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Instructional Objective

Module 7 Planning and Scheduling with the Critical Path Method Session 7.1: Planning tools and the critical path method (CPM). Instructional Objective. To prepare a critical path network plan for projects or subprojects. Overview. Planning activities Scheduling resources and

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Instructional Objective

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  1. Module 7Planning and Scheduling with the Critical Path MethodSession 7.1: Planning tools and the critical path method (CPM)

  2. Instructional Objective To prepare a critical path networkplan for projects or subprojects

  3. Overview • Planning activities • Scheduling resources and • Controlling progress

  4. On-the-job tasks • Review the WBS, responsibility matrix, master summary schedule, and level of detail • Select the appropriate scheduling tool (typically time-scaled, precedence network diagram) • Disaggregate summary activities on the master summary schedule into activities and prepare activity list(s) • Assign responsibility and resource to each activity

  5. On-the-job tasks (continued) • Estimate the duration of each activity • Establish the sequence of activities • Prepare the time-scaled precedence network diagram (or other form of schedule) • Determine the critical path • Calculate the activity float • Revise as required

  6. What is planning ? Who ? Does what? When ? and How long will it take? With what inter-relationships?

  7. Why is planning important ? • Coordination • Control • Communication • Commitment

  8. A cargo ship: an analogy Destination Course set initially Start of journey

  9. Destination External influence Course set initially Reset course Start of journey Actual travel Position surveyed A cargo ship: an analogy

  10. Planning tools • Activity lists • Bar chart (Gantt) • Network diagram family

  11. Planning tools • Network diagram family • Critical path method (CPM) • Precedence diagram (PDM) • Time-scaled precedence diagram • Arrow diagram • PERT diagram

  12. Master summary schedule House deliverable CODERESP. WEEKS From WBS summary activities or sub-projects or work package 4 8 12 16 20 24 Prepare 10 20 30 40 50 60 70 Plan (A) Site (C) Foundation (C) Frame (C) Roof (SC) Systems (SC) Plumbing (P) Electrical (E) Telephone (T) Project mgt (PM) Prepare Construct Construct Construct Install Continuous activity

  13. Rolling wave subnets Start Finish Master summary schedule Level of detail months or weeks Today Each month add a month Each month drop a month Detailed network for next period Level of detail weeks or days 3-6 months

  14. Guidelines for creating activities • Disaggregate summary activities into activities • Use “rolling wave” approach for long projects • Use unit of time based on and less than previously established control period • Use verb (action) and a noun (the thing affected), for example, buy land • Assign responsibility to only one organization or individual • Assign only one resource to each activity • Code with a “family member” • Do not disaggregate project management

  15. Master summary scheduleHouse deliverable CODERESP. WEEKS From WBS summary activities or sub-projects or work package 4 8 12 16 20 24 Prepare 10 20 30 40 50 60 70 Plan (A) Site (C) Foundation (C) Frame (C) Roof (SC) Systems (SC) Plumbing (P) Electrical (E) Telephone (T) Project mgt (PM) Prepare Construct Construct Construct Install Continuous activity

  16. Summary activity Disaggregate into activities Terminology: Activity or Task

  17. Summary activity # 10—PLAN Disaggregate into activities • Buy land • Study site • Define requirements • Finalize drawings • Select contractor • Order utilities • Plan construction

  18. Activity list for house projectSummary activity: Planning #10 # Activity Responsibility Duration Start Finish (weeks) (weeks) 100 Buy land Owner 1 0 1 101 Study site Architect 2 1 3 102 Define requirements Architect 2 1 3 103 Finalize drawings Architect 1 3 4 104 Select contractor Owner 2 4 6 105 Order utilities Architect 1 4 5 106 Plan construction Contractor 1 6 7

  19. Bar chart for house project Summary activity: Planning #10 Duration # Activity 1 2 3 4 5 6 7 (weeks) xxxx 100 Buy land 1 (Owner) xxxx xxxx 101 Study site 2 (Architect) xxxx xxxx 102 Define requirements 2 (Architect) xxxx 103 Finalize drawings 1 (Architect) xxxx xxxx 104 Select contractor 2 (Owner) 105 Order utilities 1 xxxx (Architect) xxxx 106 Plan construction 1 (Contractor)

  20. Network diagram family • Critical path method (CPM) • Precedence diagram (PDM) • Time-scaled precedence diagram • Arrow diagram • PERT diagram

  21. 101 2 105 1 Study site Order utilities Architect Architect 106 1 100 1 103 1 Finalize drawings Buy land Plan construction Contractor Owner Architect 102 104 2 2 Define requirements Activity ident. no. Selectcontractor Duration Owner Architect Activity description Resource Precedence diagram method (PDM)House projectSummary activity: Planning #10

  22. 101 2 105 1 Study site Order utilities Architect Architect 106 1 100 1 103 1 Finalize drawings Buy land Plan construction Contractor Owner Architect 102 104 2 2 Define requirements Activity ident. no. Selectcontractor Duration Owner Architect Activity description Resource Critical Path (thick lines)House projectSummary activity: Planning #10

  23. Activity Box Fence Slack or float 100 105 1 1 101 2 Buy land Order utilities Study site Owner Architect Architect 106 1 Plan construction Contractor 104 2 102 2 103 1 Finalize drawings Define requirements Select contractor Owner Architect Architect Time scale in weeks 1 2 3 4 5 6 7 Time-scaled precedence diagramHouse project Summary activity: Planning #10

  24. Key concepts • Project duration • Critical path • Float or slack

  25. Mathematical Analysis • Early start (ES) • Late start (LS) • Early finish (EF) • Late finish (LF)

  26. Table printout House projectSummary activity: Planning #10

  27. Tool comparison Tool When to use Example Bar chart Simple sequential logic with few parallel activities Road construction Network diagram Complex sequential logic with many parallel activities Bridge construction Water supply system construction

  28. Making a CPM network:The process • Create activity list form for summary activities • Disaggregate summary activities and complete activity forms • Conduct meeting with managers • Develop logical sequence • Create network diagram • Blackboard version • Computer version

  29. Activitylist Project no.________Title: _______________________________ Summary activity No._________Title _______________ Date prepared: ____________________ Responsible person: _______________________________ Description Individual responsibility Start Date* Finish date* Cost Duration No. Manpowernumber Organizational unit * To be filled in after CPM is completed.

  30. Making a PDM network:The mechanics 1. Make activities flow from left to right 2. Have one start box and one finish box 3. Draw arrows as you go 4. Draw arrows to and from end of box and parallel to horizontal 5. Can show any logic 6. Try to avoid crossing lines 7. Leave no hanging activities (danglers)

  31. Simple finish to start Hire salesmen 1 Train salesmen 3 Sell to distributors 5 Source: Mulvaney, Analysis Bar Charting

  32. Two predecessors Agree on test specification 16 Test part X 20 Obtain test equipment 18 Source: Mulvaney, Analysis Bar Charting

  33. Multiple starts after decision Prepare contractors’ list 23 Start working drawings 25 Instructarchitects to proceed (Approval) 21 Arrange access road 27 Prepare engineering subcontracts 29 Source: Mulvaney, Analysis Bar Charting

  34. Cross-relationships Obtain raw material 139 Machine part I 143 Issue job cards 141 Machine part II 145 Source: Mulvaney, Analysis Bar Charting

  35. Making a PDM network:The mechanics 1. Make activities flow from left to right 2. Have one start box and one finish box 3. Draw arrows as you go 4. Draw arrows to and from end of box and parallel to horizontal 5. Can show any logic 6. Try to avoid crossing lines 7. Leave no hanging activities (danglers)

  36. Hanging activities A Start Finish B D C E F

  37. CalculationsSolve for ES, EF, LS, and LF ES EF 0 2 ES EF ES EF 4 1 2 D A B LS LF LS LF LS LF ES EF 2 C LS LF

  38. CalculationsSolve for ES, EF, LS, and LF (continued) ES EF 7 6 2 6 0 2 Critical path 2 4 1 A D B 0 2 2 6 6 7 LS LF 2 4 2 C 4 6 Don’t take shortcuts.

  39. Mechanics of calculations From left to right Write on top Finds duration Forward pass When a choice is available, take the highest. 0 3 3 7 7 9 3 2 4 A B C 0 3 3 7 7 9 From right to left Write on bottom Finds critical path and float Backward pass When a choice is available, take the lowest.

  40. Summary • Planning is essential • Tools facilitate planning • Critical path and float are key concepts • Calculating the network is an essential skill

  41. “Sample” network calculations Problem (Weeks) 0 0 4 2 4 5 Start A C D Finish 2 1 B E

  42. “Sample” network calculationsSolution (Weeks) Critical path 0 4 4 6 0 6 11 4 2 5 Start A C D 11 0 4 4 6 6 11 Finish 0 2 2 3 2 1 11 B E Path B - E float = 8 8 10 10 11

  43. 0 1 2 3 4 5 6 7 8 9 10 11 “Sample” time-scaled precedence diagramSolution Start Finish A:::4C:2:D::5 B:2E1 1 2 3 4 5 6 7 8 B and E share path float of 8 (Total) Depending on when B is done E could have less activity float (Free)

  44. Two kinds of float or slack • Activity float (Free) • Path float (Total)

  45. Module 7Planning and Scheduling with the Critical Path MethodSession 7.1Planning Tools: Arrow Diagram and PERT Diagram

  46. Planning tools:Arrow diagram and PERT diagram • Network diagram family • Critical path method (CPM) • Precedence diagram (PDM) • Time-scaled precedence diagram • Arrow diagram • PERT diagram

  47. Objectives • Restate history • Draw distinctions • Give reasons why precedence diagrams are recommended

  48. History • Arrow • Kelly and Walker at Du Pont • How to solve scheduling problems • U.S.A., 1957 • Precedence • France • PERT • Booz-Allen and Hamilton • Polaris Submarine (US Navy) • U.S.A.

  49. Arrow diagram networkHouse project Summary activity: Planning #10 Permits 101 Utilities 102 1 3 6 2 1 Buy land 100 1 Plan construction 106 Define 102 Plan 103 Select 104 2 4 5 7 8 2 1 2 1 Duration in weeks Dotted lines are dummy activities. Dummies are zero time dependencies.

  50. (1 x shortest) + (4 x most likely) + (1 x longest) = 1.5 + 12 + 5 = 18.5 6 6 6 PERT diagram 3 time estimates Event on node Complete plans 3.08 Shortest 1.5 Most likely 3.0 Longest 5.0 Expected time 3.08 Start 0 Landbought Formula

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