Page 213 - ExtendSim User Guide
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Setup Time 1 model
In the Setup Time 1 model, a Process attribute is assigned to each item. The attribute value rep- resents how long items should be processed for – either 1, 3, or 5 minutes, depending on prob- abilities entered in the Random Number block (Value library). The delta) output connector on the right of the Get block signals when the value of the Process attribute has changed, indi- cating that the current item is of a different type than the previous item. This information is used to add a setup time to that item’s processing time, resulting in a longer total delay time for the first item of a new type, each time the type changes.
Setup Time 1 model
The delta) connector outputs 0 (for False) as long as the value of the Process attribute stays the same and outputs 1 (for True) when the attribute value changes, indicating the arrival of a new type of item. The Constant block (Value library) specifies a setup time of 3 minutes. As long as the attribute value does not change, the Constant block is multiplied by 0, adding noth- ing to the normal processing time. When the attribute value changes, the Constant value is multiplied by 1, and the 3 minute setup time is added to the value of the Process attribute to determine the processing time for that new item. You can see this if you run the simulation – the processing time is cloned onto the worksheet and will be 1, 3, or 5 minutes for most items but 4, 6, or 8 minutes for the first item that is of a new type.
Notice that each item still has its original attribute value. You do not change the attribute value in this model, it is only used to determine whether the item type has changed and thus whether the item requires a setup time. The processing time (whether equal to the attribute value or equal to the attribute value plus the setup time) is input at the D connector. The Activity block processes based on the value at the D connector, not directly based on the attribute value.
☞ While the model above shows the mathematics explicitly, the Equation block (Value library) can also be used to specify the setup time. This is illustrated in the model Setup Time 2.
Bringing an activity on-line
As discussed in the following sections, many systems, activities, or operations can be brought on and off-line based on a schedule or on the current conditions of the system.
☞ The models discussed in this section can be found in the Examples\Discrete Event\Process- ing\Bring On-Line folder. The Shift block is discussed starting on page 232 and models using the Shift block are located in the folder Examples\Discrete Event\Resources.
Scheduling activities
Activities don’t always occur randomly; they can be scheduled. This is common when you bring an activity on-line based on the time of day. This could be represented by a schedule in
Processing 187
Bringing an activity on-line
Discrete Event

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