Page 201 - ExtendSim User Guide
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Routing 175
Items going to several paths
and can only work on types 1 and 2, and the other machine can only work on type 3. The model is shown below:
Processing by Type model
A Set block assigns a Type attribute to each item. The empirical table in the Random Number block (Value library) indicates that there is a 50% probability that the item will be Type 2, and 25% probability that it will be either Type 1 or 3.
The Select Item Out block is set to Select output based on: property. It looks up the value of the Type attribute (1, 2, or 3) and selects the appropriate output (1, 2, or 3) based on entries in the block’s options table, shown at right.
Options table in Select Item Out block
Notice the use of the queues as buffers in the above model. They are used to store the items by type, with the top queue for Type 1, etc. Without the queues, the whole line could be blocked, depending on the order in which items arrive. For example, if the first three machines are all processing a Type 1 item, and a Type 1 item is the next to exit the Select Item Out block, block- ing occurs until one of the machines is finished with its item. The fourth machine will not be able to pull in an item until one of the other machines finishes processing and pulls in the new Type 1 item. Even then, it will have to wait until a Type 3 item is output before it can process anything.
☞ Named connections are used to simplify the look of this model. Without these, there would be a spaghetti of connection lines connecting the Queue blocks to the Select Item In blocks. Another option for organizing the model would be to use Throw Item and Catch Item blocks to route the items to the appropriate machines.
Discrete Event

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