1. (4) Critical Path Method
Project Tool
(4) Critical Path Method
Prof. Dr. Christian Bleis 1
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2. Finding the critical path from project start to project end
CPM – goals
Main goals
Finding the critical path from project start to project end
Economically feasible cut this path
How do I want to fulfill the Project goal??
Prof. Dr. Christian Bleis 2
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3. Process-Arrow Network Arrows = tasks, operations, process
CPM – design
Process-Arrow Network
Arrows = tasks, operations, process
Knot = event, milestone, stage
Starting
stage
End
stage
Task
Duration of the task
How do I want to fulfill the Project goal??
Prof. Dr. Christian Bleis 3
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4. CPM-Example (forward + backward calculation)
(3) Calculate material costs 1 3 3 3 4 10 11
(7) Determine cost of sale
(1) Order supplies 5 3
(4) Delivery (time) of the materials
Start 5 7 16 16 5
(6) Calculate personnel costs
Goal
(2) Set up the work plan
(8) Work execute 6 5 2
(5) Instruct co-workers 4
Duration of the task 5 6 4 10 10
Earliest date on which the Process can be completed
Latest date on which the Process can be completed
Prof. Dr. Christian Bleis 4
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5. 5 (6) Steps to create a CPM-Diagram
CPM planning involves the following steps:
Specify the individual activities.
Determine the sequence of those activities.
Draw a network diagram.
Estimate the completion time for each activity.
Identify the critical path (longest path through the network)
Update the CPM diagram as the project progresses.
Prof. Dr. Christian Bleis 5
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6. Step 5: Identify the Critical Path (a)
5 (6) Steps to create a CPM-Diagram
Step 5: Identify the Critical Path (a)
The critical path is the longest-duration path through the network.
The significance of the critical path is that the activities that lie on it cannot be delayed without delaying the project. Because of its impact on the entire project, critical path analysis is an important aspect of project planning.
… 
Prof. Dr. Christian Bleis 6
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7. Step 5: Identify the Critical Path (b)
5 (6) Steps to create a CPM-Diagram
Step 5: Identify the Critical Path (b)
The critical path can be identified by determining the following four parameters for each activity:
EST earliest start time: the earliest time at which the activity can start given that its precedent activities must be completed first.
EFT earliest finish time, equal to the earliest start time for the activity plus the time required to complete the activity.
LFT latest finish time: the latest time at which the activity can be completed without delaying the project.
LST latest start time, equal to the latest finish time minus the time required to complete the activity.
… 
Prof. Dr. Christian Bleis 7
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8. Step 5: Identify the Critical Path (c)
5 (6) Steps to create a CPM-Diagram
Step 5: Identify the Critical Path (c)
The slack time for an activity is the time
between its earliest and latest start time, or
between its earliest and latest finish time.
Slack is the amount of time that an activity can be delayed past its earliest start or earliest finish without delaying the project.
The critical path is the path through the project network in which none of the activities have slack, that is, the path for which ES=LS and EF=LF for all activities in the path.
A delay in the critical path delays the project. Similarly, to accelerate the project it is necessary to reduce the total time required for the activities in the critical path.
Prof. Dr. Christian Bleis 8
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9. Step 6: Update CPM-Diagram
5 (6) Steps to create a CPM-Diagram
Step 6: Update CPM-Diagram
As the project progresses, the actual task completion times will be known and the network diagram can be updated to include this information.
A new critical path may emerge, and structural changes may be made in the network if project requirements change.
Prof. Dr. Christian Bleis 9
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10. Example Task (No. 1) Critical Path Method Interaktionskompetenz
Prof. Dr. Christian Bleis 10
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11. CPM-Example
1. Complete the foreward Calculation of the following CPM Diagram
(3) Calculate material costs 1 3 . . 3 .. ..
(7) Determine cost of sale
(1) Order supplies 5 5 5
(4) Delivery (time) of the materials
Start 5 .. .. . . 8
(6) Calculate personnel costs
Goal
(2) Set up the work plan
(8) Work execute 3 4 2
(5) Instruct co-workers 4
Duration of the task . . 4 .. ..
Earliest date on which the Process can be completed
Latest date on which the Process can be completed
Prof. Dr. Christian Bleis 11
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12. CPM-Example
2. Complete the backward Calculation of the following CPM Diagram
(3) Calculate material costs 1 3 5 . 3 12 ..
(7) Determine cost of sale
(1) Order supplies 5 5 5
(4) Delivery (time) of the materials
Start 5 17 .. . 8
(6) Calculate personnel costs
Goal
(2) Set up the work plan
(8) Work execute 3 4 2
(5) Instruct co-workers 4
Duration of the task 4 . 4 10 ..
Earliest date on which the Process can be completed
Prof. Dr. Christian Bleis 12
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13. CPM-Example 3. Mark the Critical Path 5 9 3 12 12 5 5 5 17 17 8
(3) Calculate material costs 1 3 5 9 3 12 12
(7) Determine cost of sale
(1) Order supplies 5 5 5
(4) Delivery (time) of the materials
Start 5 17 17 8
(6) Calculate personnel costs
Goal
(2) Set up the work plan
(8) Work execute 3 4 2
(5) Instruct co-workers 4
Duration of the task 4 4 4 10 14
Latest date on which the Process can be completed
Prof. Dr. Christian Bleis 13
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14. CPM-Example (forward + backward calculation)
(3) Calculate material costs 1 3 5 9 3 12 12
(7) Determine cost of sale
(1) Order supplies 5 5 5
(4) Delivery (time) of the materials
Start 5 17 17 8
(6) Calculate personnel costs
Goal
(2) Set up the work plan
(8) Work execute 3 4 2
(5) Instruct co-workers 4
Duration of the task 4 4 4 10 14
Earliest date on which the Process can be completed
Latest date on which the Process can be completed
Prof. Dr. Christian Bleis 14
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15. Example Task (No. 2) Critical Path Method
Complete the foreward Calculation of the following CPM Diagram
Prof. Dr. Christian Bleis 15
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16. CPM-Example
1. Complete the foreward Calculation of the following CPM Diagram
(Jenny, Abb. 4.05, S.341)
Prof. Dr. Christian Bleis 16
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17. CPM-Example
2. Good, now complete the backward-Calculation of the CPM Diagram
Errechnen der Zeitwerte und Bestimmung des kritischen Weges:
Zeitwert der Vorwärtsrechnung: Beginn bei 0
dann: addieren der Zeiteinheiten nach der logischen Reihenfolge und Eintrag in das linke untere Feld des Ereigniskreises
Bedeutung: Bestimmung der frühesten Ereigniszeitpunkte
(Jenny, Abb. 4.05, S.341)
Prof. Dr. Christian Bleis 17
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18. CPM-Example 3. Mark the Critical Path (Jenny, Abb. 4.05, S.341)
Zeitwerte der Rückwärtsrechnung erhält man nach Abschluss der Vorwärtsrechnung. Anhand des kumulierten Ergebnisses wird der Netzplan rückwärtsgerechnet.
Zeitwert der Rückwärtsrechnung: vom Endereignis und dessen Zeitwert aus der Vorwärtsrechnung ausgehend
Bestimmung der spätesten Ereigniszeitpunkte durch Subtraktion der Zeitwerte
Eintrag in den rechten unteren Teil des Ereignisknotens
(Jenny, Abb. 4.05, S.341)
Prof. Dr. Christian Bleis 18
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19. CPM-Example 3. Mark the Critical Path (Jenny, Abb. 4.05, S.341)
(Jenny, Abb. 4.05, S.341)
Prof. Dr. Christian Bleis 19
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20. Benefits + Limitations
of CPM
Prof. Dr. Christian Bleis 20
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21. CPM provides the following benefits :
Benefits of CPM
CPM provides the following benefits :
Provides a graphical view of the project.
Predicts the time required to complete the project.
Shows which activities are critical to maintaining the schedule and which are not.
Prof. Dr. Christian Bleis
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22. Limitations of CPM
CPM was developed for complex but fairly routine projects with minimal uncertainty in the project completion times. For less routine projects there is more uncertainty in the completion times, and this uncertainty limits the usefulness of the deterministic CPM model.
Prof. Dr. Christian Bleis
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23. Are there other ways to visualize network planning?
Prof. Dr. Christian Bleis 23
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24. Starting with the CPM-Example
(3) Calculate material costs 1 3 3 3 4 10 11
(7) Determine cost of sale
(1) Order supplies 5 3
(4) Delivery (time) of the materials
Start 5 7 16 16 5
(6) Calculate personnel costs
Goal
(2) Set up the work plan
(8) Work execute 6 5 2
(5) Instruct co-workers 4
Duration of the task 5 6 4 10 10
Earliest date on which the Process can be completed
Latest date on which the Process can be completed
Prof. Dr. Christian Bleis 24
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25. Inventor: Morgan R. Walker and James E. Kelley (1957)
PERT – goals and design
Main goals
Monitoring of processes by checking the times of milestones
Stage-Knot-Network
Arrow = duration
Knot = event, result, milestone, stage
Stage
duration
Inventor: Morgan R. Walker and James E. Kelley (1957)
Question to be answered: What do I want to achieve during the Project?
Prof. Dr. Christian Bleis 25
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26. personnel costs calculated
PERT (with the same example) 1 3 1
Material- und
personnel costs calculated
Material
ordered 4 3 3 10 11 3 5 1 7 5
Project start
Project goal 16 16 2 4 6 5
Material
delivered and
workforce
instructed
Work plan
set up 4 5 6 10 10
Prof. Dr. Christian Bleis 26
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27. Inventor: Morgan R. Walker and James E. Kelley (1957)
MPM– goals and design
Main goals
Visualizing of complex processes with high interdependencies
Task-Knot-Network
Arrow = correlation (and/or duration)
Knot = tasks
Tasks.-No.
Task
Earliest finishing time
Earliest starting Time
EST
duration
EFT
Inventor: Morgan R. Walker and James E. Kelley (1957)
LST
LFT
Latest starting Time
Latest starting Time
Prof. Dr. Christian Bleis 27
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28. Metra-Potential-Method (MPM)
(3)
Calculate
material costs 3 4 7 6 10
(7)
(1)
Calculate costs of sale
Order Material 10 5 15 3 3
(4) 11 16 3
Supply time of the material
(0) 3 1 7 10 3 10
Projectstart
Project goal
(6) 16 16
Calculating of
personnel costs
(2) 5 5 10
(8)
Do the job
Set up work plan 6 11 10 6 16 5 5 10 16 1 6
(5)
Instruct work force 5 4 9 6 10
Prof. Dr. Christian Bleis 28
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29. Your Project
Prof. Dr. Christian Bleis 29
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30. The basic idea of this 3rd Step
(Controlling + Monitoring)
Prof. Dr. Christian Bleis 30
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31. Can you imagine different phases of a project? (I)
The traditional approach
Prof. Dr. Christian Bleis 31
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32. 6. Make Correction as needed
There are three areas where projects most commonly go wrong.
The cost of the work is too high.
The work isn't completed on time. ( CPM)
The work just isn't good enough. ( Ratios, KPI’s)
All three of these are your responsibility as project manager -- Cost, Schedule, Quality. You have to follow up early and often if you want to correct problems before its too late. Once a task is finished or has had a cost overrun, it becomes much more difficult to compensate later in the project.
Prof. Dr. Christian Bleis
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