Here's how to model cure time as a separate task using standard hours and a 7-day work week http://ed.gr/cxo9
Modeling Cure Time in Microsoft Project
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Yes, I agree Tom - defining critical activities as ‘equal to or less than 3-days total float’ is not ideal, but at the least it will provide an early warning that the schedule may be in trouble and requires inspection when that threshold is breached.
All the best,
Emily
Yes, the only fix that MSP provides for the critical path flaws is to bump the criticality threshold, but that’s not enough. If you have to bump it to 3 days, what about the legitimate 1-, 2-, and 3-day near critical paths? Can you tell them apart? What if your project is behind schedule, has 3 weeks of negative float, and has red bleeding out over half the activities? (MSP doesn’t allow a negative criticality threshold.) How can you differentiate the various critical and near critical paths then? Where do you focus your attention? How do you communicate concerns and recommendations without waving your hands?
These were the questions that prompted me to develop BPC Logic Filter (an add-in for MSP) a few years ago. Among other things, BPC Logic Filter executes algorithms that are similar to (but more useful than P6’s) longest-path and multiple-float-path calculation options. With this tool, I am able to welcome the otherwise valid scheduling techniques (e.g. multiple calendars, deadlines, late constraints, automatic resource leveling) that make Total Slack unintelligible.
Hi Emily,
1. Yes you could have used a 24-hour calendar, but I think you are right to avoid it in your example.
a. 24-hour calendar causes confusion because hours-per-day is a constant in MSP. E.g. “14.4-days duration to get 6 days of curing…what!??”
b. Curing on a 24-hour calendar will almost always have non-zero float, even for a mid-week finish (e.g. ~15 hours until the next workday begins). So you would always have to bump the criticality threshold at least a little.
2. You could have used elapsed-days duration instead of 24-hour calendar (it’s functionally identical in most respects.) Would solve the first issue but not the second.
3. The 10hx7d calendar in your example seems to be a happy medium, since it avoids possible confusion over the definition of a day and avoids the nearly-certain partial day of total float that 24-hour and elapsed-day calendars introduce (for a mid-week finish). For a weekend finish it still introduces float and the critical path flaws that Mike pointed out. Not much to do about that inside MSP.
Hi Mike,
Yes, you are correct....of course! :-)
The goal is to account for the curing of concrete on weekends. I could have created a 24-hour per day 7-day per week calendar and assigned it to the cure concrete task, but in our demonstration it is simpler to define a 10-hour per calendar with workdays including weekends. So whether one full day is defined as 8-hours, 10-hours, or 24-hours we want our concrete cure task to capture a full day of concrete curing on each weekday and, in particular, on both Saturday and Sunday. The duration of our concrete cure task is rounded to the nearest full day.
Microsoft Project does not have a longest path feature, so that is not an option. However, I could set the definition of a critical activity to ‘equal to or less than 3-days total float’. This way if Monday is a holiday and the cure process ends on the previous Friday resulting in 3-days total float your cure concrete activity will still be critical, and your schedule will maintain its whole (or continuous) critical path.
All the best,
Emily
Hi Emily
Some problems with your article
The cure time has to be set at 24 hrs per day not 10.
If the cure time ends in a holiday period the critical path is lost so you have to revert to longest path to establish the whole critical path.
The same effect can be done with a lead lag duration.
Best regards
Mike T.