Código fuente laboratorio de modulación AM

Most experienced schedulers prefer to create the logic diagram by hand rather than on a com- puter. The project management software of today provides the possibility of creating the logic diagram right on the computer. The problem is that the computer screen is small and allows only a few activity boxes to display on the screen at one time. For a small project this will work fine, but for a project of many activities, it is difficult to locate the proper predecessors and successors in order to draw the arrows between them. This results in excessive scrolling up and down and to the left and right, making it easy to create errors. Another advantage of the hand-drawn schedule is that it gives the management team the vision of the entire project. If the logic diagram is created by hand, there will be many revisions as the project devel- ops. A large eraser is frequently needed because the team’s thinking processes evolve as the

FIGURE 6.9 Hand-stamped logic diagram

project schedule develops. Also, as more people are given the opportunity for input into the schedule, new ideas come forth and cause a revision in the logic diagram. This should be encouraged. If the schedule is as well thought out as possible, the project will run much more smoothly. It is easier to erase a pencil mark than it is to remove reinforced concrete. Normally, the logic diagram is drawn a couple of times in order to simplify it and make it communicate accurately. The first draft generally results in backward arrows, inserted activities, potential loops, and basically looks like a bowl of spaghetti. Once it is drawn more neatly and the dura- tions are included, along with any special notations, it is ready to be input into the computer. Inputting the hand-drawn logic diagram into the computer is a fairly simple process; an assistant or staff person can be trained quickly. If the network logic is developed on the computer, the scheduler needs to input the information. This eliminates input from other team members and requires a lot of the manager’s time. If it is developed on paper, the critical and detailed thinking is done by management and then the staff person inputs the schedule information into the computer.

Most project managers prefer to create the project from the beginning to the end— and some prefer to create the project from the end to the beginning. Creating a schedule “in reverse” means beginning with the last activity—close-out. Before that can be done, the final clean must be completed, and so on. That “backward” way of planning is accept- able; simply stamp out the logic diagram from the end to the beginning. As always, it is important to get the team’s thoughts down on paper.

Planning is everything—creating the logic diagram is primarily a planning process, not a scheduling process—and the logic diagram is the result. The final schedule will be the primary tool used to communicate that planning process to all involved in the construction of the project. After a manager is experienced at developing a few of these logic diagrams, it becomes much easier. Once the logic diagram is completed and the durations are entered along with the start and finish dates, it then shifts from a planning process to a scheduling process.

Another technique that pays off later is to create the project logic diagram with only one beginning activity and finish the logic diagram with only one ending activity. If the project starts with two or more activities, create a single start activity and label it “start” or “begin” and give it a duration of 0 days. Do likewise if there are two or more ending activities. This is a good scheduling practice that helps check the computer input. It is easy to overlook a predecessor or successor while inputting the schedule into the computer. A helpful method for finding obvious computer input errors is to see if there is only one activity with no prede- cessors (the first activity) and only one activity with no successors (the last activity).

The use of the rubber stamp to create the logic diagram has already been discussed. The stamp decreases the amount of time it takes to create the network. Another idea is to use mail labels (Figure 6.10) to represent the activities. A sheet of mail labels with a similar activity box as used with the rubber stamp could be created on your computer and then printed. A typical mail label is large enough to handle two activity boxes. The mail label is then pasted onto the paper as the network is being created. Avery 5160 is a commonly used mail label. The original is created by using a word processing program, with the page formatted for mail labels.

Another aid some managers like to use to help create the logic diagram is sticky notes. Write the activity name on the sticky note and apply it to the network diagram. The different colors of notes can represent different trades, equipment, or other resources or problems that are being solved. The notes can be easily repositioned as needed. One caution, however, is that after the network is completed, take a few minutes to tape or glue

Chapter 6 • Creating the Network Logic Diagram 55

the notes in their final position. When the paper is rolled or folded up, unattached sticky notes reposition themselves at will.

It doesn’t matter which method is used to create the logic diagram. The important thing is that it represents the thinking of the management team as to how they plan on constructing the project.