Page 170 - ExtendSim User Guide
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144 Queueing
Queueing considerations
• Renege items immediately when the R (renege) connector gets a true value (0.5 or greater).
When either of these choices is checked, an alternate item output appears on the right of the Queue block. Items that renege leave through that Renege output. They can be routed back to the original line (as in the example below), routed elsewhere in the model, or they can exit the model.
Reneging model
In the Reneging model, parts wait in the first buffering queue until they can be heated by a fur- nace, then wait for processing in a second buffer. If too much time passes before a part is pro- cessed (such that it cools down), the part is sent back to the first buffer to wait for reheating.
Reneging model
The Options tab of the Queue that represents Buffer 2 specifies that a part will wait 5 minutes before it must be returned for reheating. The relevant information has been cloned onto the model worksheet. As seen in its Results tab, the Queue block automatically counts and reports how many items have reneged.
Jockeying is when items move from one waiting line to another in an attempt to gain some advantage. To see a good example of jockeying, go to any supermarket and watch as people leave the end of a slow moving cashier’s line to try and get onto a faster line.
The reneging feature on the Options tab of a Queue block is useful for building a model of this type of behavior. Normally, items renege if they have spent too much time in a queue. But the Queue block has a connector that can force reneging of the last item in the line. The Jockey.mox model is a good example of this.
Discrete Event

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