critical path problems

[swell estimator]

I've been able to successfully create several schedules that display the
critical path. Recently I built a schedule that came together correctly and
with the first 2 iterations I was able to create and display the critical
path.

But after some minor changes the critical path disappeared and I was unable
to get it back. I redid the Gantt chart wizard on the cp several times but I
couldn't get the cp to come back.

Any suggestions as to how I can trouble-shoot this problem?

Thanks in advance , Swell

 

[Jim Aksel]

Hi Swell -

Look for tasks with date constraints such as "Start No Earlier Than", etc.
Critical path shows best when all the tasks are "As Soon As Possible."
Perhaps you keyed a date and that will cause problems. Start/Finish dates
should be calculated by the software not the keyboard.

We usually have a final milestone and put a **Deadline Date** on that task
ensuring we will get a critical path. Deadlines are different than date
constraints.
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Jim Aksel, MVP

Check out my blog for more information:
http://www.msprojectblog.com

 

[swell estimator]

I went back and made sure all tasks were "As Soon as Possible". I also
established a milestone named "Substantial Completion" and I created a
deadline
date for the milestone.

I still can't get the critical path to show. I will go back now and check
if didn't key in a date - possibly a finish date - that may be causing the
problem I have to get this sorted out by Thursday afternoon - schedule due
Fri.

But: in the meantime could you list the various things that could cause what
I'm experiencing? Thank you - Chris

 

[Steve House [MVP]]

Keep in mind this rule of thumb: All projects should have a start milestone
and a finish milestone. All performance tasks within the project should
have at least one predecessor and at least one successor. If no other
activity is a task's predecessor, the start milestone is the predecessor.
If no other activity is the task's successor, the finish milestone is.

Keying dates in the start and/or finish columns DOES NOT set start or finish
dates or deadlines. Entering a date in the Start column creates a Start No
Earlier Than constraint. Entering one in the Finish column creates a Finish
No Earlier Than constraint.

Why could constraints cause your critical path to disappear? A critical
task is one whose delay would cause the project completion to be delayed.
So consider a project with a start milestone, two tasks A and B of 5 days
duration each, and a finish milestone, all linked in sequence finish to
start. The project starts Monday, 03 Nov. MS Project will calculate the
end date to be 14 Nov and both A and B are critical tasks. So far, so good?
Now add a SNET constraint to B by entering a start date of 17 Nov on it.
Now A will cease to be critical because A runs 03 Nov to 07 Nov, there'll be
a 5 day gap, then B will start on the 17th. Obviously A can be delayed by
1, or 2, or 3, up to 5 days before it starts to push on B and delay the
project finish.

You said the critical path completly disappeared - could both A and B cease
to be critical in the above example? Yes! Take the constraint off of B by
setting it back to ASAP again. Go to the finish milestone which should
currently be showing on 14 Nov. Your boss has given you a deadline of 21
Nov so you try to display that in the project by entering it into the Finish
column for the milestone (that's not the right way to do it but indulge me).
Now A will run from 03 Nov to 07 Nov, task B will run from 10 Nov to 14 Nov,
and the finish milestone (now with a FNET constraint caused by your
entering a desired finish date) will sit on 21 Nov with a 5 day gap between
task B's finish and the milestone. In this situation A has 5 days total
slack and 0 days free slack while B has 5 days free and 5 days total slack.
Since neither of them have zero slack, neither are critical. The problem,
of course, is the project is actually finished the moment the last task is
finished and having the milestone placed in the schedule sometime later than
that moment by virtue of its constraint is introducing an artifact that
shouldn't be there.

I'd bet dollars to donuts that something like this has happend in your
project.