Where the perfect program can be exactly linked and resources constrains accurately appplied with storage space/handling to material deliveries that then will give a just-in-time delivery as and when needed, the usage of 0 FF is somewhat interesting as it then need not be applied in such a kludgy way.
Or perhaps if you can enlighten us with a more interesting way to use 0 FF.
I presume you ask of 0 TF as I have no idea what TT is especially if that is another one of those trademark item such as Basmati rice.
Again in ideal world, with a perfectly created CPN all perfectly linked and perfectly resource constrained, 0 TF will be superfluos.
But in the real world with less than perfect CPN and quick and dirty way needed, 0 TF can be used in another somewhat interesting way too.
Say after the FRP construction of 55th floor (and all prior floors and subsequent floors) you have some builders work for lift shaft in your less-than-perfect-real-world CPN but which indicated float when you know from experience in real-world is critical or close to critical. You rather spend time to smell roses than to do the nitty gritty links/resource constraints/levelling to put that right.
Then by setting 0 TF, you get this activity to be critical. This activity is NOT delayed. The LS is pulled forward to same as ES thus presenting this to be critical. You might have 0 TF and one thousand days as FF at the same time.
Member for
20 years 2 months
Member for20 years2 months
Submitted by ulysses garcia on Mon, 2007-07-02 01:46
P3 ability to allow constraints on TF FF is one of the many small things of P3 that make it so user friendly.
Taking a multi floor high rise as example, you want a just-in-time delivery of material prior to use on each floor.
So you set delivery of etc etc etc floor by floor and FS link to install floor by floor (maybe with lag of 1 or 2 days as wished)
By setting 0 FF constraints on all delivery, you force 0 FF and thereby getting a just in time delivery. This will be done even if you do not have any other predecessor to delivery.
Otherwise, your ES times for delivery will be at earliest date, stating that you want delivery of 55th floor material ASAP even if your 55th floor will be done two years later.
By setting 0 TF constraint, you effectively force that activity to go into ASAP mode forcing LS to be same as ES.
I believe that all planners are familiar what total float is, but i am not convinced if all of us is well knowledgable of how the Zero Total Float constraint works.Can you elaborate it more..
PS. I bought a book from you P3,P5 its very informative.
You must understand how critical path calculations calculate first then the rest will make sense:
Total float is the difference between the late finish & early finish of a task.
Total float may be negative when either there is a late finish constraint earlier than the early finish, or there is a project finish constraint, earlier than the calculated early finish of a projects latest task.
A zero total float sets the early dates of a task equal to the late dates and may delay the early start all successor tasks.
Free float is the difference between the late finish of a task and the early start of the earliest successor.
Free float is never negative.
A task with zero total float consumes free float and does not delay successor tasks.
Unfortunately software packages use the term As Late As Possible loosely and some times mean Zero Total Float as in MSP and sometimes mean Zero Free Float as in SureTrak which make things even more difficult for most people converting from one software to another.
Paul E Harris
Eastwood Harris Pty Ltd, Melbourne, Australia
Planning and Scheduling Training Manual & Book Publishers & Consulting
Member for
21 years 3 monthsRE: Float Constraint
ulysses,
In an ideal world, things can be different.
Where the perfect program can be exactly linked and resources constrains accurately appplied with storage space/handling to material deliveries that then will give a just-in-time delivery as and when needed, the usage of 0 FF is somewhat interesting as it then need not be applied in such a kludgy way.
Or perhaps if you can enlighten us with a more interesting way to use 0 FF.
I presume you ask of 0 TF as I have no idea what TT is especially if that is another one of those trademark item such as Basmati rice.
Again in ideal world, with a perfectly created CPN all perfectly linked and perfectly resource constrained, 0 TF will be superfluos.
But in the real world with less than perfect CPN and quick and dirty way needed, 0 TF can be used in another somewhat interesting way too.
Say after the FRP construction of 55th floor (and all prior floors and subsequent floors) you have some builders work for lift shaft in your less-than-perfect-real-world CPN but which indicated float when you know from experience in real-world is critical or close to critical. You rather spend time to smell roses than to do the nitty gritty links/resource constraints/levelling to put that right.
Then by setting 0 TF, you get this activity to be critical. This activity is NOT delayed. The LS is pulled forward to same as ES thus presenting this to be critical. You might have 0 TF and one thousand days as FF at the same time.
Member for
20 years 2 monthsRE: Float Constraint
Chan,
Your ideas to use 0 FF is somewhat interesting, How about Zero TT how does it works
Member for
21 years 3 monthsRE: Float Constraint
ulysses,
P3 ability to allow constraints on TF FF is one of the many small things of P3 that make it so user friendly.
Taking a multi floor high rise as example, you want a just-in-time delivery of material prior to use on each floor.
So you set delivery of etc etc etc floor by floor and FS link to install floor by floor (maybe with lag of 1 or 2 days as wished)
By setting 0 FF constraints on all delivery, you force 0 FF and thereby getting a just in time delivery. This will be done even if you do not have any other predecessor to delivery.
Otherwise, your ES times for delivery will be at earliest date, stating that you want delivery of 55th floor material ASAP even if your 55th floor will be done two years later.
By setting 0 TF constraint, you effectively force that activity to go into ASAP mode forcing LS to be same as ES.
Member for
24 years 6 monthsRE: Float Constraint
Thank you for your comments on my books.
In summery and hopefully to clarify:
Zero free float delays an activity until its Free Float is consumed and does not delay any other activity.
Zero total float delays an activity even more until it has no Total Float and will delay all of it’s successors.
Paul E Harris
Eastwood Harris Pty Ltd, Melbourne, Australia
Planning and Scheduling Training Manual & Book Publishers & Consulting
www.eh.com.au
Member for
20 years 2 monthsRE: Float Constraint
Paul,
I believe that all planners are familiar what total float is, but i am not convinced if all of us is well knowledgable of how the Zero Total Float constraint works.Can you elaborate it more..
PS. I bought a book from you P3,P5 its very informative.
Member for
24 years 6 monthsRE: Float Constraint
You must understand how critical path calculations calculate first then the rest will make sense:
Total float is the difference between the late finish & early finish of a task.
Total float may be negative when either there is a late finish constraint earlier than the early finish, or there is a project finish constraint, earlier than the calculated early finish of a projects latest task.
A zero total float sets the early dates of a task equal to the late dates and may delay the early start all successor tasks.
Free float is the difference between the late finish of a task and the early start of the earliest successor.
Free float is never negative.
A task with zero total float consumes free float and does not delay successor tasks.
Unfortunately software packages use the term As Late As Possible loosely and some times mean Zero Total Float as in MSP and sometimes mean Zero Free Float as in SureTrak which make things even more difficult for most people converting from one software to another.
Paul E Harris
Eastwood Harris Pty Ltd, Melbourne, Australia
Planning and Scheduling Training Manual & Book Publishers & Consulting
www.eh.com.au