Page 197 - ExtendSim User Guide
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Routing 171
Items going to several paths
Conditional Routing model
For example, you might have a factory where most of the pro- cessing is done by two machines but excess work is handled by a third machine. ExtendSim can simulate this easily using the Decision block (Value library) and the Activity block (Item library).
The L output of a queue that is
feeding one or more machines
outputs the number of items
waiting to be processed. If this
value is greater than a certain
threshold, you can route some of the items to another machine or activate another process.
In the model, the dialog of the Decision block specifies that the Y connector outputs a true value (1) when the value at the A input is greater than 5. This activates the Gate block’s demand connector so that it lets items through to the third machine (until then, it will not accept items). When the Queue holds 5 or fewer items, the Gate closes.
You can also model this situation in the opposite manner, by having all the operation blocks process items and then shut one or more of them down under certain conditions. If you do this, items may be trapped in the shutdown operation until processing resumes.
When you bring a system on line, it may cycle on and off too frequently. See “Bringing an activity on-line” on page 187 for some methods for avoiding this.
Balancing multiple output lines
Operations are often preceded by queues before each operation, such as a staging area for each machine (as compared to the single staging area for all machines as in the “Explicit Ordering model” on page 168.) The location and ordering of placement of queues in a model can affect how the model performs.
Conditional Routing model
Discrete Event

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