Creating a network diagram can be an involved process that begins after you've determined predecessors to your activity. Here's a simple example that can help you learn how network diagrams can be useful in any project you manage.
You find out how to draw the network diagram for a sample project from the information in the table shown here:
| Activity Identifier Code | Activity Description | Immediate Predecessors |
|---|---|---|
| 1 | Load car | 3, 6 |
| 2 | Get money from bank | 5 |
| 3 | Make egg sandwiches | 7 |
| 4 | Drive to lake | 1 |
| 5 | Decide which lake | None |
| 6 | Buy gasoline | 2 |
| 7 | Boil eggs (for egg sandwiches) | 5 |
Begin your project with a single milestone and label it Start.
Find all activities in the table that have no immediate predecessors — they can all start as soon as you begin your project.
In this case, only Activity 5 has no immediate predecessors.
Begin your diagram by drawing the relationship between the Start of your project and the beginning of Activity 5.
Depict Activity 5 with a box and draw an arrow to it from the Start box.Find all activities that have your first activity as an immediate predecessor.
Activities 2 and 7 have Activity 5 as an immediate predecessor. Draw boxes to represent these two activities, and draw arrows from Activity 5 to Activities 2 and 7.
Continue in the same way with the remaining activities.
Only Activity 6 has Activity 2 as an immediate predecessor.Draw a box to represent Activity 6 and draw an arrow from Activity 2 to that box.
Only Activity 3 has Activity 7 as an immediate predecessor. So draw a box to represent Activity 3, and draw an arrow from Activity 7 to Activity 3.
Now realize that Activity 1 has both Activities 3 and 6 as immediate predecessors. Therefore, draw a box representing Activity 1 and draw arrows from Activities 3 and 6 to this box.
The rest is pretty straightforward. Because only Activity 4 has Activity 1 as its immediate predecessor, draw a box representing Activity 4 and draw an arrow from Activity 1 to Activity 4.
After adding all the activities to the diagram, draw a box to represent End, and draw an arrow from Activity 4 (the last activity you have to complete) to that box.
Completed picnic-at-the-lake network diagram.Now for an important timing-related question. How long will you and your friend take to get to the lake for your picnic? The upper path (Start, Activities 5, 2, 6, 1, 4, and End) takes 52 minutes to complete, and the lower path (Start, Activities 5, 7, 3, 1, 4, and End) takes 57 minutes to complete. Thus, it will take 57 minutes from the time you start until you arrive at the lake for your picnic, and the lower path is the critical path.