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Unformatted text preview: This approach generally keeps
people from back-end loading.
A good rule of thumb to follow is that no task should have a duration much greater than four to six weeks.
There are two ways to develop a schedule. One is to begin at the end and work back until you arrive at the
beginning. The second method is to start at the beginning and work toward the end. Usually, it is easiest to
start at the beginning.
The first step is to decide what can be done first. Sometimes several tasks can start at the same time. In that
case, you simply draw them side-by-side and start working from there. Note the progression in the diagram in
Figure 5-4. I have numbered the boxes according to the steps taken to place them. In other words, all boxes
with a 1 beside them were placed in the diagram in step 1, and so on. Note that it sometimes takes several
iterations before the sequencing can be worked out completely. Figure 5-4 CPM diagram for yard project.
This small project might be thought of as having three phases: preparation, execution, and cleanup. There are
three preparation tasks: pick up trash, put gas in equipment, and get out hedge clipper. The cleanup tasks
include bagging grass, bundling clippings, and hauling trash to the dump.
Schedules should be developed according to what is logically possible; resource allocation should be done
later. This yields the optimum schedule.
www.erpvn.net In doing this schedule diagram, I have followed a basic rule of scheduling—to diagram what is logically
possible, then deal with resource limitations. For a yard project, if no one is helping me, then there really can
be no parallel paths. On the other hand, if I can enlist help from the family or neighborhood youth, then
parallel paths are possible. The rule I suggest is that you go ahead and schedule as if it were possible to get
help. This is especially important to remember in a work setting, or you will never get a schedule put together.
You will be worrying about who will be available to do the work and end up in analysis paralysis.
Another rule is to keep all times in the same increments. Don’t mix hours and minutes—schedule everything
in minutes, then convert to hours and minutes as a last step. For this schedule, I have simply kept everything
Another rule is to keep all times in the same increments—minutes or days, for example.
I suggest that you draw your network on paper and check it for logical consistency before entering anything
into a computer scheduling program. If the network has logical errors, the computer will just give you a
garbage-in, garbage-out result, but it will look impressive, having come off a computer.
It is also important to remember that there is usually no single solution to a network problem. That is,
someone else might draw the arrow diagram a bit differently than you have done. Parts of the diagram may
have to be done in a certain order, but often there is flexibility. For example, you can’t deliver papers until
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- Fall '13