Setting date ranges with start-date to start-date and end-date to end-date dependencies

Ben Wojcikiewicz

I have a project where I am setting a range of production dates and want the sheet to auto-update if I update that there is slippage in the timeline to see how far out things push.

It is easy to schedule dependencies on the front end. For example - if I have items:

1. PO to readiness of raw materials is 2 weeks from the PO - but we have a hypothetical 8 weeks of production

2. That raw material ships for 3 days

3. It takes 2 days to put into inventory

4. Then it goes into production

I use the SS (Start to Start) dependency and have the timelines structured that it cascades as described above. That works fine if everything is static.

If raw material is not available and not that 8 weeks becomes 9 weeks, then items 2-4 need to extend out the additional week.

I tried to use a formula in the date column to account for this (set dates in item 1 and use a forumla in 2-4). I could get this to calculate in any other column except for the date colum for end-date.

Does anyone have an idea of how to set this constraint and if it is even possible?

Kahealani Kanuha

Unless I misunderstood your issue, I think you want to be using FS (Finish to Start) dependency, since each task starts when the next finishes. Then when the readiness of raw materials gets pushed back a week, the tasks that come after it get pushed back a week as well.

I think you just need a Duration column so that all the end dates get pushed back accordingly with the start dates, but I'm not positive on that.

I hope this helps!

J. Craig Williams

Ben,

To add to what Kahealani said, be aware that when Dependencies are enabled, the scheduling columns will no longer accept a formula.

The scheduling columns are those that have been identified as start, end, duration, predecessors, % complete, and allocation % in the project settings.

There are background calcs going on (if you change start date and duration is set, the end date will shift for you, for example) and the user can't override them.

Several people here have mentioned that they set up a schedule with dependencies enabled and then turn them off when the project "goes live". That allows you to add the formulas you mentioned.

Hope this helps.

Craig

Ben Wojcikiewicz

Thanks for the feedback. Finish to start would work, but is imperfect because the area where the work is being done would not be accounted for in the duration box, but would be in the the dependency box as a lag.

I think that the best option is likely what Craig suggested - as I was not aware of that practice. If I kept a duplicate of the sheet with the dependencies on - I could also re-project easily if necessary (which is neccessary more often than I'd like to admit).

Thanks again - and if anyone else wants to chime in, I'd still appreciate more thoughts and ideas.