJohnson’s Rule Example
  56. 56. 15 - 56© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule ExampleTime 0 3 10 20 28 33B ACDEWC1WC2B ACDEJobWork Center 1(drill press)Work Center 2(lathe)A 5 2B 3 6C 8 4D 10 7E 7 12
  57. 57. 15 - 57© 2011 Pearson Education, Inc. publishing as Prentice HallJohnson’s Rule ExampleTime 0 3 10 20 28 33Time 0 1 3 5 7 9 10 11 12 13 17 19 21 22 2325 27 29 31 33 35B ACDEB ACDEWC1WC2B E D C AB ACDEJobWork Center 1(drill press)Work Center 2(lathe)A 5 2B 3 6C 8 4D 10 7E 7 12
  58. 58. 15 - 58© 2011 Pearson Education, Inc. publishing as Prentice HallLimitations of Rule-BasedDispatching Systems1. Scheduling is dynamic and rulesneed to be revised to adjust tochanges2. Rules do not look upstream ordownstream3. Rules do not look beyond duedates
  59. 59. 15 - 59© 2011 Pearson Education, Inc. publishing as Prentice HallFinite Capacity Scheduling Overcomes disadvantages of rule-basedsystems by providing an interactive,computer-based graphical system May include rules and expert systems orsimulation to allow real-time response tosystem changes Initial data often from an MRP system FCS allows the balancing of deliveryneeds and efficiency
  60. 60. 15 - 60© 2011 Pearson Education, Inc. publishing as Prentice HallFinite Capacity SchedulingMRP Data• Masterschedule• BOM• InventoryPriorityrules• Expertsystems• Simulationmodels• Routing files• Work centerinformationToolingand otherresourcesSetups andrun timeFigure 15.5Interactive Finite Capacity Scheduling
  61. 61. 15 - 61© 2011 Pearson Education, Inc. publishing as Prentice HallFinite Capacity Scheduling
  62. 62. 15 - 62© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling RepetitiveFacilities Level material use can helprepetitive facilities Better satisfy customerdemand Lower inventoryinvestment Reduce batch size Better utilize equipmentand facilities
  63. 63. 15 - 63© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling RepetitiveFacilities Advantages include:1. Lower inventory levels2. Faster product throughput3. Improved component quality4. Reduced floor-space requirements5. Improved communications6. Smoother production process
  64. 64. 15 - 64© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling ServicesService systems differ from manufacturingManufacturing ServicesSchedules machinesand materialsSchedule staffInventories used tosmooth demandSeldom maintaininventoriesMachine-intensive anddemand may be smoothLabor-intensive anddemand may be variableScheduling may be boundby union contractsLegal issues may constrainflexible schedulingFew social or behavioralissuesSocial and behavioralissues may be quiteimportant
  65. 65. 15 - 65© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Services Hospitals have complex schedulingsystem to handle complex processesand material requirements Banks use a cross-trained and flexibleworkforce and part-time workers Retail stores use schedulingoptimization systems that track sales,transactions, and customer traffic tocreate work schedules in less time andwith improved customer satisfaction
  66. 66. 15 - 66© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Services Airlines must meet complex FAA andunion regulations and often use linearprogramming to develop optimalschedules 24/7 operations like police/firedepartments, emergency hot lines, andmail order businesses use flexibleworkers and variable schedules, oftencreated using computerized systems
  67. 67. 15 - 67© 2011 Pearson Education, Inc. publishing as Prentice HallDemand Management Appointment or reservationsystems FCFS sequencing rules Discounts or other promotionalschemes When demand management is notfeasible, managing capacitythrough staffing flexibility may beused
  68. 68. 15 - 68© 2011 Pearson Education, Inc. publishing as Prentice HallScheduling Service EmployeesWith Cyclical Scheduling Objective is to meet staffingrequirements with the minimumnumber of workers Schedules need to be smooth andkeep personnel happy Many techniques exist from simplealgorithms to complex linearprogramming solutions
  69. 69. 15 - 69© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling Example1. Determine the staffing requirements2. Identify two consecutive days with thelowest total requirements and assignthese as days off3. Make a new set of requirementssubtracting the days worked by the firstemployee4. Apply step 2 to the new row5. Repeat steps 3 and 4 until allrequirements have been met
  70. 70. 15 - 70© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Capacity (Employees)Excess CapacityDay M T W T F S SStaff required 5 5 6 5 4 3 3
  71. 71. 15 - 71© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Employee 2 4 4 5 4 3 3 3Capacity (Employees)Excess CapacityDay M T W T F S SStaff required 5 5 6 5 4 3 3
  72. 72. 15 - 72© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Employee 2 4 4 5 4 3 3 3Employee 3 3 3 4 3 2 3 3Capacity (Employees)Excess CapacityDay M T W T F S SStaff required 5 5 6 5 4 3 3
  73. 73. 15 - 73© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Employee 2 4 4 5 4 3 3 3Employee 3 3 3 4 3 2 3 3Employee 4 2 2 3 2 2 3 2Capacity (Employees)Excess CapacityDay M T W T F S SStaff required 5 5 6 5 4 3 3
  74. 74. 15 - 74© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Employee 2 4 4 5 4 3 3 3Employee 3 3 3 4 3 2 3 3Employee 4 2 2 3 2 2 3 2Employee 5 1 1 2 2 2 2 1Capacity (Employees)Excess CapacityDay M T W T F S SStaff required 5 5 6 5 4 3 3
  75. 75. 15 - 75© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Employee 2 4 4 5 4 3 3 3Employee 3 3 3 4 3 2 3 3Employee 4 2 2 3 2 2 3 2Employee 5 1 1 2 2 2 2 1Employee 6 1 1 1 1 1 1 0Capacity (Employees)Excess CapacityDay M T W T F S SStaff required 5 5 6 5 4 3 3
  76. 76. 15 - 76© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Employee 2 4 4 5 4 3 3 3Employee 3 3 3 4 3 2 3 3Employee 4 2 2 3 2 2 3 2Employee 5 1 1 2 2 2 2 1Employee 6 1 1 1 1 1 1 0Employee 7 1Capacity (Employees)Excess CapacityDay M T W T F S SStaff required 5 5 6 5 4 3 3
  77. 77. 15 - 77© 2011 Pearson Education, Inc. publishing as Prentice HallCyclical Scheduling ExampleM T W T F S SEmployee 1 5 5 6 5 4 3 3Employee 2 4 4 5 4 3 3 3Employee 3 3 3 4 3 2 3 3Employee 4 2 2 3 2 2 3 2Employee 5 1 1 2 2 2 2 1Employee 6 1 1 1 1 1 1 0Employee 7 1Capacity (Employees) 5 5 6 5 4 3 3Excess Capacity 0 0 0 0 0 1 0Day M T W T F S SStaff required 5 5 6 5 4 3 3
  78. 78. 15 - 78© 2011 Pearson Education, Inc. publishing as Prentice HallAll rights reserved. No part of this publication may be reproduced, stored in a retrievalsystem, or transmitted, in any form or by any means, electronic, mechanical, photocopying,recording, or otherwise, without the prior written permission of the publisher.Printed in the United States of America.

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