Rockwell Automation FactoryTalk Scheduler Users Guide - Manual (Page 60)

F ACTORY T ALK S CHEDULER U SER ’ S G UIDE
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increase until no orders remain with the same or larger campaign value. When this
occurs, the rule then switches to a decreasing campaign and begins selecting orders
that have the same or smaller campaign value. When all such orders are exhausted, it
then returns to an increasing campaign strategy. This rule continues in this fashion,
repeatedly cycling between an increasing and decreasing campaign strategy. This is
typical in many industries using ovens or furnaces to treat metals. In such cases, the
temperatures are incrementally raised to the highest level, then lowered.
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The Least Setup With Campaign rule combines the concept of the Least Setup Time
rule with the Campaign Sequence Cycle rule. The operation with the least setup time
and the closest campaign value is selected. The campaign values are only used to
resolve ties in setup.
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The associated Timed rules only consider operations with job due dates that fall
within a specified time horizon. The time horizon value must be specified in the
database. For example, you may want to follow a color campaign, but you only want
to consider the jobs that are due within the next week. This type of rule attempts to
minimize the color changeover, without having a campaign so long that it results in
overdue jobs.
Resource rules
Although the operation selection rule plays a primary role in determining the overall
quality of a production schedule, the resource selection rule can also play an important
role in this process. In the case of the Least Setup Time and the campaign operation
selection rules, the resource selection rule is automatically determined by the operation
selection rule (e.g., by selecting the Least Setup Time operation rule, the Least Setup Time
resource selection rule is automatically selected). However, for all of the remaining
operation selection rules, you must specify one of the available resource selection rules.
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Earliest End Time is the default resource selection rule. It selects the resource that
will finish the operation first. The basic strategy with this rule is to finish the operation
as soon as possible; therefore, this rule follows a similar strategy to the operation
selection rules in the minimum flow-time category.
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The Earliest Start Time rule selects the resource that will start an operation first. This
rule focuses on reducing idle time on resources, but may do so at the expense of
increasing the flow time or assigning operations to less efficient resources.
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The Latest End Time rule selects the resource that will complete the operation last.
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The Same As Previous Operation rule attempts to select the same resource that was
used for the previous operation. If the resource is not included in the valid resource
group for this operation, the default Earliest End Time rule will be applied.