Page 140 - ExtendSim User Guide
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Adding complexity
• As a count of resources that are made available to the model as a whole and released when no longer required.
• As items that are joined with other items and flow through the model with them until sepa- rated.
In both situations, items cannot continue traveling through the model unless the required resource is available.
Add a Resource Pool block (Item library) to the model and place it in any convenient place. Label the block “Attendant Resource”. In its dialog, enter Resource Pool name: Attendants, and enter Initial number: 1 (the default).
In the Queue block’s dialog:
Set the queue behavior to: Resource Pool queue.
In the table, select the Resource Pool named Attendants and set the Quantity to 1. This indicates that each car will now require one attendant to drive it through the car wash.
Delete the connections from the Activity blocks to the Exit block and add a Resource Pool Release block (Item library) after each of the two Activity blocks. Then connect from the Resource Pool Release blocks to the Exit block.
☞ As an alternative, use the Auto Insert technique to add the Resource Pool Release blocks. To do this, drop a Resource Pool Release block onto the connection line between an Activity and the Exit such that the item connector of the Resource Pool Release is on the connection line. ExtendSim will automatically break the connection, insert the Resource Pool Release block, and re-establish the connection. Do this for both Activity blocks.
In each Resource Pool Release block, select to Release by: name and choose that the name of the resource pool is Attendants.
The model should look
similar to the one at the
right. Running the model
shows that the scarcity of attendants causes a con-
straint on the process, and
fewer cars get processed
than when an attendant was
not required. In the dialog
of the Resource Pool block,
you could try increasing
the initial number of atten-
dants to 2 or 3 to explore
the effect that has on model results.
Item attributes
Most car washes allow cars to have wax applied after the wash. Attributes are a very powerful feature that give items unique properties and characteristics. You can use attributes in this model to indicate that specific cars should or should not be waxed. This is accomplished by adding an attribute to the cars coming from the Create block, then checking for the value of that attribute as the car gets washed.
Requiring resources
Discrete Event

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