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A "Late Finish" Calculated from Free Float?

7 replies [Last post]
Greg Paulson
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Hello,

Does anyone know if there is a form of a "Late Finish" that would be calculated as the latest date an activity can finish without affecting the start date of any of its successor activities? (i.e. Latest Finish where Free Float = 0)

I have fabrication and long lead activities that I do not want to drive any of my construction activities, and would like to give "drop dead" dates to our fabricators.

As a general practice, I filter my fabrication activities for Free Float = 0d to generate a list of fabrication items driving my construction dates.  Then I use this list to give a warning that fabrication is slipping.

I would prefer to generate a list of all fabrication activities that shows the finish date that would use up all of that activity's free float.

This question was touched upon in a 2007 post, but I don't see an answer that works for me.  http://planningplanet.com/forums/microsoft-project/415942/late-start-free-float

Any other suggestions are appreciated.

Thanks!

 

Greg

Replies

Rafael Davila
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Posts: 4516

Then, I must agree with your approach.

Greg Paulson
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This is a good point that is being well taken into consideration.  Our drop dead dates are only circulated internally.  I do not provide our suppliers or subcontractors with float calcs or late starts.  We give them our own due dates.

Rafael Davila
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Please be reminded that a Drop Dead Date that would be calculated as the latest date an activity can finish without affecting the start date of any of its successor activities not always is a good idea. If you give too much leeway all might be used by your suppliers, this can consume too much or all of available float.

Drop_Dead_Dates

Planning without contingency reserves is self defeating.

  • RCP_Approach
  • Success Driven Project Management Paper  -  We recommend to use optimistic schedule for setting tasks for project work force and manage project reserves. The schedule that is calculated backward from the target dates with most probable estimates of activity durations we call Critical schedule. The difference between start and finish dates in current and critical schedules we call start and finish time buffers (contingency reserves). The difference between activity (phase) cost that has defined probability to be met and optimistic cost of the same activity (phase) we call cost buffer.       

  • Start Buffer = A  =  Diff_Days_Calen (  Start_CMP2  ;   Start  ;  Calen  ) - Returns the difference in days between two dates by the given calendar.

  •   Buffer_Management_7.18.2018

Greg Paulson
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Thank you for your responses.  I also created start and finish user defined fields called Fab LS and Fab LF, then used a Global change to populate them with the late finish / start dates generated by the "as late as possible" constraint.  That allowed me to remove the constraint, but maintain the drop dead dates.

Thanks again!

Greg

Rafael Davila
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More interesting can be the calculation of Drop Dead Dates for partial deliveries of Consumable Resources such as Bricks.

As you can see in this model after consumable resources [Bricks] are leveled deliveries free float is consumed but not all float.

Rafael Davila
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No way all conceivable parameters will be provided within your software but the software shall give you the tools [functions] to calculate dates based on your calendars.

Calculate the Free Float Finish using User Defined Field and [Global Change] simple formula available in your software.  Just take a look at the formula, cannot be any easier.

Free_Float_Finish

To apply the constraint as late as possible to that activity is an option to consider if your software does not provide the functions required to make the calculations.

Good Luck

Zoltan Palffy
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Joined: 13 Jul 2009
Posts: 1940

yes apply the constraint as late as possible to that activity