Rockwell Automation FactoryTalk Scheduler Users Guide - Manual (Page 34)

F ACTORY T ALK S CHEDULER U SER ’ S G UIDE
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Although the operation could start at 4 PM , there is only one unit of labor available from
3 PM to 9 PM , so the scheduled start of the operation would be at 9 PM when there are two
units available. From 9 PM to 11 PM , the operation is at 100% efficiency—accounting for
the first two hours of the operation. From 11 PM of Day 1 to 7 AM of Day 2, there are no
units available, resulting in zero efficiency. The last four hours of the operation occur at
100% efficiency with two units available from 7
AM to 11 AM of Day 2.
You also have the option of specifying a minimum number of units that must be available
for the operation to continue (the default is zero). This minimum value must be fewer than
or equal to the total number of units requested. Let’s consider the same six-hour operation
with a minimum equal to the total number, or two units. If the operation cannot start until
1
PM on Day 1, it would be scheduled from 1 PM to 9 AM of Day 2, as shown below. This
particular process spans a 12-hour period because it requires two units during the entire
operation. Thus, it spans the time from 3
PM to 9 PM where there is only one unit available.
Consider an example where the total number of units required is five and the minimum
number of units is three. The operation could not start until there were five units available,
and it would continue as long as there were three or more units available, although it
would occur at a lower efficiency if there were only three or four units available during
that time. If the operation is started and there is a point where there are fewer than three
units available, the operation will span (at zero efficiency) this time until there are at least
three units available, at which time it would resume.
As mentioned earlier, you can also elect to not allow certain types of spanning for specific
Adjustable Pooled resources. If you make this election, it will allow spanning to occur
during off-shift states, but it will not allow spanning where the resource is unavailable
because it is being used by another operation.
7 10 1 4 7 10 1 4 7 10
AM PM AM