How to get continuous critical path?

[wixon21]

Actually I have a process of 250 tasks, hopefully everything is linked
properly with proper calendars for the resources.
I am in the middle of a critical path analysis (after 55 steps of
generating new critical pathes). Until now it was possible to shorten the
lenght of the process with giving the command "as soon as possible" when
there was a gap between the tasks, or when I had an entire critical path with
start and end date, shortening the lenght of the acticity. The aim is to have
an earlier end date with a start date (deadline).

At the moment, the critical path is not continuous, the first few steps are
included among the critical activities, then there is a break. After the
break, until the end of the project, the rest of the activites are again
critical. I modified the length of those activities that were not among the
critical activities, that resulted in shortening the full length of the
process. It means that these steps should be included in the critical path
and they were not.
How is it possible to shorten one non critical acticity and making an
impact on the project? What should be done to have an entire continuous path?
I assume there is some problem with the calendars: if for one resource
there is a previously defined working time and all his time is not used
because he finishes the activity earlier, for making the path continuous it
was necessary to adjust the working time to the end of his activity. How is
it possible to find these problems easily?

 

[Gérard Ducouret]

Wixon,
The "break" in the critical path may be generated by:
- a specific task calendar which allows working on week end
- a task duration (or a link) expressed in elapsed days "ed"
- a date constraint on a task

Hope this helps,

Gérard Ducouret

 

[Steve House]

It sounds like you attempted to schedule tasks by entering start and end
dates rather than letting Project calculate them for you. Be advised that
entering a start date sets a "Start No Earlier Than" constraint and this is
a very common cause of breaks in the critical path. Remember that in common
terms, a task is critical when a delay in it would cause the project finish
to be delayed. If I have 3 tasks, A B & C linkied in a chain and B is
starts later than the immediate end of A because of a constraint, we can
delay A's finish by up to the length of the gap without affecting the end of
task C. So A is not critical and the critical path begins at task B. If
task C is ending later than you need it to, nothing you do to shorten task A
is going to mean a thing. Only removing the constraint on B or shortening B
or C will change the overall finish of the sequence.

HTH

 

[wixon21]

Dear Gerard and Steve,

thanks a lot for your reply. I have read your answers and the solutions you
mentioned that can cause any problem I suppose are not relevant in my case.
I hope it is not a problem that I have taken the possibility to write you
personally with the intention of specifing the problem.
For a better understanding I send you two examples of the situation.

Example 1:
Y resource has its B activity until 17.30 and in its resource calendar it is
added that the recourse is available until 19.00, without any additional
activites. Z resource is responsible for the next step. In this case there
is no continuous critical path even though manually you can easily see the
proper way.
Example 2:
If you adjust the calendar to the end of the activity of Y resource, then I
get the entire critical process.

I suggest it is not the proper way of problem solving that all the time I
track the calendars and manually adjust the calendars to the activities. (It
is necessary when any acceleration is made.)
If you could provide me with email addresses, then I can send you the short
examples in MS Project,

Thanks in advance,

 

[Gérard Ducouret]

Wixon,
You can email me at the following address:
ducouret dot gerard at free dot fr

Gérard

 

[Gérard Ducouret]

Hi,

In example 1, Task B lasts 510 mn, that is to say 8,5 hours. It begins
normally at 8:00, so it finishes at 17:30, on the 14the of November.
But that 14th of November, resource Y has a calendar with 2 extra hours in
the evening. While the following task (C) can't begin before the next day,
at 8:00. So the Task B could drift during 1,5h (90mn) without disturbing any
other task : MS Project interpreted that as 90 mn of total slack. That's
quite rational.
If you adjust the calendar of resource Y, so that it finishes at 17:30, the
task has just the time needed to finish, without any slack.

If you estimate that 1,5 hour of slack is not considered as real slack, you
can set the parameter :
Tools / Options / Calculation / Tasks are critical if slack is less than...
Unfortunately, the least unit is 1 day....

Gérard Ducouret

 

[wixon21]

Hi Gerard,

many thanks for your advise, it seems to me that slacks are responsible for
the problem. But 1 day is too long in my case since in the original file I
would need slacks like 1-2 hours. (daily overtime for my resources over their
defined working time is about 1-2 hours) Is there any other solution for the
slack isssue?
With setting slack for one day, some tasks have a different finish date. How
did it come?

thanks again,


Wixon

 

[Steve House]

Slacks aren't the source of the "problem" because slacks are the sole
determinant of whether a task is a critical task or not. If a task has a
positive slack time for any reason, it is not a critical task according to
the standard definition of "critical." And according to those fundamental
definitions, your scenario doesn't exhibit any problem that needs fixing.

 

[Gérard Ducouret]

Hi,

I think a good way to handle your issue, instead of changing hours in the
resource calendar, would be the use of Overtime Work.
Display the Task Form : Window / Split
Select the Task Form, then : Format / Details / Resources Work
In the Overtime Work, enter 2h for example...

Gérard Ducouret