Project Scheduling

              Critical Path Method

Based on material from Chapter 6 of Project Management and Teamwor...
How do you schedule complex
             projects?

• Make a list of things to do?
• Use an outline?
• Draw a concept map?...
Dinner & Concert
     How much time do you need to prepare and consume the meal?

• Menu consists of soup and baked chicke...
Meal Planning Exercise
                Work Breakdown Structure
  Boil Soup           Eat Soup
   (Pot 1)             (Pot...
Critical Path Method
• Work breakdown structure ok for simple
  task with few activities
• When number of task large, a sy...
CPM - Forward Pass
Early Start (ES) - Earliest time that each activity
can start
- obtained by adding the earliest start o...
Meal Planning Exercise
           Critical Path Method - Forward Pass
0               35   35                50
    Boil S...
CPM - Backward Pass

Late Start (LS) - Latest possible starting time that
each activity can have
- calculated as the earli...
Meal Planning Exercise
           Critical Path Method - Backward Pass
0                35   35               50
     Boil...
CPM - Critical Path & Floats
Critical Path - The path for which activities cannot
be delayed
- activities on critical path...
Meal Planning Exercise
                          Critical Path

0                35   35               50
     Boil Soup  ...
CritPath Program
         http://www.ce.umn.edu/~smith


• Allows easy entry of activites
• Provides critical path calcula...
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Project Scheduling (Power Point File)

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Project Scheduling (Power Point File)

  1. 1. Project Scheduling Critical Path Method Based on material from Chapter 6 of Project Management and Teamwork, by Karl Smith
  2. 2. How do you schedule complex projects? • Make a list of things to do? • Use an outline? • Draw a concept map? • Focus on those things we know how to do first? • Use project management software?
  3. 3. Dinner & Concert How much time do you need to prepare and consume the meal? • Menu consists of soup and baked chicken • Soup must be boiled 35 minutes and will allow 15 minutes to serve and consume • Chicken dish requires 30 minutes to boil rice, 15 minutes to brown chicken in frying pan, 15 minutes to bake rice and chicken in baking dish • Sauce takes 5 minutes to prepare in frying pan and 15 minutes to boil peas • Only have two pots and one frying pan • Wine takes 5 minutes to uncork and 30 minutes to let breath before serving • Allow 25 minutes to serve and consume entrée and wine
  4. 4. Meal Planning Exercise Work Breakdown Structure Boil Soup Eat Soup (Pot 1) (Pot 1) Eat Entree Boil Peas (Pot 2) Boil Rice Bake Entree (Pot 2) Brown Chicken Prepare Sauce (Fry Pan) (Fry Pan) Activity Name Open Wine Wine Breathes (Resource)
  5. 5. Critical Path Method • Work breakdown structure ok for simple task with few activities • When number of task large, a systematic solution is to use the Critical Path Method (CPM) – to use CPM must know the duration of each activity and the predecessors of each
  6. 6. CPM - Forward Pass Early Start (ES) - Earliest time that each activity can start - obtained by adding the earliest start of its latest starting predecessor to the that predecessor’s duration - when two or more activities must be competed before the next one can start, then the maximum must be used Early Finish (EF) - Determined by summing the early start (ES) and duration
  7. 7. Meal Planning Exercise Critical Path Method - Forward Pass 0 35 35 50 Boil Soup Eat Soup 35 15 50 75 Eat Entree 25 30 45 Boil Peas 0 30 15 Boil Rice 30 45 Bake Entree 30 15 0 15 15 20 Brown Chicken Prepare Sauce 15 5 0 5 5 35 ES EF Open Wine Wine Breathes Activity Name 5 30 duration
  8. 8. CPM - Backward Pass Late Start (LS) - Latest possible starting time that each activity can have - calculated as the earliest starting successor, less the duration of the activity under consideration Late Finish (LF) - The resulting finish time based on late start (LS)
  9. 9. Meal Planning Exercise Critical Path Method - Backward Pass 0 35 35 50 Boil Soup Eat Soup 35 15 0 35 35 50 50 75 Eat Entree 25 30 45 50 75 Boil Peas 0 30 15 Boil Rice 35 50 30 45 Bake Entree 30 15 5 35 35 50 0 15 15 20 Brown Chicken Prepare Sauce 15 5 15 30 30 35 0 5 5 35 ES EF Open Wine Wine Breathes Activity Name 5 30 duration 15 20 20 50 LS LF
  10. 10. CPM - Critical Path & Floats Critical Path - The path for which activities cannot be delayed - activities on critical path will have equal earliest and latest times and are call critical Floats - The amount the termination of an activity can be delayed before delaying a successor is called free float (FF). FFi = (ESi+1) min - ESi - Di The amount of slack an activity has before it would cause the path on which it lies to become critical is called the total float (TF). TFi = LFi - EFi
  11. 11. Meal Planning Exercise Critical Path 0 35 35 50 Boil Soup Eat Soup 35 15 0 35 35 50 50 75 Eat Entree 25 30 45 50 75 Boil Peas 0 30 15 Boil Rice 35 50 30 45 Bake Entree 30 15 15 35 35 50 0 15 15 20 Brown Chicken Prepare Sauce 15 5 FF = 50 - 30 - 15 = 5 15 30 30 35 0 5 5 35 ES EF Open Wine Wine Breathes Activity Name 5 30 duration 15 20 20 50 LS LF
  12. 12. CritPath Program http://www.ce.umn.edu/~smith • Allows easy entry of activites • Provides critical path calculations (ES, EF, LS, LF, Float) and algorithm stepper • Calculates critical path • Gives associated Gantt Chart - a time-scaled network (Gantt Chart does not show interdependence)

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